98 v70 awd, bolts for driveshaft balancing

wuttheheeck · Post by **wuttheheeck** » 18 Oct 2014, 12:29

Hey all. I took out my drive/propeller shaft to replace the center bearing. As I'm reinstalling it I noticed that one of the bolts is longer. I know this is to balance out the vibrations. My question to you is how to I know where to reinstall said longer bolt? I'de like to avoid taking it to a shop but it might not be worth my time to try each location and then test driving.

Thanks!!

Post by **rmmagow** » 18 Oct 2014, 12:50

Give colorado driveshaft a call. I sort of remember reading someplace that that longer bolt really doesn't do much for balance. I think if you were to order bolts, you'd get them all one size. They should be able to give you a definitive answer.

wuttheheeck · Post by **wuttheheeck** » 18 Oct 2014, 12:59

If that were the case I should be able to pick one up at the hardware/auto store. Ill see what they have to say.

instarx · Post by **instarx** » 18 Oct 2014, 14:03

wuttheheeck wrote:Hey all. I took out my drive/propeller shaft to replace the center bearing. As I'm reinstalling it I noticed that one of the bolts is longer. I know this is to balance out the vibrations. My question to you is how to I know where to reinstall said longer bolt? I'de like to avoid taking it to a shop but it might not be worth my time to try each location and then test driving.

Thanks!!

I would be amazed if you could tell any difference no matter where you put that bolt. I don't think its possible for those bolts to do much. First, the drive shaft doesn't turn that fast; and second, the bolts are only scribing a circle about three inches in diameter so none of them have much angular momentum. Third, the difference in the weight of the bolts is small. If the shaft were a high speed shaft it might matter, but it isn't. The only reason I can think that Volvo even does it is that it must be ridiculously easy to balance the shaft to a gnat's whisker when it is being balanced for the first time, so they do it.

Ozark Hillbilly · Post by **Ozark Hillbilly** » 18 Oct 2014, 15:31

I'll bet a cyber nickle that the factory didn't install an odd sized bolt with the intention of balancing a drive shaft..

Post by **scot850** » 18 Oct 2014, 20:17

I wouldn't worry too much about it. I have removed and replace prop-shafts on RWD and AWD Volvos and never worried about this. I asked the dealer mechanics and they had never heard about this. Volvo does (or did have) different part numbers for bolts, and there is a process for 'balancing' the system. But to be blunt, I personally think it is overkill. On a 3" diameter prop-shaft, the issue is not significant. It is more important to have a well balanced shaft with good U/J's, and center bearing/support.

I'm sure someone will come back and say I'm wrong, but I fitted a 1997 AWD prop into a 1998 V70XC and it was still running smooth after 4 years when I sold it. I still have the re-built unit in my garage as I never needed it.

Neil.