I currently have a T56. I am wanting to go to an auto and would like to go with a built 4L60E but think it would be better to go to a T350 or T400. I am buying this old pontiac tank, I forget what kind of car it is and it has a 400 with either a T400 or T350 but I am thinking if has the T400. Anyways, I was going to use that transmission and have it completely gone through. What other things will I need to do the swap? Basically everything down to the last bolt would be nice. Thanks.

 

Im not sure the bellhousing bolt patters would be the same on an old BOP th400. But I may be wrong.

 

I know people hate to hear this, but you really ought to do a search. This has been gone over a lot here and there are links to a number of sites where people have been kind enough to post details, pictures, part numbers, etc.

From looking at your sig though, I am puzzled as to why you want to do the swap. IMHO, the T56 - TH400 swap makes sense only for very high power cars that are going to be optimized for drag racing. The 1:1 top gear is a PITA on the street. I have found this even with 3.42's, a much lower ratio than most people run. The best solution to this is a Gear Vendors OD, which costs over $2,000 and is heavy. All told, except for very high-po cars, you will go slower with a TH400 than with a T56. Why are you contemplating this swap?

Rich Krause

 

I have done a search and really all I have read is problems that people have had. I am wanting to slowly start getting the car ready for a track only car. I really would like the 4L60 but I am getting this Catalina for free and was going to sell the engine and thought that I could use the tranny. Well, I never thought that the bell housing bolt pattern would be different Thanks for the help.

 

Its a BOP bolt pattern on that catalina unless someone put a chevy engine in there. If its BOP, it won't fit on the lt1 obviously.

Mike

 

I am not trying to be a PITA, just trying to help. You certainly don't need to justify your plan to me but I am trying to warn you that unless you are building a race car you will not like the TH400 (unless you also buy a GV OD). I know, becuase I have "been there, done that". And there are lots better platforms than an LT1 4th gen to start with to build a race car.

That said, the swap is pretty easy. Besides the tranny you need:

tranny with pan
shifter
pedal assy (if you want two v. three pedals)
flexplate
torque converter
tranny dipstick
speedo reluctor and sensor
modifications to your tranny crossmember
driveshaft
replace stock torque arm with one that mounts to the chassis
reprogramming the PCM to get an accurate speedometer reading
tranny cooler
inspection cover (goes between bellhousing and block on the bottom)

I really suggest doing a search, you can find posts with PN and sources. My mind for details isn't so great so I can't remember that stuff. If you can't find the info, I can try to find my notes.

Good luck.

Rich krause

 

Also keep in mind that automatics usually soak up a bit more power than manuals, especially a TH400.

 

Yeah I read something a while ago that said Th400s eat up 44 hp to turn the thing. Not to mention the added weight.

I agree also on the fact that if you want to build a drag race car, you can probbaly sell your car, and get a much better platform to start with.