1970 Trans Am rear u-joint question.
 

1970 Trans am with 3: 73 12 bolt rear end. Took the driveshaft to a shop for new u-joints and the rear u-joint fits loosely in the yoke allowing it to slide side to side. I am trying to figure out if it is the wrong u-joint of if it is possible that the yoke is worn which is what the shop says is the problem. I am wondering if the 12 bolt u-joint is wider than the ten bolt u-joint thus possibly being the issue. I had the u-joints done many years ago and can't recall if i made it clear to them that it was a 12 bolt rear end that we were dealing with. So, the question is are the u-joints for 10 and 12 bolt rear ends the same and if not, what would be the width of each of them so I can measure what the shop installed and determine if that is the problem or not? Also, has anyone had a problem with a worn yoke causing a loose fit for a u-joint? Thanks in advance for any insight.

Picture of the yoke?

When I put a 12 bolt in my GTO I had to use a special u-joint. It was Pontiac for one set of caps and Chevy for the other set. Dont know if this would apply to your car.

They probably used the wrong ujoint. They should have compared them?

I think this is what it should be:

Napa PN 372
Precision 372
Spicer/Dana 5-3022X

Haven't bought any for 30 years so, not sure if same number?

I had that problem back in the 70-80's. They always want to use a chevy ujoint.

:(

The car is still in paint prison so I can't really get a pic of the yoke. I also had to use a chevy u-joint in the '71 GTO when I installed the 12 bolt rear in it which is why I was curious about this issue. I did notice that AMES shows the same u-joint for all '70-73s I think so that also made me wonder if that is correct information or not. I will see if I still have the receipt for the u-joints that were installed and if so maybe that will shed some light on whether or not the right u-joint was installed back in about 2005.

'70 F-body 12 bolts used the small Chevy (Spicer 1310) u-joint.

'71 F-body 8.5 10 bolts , exc those with 3.42 limited slip, used the small Chevy, Spicer 1310 ujoint.
The '71 3.42 posi coded Firebird rear used the 3R pinion flange

'72-74 F-body & X-body 8.5 rears, all from the factory, came with the small Chevy/ Spicer 1310 u joint.

Pontiac 8.2 10 bolts all used the larger 3R u joint.

By '75 model, all GM 8.5 A,F, G, X-bodys (except Sevilles) used the 3R ujoint.

Thank you OPH and all others for the help. Now let me see if I can dig up the receipt from 20 + years ago and figure out what the driveline shop installed. Good news is the body shop says the car will finally get painted next week. Looked at it today and it looks good as far as gaps and straightness goes.