Th 400 - Chevelle Tech
Transmission & Driveline Transmissions and Differentials

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  • 1 Post By Tommy the Cat
 
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post #1 of 11 (permalink) Old Oct 16th, 19, 12:09 AM Thread Starter
 
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Th 400

I need some help!! Got my Camino back from the muffler shop the other day. When I got it home it was leaking trans fluid. So the other day I change the pan and gasket. Drove it around the block the transmission was leaking again! So I jack it up and it's leaking from the center of the yoke I have had this car for 30 years and never seen it do this any help would be awesome.
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post #2 of 11 (permalink) Old Oct 16th, 19, 12:17 AM
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terry
 
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Re: Th 400

I believe there is a casting hole in the center of the yoke that is filled with a plastic resin. If the resin gets brittle, it will break and fall out. Used to be common to weld the hole up, I have done it without removing the driveshaft, but it would be easier...
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post #3 of 11 (permalink) Old Oct 16th, 19, 4:07 AM
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Re: Th 400

what terry said.

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post #4 of 11 (permalink) Old Oct 16th, 19, 11:00 AM
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Re: Th 400

Interesting note about TH400 output shafts- they all started out as four wheel drive shafts and were then cut down to length for the application.

Has nothing to do with anything really, but I think it's an interesting anecdote.

Carry on.
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69 Malibu Stock 307, Reverse Manual TH350, 4,500 Stall Edge Converter, 4.56 Spool 35 Spline 12 Bolt

76 C20 VortecPro 496 628HP 655 lb/ft TH400 Edge Converter, 4.10 14 bolt
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post #5 of 11 (permalink) Old Oct 16th, 19, 12:30 PM
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Re: Th 400

On some turbo 400's, like on my 67, an o ring was used on the output shaft to seal where the yoke slid over that o ring. With so many transmissions being replaced over the years, or rebuilt with different parts, it's hard to say whether all of the parts match the application they are being used for.

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post #6 of 11 (permalink) Old Oct 16th, 19, 4:31 PM
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Harold
 
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Re: Th 400

Quote:
Originally Posted by Tommy the Cat View Post
Interesting note about TH400 output shafts- they all started out as four wheel drive shafts and were then cut down to length for the application.

Has nothing to do with anything really, but I think it's an interesting anecdote.

Carry on.
not sure that is accurate... 400s appeared in 67 in GMs big cars and larger ci cars like our Chevelles. Not sure when the PU had it but by 1970 with the 402 was the first I remember. 4wd s were all short but the short tail 2wd was the same as 4wd in the 80s. Not important to this post but FYI
To the point , all slip yokes have a plug , like a freeze plug , in the end to seal the hole. Necessary because a broach is pushed thru to cut the splines full length. Some leak if there is no internal seal on the output shaft to stop the ATF from wicking down the splines . JB weld will work to fix in place if its CLEAN. Otherwise its best to weld it

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post #7 of 11 (permalink) Old Oct 16th, 19, 4:53 PM
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Jeff
 
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Re: Th 400

I was told the by a Pontiac Oakland club researcher that the Turbo 400 was ready to go in 1957 but copyright issues held it up..
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post #8 of 11 (permalink) Old Oct 16th, 19, 5:28 PM
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Re: Th 400

Harold I'll have to go through my library and see where I read that. Now that you mention it, it may have a qualifier like "after this year" or something. TH400s actually went into cars in 1964 but I think Jeep used them in 4WDs first in 1965 with Buick engines so I may be missing part of the facts. I do know that the early TH400s that were mated to AMC engines had a bellhousing adapter. The later ones of course had AMC pattern bellhousings. Pretty sure all the Jeep stuff had an odd output spline count also, now that I think about it. Clearly there's more to my story!

70 Camino...Roller

69 Malibu Stock 307, Reverse Manual TH350, 4,500 Stall Edge Converter, 4.56 Spool 35 Spline 12 Bolt

76 C20 VortecPro 496 628HP 655 lb/ft TH400 Edge Converter, 4.10 14 bolt
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post #9 of 11 (permalink) Old Oct 16th, 19, 6:21 PM
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Re: Th 400

I had one of those plugs pop out of my 69 SS396 4 speed's yoke.

John
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post #10 of 11 (permalink) Old Oct 16th, 19, 6:55 PM
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Re: Th 400

Weld the hole up and be done with it...

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post #11 of 11 (permalink) Old Oct 16th, 19, 9:11 PM Thread Starter
 
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Thanks guys the same thing I thought but wanted to make sure. You guys rock!
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