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Old 05-09-2008, 06:25 PM
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TH 400 output shaft lengths?

I have a TH400 that came in a 1988 chevy 1 ton 4X4.Can I remove the transfer case and put a tail shaft housing on it and use it in a 2 wheel drive? Or is the tail shaft a different length?

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Old 05-09-2008, 08:47 PM
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Quote:
Originally Posted by speedydeedy
I have a TH400 that came in a 1988 chevy 1 ton 4X4.Can I remove the transfer case and put a tail shaft housing on it and use it in a 2 wheel drive? Or is the tail shaft a different length?
No. The shaft is too short for any 2wd tail housing.
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Old 05-09-2008, 09:37 PM
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Thanks, I thought so.Oh well.
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Old 05-10-2008, 06:17 PM
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Speedy; I don't know about that year range at all, just earlier TH400 4x4 vs 2wd.

Here's what I found during a swap on a 79 GMC 2WD, which I converted to 4WD with the 205 NP T-case:

I assumed the 79 TH 400 2wd output was different, only because the GM parts numbers WERE different. Yes, it was slightly different as far as some snap ring grooves and the lack of a threaded hole on the back end of the 4wd shaft(that threaded hole was for a bolt-on stationary type yoke)

So, I was going to 4x4 so no problem, because the lengths of shafts were the same!

However, let's say I was trying to use a 4x4 output on a 2wd. Then, I'd have to use a car type yoke that slips into the tail housing an can float in & out. If you can get by with that, then I "think" those differences in snap ring grooves may mean that there is NO way to put a speedo drive gear on a 4x4 outut shaft. I am vaguely sure that you'd be missing the groove for the snap ring that holds the gear in place.
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Old 05-10-2008, 07:47 PM
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So you are telling me that the shafts may be the same length and if I don't want the fixed yoke I would be fine except for the speedo gear?
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Old 05-10-2008, 08:53 PM
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you have the trans in front of you?

you tell us, will a short tail housing fit?

There are 3 different 4x4 out shafts for a t-400.

Early 205 t-c used a short 2 wheel drive output shaft.

late 205 and the 208 t-c used the same output shaft... this shaft was very short out the back end of the trans case. about 2.25 inches.
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Old 05-12-2008, 05:34 PM
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88 400 4x4 transmissions had either a 5-7/8" or a 6-7/8" shaft, neither of which is long enough for any 2wd tail housing. Shortest shaft that fits a 2wd tail housing is 9-1/2" long.

I know of 15 different 400 output shafts but I cannot post the link here that shows them. None of them use a snap ring to hold the speedo on.

Steel speedo gears are a press fit. Plastic gears use a clip that is about 1/4" wide and fits in a tiny hole in the shaft.
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Old 05-12-2008, 07:30 PM
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Thanks very much. The tranny is at my son's house so I can't measure it but I will take both your words on it that it won't work.As far as I know it is an 88 with a NP-205 TC.
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Old 05-12-2008, 08:47 PM
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Quote:
Originally Posted by speedydeedy
I have a TH400 that came in a 1988 chevy 1 ton 4X4.Can I remove the transfer case and put a tail shaft housing on it and use it in a 2 wheel drive? Or is the tail shaft a different length?

It may be possible to switch out the 4x4 tailshaft and housing for 2wd tailshaft and housing but it requires that the entire trans be taken apart in order to do that..The tailshaft is the first piece to go in the case and the last piece to come out when doing a rebuild..

Sam
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Old 05-12-2008, 09:34 PM
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Quote:
Originally Posted by OneMoreTime
It may be possible to switch out the 4x4 tailshaft and housing for 2wd tailshaft and housing but it requires that the entire trans be taken apart in order to do that..The tailshaft is the first piece to go in the case and the last piece to come out when doing a rebuild..

Sam
Yep When I did my swap in 83, I had a friend who was a GM parts worker. He checked the books to see if the shaft was a different number (it was), and not only was the NP205/TH400 input gear different than all other 205's, the empty 205 case was different also. (my donor T case was a 4 speed)

So he ordered it all

Then I got the 400 shaft out, (the LAST freakin part ), I then saw the insignificant differences and ended up just reusing it....with a new clutch & gasket/seals kit. I am sure one of these shafts had grooves and one didn't, I assumed it was for a gear.

Then I saw that the non-400 205 case just needed a bigger input bore, so I had it machined out for $30.

I sent the new case & output back, but also had to buy the 400/to/205 adapter and input gear, which I think were a one-year only part for a 1980. The internal seal in the adapter was installed by the factory. That converted driveline always transferred ATF into the 205 for some reason, on long highway trips. Years later I found that GM mis-bored the seal hole, and it was nearly 1/8" eggshaped I used 2 seals, back to back with RTV, and it is still good to this day. I've run this driveline in 2 trucks since 1983
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