TH400 Slipping When Warm - Chunks in Oil Pan

[82sierradude]

My truck's TH400 2wd transmission leaks when parked and slips after it's warm. I replaced the vacuum modulator, pan gasket, and filter less than a year ago. I found what appears to be plastic chunks in the oil pan and some fine metal debris. Governor gear is fine. Thoughts? Am I looking at a rebuild?

Thanks.

 

[NickTransmissions]

My truck's TH400 2wd transmission leaks when parked and slips after it's warm. I replaced the vacuum modulator, pan gasket, and filter less than a year ago. I found what appears to be plastic chunks in the oil pan and some fine metal debris. Governor gear is fine. Thoughts? Am I looking at a rebuild?

Thanks.

Yank it out and overhaul it! Debris like that in the pan = rebuild 100% of the time.

check out my TH400 Information Thread for video tutorials, parts lists, tips/pointers and additional resources to help you with the overhaul.

 

[Snoots]

Ouch! Take Nicks' advice.

 

[nvrenuf]

@82sierradude you knew the answer before you made this post…

 

[82sierradude]

@82sierradude you knew the answer before you made this post…

I suspected that a rebuild was in order, but I wanted to exhaust all possibilities before proceeding. The ATSG manual just arrived today.

 

[82sierradude]

Yank it out and overhaul it! Debris like that in the pan = rebuild 100% of the time.

check out my TH400 Information Thread for video tutorials, parts lists, tips/pointers and additional resources to help you with the overhaul.

Thanks. Any idea which part may have shredded into pieces and ended up in the pan?

 

[AuroraGirl]

Thanks. Any idea which part may have shredded into pieces and ended up in the pan?

they dont look metal, so my guess is its friction material

 

[NickTransmissions]

Thanks. Any idea which part may have shredded into pieces and ended up in the pan?

You're welcome. Looks like a combination of bronze thrust washer which sits on the front side of the rear planet and front/rear planetary teeth but hard to tell from the pictures...Let us know what happened when you open it up...Also, gear train failure (if that is what it turns out to be) in an otherwise stock to mild-use vehicle points to a restriction somewhere in your system...Once you have the trans out, extensively flush your cooler lines, internal transmission cooler and external cooler to ensure all that debris is removed...If you cannot get the cooler(s) clear after numerous attempts, either have the radiator/cooler rebuilt or replace the radiator.

 

[82sierradude]

I finally got around to disassembling the TH400 because the truck stopped shifting out of first gear and has been sitting for months. The valve body's plastic accumulator piston is shredded to pieces. Hopefully, the internals are in good shape and the rebuild will go smoothly.

 

[Matt69olds]

Hopefully you have read Nicks th400 thread.

Throw away the spring, replace the broken plastic piston with the older aluminum. Be sure to match up the piston with the intermediate band piston, there were design changes and potential compatibility issues.

 

[82sierradude]

Hopefully you have read Nicks th400 thread.

Throw away the spring, replace the broken plastic piston with the older aluminum. Be sure to match up the piston with the intermediate band piston, there were design changes and potential compatibility issues.

Thanks. I'll take a look.

 

[bucket]

Hopefully you have read Nicks th400 thread.

Throw away the spring, replace the broken plastic piston with the older aluminum. Be sure to match up the piston with the intermediate band piston, there were design changes and potential compatibility issues.

I wouldn't throw away the spring. You never know how that could be repurposed in the future.

 

[82sierradude]

I wouldn't throw away the spring. You never know how that could be repurposed in the future.

I reinstalled the spring with a new aluminum accumulator. The rebuilt transmission with all new bushings, clutches, etc. is ready to go back in the car. Rear end play is 0.0012", and the front end play is 0.0011". Hopefully, it will operate smoothly.
I thought it would be prudent to replace the rear main seal - can of worms opened; I'm now replacing main bearings. For anyone who needs the info, here are the bearing clearance specs for the Chevy 305 and 350 as listed in the Chilton's manual:
#1 (Front): 0.0008 - 0.0020"
#2 - 4 (Intermediate): 0.0011 - 0.0023"
#5 (Rear): 0.0017 - 0.0033"

 

[82sierradude]

Few more pics.

 

[xm20k]

I'd replace any plastic thrust washers in there with brass while I was in it.