TH350/TH400 Frequently Asked Questions
TECH Resident
Joined: Mar 2012
Posts: 858
Likes: 397
From: Texas
I was having the same problem. I ended up loosening the bolt holding the torque converter and then tightening it by hand as getting it too tight initially caused the torque converter to pull away from the other bolt holes resulting in losing my clearance and causing the torque converter to bind. I then proceeded to the next one and did it the same way and so forth until they were all in. Last but not least I went back and tightened them all down. I hope this helps!
You're a bot, aren't you?
Recently finished up my blown up 4L80E to RMVB Turbo 400 swap and this thread helped tremendously. Thank you to all who have shared their experiences....
My cliff notes, which may help someone:
~ 2000 TransAm, 6.0 engine, 9" Trick Chassis rear, 1350 u-joints
~ Nearly a 120# weight savings
~ My LQ4 based engine with "flat" flexplate, required no spacers, no special converter, no shims.
~ I already had 6AN fittings on the 4L80E, as did the Turbo 400, so that was simple exchange.
~ Poly trans mount from 4L80E was used with TH400
~ Midwest Chassis lightweight "conversion" transmission crossmember was used. Fitment is great.
~ Driveshaft from 4L80E, at 41-5/8" shaft centerline to centerline, was too short.
~ "New" driveshaft length is 44.5" Centerline to Centerline.
(I lucked out and found a new Mark Williams chromoly driveshaft for cheap, but it had a PG trans yoke. I simply swapped my 4L80E/TH400 trans yoke and it is perfect.)
~ I used a Jegs XHD (by Transmission Specialties) 3200-3500 converter.
Car always was fairly decent coming up on boost, but now makes its launch 7# @ 4200 rpm, in 1.1 seconds.
Pretty much all the other details are easily found in this thread, including making the speedo work. I run a Holley ecu, but it's a hybrid setup, which still uses the factory P01 ecu for my gauges, speedo, gas gauge, etc.
Shift of choice is a Turbo Action Cheetah SCS and it's awesome.
Again, big thank you to all who have posted in this thread, and shared their tips, tricks, and experiences with the swap.
My cliff notes, which may help someone:
~ 2000 TransAm, 6.0 engine, 9" Trick Chassis rear, 1350 u-joints
~ Nearly a 120# weight savings
~ My LQ4 based engine with "flat" flexplate, required no spacers, no special converter, no shims.
~ I already had 6AN fittings on the 4L80E, as did the Turbo 400, so that was simple exchange.
~ Poly trans mount from 4L80E was used with TH400
~ Midwest Chassis lightweight "conversion" transmission crossmember was used. Fitment is great.
~ Driveshaft from 4L80E, at 41-5/8" shaft centerline to centerline, was too short.
~ "New" driveshaft length is 44.5" Centerline to Centerline.
(I lucked out and found a new Mark Williams chromoly driveshaft for cheap, but it had a PG trans yoke. I simply swapped my 4L80E/TH400 trans yoke and it is perfect.)
~ I used a Jegs XHD (by Transmission Specialties) 3200-3500 converter.
Car always was fairly decent coming up on boost, but now makes its launch 7# @ 4200 rpm, in 1.1 seconds.
Pretty much all the other details are easily found in this thread, including making the speedo work. I run a Holley ecu, but it's a hybrid setup, which still uses the factory P01 ecu for my gauges, speedo, gas gauge, etc.
Shift of choice is a Turbo Action Cheetah SCS and it's awesome.
Again, big thank you to all who have posted in this thread, and shared their tips, tricks, and experiences with the swap.
Last edited by rel3rd; Nov 29, 2024 at 01:22 PM.
If anyone can clarify or go over the "Free Speedo Mod", I'd appreciate it.
I entered the numbers mentioned in this thread, in what I believe to be the correct area, and no speedo function as yet.
I run Holley Terminator X for engine, but still have factory P01 connected and HPTuners to try and get the speedo working from the front wheel speed sensor, just haven't got that working yet.
I entered the numbers mentioned in this thread, in what I believe to be the correct area, and no speedo function as yet.
I run Holley Terminator X for engine, but still have factory P01 connected and HPTuners to try and get the speedo working from the front wheel speed sensor, just haven't got that working yet.
