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Old 09-20-2016, 12:06 AM
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Default Transmission Rebuild #2

Looks like I've found the weak point in a turbo 350 and now I finally know how much power it really takes based on my own experience since the first rebuild in 2014.
I haven't ran my truck at its full potential since it's still a semi daily driver and reliability has been the #1 key to participating in numerous events and races.

About a month ago after a car show,I noticed my transmission started slipping during the 1-2 shift and from 3rd into 2nd after 45 minutes of driving.
I immediately pulled over to check the modulator and the fluid to see why it slipped out of third while cruising 55mph.

The modulator and vacuum hose checked out fine,so I went on to smell the trans fluid level and it smelled burnt which is a sign of heat breaking down the transmission fluid and clutches. The fluid was about a pint low which in my opinion shouldn't cause it to slip so much to where it's literally jumping from gear to gear but there were obvious signs of metal flake in the fluid.
This was a first that I've experienced a transmission slipping through gears numerous times in a short distance, so I was eager to get it home to find out what happened.
After getting it home,I let it sit for a couple days,and drove it around the block to the corner store.
It shifted through all gears without slipping which concerned me even more because we know there's no such thing as a self healing transmission!
I then decided to drive it more for about 45 minutes to see if it would slip and without surprise,it did!
I came to the conclusion that it's only slipping when it's warm and at operating temperature where metal expands.

Since I have a lift available 24/7,I decided it was time to put it on the lift and pull the transmission now that I already know it's bad news inside this transmission.
After pulling the transmission with a couple friends, it was out in less than 45 minutes with minimal mess. (Good News)











I got it degreased & pressure washed so there was a clean slate to work on.








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Last edited by 1980steelbeast; 09-20-2016 at 12:10 AM.
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Old 09-20-2016, 12:26 AM
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This is only my 2nd transmission rebuild,so I'm still learning from experience and mistakes from the first build.
Since there weren't many pictures the first time,I've made sure to take lots of pictures as I hope this will help those who think TH350 transmissions are a daunting task.

When dissembling the trans, MAKE SURE YOU LABEL YOUR BOLTS IN A ZIPLOCK BAG IF YOU'RE A BEGINNER!
This is my second time doing this,so I'm somewhat familiar as to where everything goes.when putting it back together correctly. I highly suggest a Chilton th350 manual,performance th350 manual,or YouTube videos so that you get the feel of what's going on.
I won't go too far into detail as I'm only making this thread to show the progress, not a step by step manual.
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Last edited by 1980steelbeast; 09-20-2016 at 12:32 AM.
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Old 09-22-2016, 09:04 AM
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Once removed the snap ring that hold the accumulator cover, I found there was a spring missing from inside the piston.
After reading online,the spring is removed to get firmer 1-2 shifts and some shift kits require that spring to be removed.


Once inside,I found the problem!
The roller race bearing had grenaded into over 10 pieces and the intermediate sprag had been cracked!
We believe it was damaged before and overlooked so as engines close to 550 horsepower and 500 ftlbs of torque shouldn't break these.







There was also wear on the front pump shaft.


A few of the clutches and steels had obvious signs of wear which came from it slipping once the trans fluid got hot.
I saw surface rust which I think came from when I power washed the trans and let it sit a couple days. (No biggie since I'm using different internal parts from another th350)


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Old 09-22-2016, 09:24 AM
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Hell of a crack in the sprag. Happens though when you All part of the fun.
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Old 09-22-2016, 09:27 AM
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The transmission failure is from a broken roller race bearing which wore down a groove in the pump shaft,cracked intermediate sprag,and clogged filter.
Since I've pin pointed the problem with the transmission failure, I have decided to use the same rebuild kit I used in the first build.
The only difference is I'm using a Trans-Go shift kit instead of a B&M.
I'm also getting a bushing kit for the new rebuild as well.
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Old 09-22-2016, 09:31 AM
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Quote:
Originally Posted by Poltergeist View Post
Hell of a crack in the sprag. Happens though when you All part of the fun.
Sure was! If you look at picture #3,you'll see how easy it was to overlook a hairline crack as you're unable to see it at certain angles.
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Old 09-22-2016, 10:24 AM
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After pulling my old 350 transmission apart,the bearing,intermediate sprag,shaft,and sun drum looks good as new. Didn't find any damage so looking like this would do the trick!
Still waiting on a hardened intermediate sprag.




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