Team Chevelle banner

TH400 Rear Band

7K views 5 replies 3 participants last post by  Bart_Swisher 
#1 ·
I am rebuilding my TH400, (my first attempt at an auto rebuild) and I bought what is suppose to be a complete rebuild kit. It is a TCI 228800 kit. It didn't come with the wider rear band in the kit and I can't tell if it needs to be replaced but I am going to go ahead and order a new one anyway. What is the purpose of the bands? I have done a little research and have seen that some people leave out the intermediate band in drag race applications. Do they provide the engine braking etc? Sorry if this is a silly question.
 
#2 ·
A good question really.

A band is simply a friction lined metal band, that tightens around a drum or planetary element causing it to stop rotating.

Intermediate band: It's function is to provide engine braking in 2nd gear manual.
It prevents the intemediate sprag from over-running. The intermediate band is used for engine braking in 2nd by preventing the direct drum from over-running in the intermediate sprag when decelerating.

Low reverse band in the 400:
This serves to provide engine braking in 1st gear manual.
It also prevents the reaction carrier from over-running.
It also will lock down the reaction carrier to provide reverse.
 
#3 ·
rear band is already oversize for its purpose unless you are pulling heavy loads using manual low or backing 20k lbs up a hill, or racing. Its likely ok as is
 
#4 ·
Well the reason I am rebuilding the trans is, it had set for a few years before I bought it. It sat in my garage for a couple of years after I got it with no fluid in it.. Long story short, everything seemed to work fine when I initially installed it then it acted like the brakes were on when in reverse. Ultimately reverse stopped working to the point it is pretty much gone. So I pulled it out to rebuild. Any suggestions on what specifically to look for while I have it all apart?

Also, for what it is worth, I am pretty sure I lost first gear engine braking as well. When in first and let off the gas, it just kind of coasted, when I gave it gas again it was like the engine had to catch up to the tranny.
 
#5 · (Edited)
That transmission is tweaked bro, you need to rebuild it. I can't begin to speculate on exactly what is wrong with that transmission because either way it needs to come apart. It's likely that the accumulator valves are gummed up with something but who knows.


Your welcome for the explanation on how the bands work. :thumbsup:
 
#6 ·
Thanks for the advise, I did tear into the drums last night and found a host of issues.

1. forward drum piston completely frozen up with varnished fluid. Had to spray it with brake cleaner several times just to get the piston to move enough to get it out.

2. forward steels burnt beyond recognition.

3. piston seals shot on both drums, as in 1 inch long pieces of seals laying in with the plates.

4. the other drum friction plates had ZERO friction material left on the plates at all.

I don't know how this trans worked at all to begin with. I cleaned the drums and started rebuilding. So far so good, the trans isn't as complicated as I thought it would be, seems pretty straight forward. Installing the pistons with the new seals was a little tricky but patience and a feeler gauge paid off and I got them seated without damaging the seals.
 

Attachments

This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top