AMGdrivR

Hi everyone, my 2009 G550 makes a squeaking noise whenever it's in reverse. I suspected that it might be the brakes, but even with my foot off the brake pedal it still makes the same noise. I had my mechanic take a look to pin point the source of problem and he suspected that I could be a u-joint. He referred me to a shop that specializes in drivelines and the weren't able to help me. Their suggestion was to contact Mercedes to order a new drive shaft since apparently there isn't a way to fix the u-joint. . Aside from this noise, my G550 drives very well. Does anyone know what this problem could be? Thank you!

streborx

Check the parking brake.

AMGdrivR

Thank you. Could you elaborate in regards to the parking brake? Wouldn't the noise occur when the vehicle is moving forward or backward? The noise only occurs in reverse? Thank you again!

streborx

I'm assuming you have a manually operated parking brake, a lever next to the gear shift (not electronic as in current models). The lever operates a cable that mechanically moves a cam on each of the rear brake calipers. Check the movement of the cable on each caliper to make sure it moves freely with the lever operation, and isn't stuck due to corrosion from infrequent use. Brakes develop a directional wear pattern from mostly stopping forward motion, and can squeal when braking reverse. This is simple to check and rule out before tearing into the driveline as the cause.

hard top

It sounds like the driveshaft shop confirmed it is the u-joint but they wouldn't source the driveshaft with the u-joint and install it for you? It is strange to me that you can't replace just the u-joint, but I've never owned a G.

Floobydust

As suggested, check the parking brake. A simple test is to pull up on the handbrake lever while reversing - does the noise change?

I have never heard of a U-joint squeaking in one direction like that. The U-joints on G driveshafts are non-replaceable and the U-joints on later Gs are even non-greaseable. If yours have Zerk fittings, have them greased. If the noise changes, suspect the U-joint.

AMGdrivR

Thank you for clarifying Streborx. Yes, it's a manually operated parking brake. I'll give this a shot. Hopefully it's just the parking brake. Thanks again!

AMGdrivR

Thank you Floobydust. My challenge is finding an indy Mercedes mechanic that understands the drivetrain on the G class. I wish I could find one that was familiar with the G. Do you recommend I take it to a shop that specializes in 4x4's? Also, if I have to buy a new driveshaft (due to the U-joint) , would I have to purchase this directly from Mercedes? Thank you again!

Floobydust

For making a diagnosis that it is a U-joint, a good 4 X 4 shop would definitely be better than a non-MB specialist shop. Any 12 year old that can turn a 13 and14 mm wrench can replace the front or rear driveshafts, but the center, or homokinetic driveshaft would best be done by a good MB Indy or a good 4 X 4 shop.

Dorman supposedly makes aftermarket front/rear driveshafts, but I wouldn't go any where near them. Rebuild kits are available for the center shaft, but I wouldn't do that either. So really you're only choice is genuine MB. They aren't cheap, so order (or have your Indie order) it online if you can.

streborx

As Floobydust has indicated, the G's u-joints are integral to the drive shaft, and in fact seem to be CV joints rather than a conventional u-joint design with flanges joined with a 4-point knuckle. Check the rubber boots at both ends of the drive shaft for possible tears and leaking grease. If everything appears intact, a u-joint squealing noise would seem an unusual situation. I think there are shops that rebuild these kinds of driveshafts. You can buy a replacement, and ship back your core for credit, assuming it's rebuildable.