How well are the F40 transmissions holding up? I know these transmissions are rated at around 300ft/lbs, but I'm looking for some real world feed back from those that have swapped in this trans with high output engines. I am looking at doing an LS4/F40 swap, but I want some idea how much power some of you guys are putting through these transmissions and how much success, or lack there of, you are having. Thanks for your input.

Here is my story, the new replacement is doing fine but is still on restrictions at the moment as the new motor was reinstalled with 11:1 compression instead of the previous 11.5:1 and has been limited to about ~3.5 psi for the time being, instead of the previous 7-15 psi the two motors the broken tranny had been bolted to subjected it to on occasion.

I'm hoping a bad history before I received it was the cause but given how hard the car launched in comparison to the TPI IROC 383 I had with 3.73 gears, and limited slip differential, it's hard to consider anything other than it having been overwhelmed. I'll be turning the boost up on the new tranny shortly and taking it to the track. Hope I don't have to carry it back.

https://www.fiero.nl/forum/Forum2/HTML/119965.html

I know Archie has installed a lot of F40 transmissions behind the LS3. I don't know if any of those have been without being cryo-treated though, and if any have blown up.

Why do you want to do the LS4/F40 swap? Are you a masochist?

I have never heard of any of Archies f40 swaps going to the strip. As far as I know the big hp ones have been done for show and bragging rights. I could be wrong. Joseph is not bolting his f40 to an ls4 is he?

no, Joesph's is behind an LZ9

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quote Originally posted by dratts: I have never heard of any of Archies f40 swaps going to the strip. As far as I know the big hp ones have been done for show and bragging rights. I could be wrong. Joseph is not bolting his f40 to an ls4 is he?

I haven't seen any of Archie's F40/LS3 swaps at the strip either. But that doesn't mean the trans isn't reliable. Transmissions will break at some point. It depends on how you drive it. Launching at 5000+ RPM from a dig all the time will certainly break one faster than not doing so. Joseph's trans was also a junkyard pull of unknown condition, without any rebuilding/treating, and Archie only installs new 0-mile F40s, and most if not all have also been at least cryoed, if not shot-peened as well.

There's no reason I would expect my F40 to be a problem behind my LS4. But I would generally advise people who don't have a reasonably high skill of dealing with engine builds and fabrication, from doing an LS4 with a manual as a swap. It's way too much work for what you get out of it, really. There are much better/easier swaps for almost anyone, to be doing.

I know there are a lot of draw backs to the LS4, but I picked one up for dirt cheap....$450. I settled on the LS4 because it will suit what I am trying to do. I 'm not looking at building some 600hp monster. Realistically, I am wanting around 400hp and the LS4 is more than capable of delivering it with inexpensive OEM parts from other LSx engines. That and a tune should get me there. Toyed with the idea of an LLT V6, but there are tuning issues with the new controllers and limited Transmissions that you can use due to the bolt patterns. This is not going to be a drag car by any means, but I don't want to baby it either. What is the use in having 400hp if you are scared to dip in the throttle from time to time? I know that using the 4T65E-HD that came with the LS4 solves several issues, but I have seen numerous postings on how weak those trannys are. Even at stock power levels for the LS4. Any opinions are welcome as I may have missed a few options.

You wont' have any problems with an F40 for what you want. There is nothing like the great feeling of a smooth shifting new stick shift. Bleeding them is a breeze compared to a Getrag. The ratios thing is non-sense from number crunchers. I have enjoyed mine for 5+ years and still works as new. I don't baby it but I am not crazy either. Also my torque breaks the tires loose before anything else. They are so cheap that I have a brand new spare just in case. I have other interest now but when I get back to Fieros I may put some drag radials and try to break it. Not fun to spin tires all the time. Go for it. You won't regret it.

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Red: TPI V8 + 6-Speed White: 3800SC auto
304rwHP/366rwTQ

quote Originally posted by dobey: I haven't seen any of Archie's F40/LS3 swaps at the strip either. But that doesn't mean the trans isn't reliable. Transmissions will break at some point. It depends on how you drive it. Launching at 5000+ RPM from a dig all the time will certainly break one faster than not doing so. Joseph's trans was also a junkyard pull of unknown condition, without any rebuilding/treating, and Archie only installs new 0-mile F40s, and most if not all have also been at least cryoed, if not shot-peened as well. There's no reason I would expect my F40 to be a problem behind my LS4. But I would generally advise people who don't have a reasonably high skill of dealing with engine builds and fabrication, from doing an LS4 with a manual as a swap. It's way too much work for what you get out of it, really. There are much better/easier swaps for almost anyone, to be doing.

It's my hope that the used history had more to do with the failure, but I made the comparison between my V8 swap and my turbo 3.9L (modified to 4.2L high compression turbocharged) to indicate that despite being a V6 it was well within V8 level performance and that's why I'm still concerned for the new tranny. The closest thing I have to a dyno so far is a GTech test that read just over 263 lb/ft at the wheels on the base engine with the camshaft fully advanced ~10 deg on 7 psi and still being tuned at the time.

The performance between that stock motor and the modified motor in the car now is night and day with .3 more L, camshaft degreed in, a single T4 in place of the twin T3s and at the time of the failure 1.7 more compression points. It was a rocket from a stand still. I did not abuse the transmission, I don't do clutch dumps. Like the builder indicated, I believe much of its strength depends upon the dualmass flywheel being in place to manage the torque load. I'll get some form of documented performance from my engine soon I hope but until then there's no doubt my torque level was over 300 lb/ft. The stock motor was 240/240 and when I say poor tune it means there's still a bit more work to do and potential left, not that the car ran like crap which it didn't.

The gears in the F40 are factory shot peened and were not an issue in what I encountered. A smooth hard acceleration started the path of destruction but was preceeded for weeks by a problematic 5-6 shift. I've heard nothing but talk about cryo treating, I'd have to see proof of benefits before going through the trouble. It's still slick 50 performance to me.

quote Originally posted by Joseph Upson: Wheel spin is an important point to, I have 245/40R18s on the rear and no wheel spin, it just squats and goes so anyone able to break their tires loose actually have a safety fuse against what happened to me. My car felt like it had lift bars on it.

265-35-18s on the rear of mine. I heard good things about the new Mickey Thompson's 2 DR and they have them in 265-40 I think. Will need to rise the rear coil overs a bit most probably.

quote Originally posted by Joseph Upson: It's my hope that the used history had more to do with the failure, but I made the comparison between my V8 swap and my turbo 3.9L (modified to 4.2L high compression turbocharged) to indicate that despite being a V6 it was well within V8 level performance and that's why I'm still concerned for the new tranny. The closest thing I have to a dyno so far is a GTech test that read just over 263 lb/ft at the wheels on the base engine with the camshaft fully advanced ~10 deg on 7 psi and still being tuned at the time.

I wasn't trying to say your V6 wasn't making that much power, but more that it's hard to compare something of unknown history to something that's brand new and has also been treated beyond stock. Though, it will certainly be useful to know what happens with your new trans. More so, the point I was making (though perhaps I didn't make it very well), is that no trans is going to be 100% reliable. The stock transmissions in the ZR1 or even the new Sonic base coupe, could be torn up with the stock engines, with a slight tune to bring behavior closer to what we are doing with our Fieros, that opens up the possibility for breakage. Why do you think every new vehicle in the GM lineup has dual mass flywheels and fairly aggressive torque management now? Heck, in some of the cars and trucks, you don't even need to fully disable the torque management to endanger the trans.

So, while some people have ended up with broken F40s, and some others haven't, it will still be plenty reliable for most anyone doing a swap. Whether it's worth it in terms of cost/engineering, is another question though.

There seems to be a lot of unfounded dissent toward the F40 on this forum, though. And that's unfortunate, as it is a pretty brilliant trans, though perhaps a bit costly for most people. I do wonder if any of the changes made to the MU9 (outside the gearing changes) are useful for improving reliability, though.

quote Originally posted by dobey: I wasn't trying to say your V6 wasn't making that much power, but more that it's hard to compare something of unknown history to something that's brand new and has also been treated beyond stock. Though, it will certainly be useful to know what happens with your new trans. More so, the point I was making (though perhaps I didn't make it very well), is that no trans is going to be 100% reliable. The stock transmissions in the ZR1 or even the new Sonic base coupe, could be torn up with the stock engines, with a slight tune to bring behavior closer to what we are doing with our Fieros, that opens up the possibility for breakage. Why do you think every new vehicle in the GM lineup has dual mass flywheels and fairly aggressive torque management now? Heck, in some of the cars and trucks, you don't even need to fully disable the torque management to endanger the trans. So, while some people have ended up with broken F40s, and some others haven't, it will still be plenty reliable for most anyone doing a swap. Whether it's worth it in terms of cost/engineering, is another question though. There seems to be a lot of unfounded dissent toward the F40 on this forum, though. And that's unfortunate, as it is a pretty brilliant trans, though perhaps a bit costly for most people. I do wonder if any of the changes made to the MU9 (outside the gearing changes) are useful for improving reliability, though.

That clarification wasn't intended for you. You brought up some points that reminded me of one particular individual on the forum that rears his head in a manner to provoke baseless argument and he knows who he is. I just decided to take a pre emptive strike to discourage it, as well as be clear that it's a toss up between used status and high torque loads as the cause of the failure. I agree with what you've said.

quote Originally posted by Joseph Upson: That clarification wasn't intended for you. You brought up some points that reminded me of one particular individual on the forum that rears his head in a manner to provoke baseless argument and he knows who he is. I just decided to take a pre emptive strike to discourage it, as well as be clear that it's a toss up between used status and high torque loads as the cause of the failure. I agree with what you've said.

Ah, OK.

I'm running between 200 and 249 (depending on my tune) ft*lbs of torque and I've snapped an axle thru the inner tripot casing one time and and axle and HELD wheelbearing thru the same plane at the same time. Transmission is fine. The axle-snapping is more to do with the fact that HELD's bumpsteer correction kit doesn't let my axles go thru the splines at the bearings like it should. I race at Seekonk Speeday so I do clutch dumps.

The inner axle end snapped during a 6000rpm dump to warm up my 255/55/16 tires going uphill on the track.. O_o
I'm switching to 275/45/17's...
Most of my dumps are at the Start/Finish line and circa 3000rpm for a perfect launch as Fiero's don't benefit/need tire-warming like other cars do...

quote Originally posted by dobey: You want 400 HP at the wheels, or at the flywheel? Do you plan to keep the DoD equipment? All stock GM transmissions are weak for the stock power levels of the transmissions they're mated to, really. Burning up clutches in an automatic in a car that doesn't have torque management is not hard to do; especially in the heavier cars.

I'm looking at 400 at the flywheel. The plans I have now include ditching the DOD equipment and going with standard lifters, different cam (haven't decided on the specs yet), Z06 valve springs on ported/polished 243 heads, replacing the DOD cover with one from Milodon that is flat so that I can use an LS2 intake, manifold and T/B mounted 180 and a remote mount electric water pump. I just need to find a solution for a flywheel. I have been following fieroguru's post, but he has been on a break for a while now. So if anyone knows a vendor that makes a one, I would be interested.

GM should have never put a 4T65E HD behind the LS4. It is an old design that was not meant to take high output engines. The LS4 was capable of making so much more power than it did by just getting a better flowing intake and exhaust manifolds. It was limited by that slush box.

quote Originally posted by mnm080977: I'm looking at 400 at the flywheel. The plans I have now include ditching the DOD equipment and going with standard lifters, different cam (haven't decided on the specs yet), Z06 valve springs on ported/polished 243 heads, replacing the DOD cover with one from Milodon that is flat so that I can use an LS2 intake, manifold and T/B mounted 180 and a remote mount electric water pump. I just need to find a solution for a flywheel. I have been following fieroguru's post, but he has been on a break for a while now. So if anyone knows a vendor that makes a one, I would be interested. GM should have never put a 4T65E HD behind the LS4. It is an old design that was not meant to take high output engines. The LS4 was capable of making so much more power than it did by just getting a better flowing intake and exhaust manifolds. It was limited by that slush box.

Unfortunately, nobody makes a flywheel/clutch setup for the LS4+F40 combo. I expect my build will be around 400 at the flywheel though. I'm dropping displacement down to 4.8L, using the LS2 intake, dropping the DOD, using LS6 lifters, and LS1 cam. I'll be building custom headers/exhaust, though. And, I had the heads milled 0.015 to give a tiny bump in compression, but should be able to still use the same length pushrods.

As for the LS4 making power, the 4t65 is hardly the limiting factor. Marketing, EPA regs, and the DOD are more so. Because it's in a car, it had to meet certain MPG and emissions requirements. Then of course, all of the FWD transaxles are too weak to consistently stand up to 400+ ft-lbs of torque. But again, as I said, even the tiny Ecotecs in the Sonics could shred the transmissions they come bolted to, with some over-aggressive driving, and turning down/off the torque management in the ECM. These cars aren't getting built and sold by GM, Toyota, etc… to be heavily modded to make a bunch of power, and still use the stock trans. They're being built to meet the CAFE standards under normal driving conditions by the majority of the population. Fact is, if you're going to build up your engine to make significantly more power than stock, you're going to need to build up the trans too, if you plan to consistently drive it hard. Regardless of whether it's an auto or stick.

quote Originally posted by mnm080977: GM should have never put a 4T65E HD behind the LS4. It is an old design that was not meant to take high output engines. The LS4 was capable of making so much more power than it did by just getting a better flowing intake and exhaust manifolds. It was limited by that slush box.

The 4 speed was the toughest transmission they had short of the 4T80E... If they'd used the new 6 speed transmissions, the engine would have been even more limited.
The 4 speed can be upgraded significantly.
The intake manifold had to fit around the DOD *AND* under the Impala hood line... Think about all the compromises that had to be made in order to get that engine simply to fit...

[This message has been edited by Will (edited 08-22-2012).]

quote Originally posted by Will: The 4 speed was the toughest transmission they had short of the 4T80E... If they'd used the new 6 speed transmissions, the engine would have been even more limited. The 4 speed can be upgraded significantly. The intake manifold had to fit around the DOD *AND* under the Impala hood line... Think about all the compromises that had to be made in order to get that engine simply to fit...

I take it you are referring to the 4T65e? or the Muncie?

------------------
there's a Group on 60degreeV6.com for us 660 Fiero owners!

Fiero Owner's group on 60degreeV6.com

I know these lines Look crooked on paper, but I swear I've got them straight in my head.

quote GM should have never put a 4T65E HD behind the LS4. It is an old design that was not meant to take high output engines. The LS4 was capable of making so much more power than it did by just getting a better flowing intake and exhaust manifolds. It was limited by that slush box.

Yeah? You must have alot more experience with these HORRIBLE than I do.

http://www.youtube.com/watch?v=524GMEXvqLk

quote Originally posted by ericjon262: I take it you are referring to the 4T65e? or the Muncie?

4T65E... they never put the Muncie with the LS4...