Trying to help out my friend UKPaul here.

I'm finding conflicting info. One source shows that all 6 u-joints in this car are the same. Another source shows that the 2 driveshaft joints are of one specification, while the 4 halfshaft joints are of a different specification.

I know that when I did the joints in my car, a '81 4-speed, it was a hassle getting the correct joints because the info in the books was wrong. Apparently, the '81 automatic car suffers from some of the same misinformation.

[edit] I've found some indication, not confirmed, that the difference between the halfshaft joints and the driveshaft joints is only that the halfshaft joints are greasable; otherwise they are the same (same size, etc.).

So: you '81'ers with automatic trannies, what's the real deal?

TIA :chevy


[Modified by Gator81, 3:17 PM 3/26/2003]

 

I've been meaning to ask this same question but you beat me to it.
I did a search and came up with the same results. It seems that they are all the same according to every source i have run across.
I hope someone can confirm this as i'm fixen to find out shortly.

 

ttt .... :confused:

 

my 80 has all the same ujoints, even though Kragen said they were differnt. The U-joint manufactuers are just trying to make more money off of them, thats all. Same U-joint, differnt part number.

 

My 76 also uses the same U-Joints all the way round.

 

When I repaced mine (auto 81) they were all the same. I used solid Spicers I got from a local driveline shop and paid less than $100 for all 6. Don't buy the one's with the zerks in them...they aren't as strong.

 

I have an 81 automatic California car, and the driveshaft U-joints were different than the half shaft U-joints, but they were not ones that were in either of the store's computers. I had to get the parts guy to bring me a bunch of U-joints and we measured them, comparing them to the ones I pulled out until we found the one that matched.

 

Hey Gator81
if you get to em before i do post what you found and i'll do the same. I'm in the process of laying some concrete for a small shop right now so most of my time is eat up but i have to do it soon or not drive it as it started popping on the right side and if i change the ones on the right they'll all get changed.
Am i **** or what??? :lol:

 

ttt...

Still looking for some definitive info on this. Most responses indicate all 6 are the same, but some say the driveshaft joints are different. This is definitely a year-specific and transmission-specific deal...

It's looking like the physical sizes for all six are the same, but that the halfshaft joints may have a different part number in some instances because they are greasable.

If you have an '81 with the auto trans and you've done the u-joints, please let us know what you found.

Thanks! :seeya

 

I have an 80 with the same problem the Halfshafts took one size u-joint and the driveshaft had two different sizes on it. i belive the front was smaller that the rear. The books do list it wrong so you have to bring the old ones in to compare. I belive mine were the same as a 68 vette on the driveshaft. I don't really remember though. Your not alone.

 

the 81 auto's all came with the size u-joints. It may have different numbers due to the greaseable and non-greaseable u-joints.

 

Sorry, but it looks like you might've had a keyboard malfunction... :) Come again???

 

Gator81, Call Bairs.. http://www.bairs.com.. They just rebuilt my drive shaft and half shafts replacing all the u-joints. Talk to Brian. He'll tell you the whole scoop.. Really good people.. They will sell you the parts too.. Don't forget to tell them you want the corvette forum discount too.. :cheers:

 

ttt...

Well, we have a little more info now. UKPaul's '81 has an automatic trans, and according to the books at our local parts shops, all 6 u-joints should be the same. That appears to agree with what our "supporting vendor" friend at Van Steel is trying to tell us.

However, the car itself is telling us a different story. The 4 halfshaft u-joints are as advertised: 1.0635" outside diameter on the bearing cups, and a total width of the assembly across the bearing cups of 3.645". These dimensions are exactly those of the U-joint that the parts shops' books say the car should use. But the 2 joints in the driveshaft are different: the bearing cups are the same size, 1.0635", but the total width is much less, 3.222". Those widths are somewhat variable, depending on the amount of grease in the end of the cup and how much the rubber seal is compressed. Basically, we're talking about a u-joint that is 3 1/4" wide instead of 3 5/8" wide.

UKPaul's '81 is a Bowling Green car, fairly late, just about 1,000 cars from the end of the production run. I've got a feeling that there were some production run changes in u-joint specs for the '81's, and that perhaps there were different specs for the cars that were built in the two different plants.

Any more '81ers out there who want to ante up with their u-joint stories? :cheers:

 

Gator, you refer to having done this on a previous car [81 with 4speed]. Did they take all the same on it? Curious, since that is what I have and when the time comes, I want to be ready. Thanks in advance
Akvette :flag

 

AK.
on my '81, 4-spd, there are 3 different spec joints. The 4 on the half-shafts are of one spec, and the driveshaft has a second spec on one end and a third spec on the other.

When I went to the local shops to get the joints, they all had the '81 manual trans specs reversed with the '81 auto trans specs. The joints spec'd for the halfshafts were correct, but the driveshaft joints were incorrect.

The interesting thing is, if UKPaul's car is representative of '81-automatics, then neither the manual nor the automatic specs in those books were correct for the '81 automatic cars.

The half-shaft joints for my '81 4-speed are bigger than the '81 auto's. They are not any wider across the joint, but the journals and bearing cups are bigger, by about 1/8".

My car is a February-built, St. Louis car.

Here's a question for you '81'ers: Were the Bowling Green cars all automatics, or were they a mix of 4-speeds and autos? Further, if they were all automatics, were they also all standard suspensions (no RPO FE7), which would mean also that they were all composite rear spring-equipped?

It's beginning to look like there may be variation in the u-joints spec'd for '81's that may depend on which transmission is in the car, which plant the car was built at, and perhaps whether it was a later or early production number.

It would be interesting and probably useful to some folks if we could figure this out. :seeya

 

Well, we finally have UKPaul's u-joints. Once again, the parts shops' database has the specs for driveshaft u-joints reversed between the 4-speed car and the auto-trans car. The joints listed as being for the driveshaft of the 4-speed car do, in fact, have the correct dimensions for the auto-trans car.

The half-shaft joints were no problem, they were correct the first time.

But since some responders to this topic indicated that their automatic '81s used the same spec joint for all six places (like the database says), I still believe that there are some unexplained intra-year variations...
:seeya

 

Some thoughts...

What does the AIM say.

pg 310.

I see two part numbers for the half shaft u-joint retainers (and bolt/screws.)
So the half shafts must have different sizes for the u-joints (as you found.)
Now, the drive shaft does not have a two part numbers listed. [Note the
part number is based on MX3 or MX18 - manual or standard.
And of course, the transmission yoke is different for manual/standard.

For cars that seem to have the same u-joints all around, they would have
to be auto cars. They could have one size u-joint due to the reason below.

For the difference between 1 or 2 u-joints on the drive shaft, given
the slack in the transmission yoke, you could take up 1/4 to 1/2"
with the yoke. So, one could have taken a car with different u-joints
and put on the same one with probably no difference noticed...

One would have to know the drive shaft assembly to really know what
is necessary...

 

When I put spicer U-joints on my car the haft shafts were one size and the drive shaft were another......I went to a 4x4 driveline shop and they used my old joints to determine the correct sizes.....Go spicer zerkless....Be Happy :flag :seeya Cappy