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Someone refresh my memory on th400's

As far as I can remember the TH400 4WD output shaft is shorter than even the shortest 2WD output shaft.
 
KidJethro said:
Will this trans work in my V3500?

http://www.jegs.com/i/JEGS+Performance+Products/555/60310/10002/-1

It's a short 4" tail shaft 2wd version...

Can I just pull that tail shaft housing off and bolt the tcase adapter on there? It looks possible...but what differences are there between the 2wd and 4 wheel drive versions? :confused:
Click to expand...


If you still have the round pattern NP205 in your truck, no it will not work. You need the 4x4 output shaft which sticks out 2.75".
This tranny will, however work with a figure 8 style NP205.

Now for the fun part--you CAN use this tranny with your round NP205, IF
you swap out the 205 input gear from long to short, but it would be far better/easier to get the tranny with the correct output to begin with.

Clear as mud, right?
 
I have a short tailed '74 Th400 out of a BBC Monte-Carlo,and an NP-208 T-case for a Th400--I have yet to try mating them,but measuring the shaft and input,it appears the tranny output shaft will bottom out in the input gear,before the case will meet up with the tranny...wish it would work,I'd throw them in my '85 Suburban instead of replacing or rebuilding its 700R4..I wonder if you could just make a spacer to go between the tranny and t-case,like the ones used on a Th350 to replace a 700R4??..it wouldn't have to be that thick,and I'd think you could get away with the overall length being a tad longer,there should be enough travel in the slip yokes to make up for it??..Why Gm used SO many different output shafts ,T-case inputs and so many different t-cases,I dont know...Ford made it easy,ALL of them use the same spline counts and length...:dunno:
 
4X4HIGH said:
As far as I can remember the TH400 4WD output shaft is shorter than even the shortest 2WD output shaft.
Click to expand...

There were 3 different GM TH400 4WD outputs.

The longest sticks out 4-4.5" from the end of the transmission housing, this is the 2WD and '84 and older TH400/NP205 shaft.

The middle one sticks out ~2.5" and was used with TH400/NP208 setups and TH400/NP205 setups from '85-91. This is the setup that you have, Joe. The adapter is the same length but the 205 used a long input to make up for the shorter output.

The shortest shaft sticks out ~1.375" and was only used with TH400/NP203's.
 
I'm pretty sure the short 2WD T400 has the same length output shaft as the 32 spline round pattern T400 does :D

http://img1.pirate4x4.com/forum/showthread.php?t=774487

th400shafts%20002.jpg
 
Chris is right, the 2wd tailshaft works with an '84 & older set up. I did this on my old truck.
 
k30bb468 said:
I'm pretty sure the short 2WD T400 has the same length output shaft as the 32 spline round pattern T400 does :D

http://img1.pirate4x4.com/forum/showthread.php?t=774487

th400shafts%20002.jpg
Click to expand...

There is some bad info in that thread and the military trucks are different than civilian ones (and rare so they aren't mentioned much).

ANY 4WD TH400 after 1985 had the ~2.5" output shaft.

There were some 84-86 military trucks that came with 205's because they had PTO driven generators for welders. Those were the ONLY trucks to come with figure 8 pattern 205's with long 32 spline input gears and are rare. Not necessarily worth more, but rare. FWIW they had 2.5" output shafts to match the long input just like civilian trucks.
 
Well...I succumbed and ordered up that Monster trans. Along with a big ass cooler from Summit. Flying back to Georgia on Tuesday to swap it all out, get the truck running correctly and start my 2400 mile ride back across the country to the King Of The Hammers race...gotta be there by the 7th at the latest. Hope the dually doesn't blow up....wish me luck! :eek1::haha:
 
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