Turbo 400 Build

[hotrodpc]

The 86 C20 I bought for $100 had a bad Turbo 400 in it and a piece of broken glass in the rear sliding window. So here we go with some pics of the carnage and the rebuild. This was actually almost a FREE rebuild, but because I upgraded 1 paticular part. I have $25 in this trans. I'll explain as the thread progresses !!! So chill and watch it come together. Feel free to post or ask questions if you have any. The pics are not alot in detail, but if someone gets some education out of it. It'll be worth it.

This trans had 173,000 miles on it when it went. The people I bought the truck from, were moving from Arkansas to Dyess, AFB in Abiliene, TX. They were towing a tandem axle enclosed U haul trailer, and the bed was full too. They made it 15 miles of Dyess, AFB when it blew.

Here is a pic of the trans out of the turck. You can see the color of the spilled trans fluid from the dipstick tube hole in the case. No, that is not motor oil. Certain to be some ugly stuff found inside this one with the fluid looking like that. You can only imagine the smell.

 

[davbell22602]

Yikes!

 

[Zembonez]

 

[RebelThunder]

Looks like she got a little warm in there....

 

[hotrodpc]

Here are some pics of the trans on the trans table already partially disassembled. From this point right here is where all the hell starts. The intermediate drum is hung up, stuck, or welded somehow and I am having big problems getting the transmission any further apart from this point. Making it even more evident there is carnage inside somewhere. At this point I am assuming its an intermediate sprag failure.

 

[hotrodpc]

Looks like she got a little warm in there....

Just a little bit !!! Probably is or at least a close 2nd for the worst burnt trans I had ever taken rebuilt. Certinaly the worst T400 I have ever rebuilt.

 

[Zembonez]

Does all of that heat have any detrimental effect on the case?

 

[hotrodpc]

Does all of that heat have any detrimental effect on the case?

It sure can. You can get heat check in the case and causes cracks and also case lugs to break or get so soft they can be pushed around and chewed up. This one obviously got hot. But was spared. Next pics will show case lugs are OK. Probably what saved this case, was it was a new enough model trans, that it has a little thinner center support which makes room for a a big snap ring looking part that works as a thrust washer of sorts (but isn't) and it saves the case. I'll be talking more about that as I go along since this was HotRodPC build, and a little differant than many standard shops would take the time to do. I kept the best of the 2 differant model THM400 transmission design and upgrades through out the years.

 

[hotrodpc]

FINALLY !!! I was able to pry, pull, wedge and manipulate the input shaft assembly including the forward and direct clutch drums out of the case. I was able to do this, by removing the retaining bolt for the center support under the vavle body. This is what it looks like now. Notice its getting darker, more crispy, and that part of the Center Support came out with it, which isn't supposed to. Also see the tan fiber parts wrapped around the springs. Domino affect, one thing went wrong and destroyed other parts as well.

This is the center support. Hard to see if you don't know what you are at looking at, but look at the top of the of the apply piston and you see the fiberous part chewed up and stuck in there.

Now the center support is out of the case. The center support is what gives a T400 alot of its strength also used in 4L80-E too. T350 and 700r4, 4L60-E DO NOT use a center support.

 

[Alljackedup408]

nasty nasty! Ive seen a couple bad ones at the dealer myself.. that ones nasty in color.. and im sure smells like shiot.