I removed the driveshaft from my 85 to replace the u-joints and noticed that it has what looks like a little harmonic balancer on the front of it on the yoke that fits into the transmission. It appears that the outer ring of that balancer has slipped back about 1/4 inch or so and now I'm worried that it has caused the driveshaft to become out of balance. The car has a relatively minor high frequency vibration at highway speed which made me think that the u-joints were going bad which is why I removed the driveshaft to replace the u-joints. The front u-joint feels like it needs to be replaced so I'm glad that I removed the driveshaft to do the job but now I'm wondering if it will still vibrate because of that balancer ring that has slipped. I went on eBay to try to find another driveshaft with a good balancer on it and all I can find is only one driveshaft that will fit a c4 with a 4+3 stick shift trans and it doesn't have the balancer on it at all, it has a regular old yoke on it. I have a feeling that the yoke on that one was replaced with a standard yoke because it's balancer probably went bad too. There's tons of automatic transmission diveshafts for sale and a few 6 speed trans driveshafts for sale on ebay but only one for a car with a 4+3 and I think it is probably out of balance if indeed it's yoke was replaced with a standard yoke. Will a driveshaft from an automatic car or a 6 speed car work in a car with a 4+3 or are the lengths and/or spline count on the yokes different? Should I just put the new u-joints in the driveshaft that I have and hope for the best, hope its still in balance with the slipped ring on it's balancer? Is that balancer thing even needed? Is it really for balancing purposes or is it for something else? What should I do?

 

Many/most just remove the ring(dampener) and 'drive-on'. If you've no issues with the finish of the slip-yoke and leaks then I'd consider that. Generally no one balances the shaft after they remove it but if you've suspected issues now would be the time since you're doing 2 u-joints.

There should be drive-line shops in the area that can accommodate you.

Replacement slip-yokes less the dampener have been used for years.

 

Thanks for the reply. If that balancer looking thing on the front yoke isn't for balancing then my guess is that it's some sort of vibration dampener. I'd like to hear from some people that removed it to see if they noticed any vibrations after removing it. Chevy put it there for some reason or another which is why I'm kind of hesitant to remove it. The way it is right now is probably causing some vibration though with the ring having slipped back and all. I'll probably remove the ring (or maybe try to press it forward back into position?) and put the new u-joints in and see how it drives afterward but until I know for sure that removing it won't cause any balance or vibration issues I'll be wondering if it was the right thing to do if I remove it. Does anybody sell new driveshaft yokes with the balancer/dampener on it? If so please post a link to where it can be bought.

 

NO THEY DON'T - spend the money, do the u-joints and balance. You don't even know where the 'ring' needs to be positioned. Any attempt to relocate will further destroy the bond.

 

Yeah I'm kinda leery on trying to push the ring back into position but I figured I'd mention it anyway. If it's a common practice to just remove the ring or replace the yoke with a standard yoke and call it a day I'd like to hear from some people that did that and get thier input on it.

 

I agree. The DAMPER (it's not a "balancer", since it's neutral balanced) is an unnecessary device that some engineer must have calculated a need for...for some NVH criteria that none of us will ever notice or car about.

I can't for the life of me, even figure what the damper is supposed to be damping. Rotational velocity at either end of the shaft should be constant. Ditch the ring and move one.

 

I removed mine and the car still runs.

 

I haven't installed the u-joints yet, I just got the driveshaft out last night. As for the ring, there aren't any drill holes, scallops, or weights on it to suggest that its a balanced component, my guess at this point is that it's strictly a vibration dampener. I still wonder why the factory installed it though, you would think that a balanced driveshaft wouldn't vibrate and therefore wouldn't need a vibration dampener.

 

You're right; a balanced drive shaft won't vibrate...it's balanced. The damper is not intended to "balance" vibrations. It's intended to dampen torsional vibrations; the accelerating and decelerating of a rotating shaft. You'll not the similarity in it's design, to the harmonic damper on the front of the engine/crank shaft. The function of that damper is to quell the harmonic twisting that the crankshaft experiences as it's "hit" by power pulses, across it's length -the crank twists like a torsion bar spring, and that twisting can start to "bounce" back and forth, like an uncontrolled spring. The harmonic damper on the front mitigates that (or tries to).

There shouldn't be any meaningful torsional vibrations -or change in rotational speed of the trans output shaft as it rotates, that would need damping.

 

Well I would hope it still runs, lol, but did you notice any vibrations or anything after you removed it?

 

Everything you're saying makes perfect sense so I wonder why the factory put it there, what were they trying to achieve with it?

 

Nope. Knock it off the rest of the way and you'll be fine.

 

I wonder the same thing. some car have 'em...some don't. I think it was a waste of money and weight.

 

GM - FOMOCO - CMC/JEEP > everyone has used these. FOMOCO until 2000 or maybe later. I always assumed that it's intention was to dampen 'entire drive-line' issues and NOT just the drive-shaft.

I always thought that at speed in an overdrive situation and reduced RPM required there would always be related 'harmonic' issues. The axle ratio choices made for convenience and economy likely added to it's use. Not wanting to deal with customer complaints it very likely served a 'purpose' for new builds.

I believe that maybe the early Monza V8 that didn't have a dampener it was added as a weight to the transmission mount bracket. My sister had one of these and I recall issues for her.

Dampeners of some sort are added to almost all late model RWD cars I believe.

 

IDK. My wife's CTS-V doesn't have one...but my Duramax does.

Engine pulses are dampened by the clutch damping springs or the converter clutches damping springs. The DS damper seems to me like it would only exist to dampen drive line torsion...which it's on the wrong side of the joint to do that, IMO. It would be nice to have an engineer who could explain what torsional inputs it's there to dampen, and why is it on some cars and not on others.

 

What year CTS-V? Doesn't it have a 'coupling' which actually amounts to a dampener I'd think?

Regardless the OP needs to remove and 'drive-on' - if he's sealing issues because of slip-yoke finish replace and drive-on. OP mentions issues that he thought drive-line related. Do u-joints and a balance 'once' and be done. A C4 drive-shaft most wouldn't like to do repetitively trying to resolve such a simple issue. $$$'s spent for the balance is a once and done no need to go behind yourself.

 

I pressed the ring off of the dampener (it was so loose I almost could have removed it by hand), installed the new u-joints, and took it out for a drive. Its much better than it was, it doesn't vibrate at highway speeds anymore.

 

'05. It has a rubber coupler. IDK what the coupler would dampen, either.

 

Good to see the OP 'remove and drove on' - He'll know soon enough if it's a done deal for him or not.

The CTS-V has had 'coupling vibration' issues mentioned for years. There's been various attempts at a 'fix' but years ago I believe a friend used this. I don't know if this specifically but very similar if it wasn't

This was from '12 and I'm sure you're likely a forum member so you should be able to see the snapshots.

http://www.cadillacforums.com/forums...c-install.html

You need to read the 'entire' thread. The friend never mentioned issues and I don't know whose 'kit' specifically but I'll ask if he recalls.

 

Ha....my wife's V vibrates above 75 and it's the driveshaft. That thing is a heavy, dumb piece of ****. The center bearing started to go out; make noise...can't replace it....the DS assy is ~$1200. F-that, I said. I took my "hypodermic" grease needle and shot grease through the seal and shut it up over a year ago. It's still working. It's vibe'd since we got the car though (@28k miles). Irritating. I'll read the whole thread tonight. Thanks for the link.