Just as the title says. Not sure where to begin. It was all fairly easy and straight forward, but now got a bad vibration starting around 30mph. I took it it up to 50 and it smoothed out a bit, but it's parked for now. I got both discs from Rockauto and they had the OEM part # on them. When I first noticed the vibration I put it back on the lift removed and checked all the bolts reinstalled with no change...

 

Check the old ones and see if the phasing is correct. You could have swapped the position of the drive shafts relative to one and another. You should always mark parts when taking them off so that you can go back home as it were. Woody

 

what he said... a simple felt marker can go a long way....

 

Yes, I know. It was very stupid of me. I got to talking to my friend and did not index either end, and I'm always so **** about doing that. I feel very stupid right now. How can I check them, please? Are there any marks to look for?

 

Just me but Id look for undercoat, overspray, of rust stains that may assist you.

Failing that, Id mark the shafts and attempt to rotate the shafts 1/3 at a time, you have a 2 out of 3 chance of getting it right the first time.

Your lost and alone in the woods. What do you do. Nothing, sit down and think where you are now, and record any steps you plan on taking.

Id number the shafts and use different numbers front and back .........1-1, 1-2, 1-3 and 2-1, 2-2, and 2-3 so you know where it all goes ( the bolt holes and shaft ears ).

All you did was replace the rubber doobies, should be repairable without too much work IF YOU HAVE A LIFT.

Let us know how your doing.........Woody OH make notes so you can review your activities

OH yes you should spin the wheels to see how the shafts move, engine off, take it out of gear before raising the car ON A LIFT

 

Well, that's what I was planning to do. Index rear 1 bolt, then 1 bolt, then front 1 and repeat rear etc till I find the sweet spot. Hoped maybe there was some markings. Yes, I really should have marked it, but would have thought it would all be better balanced. Also, find it very odd that there is only 1 u-joint in the shaft and it doesn't't cause problems. Being an IRS, the discs and u-joint seems overkill. Still unsure why the 2-piece for such a little car...

Oh, well. Guess I'll be driving the wife's luxo-barge while I work it out. That puts her in my old K5 which she likes anyway. I'll keep you guys posted.

I can get to the rear disc without a lift, and I can head back to my buddy's house for the front.

Thanks...

 

Well, I rotated the rear disc one bolt. Drives much better, but still a bit of a vibration. Exhaust was too hot to be messing with another turn. I'll try again tomorrow. Surprisingly, I didn't even have to jack it up to get to it... Hope one more third turn does it.

 

did you use the same rock auto part for both the front and rear?
i dug into it a few weeks ago, the fronts and rears are different according to mercedes and they are also differnt from the s/c to n/a cars. i assume rock auto has the n/a disc listed for the srt6. i have not had a rockauto disc in my hand to confirm it though.

 

Yes, I used the same disc front and back. Both OE discs had the same part number that was marked on the new discs.

 

Did you make sure the steel bushings that stick out of the rubber disc face and fit into the yoke countersinks?

 

Yes, all the bushings are engaged with their respective yoke.

I turned the rear disc another bolt last night with little if any change, then moved to the front, again no apparent change. I'll move back to the rear disc again tonight. I figure I've tried four of the nine combinations. I just hope one of them works. If not, I guess I'll put the originals back in, and see what happens. I've found they're not hard to get to without a lift. Helps to have an assistant though to apply the brake...

 

Can you rule out rear drive shaft misalignment? Both drive shafts should be in almost perfect alignment. The disks won't perform well at more than 1 degree angle. I'm guessing you are getting the vibration now cuz the new disc is stiffer and has less give than the old one

 

I respectfully disagree, the flex disc is in there for flex.

Have you laid eyes on the carrier bearing in the center of the driveshaft, ROB had a bad one long ago and had odd issues, . . . .with the car that is.

Woody

 

Well, starting to suspect carrier bearing. It would appear there is a rubber bushing surrounding it, which seems a bit odd, but then so does everything about this driveshaft setup. When I spin the driveshaft very slow I can see a little radial movement in the bearing. Seems odd that indexing the shaft would make it better. The vibe is just almost gone... Almost... Guess I'll be looking for a new bearing. Hope it's not ungodly expensive or hard to find.

 

Well, I "think" I found it... Got to thinking about the carrier bearing issue, and what it was actually doing and realized if it were the bearing it wouldn't be "wobbling" in the way that it was. So, decided to just pull the discs and have a look. Pulled the front one first, since that seemed more logical based on the motion of the bearing. Took it over to a flat sheet of steel. One side all three sleeves sit nice and flush, the other side all three angle out, so only the inner edge touched the steel plate. Then I realized that when installing the second and third bolts were a bit difficult to install, but I thought this is a rubber disc, it will give a little. Bad idea.

Apparently none of the sleeves seated fully in the trans yoke, which is the hardest to see, because of the trans cross member. This caused them to shave a bit of material off the "inside" OD of each sleeve. However, since the out edge was somewhat seated, they appeared correct from looking around the cross member.

So, I will be putting the old discs back on tomorrow, and contacting rockauto. Hoping I can send both discs back, and get better quality elsewhere. If not, I've learned an $80 plus shipping lesson.

BTW, the original front disc looks a lot better than the original rear disc. The front doesn't appear to have any cracks, just the chalky rough surface texture. The cracks in the rear aren't very big. I'll take some pix before re-installing. I think they'll be okay until I can get another set.

 

U might be right about inferior quality. I just recalled that when I replaced my disc, the bolts weren't quiet the same length. Check your bolts. Using a caliper and a kitchen scale, I ground the differences. It's real easy to loosen the hanger bearing and move it so the shaft is in a better alignment. Doing these two tasks will reduce vibration, seriously

 

Yes, there were three shorter bolts, but I spaced them out equally. The disc is not going back on my car. If Rockauto won't take it back, I guess I'll trash it. The rear one seems okay, so if they won't take it I'll put it back on.

 

Vibration is gone, and URO discs are back in their boxes waiting for me to contact rockauto. BTW, the rear disc had the same problem, just not as bad.

I will officially say, I do NOT recommend these. I will be looking for the brand all the MB guys seem to be using. Can't remember what it is, but it starts with an L.

Also, I will say (aside from the bad parts, obviously) this job was much easier than I anticipated, and a lift is by no means necessary. A jack isn't even necessary for the rear disc.

 

Speak for yourself, you must not weigh 250 like I do .......
( not that I am particularly proud of it )

 

Hmm... 225 on most days. Trying to get that down a bit more.