Pep Boys replaced the second rear brake caliper a week ago and I have driven just a bit. Yesterday I was on the expressway at 65mph and got a really a non-smooth ride - totally new - and I thought it was a back wheel out of balance. The steering wheel was pretty smooth and I thought I felt it in my legs so suspected a back wheel. Got all four wheels rebalanced today and it did not help.

It really rides rough, especially it seems when I hit the brakes to slow down on the expressway. Could this be a bad universal joint on my drive shaft or could it be something Pep Boys did in installing the left rear caliper? I think it even feels funny now at 35 mph and it has always been had a really smooth ride before. Maybe a coincidence about replacing the rear caliper at the same time?

Could I climb under it and test the drive shaft by shaking it to see if it feel loose? Not sure Mercedes are built like my old '57 Chevy.

How are your flex disks? Sometimes you can have a bad crack that you cannot see until you remove the flex disk and then you go when you realize that you were about 2 weeks from Bad Flex Disc

BTDT

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On My W123 the Front Flex Disc is vary had to get a good look at. Don't know if it is the same on yours.

After you have driven a while check and see if any of the Wheels is hotter than the other (do that carefully). If the one the PepBoys worked is are hotter than the others it could be dragging or the Air it needs to be re-bled out of it.

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84 300D, 82 Volvo 244Gl Diesel

Wheels are cool; that's how I knew I needed to replace both rear calipers. However, I believe the flex disc is original to the car; never remember having replaced it before.

My intuition tells me it might be flex disc or universal or does it not have a typical universal joint? Is the flex disc something I can do myself? How do I determine that it is bad on a SD? Does the drive shaft wobble if I shake it?

The flex discs are checked visually; cracks mean it's in need of replacing.

There are other parts that can go bad - the center bearing and support, as well as centering bushings at each end.

It is a DIY type job, yes, just follow the factory service manual.

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Inspect the center bearing while you're under the car.

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83 SD

84 CD

By inspect do you mean just visual or do I grab and shake it and look for loose-ness?

Both, actually.

Try and turn the shaft while in park. Is there any play?

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83 SD

84 CD

Thanks. Will try and report back.

I'd wonder if a caliper is dragging and has caused the rotor to warp.

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My thinking is they just replaced the calipers and didn't turn the rotors. Turning the rotors would:
Show if the rotors are warped
Smooth out the braking
Make the pads last much longer

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Sam

84 300SD 350K+ miles ( Blue Belle )

Dunno about p-boys but a lot of shops I know of don't turn rotors/drums anymore. They either advise replacement or slap pads/shoes on the old stuff.

With so many places out of the turning business (the NAPA closed their machine shop entirely), I usually just order new rotors when I do brakes. For many of my cars the new stuff is cheap anyway.

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I believe yout SD is the same and there is at least one real U-joint on it. However, if it is like the W123s the U-joint is Staked in. That means that the U-joint is not Bolted in and Metal on the inside diamter of the Bearing bores is dented over to hold the Bearings in.

Mercedes wants you to replace that whole section of Drive Shaft that the U-joint is attached to.
However, a few People like Myself replace the U-joint anyway. I have a Thread on that and another Member has one and there is some over on Benz World.

Some People have sent their drive Shafts to a Shop for rebuild and balancing. It also seems that they reaplace the Drive Shaft Support and Bearing when they do the job.

Some of the info is in the threads. However, it seams like there is less Shops wiliing to do the Job partly due to the 3 prong hook up on it.

If you end up dropping the Drive Shaft to replace the Flex Discs those ends also have a centering bearing. The Centering Bearings need to be checked for wear and when installed you need to put some grease inside.

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84 300D, 82 Volvo 244Gl Diesel