Hello!

I am in the middle of a TH350 rebuild and so far so good, the transmission seems to be in excellent condition and I have found lots of useful material online for completing this job.
However, it seems that the previous rebuilder (at least 20+ years ago) has been using less than the stock amount of piston return springs on low/reverse clutch piston and forward clutch piston.
Both of these clutch pistons are missing two springs and on both the missing springs were placed opposite from each other so it seems to be on purpose.

Should I buy replacement springs and use them as they were supposed to be used originally?
Why would somebody do this, use two less, and only on these pistons, not all?

I took the transmission off from my 71 cutlass and I think it was working just fine (apart from transmission oil leaks, thus the rebuild)

 

Thats pretty common. I have no clue if HydraMatic did that as a cost saving move, or if it’s part of certain calibrations. When the went to the later design piston without the spring locating pockets, and the springs staked to the retainer they included all the springs.

I wouldn’t worry about it. Just be thankful it has as many springs as it does. There is an idiot old timer around here that use to build “racing” transmissions. One of his “tricks” was to eliminate every other spring. His theory was less spring pressure to overcome, equals a quicker shift. While that’s true,, there isnt enough spring pressure to overcome centrifugal force. The result os hot spots on the steel plates.

 

Alright, thank you for the answer, I will continue my rebuild with these springs.

(that is also a relief because I could not find new spring sets easily here outside the US)

 

Just chiming in to agree. It's common to remove or partially replace springs to tune the application and release of a clutch. Removing springs makes the clutch faster. Replacing with stiffer springs makes it slower. Speeding up the forward and L/R is usually desired for a performance build. Don't sweat it. Just make certain all the springs feel the same and the retainer is flat.

 

While removing springs will theoretically make the clutch apply faster, the bigger drawback is centrifugal apply of the clutch. The tiny amount of fluid left in the drum when released will “climb” to the outside of the drum at high rpm. The drum spinning and fluid climbing to the edge of the drum will apply enough pressure to partially apply the clutch. Not enough to fully apply it, but definitely enough to cause it to drag. That’s the reason for the tiny bleed hole drilled into th400 drums with manual or transbrake valve bodies.

I put a spring in every spot on a direct clutch, regardless of original application. It takes a minimal amount of pressure to overcome the spring tension of the return springs. One the forward clutch, it’s not critical.