Driveshaft Balance

[TJRON]

I'm setting up a new differential and I thought it might be a good idea to have my driveshaft balanced to eliminate any vibes that might come from there. If I have rear vibes now, I will know it's probably do to my set up.
Anyhow, My friend works in a drive line shop so he brought in in for me and got it done for $20. He said the balancer spent damn near an hour on it and I can't believe the amount of weight that had to be added in a different spot than the old weights were. It was tweeked a bit from hitting something but I didn't know that.
I was told on most of the SYE kits they have installed, hardly any of the driveshafts are close to being balanced. They use nothing but the Terra kits 'cause they are the closest.
It's also my understanding as soon as I bump it, it will be off balance again. Does that seem right that it can get off balance with just a scrape or two? Oh well, at least I will know how it's suppose to be!
Ron

I like the way my Jeep is now..... I'd just like it, well, a little higher off the ground with more ground clearance!

[BMRisko]

Hmm, I'm wondering if an out-of-balance shaft could be the cause of my highway vibes. I suspect its u-joints, but the out-of-balance shaft does make sense. I didn't know they could become out-of-balanced so easily. I know my pinion angle is pretty dead on, but the front pinion seal is failing , so maybe some vibes are causing it to wear away. Oops, kinda got off-topic...

'93 ZJ, V8, 5.5", 33" SSRs, ARB, etc.

[TJRON]

I remember reading that after re-gearing, the drive shaft is turning like 80mph at 60mph and any imbalance will be amplified. Whack it a few times and things get worse.

I like the way my Jeep is now..... I'd just like it, well, a little higher off the ground with more ground clearance!

[Stu Olson]

Ron,

I don't think I can agree with your regearing statement, assuming one followed through with the entire process.

With stock tires and gearing, you are turning XXX RPMs at the drive shaft on the highway.

So...let's put 4.56 gears in the diff. Yes, you will now be turning XXX + YY RPMs with the drive shaft in order to maintain the previous noted highway speed (this kind of goes with your doing 80 to get 60 MPH statement).

But...we usually (should?) add larger tires to match up with our gearing so that our highway driveshaft RPMs are now back in the XXX range.

Granted, the above assumes we are matching tires and gears to obtain something close to a factory configuration. A slight change in tire or gear size will can certainly put your RPMs higher up (or down) the scale for a set highway speed....but more than likely not at the 80 MPH to 60 MPH difference.

In the near future I'm going to build a thingy for the back of my Jeep and carry more stuff.
http://www.stu-offroad.com

[TJRON]

Smart Ass!



You are right of course!
Thanks for the much needed help. I'll think harder next time.
Ron

I like the way my Jeep is now..... I'd just like it, well, a little higher off the ground with more ground clearance!

[Robert J. Yates]

I had to have my brand new custom CV rear driveshaft re-balanced a couple of months after I installed it. It wasn't "bumped" either, just badly balanced when it was delivered to me. As a result, I only deal with a local guy who is 10 minutes away from my houe and will let me watch the work. I no longer trust kits or folks that have to ship driveshafts.

98 TJ Sport
D44ARB/D30Detroit/Teralow/35" MTr's

[Jeff Weston]

My CV shaft supplied with my RE 4.5" kit was out of balance from the get-go. I had it re-balanced at a driveshaft shop right next to my office for $40. Balancing it still didn't fix the fact that the RE hack & tap yoke had improper machined splines so I had BAD vibes.

Jeff