I did a search recently on LT1 Tech regarding a driveshaft vibration problem I've been having since I installed my 4.10:1 ratio rear end, and learned that evidently when GM balances driveshafts from the factory, they balance both the driveshaft assembly with the differential pinion "yolk".

Now keep in mind that the way I got 4.10 gears in my car was by buying the whole rear end assembly which already had the 4.10 gear set in it, from a local board member. All I did then was to just "swap out" the whole rear end/axle assembly. I thought that the vibration problem was certainly partly due to the fact that my old driveshaft was, of course, turning many more RPM's at any given MPH just due to the lower (4.10 vs 3.42)gears. I would get a real "nasty" vibration starting at about 75/80 MPH and getting MUCH worse up through 90/95 MPH, I could even feel it through my clutch pedal!!! I was just about to "bite the bullet" and get an aluminun LS1 driveshaft, when I did the search, and found out that little piece of info regarding GM balancing the driveshaft with the yolk. Since I also had a different yolk now in my car, due to the whole axle being swapped, I thought I'd try just UNBOLTING MY DRIVESHAFT FROM THE YOLK, AND REVERSING IT 180 DEGREES. Wow, my vibration problem is GONE!!!! The car is now "rock solid" and totally smooth at any speed.

If ANY of you are having vibration problems with you driveline, the FIRST thing I would do would be to reverse the driveshaft to yolk coupling. It's QUICK to do, totally FREE to do, and at least in my case, IT WORKED GREAT!!!!

 

Where did you find this information about GM balancing the driveshaft with the differential pinion yoke?

Not trying to flame you, but I think you mean they balance the driveshaft with the transmission yoke.

Either way, reinstalling the driveshaft 180 degrees relative to the pinion is a good, free way to try to reduce vibration.

Another trick is to use a couple of hose clamps on either end of the DS, to help balance the total rotating assembly. This is a trial and error process, but works. Mount a couple of clamps on the diff. end of the driveshaft, then drive. if no improvement, rotate them 90 degrees. do this 4 times; if no improvement, move them to the front of the DS, and repeat.

 

AAAAAAAAAAAAAAHHHHHHHH Yes That thought Had crossed my mind before. I am gunna drive mine pretty fast and if I get the vibration then I will do that MOD!!! (but then if GM does it right why would it vibrate in the first place?) mmmmm

I will try it if I neet to.

thanks bro.

**There is nothing faster and cheaper than a 1/4 mile pass down a steep hill!!! (grin)

 

why does that matter, rotating it 180 degrees??? I just don't understand what that has to do with it?? Can somebody explain it to me??

I have a 94'z w/A4 with a BAD vibration from 65mph-up....I just thought it was my poly tranny mount, or my DS was just bent a little.

 

I did that in a friend on mines 96'Z28 M6 and I reduced the vibration quite a bit.I seem that the 6 speed cars have more vibration than the auto do.

 

that does not work on all cars, you got lucky

 

If there is excess weight on one side of the driveshaft and on the same side on the yoke, that can cause vibration. If you change the phase 180º between the two, this will act to offset and counterbalance them.

Even a little bend in a driveshaft will cause vibration.

 

PGR, I got the info about GM balancing the driveshaft with the DIFFERENTIAL yolk, right here on LT1 Tech I did several searchs using keywords like: "Driveshaft Vibration Problem", "Driveshaft Balance Problem", "Drive Shaft Vibration", etc. To show you how widespread this problem is, when you do these searches, you will literally get 100's of threads discussing driveshaft vibration problems of some sort. I can't remember the EXACT thread I saw this info in, but if you want to search LT1 Tech again, I can assure you it's in there somewhere. I also am positive in the fact that this thread was talking about the DIFFERENTIAL PINION yolk, because the "transmission" yolk is attached to the front of the driveshaft with the front u-joint, and I personally ALWAYS assumed that the driveshaft was balanced with the TRANSMISSION yolk AND front and rear u-joints already assembled to it. It was indeed the very fact that this thread was TELLING me that the "differential" yolk was ALSO part of the balanced assembly; that I even gave a thought to reversing the driveshaft 180 degrees Also keep in mind that in my case, I did NOT replace either the front or rear u-joints or transmission yolk on my driveshaft assembly when I did the axle swap. So really the ONLY thing that did change in my case was the introduction of a different pinion yolk, which was already on the 4.10 axle.

flyinZ, shoebox is exactly right! If, for example, the pinion yolk was manufactured 1 ounce "off", and the driveshaft was then balanced 1 ounce "on" to compensate for the yolk inbalance and then mated to it; then if you disassembled the two parts and REVERSED them, they would now be "unbalanced" by 2 ounces. You get it? (Rather then canceling each other out, they would instead "add up" to cause an unbalanced condition).

Guys, I'm definately NOT trying to flame anyone here I'm just saying that if the differential yolk was NOT part of the original balanced driveshaft assembly as it came from GM, then how could my vibration problem have been solved by just flipping the driveshaft around???

 

GM does make mistakes we are all human, doesnt make us feel any better i know. GM may have balanced the driveshaft with the yoke on most of the cars, but GM either "forgot" or didnt even bother to balance some driveshafts at all. 94 and up Fbody cars have some freaks in there ranks with an unbalanced shaft. Gm has service bullitin on it call a dealer and see if you cars may be one of them.

 

I had the infamous vibe shaft problem, and considered going to the aluminum shaft but heard of people shattering these things on hard lauches, they aren't NHRA legal when you get below certain times, vibrations from alum. shaft, etc. So, I took my good old steel shaft and had it professionaly balanced. While at the shop, I spoke to the tech. who informed me that GM drive shafts are notoriously unbalanced. They are OK for mom and pop's grocery getter, but otherwise not.

He felt that my shaft was actually in very good balance considering it was a GM shaft but it was a bit off. Runout, was perfectly acceptable. For the princely sum of 50$ Cdn. my shaft is as smooth as silk now. A very worthwhile investment.

 

Rotating the driveshaft 180 degrees relative to the pinion can also add or subtract on the tolerance stack-up of the assembly. The driveshaft may have too much run-out mounted one way, and the runout may be less mounted the other. Mass combined with runout = mass imbalance.

Maybe GM did balance these shafts with the pinion yoke attached, but they either did a lousy job, or they didn't do all of them.

BTW, my '94 had a vibrating drive shaft. The dealership sent the shaft out to a local shop and had it balanced. It made no difference. The guy at the DS shop said the balance was fine to begin with. A year later, a TSB came ot that specified the replacement of the transmission yoke/damper assy, apparently many were machine out of spec. Dealership replaced the assy, 90% of the vibration dissappeared.

At 178k miles, I doubt I'll spend any more money to improve the vibration further with a AL DS, etc.