87 560SL differential replacement questions
 

My girlfriends '87 560SL has been making a low pitched whurring noise from the center rear of the car. It was doing this when I met her a year ago, so I dont know for how long. I suspected the differential, so she took it to her mechanic, actually two mechanics who said it was in all probabbility the differential. They quoted an astonomical price to replace it 4000.+ I have located a NOS differential for this car for 400., and plan on installing it myself within a week or two. I have mostly worked on US cars and Porsches, which I have done engine rebuilds etc. I feel that I can handle this job, but was wondering if there were any special tricks. Also I would like to make sure the diagnosis is right before I start. Is there any way to confirm the noise is comming from the differential, and not a wheel bearing, or drive shaft bearing. The noise does not change when cornering hard right or left. The noise coasts down with the cars speed, and is evident untill the car reaches about 5 MPH or so. The flex plate has been replaced, and the differential oil was checked, and I believe changed. The 911 uses the same basic type axle shafts and CV joints. Is there anything to it besides disconecting the axle shafts and drive shaft at the dif. placing a floor jack undernieth, then undoing the forward mounting bolts, and the mount in the rear, and lowering away?? Any special tools required? Looked like the rear mount that goes thru the mounting ring at the rear of the dif. requires a large torx tool or somthing.

Your help would be much appreciated. Also If I were to have purchased a new differential from a dealer, how much would I have to pay for the part.?

Thanks

Rod

You've got the basic procedure right, but maybe not the diagnosis.

Usually you get a more of a whine from a differential than a hum. And I translate "in all probability" from a mechanic as "we don't know, so let's start by replacing the most expensive part."

I would get the car up on a lift or stands and have listen with a hose to my ear or one of those stethescopes before replacing the differential.

I personally would suspect CV joints or tire noise before the differential.

This is a tough one. Good luck.

It is a low pitched whine. We have replaced the tires. Are you saying that I should put the car up on stands, then start it, and put it in gear, and run it off the ground? I can do this. There was someone on the other tech forum that said somthing about getting up to speed, engaging the cruise control, then shifting to neutral. If the sound went away, it was somthing else. Ever heard of this? I dont remember if it applied to this model. I can get my money back on the differential if I put it in, and it is not the problem. I will try and run the car in drive, off the ground, and see if I can detect the noise. Thanks for your information.

Rod

You might want to take a look at the center bearing or even replace it and the rubber carrier only becaues its cheep.

John Roncallo

560 differential noise solved! but need help
 

Today I put the car up on stands, and ran it in drive. It is not the differential. I traced the noise to the driver side rear wheel bearing. I did this with a stethoscope, after bringing the car up to speed, then letting off on the throttle. I held the speed where the noise was occuring, by putting a weght on the gas pedal. After I isolated the noise, I removed the wheel, caliper, rotor, ebrake assy, and axle assy on that side. spinning the hub by hand feels very rough. I dont know if I followed the right proceedure, but I removed the large nut under the dust cap cover, at a swivel bearing, removed the sway bar attaching bolt, and a C shaped clamp. I then separated the whole spindle, and backing plate assy from the control arm. I am afraid to go any further with this, but I have some questions. Is there a special tool required to get the casilated nut off at the back side where the axle splines into the hub. Looks like this is the wheel bearing adjustment. and spindle retaining nut. It was peened over in a slotted area. I straightened this out, but could not get the nut loose with a hammer and drift pin. Is this a right hand or left hand thread? Is it better for me to take the assy to a shop to have the needed bearings replaced. I have shrunk, heated, and pressed on bearings on other machinery in the past. Is this beyond the do it yourself stage??. The large nut under the dust cap, that I took off did not seem to be very tight. It had a blue locktite substance on it. I gues tightening this sets the bearing in this swivel joint. Are they just depending on the thread locker to retain this nut. Why no cotter key? I may be in over my head. Help.

Thanks

Rod

Axle Bearing Replacement
 

Rod, Click on 'Special Tools' at the top of this page. Find section 35. Go to page 38. P/N 915-0207 is what you want. Call or Email Fastlane Phil. Dave.

Nice wrench!

Got that tool, and a rear bearing kit comming.

Tkx

Rod

Is this really the correct tool? I just received P/N 915-0207 from Baum Tools and the OD is about 1mm too large to fit into my wheel bearing groove nuts on my W123. I called and they said I needed the 915-0107 tool. However, I looked up this tool and it is listed for the differential pinion groove nut. Doesn't make sense.

The 915-0207 was correct for my C107 rear wheel bearings.