Driveshaft U Joint Sizes

68/70Vette

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What are the largest size U Joints that can be used for a 70 Corvette driveshaft?

I purchased a TKO 600 and as part of the package I'll receive a new driveshaft. It's a Keisler TKO 600 kit. After installing the tranny and the differential they want you to measure for the driveshaft length...they tell how to measure, etc....so I did and called them up to order the driveshaft. My differential has a Tom's billet 1350 Yoke so I wanted a 1350 UJoint for the diff end of the driveshft. I asked for a 1350 U-Joint for the tranny slip yoke also. I was told, I could only install a 1310 U-Joint unless I wanted to cut an opening in the tranny tunnel. I didn't say anything, but this made me angry...why did I spend thousands of dollars buying high strength Tom's differential stuff (30/31 spline spindles, tuned differential case, hardened spiders, big half axles, and of course all 1350 U-Joints for the half axles) and $3500 for the 650 ft-lb rated TKO-600 transmission ...only to be told that I had to use a stock relatively weak 1310 U-Joint? One weak link just negates everything.

So....last Friday, I crawled under my 68, it has a TKO 600 and a 1310 U Joint. (It has basically a stock rear driveline with all 1310 U Joints). Sure enough it's a close fit. I estimate the 68's tranny slip yoke 1310 U Joint misses the tunnel by 1/4 to 3/8 of an inch.

So, my number 1 plan is to call back and order a 1350 U Joint for the tranny slip joint, anyhow. But I'm kinda leaning to ordering a 1330 U Joint. I know that the tranny slip yoke for the Richmond 5 speed uses a 1330 U Joint. I had no fit problem with this configuration in a 69 Vette. Also I think the L88 cars had 1330 U Joints. I bought a NOS driveshaft in the mid 70's for, best I can remember an L88. I still have the drive shaft and it's configured for 1330's. So what about ordering a 1330 U joint for the 70 tranny slip yoke? I have a 3.73:1 diff ratio, so the foot pound ratings from my driveshaft U Joints can be rated as 1/3.73 times the ratings of the 1350's??

Any of you running tranny slip yoke U Joints bigger than 1310's?

U Joint sizes:

1310: 3 1/4 inch yoke expanse, 1 1/16 inch cap diameter
1330: 3 5/8 inch yoke expanse, 1 1/16 inch cap diameter
1350: 3 5/8 inch yoke expanse, 1 3/16 inch cap diameter

Thanks
 
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I've had 1330 joints on 68 with a TKO500. It's close on early cars and probably not a big deal to clearance the tunnel.

It is kind of weird that they advertise big HP capability but want you to use the smallest joint.
 
I'll have to get under the 79 to make sure but I "think" I got 1350 Ujoint for the tranny slip yoke and in the rear I needed a bastard joint 1350 to 1310 to fit the diff input yoke ...
 
I've been told the 1330 u-joints are actually weaker than the 1310.
Argggh. Surprising. What is the word for the X part of the U Joint? With a 1330, the X diameter (expanse) is larger, but the diameter of the castings of the X is the same size as a 1310. Maybe this makes it weaker, or at least not any stronger. Thanks!!!
 
I've had 1330 joints on 68 with a TKO500. It's close on early cars and probably not a big deal to clearance the tunnel.

It is kind of weird that they advertise big HP capability but want you to use the smallest joint.

Copy that. Why buy a 650 foot-pound rated tranny for $3500, when they want you to use the dimunitive U-Joints for the factory Muncie??????
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Question: Why did I buy a TKO 600 for my 68 with a basically stock rear end driveline. Answer, because the gear ratios of the TKO appeared to be nearly exactly similar to the Muncie in first, second, third, and fourth gear. With my 3.5:1 rear end in the 68, the TKO 5th gear dropped me down to a ~2000 rpm cruising speed at 70 mph instead of ~3000 rpm with the Muncie. I really like the short shift of the TKO and the ease and feel of shifting. It's certainly nothing like my original Doug Nash 5 speed. I took it our for a first time cruise with my Corvette Club (circa mid 1970) and ended up with a blister in the palm of my hand. The Doug Nash became the Richmond 5 speed of today. I have a Richmond 5 speed tranny and have only dry shifted it. I don't know if the Richmond 5 speed is as smooth as the TKO 600.
 
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I'll have to get under the 79 to make sure but I "think" I got 1350 Ujoint for the tranny slip yoke and in the rear I needed a bastard joint 1350 to 1310 to fit the diff input yoke ...

Thanks, may I ask how you ended up with a 1350 U Joint at the tranny slip joint?

Ok, let's say that for some bizarre reason, I absolutely positively must order a driveshaft with a 1310 on one end and a 1350 on the other end. For a high HP car, the 1310 is going to blow out first. If I order my driveshaft according to Keisler's recommendation, I'll end up with a 1310 at the tranny yoke and a 1350 at the diff yoke. If the 1310 tranny yoke U joint has a catastrophic failure, I'm going to end up with a driveshaft whipping around in the tunnel doing massive damage. If I have a 1350 at the tranny end, and a 1310 at the diff, distraction of the diff 1310 is not going to cause much of a problem. So.. for driveline safety, I think you need the most strength at the tranny yoke, not the diff yoke. .............................

One good thing. If the tranny U Joint fails, the driveshaft will flop violently around destroying a whole lot of stuff, but it won't drop down to the ground level; i.e. no pole vaulting problem. The differential in front of the crossmember prevents this.
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Hope it's not too inconvenient to get under the car. I normally do all my stuff in the back yard concrete and garage. I did check out the 68 TKO 600 clearance in the front driveway and attracted the neighbors. With the 68 jacked up, they were curious. I have a lot of jack stands. My 70 takes up eight jack stands. Four for the original frame and body and four for the new frame. To have a look at my 68, I had to go buy four more jack stands!!!!! I have three floor jacks and a bunch of hydraulic bottle jacks. When push comes to shove, I'm going to get'er up!
 
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I'll take a better look tonight, in the meantime, can you trll from these photos ???

Looks noticeably larger than an inch, so it's probably a 1350. The 1310 and 1330 caps are 1 1/16 and the 1350 cap is 1 3/16.
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Anyhow, just a few minutes ago I ordered a driveshaft with all 1350 U joints. If I have to notch the tunnel a little bit, that'll be OK. Sometime in the mid 1970's, Corvette's came with rubber frame to body bushings/spacers instead of solid auminum bushings/spacers. The rubber bushings lifted the body off the frame a little bit more and this would create more room in the transmission tunnel. I guess I have an option of going for the rubber to create more room, but I probably won't. .
 
I've been told the 1330 u-joints are actually weaker than the 1310.
Argggh. Surprising. What is the word for the X part of the U Joint? With a 1330, the X diameter (expanse) is larger, but the diameter of the castings of the X is the same size as a 1310. Maybe this makes it weaker, or at least not any stronger. Thanks!!!

Mike Dyer is the source of my info. Maybe he'll chime in here. He does know his chit.
 
I'll take a better look tonight, in the meantime, can you trll from these photos ???

Looks noticeably larger than an inch, so it's probably a 1350. The 1310 and 1330 caps are 1 1/16 and the 1350 cap is 1 3/16.
...................

Anyhow, just a few minutes ago I ordered a driveshaft with all 1350 U joints. If I have to notch the tunnel a little bit, that'll be OK. Sometime in the mid 1970's, Corvette's came with rubber frame to body bushings/spacers instead of solid auminum bushings/spacers. The rubber bushings lifted the body off the frame a little bit more and this would create more room in the transmission tunnel. I guess I have an option of going for the rubber to create more room, but I probably won't. .

just found the box for my rear Ujoint, it's a 1330 to 1310 bastard joint. The front joint seems to be 1350 and it's a very tight fit to the tunnel...I hit it a few times with a hammer to get clearance , actually forgot about that :)
 
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