Driveshaft clock or no?

[SSC's76]

Changed my U-joints toady, dident bother to mark the shaft as far as I know it doesent need to be clocked in any certain posistion. I ask because there is a slight bit of vibration now that wasent noticeable even with the two screwed up U-joints.

Edit: This is the 100000000 time its been out so I couldent have been lucky every time but now right? BTW U-Joints went in nice no binding whatsoever.

[87 STEPPER]

You should always do it if you can cuz the shaft has small balance weights spot welded to it and its balanced in that position.

But since you r&r the u joints and there not exactlly mfg. to close tollerances as far as weight go's so it may not matter anyways if you did clock it .

You may have to take it to a drive line shop for ballancing.

[1FaastC10]

u joints shouldnt make that much of a difference in the weight. my guess would be that your rear joint is favoring one side of the yoke more than the other. while it wont bind like that, it will definitely give you a vibration. get it checked out ASAP, because an imbalanced driveshaft will eat your pinion bearings in a very short time.

[SSC's76]

I re-checked it an hour ago, everything is set in correctly swaped the yoke around, dident make any difference. Checked for excessive heat too since that would be an indicator or side load or a faulty/damaged roller bearing, nothing found. I've actually been debating to spend the $80 to have the DS ballanced but Ive been holding off in hopes of finding an aluminum replacment.

[Tom]

Originally Posted by 87 STEPPER

You should always do it if you can cuz the shaft has small balance weights spot welded to it and its balanced in that position.

I don't get it. Its balanced to spin, not to sit in one spacific spot. And the position of the shaft is constantly spinning on the machine which dosen't use the rear end or the tranny to help balance, so why would the position of the weight matter at all? As long as the weight itself isen't moved on the shaft then it shouldn't matter one little bit which position the shaft is put back in...

[87 STEPPER]

What you say sounds good!

But the factory GM maintenance manual tells you to mark/clock the position of it when it is removed so it can be put back in the original positoin.

It probably wouldn't matter any ways as old of a truck that he has who knows how many times its been removed and replaced.

Im lucky i bought my truck new and i clocked it with a center punch so i'll never have a problem knowing what way it need to be weather it makes a differance or not.

[SSC's76]

Yea, my truck was bought new too, too bad it was a couple years before I was born.

Anyway it happened, drove out to the county to help my brother drove back into town went back to the county then was heading home. 70MPH BHHHHHHHHHRRRRRWHHHAAAAAAAAAAAAAAATTTTTTTTTTTT. The front u joint snaped in half!!! It's still in the yoke in sevral peices must have had a hairline crack that would expand under load to cause the vibe. Now my truck is stuck 8 miles away. At least I made it to the motorsports park entrance where I shouldent get a ticket. I just hope nothing got too chewed up or it will be tuesday before I'm able to get another DS.

[KShortell]

Originally Posted by SSC's76

1976 C10 SWB Med FMB

You can't get it wrong on a 2WD driveshaft. GM keyed the slip yokes to only go on one way. The 4WD driveshafts didn't have this and you do have to pay attention in that case.

But, since you've got a 4x2, I'd have to say to start looking elsewhere than the U-joints.

Good luck!

[SSC's76]

Originally Posted by KShortell

You can't get it wrong on a 2WD driveshaft. GM keyed the slip yokes to only go on one way. The 4WD driveshafts didn't have this and you do have to pay attention in that case.

But, since you've got a 4x2, I'd have to say to start looking elsewhere than the U-joints.

Good luck!

Yea but if you read the post above it was the u-joint, it snaped in two.
I was able to fix it sat night. I took the driveshaft out ran it to the shop put another U-joint in went back and got it going. I ran it up to 4k in 3rd a tad over 100 with no vibration at all now.

To give an idea of how bad it was vibrating all the header bolts came loose. I've never had to tighten these ARP bolts since they were installed 3 years ago until this happened.