no "archie style" burnout videos? I mean it is a V8....
I don't think the customer would appreciate me burning up his new tires. Besides, what's the point? 4cyl-powered cars can do burnouts. I honestly don't understand why some people get so excited over burnouts. It doesn't prove anything nor does it show how powerful the engine is; rather it can be destructive on not only the tires but also the transmission. I'm more interested in the car hooking and darting away from a stop as quickly as possible.
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Originally posted by Erik: Can you describe the sound of the exhaust any better? Maybe a sound clip would better do that
There is a link to a sound clip of the engine running on page 7 of this thread.
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02:35 AM
Feb 26th, 2008
SAFASTRO Member
Posts: 604 From: Calgary, Alberta, Canada Registered: Nov 2006
WOW......alot of good info here. I just skimmed throught this thread, and will have to go back an reread it more thoroughly!! I have a great opportunity here, that I just can't pass up on. A friend of mine purchased a 2006 Malibu with the 3.5 V6 and the 4T65-E tranny. He only has 3500km on it now, and in about a month or 2, he is swapping in a 3.9 setup from a malibu SS. This comes to my chance of a lifetime. He is GIVING me his current setup for FREE!!!! I asked what parts I would need to get, since he works at a parts counter at a local dealer, such as alternator, belts, pulleys, etc.......he said, "NOTHING, it all comes with it!".......what the heck, did I hear him right?? He says, yeah, everything comes with it including the tranny!!! I'm still in a bit of shock , since at first I thought I was only getting the main block and intake and minor stuff, but when he told me I get "THE WORKS", I almost lost it. I hope you guys will be able to talk me through a few things.....I'm no electronics genious.........I have rebuilt and installed many carbed V8's, but am I getting in over my head here???
Because the 5.3 L4 is kinda big, Ryan gave me three options...1) Install a complete system with the dual cats and mufflers, but this would require him cutting into the bottom of the trunk space because of the amount of room left and angle based on the girth of the LS4, 2) Don't alter the trunk at all, but would have to choose to install a partial system and use one of those flexible steel weave joint connectors?, or 3) Build (and pay for) two sets of exhaust systems that can be interchanged based on need.
As you can see from the picture, I chose option 2. I think I only have one more e-check with Ohio DMV before the car is grandfathered and won't require it at all. So I went with using the Cat exhaust. I've had those old straight pipe racing exhausts from wayy back in the day for the longest time on the car, so I'm hoping the engine isn't too loud w/out the mufflers. Ryan seems to think it's not too bad. It definitely growls, but not the wake the neighborhood roar. We'll see!
Once I get past any more e-checks, I may revert to the mufflers, but if the sound isn't rude, I'll keep it as is. I thought of intalling muffler tips, but I fell in love with the Corvette tips, and well...the rest is history!
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02:09 PM
Amida Member
Posts: 2355 From: Seattle, WA. USA Registered: Jul 2003
Sorry I haven't posted in a while. The weather around here has gotten pretty bad lately and I don't really want to drive a customer's car in such conditions (nor when the roads are wet with slush and salt). So there hasn't been much else I have been able to do to the car. Plus I came down with that nasty head cold that is going around and I really haven't been feeling well enough to do too much out in the shop.
-ryan
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04:02 PM
Mar 4th, 2008
Darth Fiero Member
Posts: 5921 From: Waterloo, Indiana Registered: Oct 2002
I have been asked a couple of times about how exactly the DoD system functions to save fuel. So I will explain it here. Below is a portion of GM's explaination...
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To provide maximum fuel economy under light load driving conditions, the engine control module (ECM) will command the displacement on demand (DoD) system to deactivate engine cylinders 1 and 7 on the left bank, and cylinders 4 and 6 on the right bank, switching to a V4 mode. The engine will operate on 8 cylinders, or V8 mode, during engine starting, engine idling, and medium to heavy throttle applications.
When commanded ON, the ECM will determine what cylinder is firing, and begin deactivation on the next closest DoD cylinder in firing order sequence. The Gen IV engine has a firing order of 1-8-7-2-6-5-4-3. If cylinder number 1 is on its combustion event when DoD is commanded ON, the next cylinder in the firing order sequence that can be deactivated is cylinder number 7. If cylinder number 5 is on its combustion event when DoD is commanded.
Cylinder deactivation is accomplished by not allowing the intake and exhaust valves to open on the selected cylinders by using special valve lifters. The deactivation lifters contain spring loaded locking pins that connect the internal pin housing of the lifter to the outer housing. The pin housing contains the lifter plunger and pushrod seat which interfaces with the pushrod. The outer housing contacts the camshaft lobe through a roller. During V8 mode, the locking pins are pushed outward by spring force, locking the pin housing and outer housing together causing the lifter to function as a normal lifter. When V4 mode is commanded ON, the locking pins are pushed inward with engine oil pressure directed from the valve lifter oil manifold (VLOM) assembly solenoids. When the lifter pin housing is unlocked from the outer housing, the internal pin housing will remain stationary, while the outer housing will move with the profile of the camshaft lobe, which results in the valve remaining closed. One VLOM solenoid controls both the intake and exhaust valves for each deactivating cylinder. There are 2 distinct oil passages going to each DoD lifter bore, one for the hydraulic lash-adjusting feature of the lifter, and one for controlling the locking pins used for cylinder deactivation.
Although both intake and exhaust valve lifters are controlled by the same solenoid in the VLOM, the intake and exhaust valves do not become deactivated at the same time. Cylinder deactivation is timed so that the cylinder is on an intake event. During an intake event, the intake cam lobe is pushing the valve lifter upwards to open the intake valve against the force of the valve spring. The force exerted by the valve spring is acting on the side of the lifter locking pins, preventing them from moving until the intake valve has closed. When the intake valve lifter reaches the base circle of the camshaft lobe, the valve spring force is reduced, allowing the locking pins to move, deactivating the intake valve. However, when DoD is commanded ON, the exhaust valve for the deactivated cylinder is in the closed position, allowing the locking pins on the valve lifter to move immediately, and deactivate the exhaust valve.
By deactivating the exhaust valve first, this allows the capture of a burnt air/fuel charge or exhaust gas charge in the combustion chamber. The capture of exhaust gases in the combustion chamber will contribute to a reduction in oil consumption, noise and vibration levels, and exhaust emissions when operating in V4 mode. During the transition from V8 to V4 mode, the fuel injectors will be turned OFF on the deactivated cylinders. The ignition system secondary voltage or spark is still present across the spark plug electrodes on the deactivated cylinders. If all enabling conditions are met and maintained for DoD operation, the ECM calibrations will limit cylinder deactivation to a cycle time of 10 minutes in V4 mode, and then return to V8 mode for 1 minute.
Switching between V8 and V4 mode is accomplished in less than 250 milliseconds, making the transitions seamless and transparent to the vehicle operator. The 250 milliseconds includes the time for the ECM to sequence the transitions, the response time for the VLOM solenoids to energize, and the time for the DoD valve lifters to deactivate, all within 2 revolutions of the engine crankshaft.
So what you can take from this is GM decided they had to leave something in those deactivated cylinders to prevent oil from being sucked into them if they were just allowed to pull a vacuum on every down stroke (which is what you would have if the intake valve was the first to get shut off when entering DoD mode). Appearantly they found that the pumping loss (from having to pump spent exhaust gases) outweighed the side-effects from having cylinders filled with nothing.
As far as real-world trials are concerned, you need to keep in mind that in order for this system to function, there must be a relatively light load on the engine. This means that you can't be blazing down the interstate at 80+ MPH and expect the engine to drop into V4 mode. In fact I found in my road tests that heading into a 10-15mph wind on a level grade, 73mph is about as fast as you could go before the system would need to drop back into V8 mode. And if you started going up any hills, the system would be quicker to go back into V8 mode as well.
As mentioned before, according to the DIC fuel mileage computer readout, there is quite a bit of difference in fuel economy in V4 mode vs. V8 mode. At steady 55mph highway speeds, I'm typically seeing about 22-25mpg in V8 mode and that increases to over 30mpg once then engine enters V4 mode. These figures do decrease slightly as the vehicle nears that speed threshold where the DoD system will no longer be able to function due to wind resistance. At that point, I'm seeing about 28mpg in V4 mode and less than 20mpg in V8 mode. Again all these readings are taken right off the DIC so I don't know how accurate they are. But after you factor everything in (depending on driving habits) I would say this LS4 probably gets the same fuel economy as a L67.
Now concerning long-term durability of the engine (especially since you will only ever have the same 4 cylinders deactivating); appearantly there isn't an issue. I, myself was concerned of such an issue but my friends at the GM dealers haven't reported any instances of such irregular wear issues and there are some of these cars nearing 100,000 miles on them by now. GM has and is offering these engines in cars which are being sold with 100,000 mile powertrain warranties. So it stands to reason that they wouldn't be putting such a warranty on this engine if it can't last. The better news is that putting this engine into a lighter car would seem to reduce the load on the engine; which means over its lifetime it won't have to work as hard (depending on driving habits). Which should translate to the engine lasting longer.
My opinion on this subject is this: everybody is concerned with gas prices. As prices continue to skyrocket at the pump, more and more people are having to make that decision between engine power output and fuel economy. I think the LS4 brings a nice balance to the equation; based on today's technology. Hybrids (gas engines w/ electric assist) seem to work better for city driving and haven't really shown marked improvement on the highway. I think that's where the cylinder-deactivation technology has an edge. I'm sure the point will come in the future where I will end up doing a hybrid swap to a Fiero; but for now the DoD technology seems to work pretty good.
Update...West Coast Fiero Performance Springs & Coil Over Kit
As you may remember, I purchased the Performance Spring and Rear Coilover kit from WCF. This kit drops the front stance of the 87' Fiero about 1.5 inches. Rear height is adjustable up to 2.0 inches lower, but Ryan recommended keeping the rear slightly higher than the front for better stability in lieu of the increased power of the LS4 swap. I think he's got it dropped about 1.0 inch.
According to WCF, the springs were developed to be used for the race track, and I chose 400 lb/in travel which is significantly stiffer than the 200 lb/in springs of the stock 87' Fiero. I also opted for a staggered wheel/tire setup going with 17x7 w/ 40 os (225/40) in the front and 18x8 w/ 40 os (265/30) in the rear. Rims are Motegi SP7s.
Verdict: The first go round, the rear setup was perfect. Plenty of room for the wider 265 tires and the coilover springs. I could probably go 275 if I relocated the spring perches and changed offset, but 265 is plenty wide unless I wanted to go wide body. I've prioritized going for a track ready street car over spectacular looks and gawks that a wide body or chop top would give me. Maybe next car project I'll get visually inventive like some of the beautiful cars of some of the PFF members!
The front was much more challenging! The basic 1.5 inch drop, paired with the 17x225x40 was too much. While the look was kinda hot, as it seemed like the car was slammed, Ryan could barely get two fingers in between the tire and the inside fender! Even though Ryan moved the bump stop and shaved it back a bit, any major bump caused the car to ride hard on the stop, and on aggressive test runs he felt that it was just too harsh of a ride on severely bumpy roads. It would probably be okay for track surfaces, but he felt I would soon grow tired of the harshness as a daily driver. I contacted Chris at WCF and explained the issue and he and Ryan got on a conference call. Chris was extremely cooperative and helpful. I call this out, as I've read that some folks have reported issues when dealing with WCF. I have always had good experiences with them, especially with this kit. The solution was to install 5/8" spacers for the front setup, which WCF cut for me and sent out directly to Ryan. The spacers raised the front end up by about 1/2 - 3/4 of an inch. Ryan says the ride quality IS SO MUCH BETTER now that it's not riding hard on the the bump stops. He test drove it down a bumpy concrete road and it seems to ride nicely now -- no problems.
So now I think Ryan just needs to program a few more Key Fobs for the remote start and keyless entry function, find a place to locate the compass module, and schedule time on a Dyno machine to get some ball park spec numbers. He'll then HPTune the engine based on the results and if the weather cooperates, I should be able to pickup my baby this month! I CAN'T FRIKEN WAIT!!
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09:07 PM
Rickady88GT Member
Posts: 10648 From: Central CA Registered: Dec 2002
Congrats! Sounds like it coming along nicely. Itching to drive it a little?
I think I have the same springs on mine. Right now with 205/45-16's it seems fine but I am going up to a 225/45-17 in the front so I figure some spacers will be needed also. I was a bit worried about the 400lb springs being too rough but it sounds like they will work. Only time will tell. Congrats again on it all coming together.
[This message has been edited by Fieroseverywhere (edited 03-13-2008).]
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02:38 PM
Darth Fiero Member
Posts: 5921 From: Waterloo, Indiana Registered: Oct 2002
The front was much more challenging! The basic 1.5 inch drop, paired with the 17x225x40 was too much. While the look was kinda hot, as it seemed like the car was slammed, Ryan could barely get two fingers in between the tire and the inside fender!
Correction: I couldn't even get 1 finger half way in between the tire and the fender! Therefore I was hesitant to trim the bumpstops any more for fear the tire could come in contact with the fender if you hit a big bump. The spring spacers I just installed seemed to give us enough of a ride height increase to correct this issue but no soo much that it ruined the looks of a "lowered car" that blkcofy was wanting.
Since the weather has FINALLY decided to cooperate around here, I am taking the opportunity to get some much needed road testing and tuning done.
There's been alot of arguing and debating over folks posting real numbers of their swaps, so I started another thread to "celebrate" everyone's efforts versus the ongoing pissing match we've often gotten ourselves into. So far, not so bad in terms of everyone playing nice. Ryan's posted the results on that thread, but wanted to keep folks updated who've followed this original thread as well...
We executed 3 pulls:
As you can see from the results above, all three pulls were pretty consistant. I had them remove two of the pulls from the graph and just print out the best (HP) one:
Max WHP: 271.20 Max WTQ: 277.07
You can see on the dyno charts that the weather conditions were better than SAE ideal, thus the correction factor was less than 100% (meaning the engine was actually putting down more power to the dyno than these SAE corrected graphs show). Also you can see the AFR's didn't look bad at all (dashed line on the AFR graph represents 13.0:1). The beginning of the dyno pull did start out a little lean because they were easing into the throttle; but by about 4500rpm, the AFR's were near-perfect for what I wanted to see.
TiredGXP mentioned that people taking their stock LS4-powered Grand Prix GXP's to the dyno were getting anywhere from 230whp (a 24% loss thru the drivetrain) to 252whp (a 17% loss thru the drivetrain). If you apply the same loss % factor to the dyno runs I did today, then we can figure blkcofy's engine is producing:
317.3 ~ 336.3 @crank hp 324.2 ~ 343.6 @crank tq
Assuming a 24% drivetrain loss, that means the mods done to this engine have gained about 33hp and 20tq at the crank. Of course there's no way to measure the actual loss thru blkcofy's drivetrain unless we pull the engine and put it on a dyno by itself. Also we have to assume the dyno numbers I got today aren't going to exactly match the dyno numbers other people are getting.
Hopefully today's dyno test puts blkcofy's mind at ease. I knew the mustang dyno's conflicting dyno / simulated 1/4 mile sprint test just didn't sound right. I think today's results prove that point.
-ryan
[This message has been edited by blkcofy (edited 03-28-2008).]
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10:47 AM
Oreif Member
Posts: 16460 From: Schaumburg, IL Registered: Jan 2000
regarding the sleeves you made for the bushings, what about are the dimensions of the recess, length, and most importantly the dimensions of the raw tube stock you purchased for it?
[This message has been edited by darkhorizon (edited 03-28-2008).]
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04:04 PM
Apr 7th, 2008
Rickady88GT Member
Posts: 10648 From: Central CA Registered: Dec 2002
How hard would it be to add the Tap Shift and remote start to the LS4 drive train if the entire wire harness and BCM are used? Are the options that are already programed into the TCM, BCM and just need the to be plugged in?
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02:27 PM
Darth Fiero Member
Posts: 5921 From: Waterloo, Indiana Registered: Oct 2002
How hard would it be to add the Tap Shift and remote start to the LS4 drive train if the entire wire harness and BCM are used? Are the options that are already programed into the TCM, BCM and just need the to be plugged in?
The TAPShift function doesn't go thru the BCM at all. In fact, it's controlled by only one wire that comes out of the TCM (the tapshift buttons have a series of different value resistors wired to them, that's how the TCM can determine which button you push using only one signal wire).
The remote start requires the BCM. In order for the remote start to function, the BCM needs to see a host of signals (hood/door pin switches, igntion switch, brake pedal position sensor, etc etc). I don't think you are going to be able to just grab an entire interior harness out of a GXP for the BCM and install that into a Fiero either. Nor would you want to. There are about 100 wires/circuits I eliminated from the BCM install I did during this LS4 swap because I just didn't see the point of having every circuit in the car (yes even the windshield wipers) going thru the BCM.
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09:30 PM
Apr 8th, 2008
Fierobsessed Member
Posts: 4782 From: Las Vegas, NV Registered: Dec 2001
The TAPShift function doesn't go thru the BCM at all. In fact, it's controlled by only one wire that comes out of the TCM (the tapshift buttons have a series of different value resistors wired to them, that's how the TCM can determine which button you push using only one signal wire).
Thats funny, I just found that the radio's from the mid 90's with steering controls operate the same way. I am currently trying to get my ECM to talk to my radio using a PWM to mimic the voltage levels the resistors in the steering controls produce... I guess I am a geek? I am trying to featurize my car a little.
I found that the resistors create voltages ranging from 1-5V in approximatly half volt increments. Fun
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01:56 AM
Rickady88GT Member
Posts: 10648 From: Central CA Registered: Dec 2002
So are the TCM's all capable of a Tap Shift option, do they all have the same programming for it? Can I just use a Solstice or Malibu steering wheel and column that has the buttons on it? I do plan to swap an entire wire harness into the Fiero so the circuits will be there anyway. I plan to do this for the dash and its related Heater and A/C system as well as the other "modern" conveniences. So I just wonder if the remote start could be added to the car as if it were still in the Montecarlo?
Thanks, Rick
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02:02 AM
Darth Fiero Member
Posts: 5921 From: Waterloo, Indiana Registered: Oct 2002
So are the TCM's all capable of a Tap Shift option, do they all have the same programming for it? Can I just use a Solstice or Malibu steering wheel and column that has the buttons on it?
Not exactly. The TCM you are using must have the same service number as one that came with the TAPShift option. Then it must be programmed with the correct OS that supports TAPShift. Then finally, your transmission must be set up for TAPShift. Mechanically, the TAPShift and Non-TAPShift auto transmissions are different.
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I do plan to swap an entire wire harness into the Fiero so the circuits will be there anyway. I plan to do this for the dash and its related Heater and A/C system as well as the other "modern" conveniences. So I just wonder if the remote start could be added to the car as if it were still in the Montecarlo?
Thanks, Rick
The remote start function is part of the keyless entry and factory alarm systems; at least they share many of the same sensors and components. In fact, a lot of new GM cars and trucks being sold today are remote-start capable, even if they don't come off the showroom floor with remote start enabled. You can buy the remote fobs from GM Parts as a kit that comes with a remote start activation code which you can use to have your vehicle's computers reprogrammed to enable remote start.
But as I said before, the BCM is going to need to see several inputs in order to allow for remote start operation.
Darth, would you happen to know the mechanical differances between the 2 trannies?
Yes, but not in great detail. IIRC, in manual mode, fluid gets routed to the 1-2 band and 3rd clutch circuits at various times for engine braking. My trans guy told me there is a difference concerning the way fluid pressure is modulated in these manual modes vs. a normal 65-E trans. Basically he said you don't want to put a TAPShift computer onto a standard 65-E trans because the manual shifting of it could result in violent shifts and such which could obviously shorten its life. If you want more detailed information, you can contact him via his website: http://www.tripleedgeperformance.com/
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06:00 PM
Apr 9th, 2008
Rickady88GT Member
Posts: 10648 From: Central CA Registered: Dec 2002
I noticed that the inner CV joint on my 06 65E has the same exact shape as the F40 inner CV and they use three huge roller bearings inside instead of the typical Fiero style needle bearing. The rollers used inside the inner joint (tripot) looks like sealed bearings that may not use the CV grease for lubrication of it's internal rollers. The grease looks like it lubes the outer surface of the rollers that contacts the try pot inner walls. The inner joint seems larger than the Manual Fiero CV's? I will try to get the male inner CV and slide it in the F40 to see if it has the same splines.
Is there any way to tell if the tranny is tap shift compatible. Or what will it take to convert on to tap shift?
Darth do you have any wire diagrams that I could Use?
Thanks, Rick
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02:17 AM
PFF
System Bot
Apr 10th, 2008
RONT4.9 Member
Posts: 85 From: Myrtle Point OR. Registered: Oct 2007
I noticed that the inner CV joint on my 06 65E has the same exact shape as the F40 inner CV and they use three huge roller bearings inside instead of the typical Fiero style needle bearing. The rollers used inside the inner joint (tripot) looks like sealed bearings that may not use the CV grease for lubrication of it's internal rollers. The grease looks like it lubes the outer surface of the rollers that contacts the try pot inner walls. The inner joint seems larger than the Manual Fiero CV's? I will try to get the male inner CV and slide it in the F40 to see if it has the same splines.
Is there any way to tell if the tranny is tap shift compatible. Or what will it take to convert on to tap shift?
Darth do you have any wire diagrams that I could Use?
Thanks, Rick
I had the same problem with my 06 axles. My solution was: Dr. side = tripot and guts from 98/99 lumina n/a 3800. Shaft from 94 berretta. Outer cv from manual fiero. Pass. side = p/s tripot and guts from 97 Riviera 3800sc. Axle shaft from d/s of same Riviera. Outer cv housing from fiero with the cage and balls from the Riviera. ( of coarse it depends on whare you mount your engine) Mine is in a 88 coupe. Hope this helps. Bye the way, the 06 gxp manuals show some different valves in the tap shift trans.
Yes, but not in great detail. IIRC, in manual mode, fluid gets routed to the 1-2 band and 3rd clutch circuits at various times for engine braking. My trans guy told me there is a difference concerning the way fluid pressure is modulated in these manual modes vs. a normal 65-E trans. Basically he said you don't want to put a TAPShift computer onto a standard 65-E trans because the manual shifting of it could result in violent shifts and such which could obviously shorten its life. If you want more detailed information, you can contact him via his website: http://www.tripleedgeperformance.com/
Thanks for link !
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ARCHIES JUNK IS FASTER THAN SHAUNNA'S JUNK
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10:16 AM
Rickady88GT Member
Posts: 10648 From: Central CA Registered: Dec 2002
I had the same problem with my 06 axles. My solution was: Dr. side = tripot and guts from 98/99 lumina n/a 3800. Shaft from 94 berretta. Outer cv from manual fiero. Pass. side = p/s tripot and guts from 97 Riviera 3800sc. Axle shaft from d/s of same Riviera. Outer cv housing from fiero with the cage and balls from the Riviera. ( of coarse it depends on whare you mount your engine) Mine is in a 88 coupe. Hope this helps. Bye the way, the 06 gxp manuals show some different valves in the tap shift trans.
So on the inner CV joint, the splines are the same on the 06 65HD as they are in the Lumina and Riviera nonHD and the outer shell of the tri pot are different?
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11:26 AM
Darth Fiero Member
Posts: 5921 From: Waterloo, Indiana Registered: Oct 2002
So on the inner CV joint, the splines are the same on the 06 65HD as they are in the Lumina and Riviera nonHD and the outer shell of the tri pot are different?
That's correct, the lumina 3800 (non hd) and the Riviera with hd are both 34 splines. The 06gxp has 34 splines. However, if you take apart the outer cv (next to the wheel) on the 06 gxp axle you will find it has 8 balls instead of 6 and the axle end is different. I found that the gxp axle shaft would not interchange with ANYTHING. Good Luck
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05:11 PM
Rickady88GT Member
Posts: 10648 From: Central CA Registered: Dec 2002
That's correct, the lumina 3800 (non hd) and the Riviera with hd are both 34 splines. The 06gxp has 34 splines. However, if you take apart the outer cv (next to the wheel) on the 06 gxp axle you will find it has 8 balls instead of 6 and the axle end is different. I found that the gxp axle shaft would not interchange with ANYTHING. Good Luck
OK, thanks. Are the LS4 axle shafts larger in diameter than the Fiero manual axles or is it just a different spline on the outer end? How much longer are the axles from the LS4 than are needed? Can you swap left for right and get a better match for the Fiero?
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07:29 PM
Apr 11th, 2008
RONT4.9 Member
Posts: 85 From: Myrtle Point OR. Registered: Oct 2007
OK, thanks. Are the LS4 axle shafts larger in diameter than the Fiero manual axles or is it just a different spline on the outer end? How much longer are the axles from the LS4 than are needed? Can you swap left for right and get a better match for the Fiero?
Yes, the diameter of the splines is bigger. I couldn't get it to fit into any of the housings that would fit the Fiero spindle. It also attaches to the housing differently. (no visable snap ring) I also found that neither axle length would work with my install.
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12:57 AM
Will Member
Posts: 14250 From: Where you least expect me Registered: Jun 2000
Yes, but not in great detail. IIRC, in manual mode, fluid gets routed to the 1-2 band and 3rd clutch circuits at various times for engine braking. My trans guy told me there is a difference concerning the way fluid pressure is modulated in these manual modes vs. a normal 65-E trans. Basically he said you don't want to put a TAPShift computer onto a standard 65-E trans because the manual shifting of it could result in violent shifts and such which could obviously shorten its life. If you want more detailed information, you can contact him via his website: http://www.tripleedgeperformance.com/
In a conventional transmission, with the shifter in D, but the transmission currently in 1st, there is no engine braking because the sprag is holding the output rather than the L/R clutch. There's probably something similar going on in 2nd, but I haven't looked at it in a while.
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08:16 AM
Darth Fiero Member
Posts: 5921 From: Waterloo, Indiana Registered: Oct 2002
In a conventional transmission, with the shifter in D, but the transmission currently in 1st, there is no engine braking because the sprag is holding the output rather than the L/R clutch. There's probably something similar going on in 2nd, but I haven't looked at it in a while.
Right, without some kind of "overrun" clutch to hold the component the sprag (one-way roller clutch) is attached to, that component can overrun and thus there will be no engine braking. But in that same transmission, if you pull the shifter back into low range, then your low/overrun clutches will come on and provide for engine braking. But conventional transmissions were never designed to be "manually" shifted on a regular basis.
Now, lets say you are running an aftermarket trans controller on a standard auto transmission. And lets say this aftermarket controller allows for some sort of TAPShift type control of the trans. The problem you are going to run into here is if you leave the gear selector in OD and downshift to low gears while moving at significant road speed but then let off the gas, the engine is going to be allowed to return to idle speeds because of the sprags overrunning. If you immediately jump back on the gas, the engine is going to rev up quickly until the engine RPM reaches the point in which it would be at in that current trans gear at that road speed. At that point the sprag will lock up and then transfer power again. The trouble is what just happened here can put great stress on the sprag. I have seen cases where the sprag can actually explode inside the trans because of something like this happening to it. In the actual TAPShift trans, certain bands and/or overrun clutches are engaged to help take some of the load off the sprags during these situations.
IIRC, the all-new 6-speed auto FWD transmissions have done away with sprags and bands altogether and all they are running now are direct clutches. What's got me wondering is will one of the computers that is in these new 6-speed auto trannys communicate properly with an LS4 ECM???
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