bassn_07

Hey Guys,

For the past month or so I've been feeling a slight vibration when backing up. I never feel it going forward only in reverse with the brake fully disengaged . I'm thinking it might be my brakes but not sure, any thoughts?

jangy

Differential

could also be the parking brake?

bassn_07

Parking brake? Do you mean the parking brakes aren't fully disengaged when I back up or am I forgetting to release?

I guess the best thing is to take it in and see what's up.

Marcus Frost

Sounds like a diff issue to me Alan, hard to say though. Where do you feel the vibration? In your steering wheel in in your seat? Does it happen all the time? Are you going straight or at an angle? Do you have an aftermarket LSD?

-m

jangy

MAYBE the parking brake is not fully pulling in or has an angle to the leftover pads. Bicycles are notorious for it. A simple replacement of the pads would tell.

I still think diff. If not, your subframe may be shifting? Take it to MB and please report back. Added power has to bring strain.

bassn_07

It's intermittent and it feels like it's coming from the front. This morning I didn't feel anything and it's always in reverse.

jangy

2 piece rotors? Check the hardware. See how much play there is. There should be some, since they are floating but not too much. Worst case, $400 for new hardware and you are off again.

CharlyE500

I think its the engine mount. When engine mount leaks, the car vibrate when u back up, I have that problem with my W210 E430 before.....

bassn_07

Jangy, If it's brake related would that effect the braking itself. I've notice that I need to apply a little more brake recently and maybe that's the case.

jangy

Great point.

jangy

It could affect the "feel". It basically adds play so your brakes will be slightly later to respond. Since we have no feel in our pedal, you get no push back. the only sensation we get is the car actually grabbing. When that gets shifted, you may get the feeling that you need to apply more pressure.

The same thing happened to my rotors and I am finding out that that is typical given the way i drive. Most of my friends with 2 piece rotors that happen to drag race, etc. end up replacing the hardware quite often.

Even if that is not the issue, you should do a routine check on them as it is very hard to notice unless the car is on a lift.


Just to add to it. If they are as loose as mine were, you should be able to hear a clicking noise when moving very slowly (foot off brake, obviously) as the weight shifts. Try rolling SLOWLY next to a building and see if it has a click. That would be the rotor moving within its floating zone. The more clicking the more float.

bassn_07

Thanks everyone. My car will be going in and a few people also believe it could be the tranny mounts.... We'll see.

Thanks again for all the input and I'll update once I find out.

ECBAOBAO

SBC?

jangy

no

Ali_E55

maybe reverse clustch !!

or

engine mount.

post what they reply to you.

MB_Forever

It's a slight possibility, but it could also be the rear sub frame mounts.... although that would cause vibration while going backward and forward not just in one direction. The differential seems like a more plausible cause.

ECBAOBAO

well when i posted about this a while ago, everyone told me it was the sbc pump when im in reverse and my foot is on the break

jangy

I'm just messing with you and yes, the vibration of the pump building pressure is true but it has nothing to do with reverse. Could it be that you guys start it and jump into reverse?

bassn_07

I always wait for my idle to come down before going into reverse when the car is cold.

Marcus Frost

It could very well be a mount, although I'd be surprised if it was a motor mount that you only felt it in reverse, although it could happen.

SBC sounds like a possible culprit as well, although I've never seen that personally.

-m

jangy

Then the brake pump would have already done its thing. You can pop the hood and listen for it. It sounds just like an aquarium air pump.

markabcls55

A few more questions to answer, if you please...

What is the frequency of the vibration?...as in, is it speed related or a constant buzz?...and is it always cold start, as in backing out of garage...or anytime in reverse, even after being warmed up?

Does it "crab" side to side...as in, a rocking motion?

Do you think you're comfortable with having a proper alignment...as in, do you have some sort of abnormal tire wear or handling concerns? (perhaps a one-off specialty alignment)

How's the diff sound in turning <right/left> tight circles within...say an asphalt parking lot?

Just trying to understand the odd quirks of these beasts and perhaps some <possible>value added info, if I can.

Max.H

Hope its nothing major and you get it fixed.

bassn_07

Me too. I should have addressed it a while ago. I have a good hookup at my local MB so I feel confident that they'll resolve the issue. I'm hoping somethng simple like motor or tranny mounts.

bassn_07

It seems that the transmission mounts were worn and needed to be replaced but he couldn't duplicate the problem because of it being intermittent. Engine mounts were fine with no leaking and all else is well. All in all I feel better and can't wait to pick my car up tomorrow.