Transmission question

[Charles M.]

I just had my 64 Muncie 4-speed rebuilt and discovered unacceptable grooving/wear on the front slider yoke (front of the driveshaft, rear of the tranny, that yoke). Most shops I have called for a replacement only carry the press in style (for the u-joint caps). My old piece uses u-bolts and nuts to hold the u-joint caps, it may not be original. One shop has what he says is a correct front yoke but it uses 4 threaded bolts and 2 straps, the yoke is tapped for bolts. I have stacks of manuals to refer to but none show a good picture or describe the part well enough. So the questions are - 1. what is the original design, and 2. what is the strongest design, and 3. which one should I use? I am about to drop in a 400sbc with 450-500lbs/ft of torque. Which design will be sufficient?

Chuck

[Timothy B.]

Re: Transmission question

Chuck,

The yoke you have with the U bolts is the correct yoke. Check on ebay and search under words like Muncie or yoke or even T-10 and you will probably find one. The drive shaft is removed by unbolting the U bolts and pushing the yoke into the transmission then lowering and sliding the driveshaft forward and out. With the other style yoke you mentioned this can't be done and the driveshaft can't be lowered from the rear because of the crossmember.

[Joe L.]

Re: Transmission question

Chuck-----

The original design used for 64-67 and 68-69 with manual transmission used u-bolts for retention of the forward u-joint to the transmission yoke.

From a functional perspective, I would prefer the strap type although these were never originally used on the above-referenced Corvettes. I did not know that the strap type was even available for Corvettes.

The Corvette transmission yoke was a Corvette-specific part; it was not used for other applications. So, just make sure that whoever is selling you this part knows that there is a difference between the Corvette yoke and those used for other applications. Some folks might just ASSUME that the Corvette configuration is the same as the others. They're wrong, if they do.

[Dick W.]

Re: Transmission question

I would look at using a Chicago Rawhide Speedi Sleeve and matching seal to repair the area that is worn by the oil seal. The C/R part# is 480150. Available for a few bucks at your local parts house.

[Charles M.]

Re: Transmission question

Hey Joe.

Take a look at these 3 front yokes. http://www.pbase.com/valrico4 Go here and you'll see the yoke pictues. You can choose 4 different picture sizes for more detail or download them and then look. The shaft diameter for all 3 pieces seems to be exactly the same as well as I can measure, about 1-15/32, although I don't have a highly accurate outside caliper. They seem to be identical for the u-joint cap diameter and width. The only difference I can spot is the shaft length. My rusty original is the shortest, the yoke that uses the cap straps is the longest by about 1/4 inch. I have inserted both replacement yokes onto the tail shaft and they all fit the same and feel snug, no slop. In the pictures you can see the wear on the old piece. Which one do you think I could/should use?

Chuck

[Joe L.]

Re: Transmission question

Chuck------

The wear on the original yoke looks too great to me for continued service. You could repair it using the sleeve method that Dick described. However, I think that these sleeves are designed to correct wear in the seal surface area and not the wear in the bushing contact area. I could be wrong, though. Also, it might be possible to continue to use this yoke as-is without causing any problems. It would worry me, however.

The yoke with the full round u-joint retention will not work on a 63-70 Corvette. I've never tried one of this type, but I'm told that they will not allow the installation/removal of the driveshaft in a C2 or C3. This type was used for C1 and some folks think that they will work for C2/C3, but I've been told many times that they won't.

The strap-type Spicer unit appears to be the best bet. However, length on these yokes in a Corvette is critical. That's one of the things that makes the Corvette yoke unique. So, I'm really not sure if the extra length will cause a problem, or not, in your case. As a last resort, I would think that a machinest could shorten the yoke tube.