Unless the car has something like a Dana rear (some years do), all you really need to do is count the number of bolts on the rear of the housing.  It should be either 10- or 12-bolts.  You often hear Chevy rears referred to as 10- or 12-bolt rears. 

 

I think that after 1979, GM went to the Dana style.

The 8.5, or 8.75, etc., refers to the diameter of the ring gear in the diff. Different gear ratios would result in needing a different size carrier, and that's where the size designation comes in.

How many teeth are on the yoke?....HUH?
What the heck does that mean? There are no "teeth" on the yoke, as far as I know...perhaps you are referring to the splines?
I've never heard that question asked, whether for teeth OR splines...I'm curious now as to why you are axing?

[QUOTE=Adams' Apple]The 8.5, or 8.75, etc., refers to the diameter of the ring gear in the diff. Different gear ratios would result in needing a different size carrier, and that's where the size designation comes in.

How many teeth are on the yoke?....HUH?
What the heck does that mean? There are no "teeth" on the yoke, as far as I know...perhaps you are referring to the splines?
I've never heard that question asked, whether for teeth OR splines...I'm curious now as to why you are axing?[/QUOTE] I'm upgrading the yoke in the TH400 with a Hughes billit (1350 universal) style yoke (32 teeth). I am thinking of up-grading the drive shaft to a Chromemoly 3", which has a 1350 universal at both ends. The rear yoke is a 1330 style universal. I know that I can purchase a 1350/1330 combination universal that connect the drive shaft to the rear end yoke. The weakest link would be the 1330 at the yoke.

Larry, the truth of it all "people have always told me that I like to over-do things" I really don't think that's possible. But I do HATE, being late for Church on Sundays..........the Priests don't like it either! 

[QUOTE=corvette440hp]I'm refering to my vette's differential (of course). The question is on the "74", what is the rear axle called........GM 8.5, 8.75 or what? Next the pinion flange (yoke) has the 4 1/4" width to except the universal. I know that the earlier years used a shorter width. The new question is: how many teeth are on the yoke? Thanks for your attention on this. [/QUOTE] Here are the answers to my questions (if anyone is interested):       1. The rear axle is called a GM 8.2.      2. It's a 10 bolt (ring gear bolt count.)      3. It's a Series 3 Eaton Posi unit, which means it can go from 3.90, to 3.73, etc.     4. A series 4 carrier (Eaton Posi) will house 4.11 and 4.56 gears.     5. The pinion yoke spline count is 25.     6. The side yokes (also at times called stub shafts) are a 17 spline count......that connects to the 1350 universals on the half shafts. Hopefully this will help any GEARHEADS that are interested in this.     corvette440hp2008-04-16 14:55:41

If you are going inside to build up the rear check out tomsdifferentials.com He has some bullitproof rear endstuff.From mild to wild. If you are going to push some horepower or just want to repair/strengthen the diff check him out. Can you say 12" ring gears in the diff? How about 1480 universals with their 3 1/2" axles. I put on his larger bearing cap to help hold the weakest side (left)of the C-3's diff. It uses 1/2" bolts vs 7/16" and the cap is a solid steel billet piece. It helps hold the side where the ring gear puts the most stress on the rear. No fear. They love to talk tech too.custom762008-04-18 14:36:10

[QUOTE=custom76] If you are going inside to build up the rear check out tomsdifferentials.com He has some bullitproof rear endstuff.From mild to wild. If you are going to push some horepower or just want to repair/strengthen the diff check him out. Can you say 12" ring gears in the diff? How about 1480 universals with their 3 1/2" axles. I put on his larger bearing cap to help hold the weakest side (left)of the C-3's diff. It uses 1/2" bolts vs 7/16" and the cap is a solid steel billet piece. It helps hold the side where the ring gear puts the most stress on the rear. No fear. They love to talk tech too.[/QUOTE] Thank you, You are entirely correct............Toms is the place. I didn't even know about them until I sent everything out to Duntov in Texas. They put in the 3.70 Richmond Gear Set. Loaded everything on the newer Eaton Posi Carrier. I aslo went with the air craft quality hardened side yokes that are capable of 700 hp. I also had the gears REM coated. Tom's will propable support 1,200 hp. You certainly sound like a real gearhead................thank you......there might be a few of us out there............