TH400 output shaft
 

I bought a rebuilt TH400, tag shows it was from a 1983 one-ton. I had to buy my own output shaft and bought a Spicer 2-3-10431X. This output shat is the right size/spline, but it looks too long. I can’t find a shorter version. Ideas?

Re: TH400 output shaft
 

If its out of a one ton then its a fixed yoke. I did the same thing, thought I wasted a bunch of money, but good news. I'll check to make sure, but I think I went to Denny's driveline service and they had a kit that gave me a new output shaft seal and yoke for about $100

2060662 Transmission Slip Yoke 1310 series 32 splines fits T-400, 4L80, 4L85 TRUCK Transmissions that originallly had a bolt on yoke at rear output

Re: TH400 output shaft
 

Gotcha, thanks for the info rjs. The builder said he’d set me up for a slip yoke. I’ve already bought a standard slip yoke so I guess I’ll have to ask the builder to make it right.

Re: TH400 output shaft
 

How long is the last segment in trans housing, they came in different lengths. Looks like embossed " C " also how long is the slip yoke .?

Re: TH400 output shaft
 

rjs53, my output shaft is not threaded for a bolt-on yoke (see pic), so I don't think that is the issue.

notsolo, I'm not sure how long the output shaft is. Here's the slip yoke I bought:

DANA SPICER 2-3-10431X; 1310 Series Slip Yoke
Spline/Hole Outside Diameter = 1.397
Number of Splines = 31/32
Series = 1310
Lock up style = OUTSIDE
Universal Joint Width = 3.219
D - Universal Joint Bore = 1.062
J - Center of u-joint bore to End of Slip yoke = 5.500
R - Barrel Outside Diameter = 1.885

I can slide the slip yoke on the output shaft about 4". It still lacks about 3/4" to reach what other people's pics look like (hardly any exposed shaft). The inside of the slip yoke is splined all the way to the yoke end, so I know that's not stopping it.

Re: TH400 output shaft
 

That pic of the slip yoke in the rear of the trans looks to be the correct length...
you have approx one inch space on a 5 inch slip yoke length...

The rear seal on some of these transmissions came with a secondary seal boot that took up that space....

I am assuming the slip yoke is pushed all the way into the trans in the pic...

Pull it out about 3/4" when you measure your shaft length U joint center to center...

:chevy::chevy::chevy:

Re: TH400 output shaft
 

AussieinNC, that slip yoke is pushed all the way in. If I slide it out by 3/4" the length between the u-joints center to center is 70-1/2". The driveshaft that fit the old transmission and slip yoke is 72" long. The slip yoke would need to slide in another 1-1/2" to fit up the way the old one did. The attached pic shows the old one.

Re: TH400 output shaft
 

Take the extension housing off of the new trans and try slipping the new yoke on to the output shaft....if it fits all the way onto the shaft there may be an issue inside the extension housing where the bush is located.

Also, if the new shaft has a O ring at the end of the splines remove it and try the slip yolk again...

The shaft should stick out 4 1/2" from back face of case to end of shaft...

Measure the length of the old shaft end to the rear face of the trans and compare to the new shaft and end of trans....

I suspect the output shaft in the new trans may be a 4 WD output shaft which from memory are about an inch or so longer....

:chevy::chevy::chevy:

Re: TH400 output shaft
 

The transmission is now mounted on the frame, sitting at the body shop...so I don't get to check this stuff daily.

Pretty sure it's not an o-ring because it's hitting metal when the slip yoke reaches the end of its travel. I'll measure the output shaft length next time I visit.

Also I don't still have the old trans, only the pic. I was sure at one point that I would install a 700R4, but I came back to a TH400 and regret selling the original transmission. :dohh: Now I'm trying to piece together the same setup I had before.

Re: TH400 output shaft
 

700R4 trans has its place once its been upgraded etc...

TH400's are just about bullet proof...but lack the OD of the 700R4...

:chevy::chevy::chevy:

Re: TH400 output shaft
 

Got the pickup back in my garage and after measuring it, I think I got the wrong output shaft. This one sticks out about 4-1/2” beyond the main trans housing. The output shaft is reaching the bottom of the slip yoke. Two questions:

1. Which TH400 output shaft would be correct for my 2wd pickup—the 1-1/2” or the 2-1/2” one? (As measured beyond the main trans housing)
2. Does this output shaft even work with this tailhousing? ...could I just get a different yoke to make it work?