ok im throwing in a 3400 v6 in my fiero and i have two tranny to put in but i dont know which one. i know the getrag is stronger but the isuzu has way better gearing. now with a centerforce clutch setup can the isuzu tranny hold about 350 hp and around 275 torque????? i know the getrag will but the gearing sucks in my opinion compared to the isuzu. the reason i know this is because two friends i know have two formulas and one has the isuzu and the other had the getrag and when they raced the isuzu tranny won by a good margin. if i can get my isuzu to hold at 250 to 275 torque ill be happy thanks all
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06:25 PM
PFF
System Bot
California Kid Member
Posts: 9541 From: Metro Detroit Area, Michigan Registered: Jul 2001
Hi. I think the main weakness in the Isuzu trans is the fact it has aluminum shift forks which could break with some heavy gear banging. Otherwise the Isuzu holds up fine with my 350 chevy which surely puts out 275 ft/lbs of torque. I'm pretty rough with it. I like to make it hook up, not spin Later, Tim
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07:25 PM
ITB 2M4 Member
Posts: 194 From: N. Ft. Myers, Fl, USA Registered: Nov 2001
I need to know about the gearing as well. I have the 4.10 4spd. in my race car, but the rpm drop from 3rd to 4th gear is too great for the balanced and blueprinted, but otherwise stock 2.5L. 4th is an overdrive gear, and I've heard that one of the 5spd. trannies has a 4th gear that is still greater than 1:1. And it still has fifth gear for when I go to Daytona. At Moroso, Sebring, and Homestead, all I use is 3rd and 4th, so closer gearing between the two would help greatly.
Also, I have an '85 SE parts car with a 5spd. in it. Any idea which one it would be?
well i tried to find my fiero parts book with the gearing in the tranny but i just moved and its in one of these boxes and i just cant find it at the time but i can tell you a little info on how the gearing of the isuzu is better..
its like the difference between the economy 4 speed and the performance 4 speed the gearing in the performance one is longer meaning that when you shift the rpms in you car drop to the point where you still have a good bit to reach your redline but at the same time have a point where your hp is good too. you know how everybody raves that the fiero has a 0-30 that tied that diablo????????its the gearing the 1st gear ratio on the getrag is damn good but when you shift into second the rpms drop so far that the car has to struggle to get thet peak hp again now if the rpms didnt drop so far the fiero with only 140 hp will stay with the diablo for a little more.
let me try to explain....... you ever wonder why when you have two cars with the same hp weight torque race and one beats the other ?????? its not the driver or the track or the tires.... its the tranny.
take for instance any tranny you can essentially take out the gears and replace them with new ones larger or smaller based on how you want to drive. you can have your tranny on 1st gear shift at your redline lets say 7000 rpm and when you shift the tranny in second your rpms drop only to 6000 and before you know it you hav to shift again your car will have a 0-60 better than a corvette but will only go about 80 mph top speed if that. now take that same tranny change the gear ratio and in first gear have it to shift at 7000 like the other car but this time with the different gearing the cars rmp drops to lets say 4500 and it has to be wound again to achive that peak horsepower now this car will be slower off the line but will have a higher top speednow thats the difference between the getrag and the isuzu.
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09:28 AM
85GToronto Member
Posts: 927 From: Red Deer, Alberta, Canada Registered: Dec 2001
"General Information MD9 3-SPEED AUTO 125THC ONLY AUTO USED MG2 5-SPEED MANUAL MUNCIE 3.61 RATIO V6 ONLY MT2 5-SPEED MANUAL ISUZU 3.35 RATIO L4 ONLY MY8 4-SPEED MANUAL MUNCIE 3.32 RATIO 1984 L4 ONLY M17 4-SPEED MANUAL MUNCIE 3.65 RATIO V6 ONLY M19 4-SPEED MANUAL MUNCIE 4.10 RATIO 1984 L4 ONLY
Note: MG2 is the Getrag-designed Muncie built transaxle Note: the V6 Muncie is stronger than the L4.
Originally posted by 85GToronto: Online Fiero service guide......
MG2 5-SPEED MANUAL MUNCIE 3.61 RATIO V6 ONLY MY8 4-SPEED MANUAL MUNCIE 3.32 RATIO 1984 L4 ONLY
Note: MG2 is the Getrag-designed Muncie built transaxle Note: the V6 Muncie is stronger than the L4.
So for use with a Caddy 4.9, Would I be better off with the beefier 5speed MG2 with the 3.61 ratio, or should I lose a 5th gear and go with the 3.32 for the 4cyl? I think the 4.9 will have the torque to handle the 3.32 gearing but it is a weaker tranny. Any other info on this appreciated, I don't really know much about what works real world, but need to make my selection soon...
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02:27 PM
85GToronto Member
Posts: 927 From: Red Deer, Alberta, Canada Registered: Dec 2001
I figure I should make it clear that is a quote from the Online Fiero Service Guide, I didn't write any of that, hehe Its a very good site if you haven't seen it, lots of useful tips/info there, just do a search for that name.
I wish I could answer your question. Once I get the details worked out in my V8 swap I am using the 4 speed Muncie at first, mainly because thats what is in the car at the moment and I also have a spare. I'd like to find a Getrag but mainly based on improved fuel economy as opposed to a strength issue. I am not sure what I would do if I came across a cheap Isuzu, I'll cross that bridge when and if I come to it! I'm told I will like the gearing on the Muncie at first but I won't like the highway fuel economy, or lack thereof. We'll see........
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04:05 PM
PFF
System Bot
ITB 2M4 Member
Posts: 194 From: N. Ft. Myers, Fl, USA Registered: Nov 2001
In contradiction to what the OSG says, I've heard that the 4-spd is the strongest of the three manual transmissions. Webster made some racing gear sets for that trans, too. There are probably still some of these around if you know where to look (I don't).
ITB 2M4:
I'm running the 4.10 4-spd behind the V6 in my rally car and the gearing isn't quite right so I'm also looking at other transmission options.
The 2.0l Cavaliers in the mid '80s had an Isuzu transmission. It has a final drive of 3.83 and as far as I've been able to find out the rest of the ratios are the same as the Fiero Isuzu. The other 2.0l J-body cars won't work because they had the OHC motor and the bellhousing bolt pattern is different.
This transmission looks ideal for my purposes so you might want to crunch some numbers and see if you think it'll work for you.
------------------ Doug Chase Duvall, WA '88 Fiero Formula 5-spd (autocrosser) '88 Fiero GT 5-spd (daily driver) '85 Fiero GT 4-spd (rally car) '86 Fiero GT 5-spd (organ doner for rally car) '86 Fiero GT 4-spd (fixer-upper, 4 sale soon)
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04:57 PM
Mar 27th, 2002
85GToronto Member
Posts: 927 From: Red Deer, Alberta, Canada Registered: Dec 2001
I've also heard the same thing Doug from various sources, which is another reason I'm not going to do the leg work to change my car, at first anyway. It seems its either the Getrag or the Muncie 4 so I guess it comes down to what ratio's you prefer, or in my case what is easiest. I'll get it running then decide later.
watts: I cannot thank you enough for posting those pics. I have never seen the two side by side. From looking at my old pics my 87 GT had the Getrag 5 speed. Again, I refer you to my signature
------------------ I shall be kicking myself for selling my 87 GT until I replace it.
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07:20 PM
Mar 28th, 2002
ITB 2M4 Member
Posts: 194 From: N. Ft. Myers, Fl, USA Registered: Nov 2001
I'm running the 4.10 4-spd behind the V6 in my rally car and the gearing isn't quite right so I'm also looking at other transmission options.
The 2.0l Cavaliers in the mid '80s had an Isuzu transmission. It has a final drive of 3.83 and as far as I've been able to find out the rest of the ratios are the same as the Fiero Isuzu. The other 2.0l J-body cars won't work because they had the OHC motor and the bellhousing bolt pattern is different.
This transmission looks ideal for my purposes so you might want to crunch some numbers and see if you think it'll work for you.
Have you tried swapping out the 4.10 final? I've got my old 4.10 that the "professionals" at the last place I had an engine built at destroyed. The internals are still good, but the flywheel came lose and tore up the housing. Has anybody tried this? BTW, thanks for the info!
Originally posted by Jncomutt: So for use with a Caddy 4.9, Would I be better off with the beefier 5speed MG2 with the 3.61 ratio, or should I lose a 5th gear and go with the 3.32 for the 4cyl? I think the 4.9 will have the torque to handle the 3.32 gearing but it is a weaker tranny. Any other info on this appreciated, I don't really know much about what works real world, but need to make my selection soon...
The Getrag tranny is geared WAAAaaayyyy too high for the 4.9 torque. Plus you will have a top end of about 90 because of the limited RPM with this tranny.
I currently have a 3.35:1 ratio Isuzu in my 4.9, and that's on the cusp of still being too high.The Isuzu is giving me no problems, and I drive the car very "spirited", plus autocross, High Speed Touring at Hallett, and drag the car.
My next 4.9 - the $2003 Challenge car - will have a 2.84:1 ratio TH125 with a shift kit. I think that will get the power down a little better (and give me a higher top end).
G
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02:39 PM
Doug Chase Member
Posts: 1487 From: Seattle area, Washington State, USA Registered: Sep 2001
Sorry, I was a little vague there wasn't I? I meant to ask, have you swapped out the 4.10 final gear into a five speed tranny? The rules for Improved Touring say that as long as I can fit it in the stock tranny housing, I can use it. Putting the 4.10 ratio in in place of the 3.35 would sure help.
one question for all fiero buffs !!!!!!!!!!!!!!!!! can an 5 speed isuzu tranny handle a 3400 tdc hp and torque with a centerforce clutch setup?????????????????????????????????
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07:09 PM
Mar 31st, 2002
cadero2dmax Member
Posts: 1266 From: Brighton, CO Registered: Oct 2001
Originally posted by SUPERDUTY TT FIERO: one question for all fiero buffs !!!!!!!!!!!!!!!!! can an 5 speed isuzu tranny handle a 3400 tdc hp and torque with a centerforce clutch setup?????????????????????????????????
YES!!!!!
Archie can give you multiple instances of the Isuzu behind SBC's, and I can tell you my 4.9/Isuzu has given me no problems (using a Centerforce clutch).
This is interesting... I always thought the reason everyone wanted 5 speeds is for the 'overdrive' gear for lower rpms at the top. If I read this right, the '84 4 speed would give you the lowest rpms, although the gears are spaced further apart.
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03:36 PM
Doug Chase Member
Posts: 1487 From: Seattle area, Washington State, USA Registered: Sep 2001
Originally posted by ITB 2M4: I meant to ask, have you swapped out the 4.10 final gear into a five speed tranny?
Nope, I haven't done that. In fact, I haven't even split the cases on a 4-spd or an Isuzu so I don't know if this would work. I'd be surprised if it would.
