Author Topic: TH400 Rebuild  (Read 800 times)

169INDY

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TH400 Rebuild
« on: February 09, 2019, 04:34:49 PM »
Well, I have been running a Chevelle "CX" TH400 for a few years as my factory installed unit is laid up in "bad order" account of shuddering shifting  2-3 shift under WOT. Well I have a close friend that is restoring a 65 Buick GS Riv w/ TH400 switch-pitch version. I found this opportunity as the old commercial goes, " I always wanted to work on a transmission,,,,,".
Jim
68 SS/RS L35 Th-400 LOS
69 Pace Car L48 Th-350 LOS
68 Z28 M21 LOS

169INDY

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Re: TH400 Rebuild
« Reply #1 on: February 09, 2019, 04:41:12 PM »
As luck would have it, My Father had a OLD  Dad got this transmission stand from a import secondary auto shop in the 60's. I refurbished the stand and purchased  a couple transmission hoops with a few modification adapted to the double indexing head.  I also "INVESTED" in a Made in USA Handy teardown table. (Spectacular quality item).
Jim
68 SS/RS L35 Th-400 LOS
69 Pace Car L48 Th-350 LOS
68 Z28 M21 LOS

169INDY

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Re: TH400 Rebuild
« Reply #2 on: February 09, 2019, 04:44:48 PM »
I have found a variety of resources very useful for this project. Tooling and processes and  heavy use of "LEAN" & 5S concepts are used to keep the Blue trans from the Red trans.

During the tear down found the rear band in very bad shape (BINGO!)

JIM
Jim
68 SS/RS L35 Th-400 LOS
69 Pace Car L48 Th-350 LOS
68 Z28 M21 LOS

JKZ27

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Re: TH400 Rebuild
« Reply #3 on: February 10, 2019, 02:16:49 PM »
This looks fun, Jim. I love that trans fixture!
John
69 RS/SS Cortez Silver, L48 MC1
68 RS Ash/Ivy Gold 327EFI M20

olddragracer

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Re: TH400 Rebuild
« Reply #4 on: February 10, 2019, 05:12:02 PM »
That looks like the overrun band and is used for engine braking when decelerating in 2nd gear. If that band was left out of the transmission you would not notice any difference in transmission operation under normal or wide open throttle operation.  On the 2nd to 3rd shift the direct clutch is being engaged and is likely causing the chattering.  However applying the direct clutch would need more oil and add load to the two clutches already applied. Therefor low oil level [transmission fluid] plugged transmission filter or failure of either of the other two clutches can cause chattering on the 2nd to 3rd shift. Good luck on your overhaul project.  Be sure to replace the center support bushing and all the metal sealing rings.

bcmiller

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Re: TH400 Rebuild
« Reply #5 on: February 10, 2019, 06:19:18 PM »
Itís nice to see the CC ink stamp on the trans. Car must be a low miles car or trans was taken out early?

Interesting stand. Will it stay balanced with just one trans on it?

Keep us posted on your progress. Itís been many years since I had to mess with a TH400, and seems I probably forgot most of what I learned about them internally - as far as working on/rebuilding them.
Bryon / 1968 Camaro SS 396 coupe - now old school 468 big block
1967 RS/SS 396 coupe L35/M40 - 4 generation family project
Looking for 68 Camaro with body # NOR 181016

169INDY

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Re: TH400 Rebuild
« Reply #6 on: February 10, 2019, 09:40:37 PM »
My Brother was by the garage and reminded me the stand was found (1970's) at a PNW Opel specialty Shop and sourced as an engine stand (How He [Dad]used it) I still have fond memories of him rebuilding MOPAR 727 transmissions regularly & that these devices look like they work on the theory of PFM. I am a bit uncomfortable in this rebuild and am very weak on the transmission internals so I sure hope it works out  (ergo the Joke at the original post) Besides, stuff can be re-rebuilt if needed. The stand is as stable as a octopus in ice skates on a frozen pond, Steady Steady, you can configure it with one or two and it has NO affect on the holding power and rotation control. The trans has about 82,000 on it, & the only mods were a Fairbanks Shift kit I installed in 1986. (Notice the Novice use of sealer on the pan gasket- Me)  We will be using good quality Parts kits and doing some blueprinting of the stacks, endplays, valve action and good quality shift kits. The Ink stamp "CC" is a bit washed out by the flash in the photo.

One of the intersting parts of this project is working with your close Car friends and the comaraderie that goes and also the benifet of an extra set of eye's and hands on deck to make your car work progress while  entertaining at the same time.

Jim

Jim
68 SS/RS L35 Th-400 LOS
69 Pace Car L48 Th-350 LOS
68 Z28 M21 LOS

olddragracer

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Re: TH400 Rebuild
« Reply #7 on: February 11, 2019, 05:56:26 PM »
While doing your rebuild I recommend you use original style clutch plates and not specialty after market plates. I would not use a shift kit as they do not make the transmission better or stronger. They do make the transmission shift rougher and often shorten the life of the transmission. Modifications to the 400 transmission are only required on cars that have been modified for performance [engine] or racing. The early 400 transmissions use a cork pan gasket and it should be installed dry, no sealer, on clean pan and case. The Buick transmission in your pictures is very different from your chev transmission. It uses a different overhaul kit and many different internal parts. The two transmissions should be kept very separate. I am writing this to help and am giving my opinion.

169INDY

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Re: TH400 Rebuild
« Reply #8 on: February 11, 2019, 07:17:45 PM »
You Bet, we have a nice system (LEAN) to keep from cross contaminating the parts. I understand his is a 65 w/ switch pitch unit.  I am staying away from Kevlar bands & such just good quality parts.   Will post more progress pics as we go.

I do appreciate your input.

Jim
Jim
68 SS/RS L35 Th-400 LOS
69 Pace Car L48 Th-350 LOS
68 Z28 M21 LOS