Who's running a FWD LS4 with the factory automatic transmission? Any reliability issues?
I've been doing some reading on LS1Tech and a common theme in the factory LS4 cars seems to be transmission problems. It's to the point where they say it's not a matter of "if" but "when" you have tranny issues. Any issues with swapped Fieros? Since the Fiero weighs less, it may not be as much of an issue.

How about tuning the setup? Do you keep the factory torque management? Active Fuel Management?

All the running LS4 swaps I know of have the DoD (AFM) retained, currently. I haven't seen anyone reporting trans problems with them in the Fieros. But I don't think the guys that currently have them in their Fiero are consistently beating the crap out of them, while I think the LS1tech guys with trans problems with the LS4 have been constantly trying to see "what they can do" or overusing tapshift.

I haven't even seen Don Kraus complain about the trans in his thread, and he's using the LS4 trans behind a 427 LSx motor.

quote Originally posted by dobey:I haven't even seen Don Kraus complain about the trans in his thread, and he's using the LS4 trans behind a 427 LSx motor.

Well that's certainly a good tortue test for the transmission!
I think weight helps a lot and using a fluid cooler as well.

All of GMs transmissions are not "if" but "when they fail types....Seems all GM tranmissions like to fail in the 125-160K range depending on how they where driven during that time...I did read a long while back about the LS4 trans having issues but did not read up on it much...If the failures are from breaking parts then in the Fiero they should not be a problem...

Edit to say:Maybe I will finish my LS4 install this year....Once it is on the road and the bugs worked out I will be tracking it to the track and giving it a good beating.....

[This message has been edited by MstangsBware (edited 09-30-2011).]

I know dratts managed to snap an input shaft when they finally got his turbo'ed LS4 into boost doing tuning..

Joe's replacing it with a hardened part now..

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Currently in the middle of my 88 + 3800NA swap

quote Originally posted by dobey: I haven't even seen Don Kraus complain about the trans in his thread, and he's using the LS4 trans behind a 427 LSx motor.

Check the build thread. Unless I'm mistaken, the trans has been taken apart and "gone through".

quote Originally posted by aaronkoch: I know dratts managed to snap an input shaft when they finally got his turbo'ed LS4 into boost doing tuning.. Joe's replacing it with a hardened part now..

Ah right, I had forgotten he broke the input shaft, but that was after the cartuning turbo kit.

While LS1 tech has a documented 171 cases of transmission failure for the members on that board, it isn't a super high failure rate. Considering we are stiull in single digits on the # of Fieros with swapped LS4's, it isn't any surprize that we haven't seen any failures. Add to this that at least 2 (maybe more) of the swapped fieros were installed with beefed up transmissions from the start.

It appears the torque converter, line pressure and overall fluid temp is what kills the LS4 4T65e-hd. The clutch material in the torque converter breaks up and takes out the transmission. If you are running an LS4/4T65e-hd the first investement should be on a transmission cooler and closely monitor the transmission temps.

I sold the 4T65e-HD from my LS4 to a local guy and it was going to be the 3rd transmission he has installed on his 2007.

[This message has been edited by fieroguru (edited 09-30-2011).]

quote Originally posted by fieroguru: It appears the torque converter, line pressure and overall fluid temp is what kills the LS4 4T65e-hd. The clutch material in the torque converter breaks up and takes out the transmission. If you are running an LS4/4T65e-hd the first investement should be on a transmission cooler and closely monitor the transmission temps. I sold the 4T65e-HD from my LS4 to a local guy and it was going to be the 3rd transmission he has installed on his 2007.

First investment sounds like it should also include a torque converter. Did the guy who bought your trans get a better one than stock, for his third trans?

We replaced the input shaft with a 300m shaft. As far as I know nobody has broke one of these yet. I also replaced the chain with a 7/8" chain. I've been told to treat the chain as a maintenance item. They will stretch. Kevin actually machines his transmission to make room for extra 3rd gear clutches. One of the guys who had a built tranny with the unobtainable 1" chain for sale said that he had blown out three 3rd gear clutches. I hope that I don't have to deal with the clutches. I only plan on a dyno pull and a 1/4 mile run just to certify what I have. I'm not going to compete with it. The only thing the ls4.tranny has over the 3800 tranny is a beefier differential. If you want to throw the money at them, you can't find a stronger transmission for a transverse fiero. The 4t65 can be built to handle more hp than the 4t80 and it's 100 lbs lighter.

quote Originally posted by dobey: First investment sounds like it should also include a torque converter. Did the guy who bought your trans get a better one than stock, for his third trans?

For the screaming deal he got on it, he got a bone stock transmission. I did let him know why they tend to fail and suggested the upgrades to him.

quote Originally posted by dratts: We replaced the input shaft with a 300m shaft. As far as I know nobody has broke one of these yet.

Actually, another LS4/cartuning turbo setup fragged one last week.
http://ls1tech.com/forums/l...nse-input-shaft.html

Well so much for unbreakable. GMs racing tranny uses a 300m shaft that is a little thicker. Smaller inside diameter.

quote Originally posted by dratts: First time out with the 300m input shaft and I'm pretty sure that I sheared it. We have Kevins shift kit in it and it shifts pretty hard. I was getting on it on a freeway on ramp and it made a big bang when it shifted. Then nothing but neutral and park.

That sucks...

Did you ever make contact with the guy on LS1 Tech with the 409 Turbo bolted to the LS4 4T65e-hd? His transmission has quite a few billet upgrades to withstand the power. Here are some of his parts:

Cyro treated GM Racing 300m input shaft:
https://lh6.googleusercontent.com/-bpOduoacaEc/SnMYzvZUJFI/AAAAAAAAA8k/2AQyeNzTy1M/s720/DSCN2810.JPG
GM Racing 1" chain:
https://lh3.googleusercontent.com/--Kq-kY6DdGo/SnMunzf8aYI/AAAAAAAAA9U/b2Dl2FEPDmc/s720/DSCN2826.JPG
Billet 4th gear ($2000 piece)
https://lh3.googleusercontent.com/-xSGeHa8yDE4/SnMuphfJ-MI/AAAAAAAAA9Y/_WHlhWM_b98/s720/DSCN2827.JPG

All these internal parts were cyro treated:
https://lh4.googleusercontent.com/-MYhvhlBW76M/SnMYnNeM_qI/AAAAAAAAA8A/hYvDAsi4qNc/s720/DSCN2799.JPG
https://lh6.googleusercontent.com/-8oQc7zUtb_Q/SnMYo3VvBrI/AAAAAAAAA8E/K6bgre9DedI/s720/DSCN2800.JPG
https://lh3.googleusercontent.com/-luo7TnwYqSg/SnMYqK3fX1I/AAAAAAAAA8I/WZRWZzKr0fA/s128/DSCN2801.JPG
https://lh3.googleusercontent.com/-Lqc-NipUvs0/SnMYtBdLpzI/AAAAAAAAA8U/NwpLMiYB__E/s128/DSCN2804.JPG
https://lh5.googleusercontent.com/-E_-7JpimPn8/SnMYuGa9ICI/AAAAAAAAA8Y/mijIoK_Q5pQ/s128/DSCN2807.JPG

[This message has been edited by fieroguru (edited 10-02-2011).]

I can't help but wonder if the hard tap shift isn't a big part of the prolem. The first time Joe got on it with the tap shift it broke the stock input shaft. We knew that the input shaft was a weak point. This was the first time out for me with the tap shift and it shifted really hard. The 1" chain is really hard to get ahold of. Does cryo treating make a part stronger without making it more brittle? I was expecting that my next problems would be clutches, not my brand new 300m input shaft. I just read about the 409 (he says 427 destroked to 401), but anyway he spent $15,000 just for the block. Obviously I can't keep up with him. He was putting down 800hp to the wheels.

[This message has been edited by dratts (edited 10-02-2011).]