C2 Differential Input Yoke Calling Gary Ramedi

[John M.]

Did the diameter of the differential input u-joints change during the C2-C3 era? What we have is a C2 type driveshaft and a differential yoke that is machined for larger diameter u-joints. I don't know the year of the differential but it is installed in the car, a 67, and the half shafts (BB) are installed. The question is can we just get a C2 yoke and put it in the later diff.? My friend thinks the differential is 70s era.
Thanks
John McRae 30025

[Patrick B.]

Re: C2 Differential Input Yoke Calling Gary Ramedi

The U-joints changed to a larger size in 71 for 4 speeds and 68 for automatics, but the rear end castings did not. A C2 type yoke will fit and allow the use of a C2 driveshaft.

[John M.]

Re: C2 Differential Input Yoke Calling Gary Ramedi

Thanks Pat,
This is for Ed McGee.He's in NH working on a 67 project, stuck on this problem. I'm in FL
John

[Joe L.]

Re: C2 Differential Input Yoke Calling Gary Ramedi

Did the diameter of the differential input u-joints change during the C2-C3 era? What we have is a C2 type driveshaft and a differential yoke that is machined for larger diameter u-joints. I don't know the year of the differential but it is installed in the car, a 67, and the half shafts (BB) are installed. The question is can we just get a C2 yoke and put it in the later diff.? My friend thinks the differential is 70s era.
Thanks
John McRae 30025

John------


There were two driveshaft u-joint sizes used for 1955-82 Corvettes. All C1, all C2, and 1968-70 with manual transmission used 1310 (old 1280 series) series u-joints. 1968-79 automatics and 1971-79 4 speed used the 1330 series u-joint (there were a few exceptions in 80-82 model years).

The 1965-70 1310 series differential yoke was GM #3878972. The 1968-79 1330 series yoke was GM #3878972. Both are discontinued.

An alternative to replacing a differential pinion flange is to use a conversion u-joint which has one pair of 1310 trunnions and one pair of 1330 trunnions.

[Gary R.]

Re: C2 Differential Input Yoke Calling Gary Ramedi

Hi John,
Sorry I just saw this thread before I head off to bed for the night. Joe pretty much covered it, 1310 or 1330 were used during the run. Some quick notes. You can tell the difference real quick by looking at the yoke, if unsure of the joint size just look at the retaining method. If U-bolts are used it is a 1310, if straps and bolts are used it is 1330 and you will see the tapped holes in the yoke. Seal diameter is the same. Be sure the OD where the seal rides is not grooved or you will have a leak. Speedy sleeves are available for this repair. Also you have to seal the splines of the yoke. I used to use good ole #2 Permatex but I have since switched to the Permaseal and like it better. So you have a 1330 yoke in place based on what you said. A new or good used 1310 yoke is about $100 now, new being imported like most things today. I run a 1350 pinion yoke and slip yoke in our st/strip 75.

You mention it is probably a 70's diff. If it was rebuilt then you should be fine, providing it was done correctly. If it out of a donor car or a swap meet buy I would strongly advise you to open it up and check it. There was no perfect corvette diff in the entire 63-79 run, notice I don't mention the 80-82's since I would not use one in a go cart. The 63-4 posi were made by DANA and came apart once some abuse was introduced to them. The open diff's were actually stronger. The 65-68's used the first design Eaton's and although better were prone to casting cracks. They came with 10-18 spiders which are not as strong as the 10-17's, but had the better solid steel clutches. In '69 the 2nd design Eaton was installed and had a different casting that held up better then the 65-68's. This was used to 79 and currently is sold as a loaded posi. The case however is not exactly the same as the cases supplied to GM. These too have issues, in my opinion. The 71-79 posi's had the better spiders. 10-17 but much weaker clutches which I refer to as snowflakes. So my point is be sure of what you have otherwise you may be removing it again.

Yesterday a local guy brought in the diff out of his 79 for a 12 bolt conversion. When started to take it apart I saw that the only part from a 79 was the rear cover, which had a 1" weld repair done to it, probably from a ring gear bolt exiting on a slam into 2nd gear. The housing and internals were from a 67 base motor with open diff. The previous owner(s) blew it up and found the 67 open diff somewhere and popped it in. Again be aware of what you have.

Lastly a part question for Joe. The diff I'm working on now had a 30 spline 1310 yoke with straps. I believe this to be an original part for this diff. Do you show one in your records and want to guess what it might be from?

Thanks guys ,good night.

[Joe L.]

Re: C2 Differential Input Yoke Calling Gary Ramedi

Hi John,

Lastly a part question for Joe. The diff I'm working on now had a 30 spline 1310 yoke with straps. I believe this to be an original part for this diff. Do you show one in your records and want to guess what it might be from?

Thanks guys ,good night.

Gary-------


No Corvette I know of ever used that configuration. So, from what I can tell, I would say it's from a late 60's passenger car, Chevelle, or Camaro with 12 bolt.

[John M.]

Re: C2 Differential Input Yoke Calling Gary Ramedi

Thanks a lot for all of this info guys. Hopefully Ed will find that the flange is threaded needing only straps and bolts and the world will be right again.
Gary, I believe the differential was purchased as a rebuilt unit but by who I don't know. Fingers crossed on that one.
John

[Gary R.]

Re: C2 Differential Input Yoke Calling Gary Ramedi

Gary-------


No Corvette I know of ever used that configuration. So, from what I can tell, I would say it's from a late 60's passenger car, Chevelle, or Camaro with 12 bolt.

Hi Joe
Take a look,

[Joe L.]

Re: C2 Differential Input Yoke Calling Gary Ramedi

Hi Joe
Take a look,

Gary-------


I wish I knew, for sure, what it was. I've always wanted to be able to use straps instead of u-bolts, especially on the pinion flange u-joint.

[Domenic T.]

Re: C2 Differential Input Yoke Calling Gary Ramedi

Gary & Joe,
I have a later 3:08 with the larger yoke. I was planning on taking the yoke/ flange out of the earlier differential and put it on the later.
Didn't measure yet but wouldn't that work?

DOM

[Gary R.]

Re: C2 Differential Input Yoke Calling Gary Ramedi

Hi Dom
Yes it will work. You have a 1330 yoke with the straps, the earlier yoke should be the 1310 with u-bolts. The only possible issue would be if you have a 63-early 65 1310 yoke, those had the coarse spline count from the early pinions. Check the splines and check the OD for a wear groove