So I'm in the middle of rebuilding my 12-bolt and while I was doing it I wanted to plan ahead for putting in a TKO600 (in a year or two). The engine in my 68 was dyno'd at about 450 hp. I won't be using slicks. Should I pay $120 for a new 1330 or 1350 yoke on the rearend now that I've got it torn apart or is my stock 1310 yoke going to be good enough? I can buy the 1310 to 1330 U-joints if I upgrade the yoke. What size u-joints do they typically use on the slip yoke side of the driveline? Thanks.

Yes I believe you should buy them. But I know of guys running worse in the 9's on 10 bolt rear ends with no problems. It's cheap insurance.

Jim

hmmm, when I did mine, I was told that a 1330 yoke for a GM rear did not exist.

I searched anyway, but could not find one.

As I didn't want to spend the bucks to change out my 1330 trans yoke to a 1350, and I didn't want my rear to be stronger than my front (see JimM's "weakest link" theory!) I stayed with the 1310 rear joint.

Yep, Tom's Differential's makes billet GM 12-bolt yokes for 1310, 1330, 3R (hair bigger than 1330), and 1350. Doesn't look like they have the 1330 for the 10-bolt, but they do have the 3R and 1350 yokes.

Yeah, I was told not to make the rear u-joint stronger than the front one.

Bryan, just a thought but if your planning on changing to a TKO 600 why not wait till then to change anything in the drive line. The reason I say this is you will need to either have your driveline shortened or get a new one. I had Denny's driveline make a nitros ready driveline with the 1350 joints and the driveline is good for around 900HP and Denny's drivelines does some of the best balancing on drivelines around. When your all done you have a stout set up.

The reason I wanted to do it now is I could put the bigger yoke on and still use the old driveline by using a combo u-joint (1310 to 1330 or whatever). I didn't want to have to redo the crush sleeve and everything later on when I went to a new yoke with the new tranny. I've got the 12-bolt torn apart now.

OK, here is some infor from Classic Chevy 5 speed that may help in you decision.

Choosing the proper driveshaft for your application
There are several factors that you need to consider when selecting the best driveshaft/slip yoke/ujoint combination – especially if you have a high horsepower motor or if you are using slick tires, nitrous or other power adders (superchargers, blowers, etc.). The following are general guidelines for driveshaft selection:
Generally speaking, if your car is mostly street driven (occasional street fun and mild strip action), has street tires (not slicks), and is under 500 HP, the stock size driveshaft (3” steel) and stock size rear ujoint (1310) will probably be adequate.
•If you are above 500HP with street tires, you should consider a 3.5” diameter driveshaft and the larger 1330 ujoint and 1330 rear pinion yoke.
•If your motor is producing more than 500HP and you have slicks, or if you are using a blower or nitrous, you should consider a 3.5” or 4” diameter shaft with 1350 ujoints. This will require upgrading to a 1350 pinion yoke to match the larger ujoints.
•Some people like to use aluminum driveshafts instead of steel. The aluminum driveshaft costs a bit more money but offers the following benefits: same strength as steel, 30%-40% lighter than steel, and can absorb vibrations better. If weight savings is not an issue a steel driveshaft should be adequate.

If you're going through the trouble, go ahead with the 1350's. 1330's have the same sized caps as a 1310 but have the size (length) of the 1350. 1330 is a bit of an oddball and your yoke options may be limited with that u-joint.

FWIW...

Keep in mind , you will be using the C6 slip yoke with your TKO. Normally comes with the Kit.

So what size u-joints does the C6 slip yoke have? Thanks.

So what size u-joints does the C6 slip yoke have? Thanks.

1330. That's why I ended up with 1330 in front and 1310 in back, didn't want to replace that yoke.

I went with a billet yoke and 1350 U Joints. I figured why not go as bullet proof as possible. Got them from Denny's and he shipped them the same day I called. Once the transmission from the real Art Carr is here and we can make measurements Denny's will also make me a drive shaft. He was good to work with over the phone and is dedicated to making sure people get what they need as far as a robust design.