Bad diff ... W115

[vwnate1]

Henry ;

It sounds like you're on the way to a solution .

I was junkyarding today and looked at the M-b in Fontana , turns out it's a 1966 W108, sorry .

I have no idea if it'd fit and didn't crawl under the car to check the ratio .


I no longer chase parts for others I have so much crap I got stuck with that I'm taking a lo$$ on and scrapping out ~ I'm old & disabled, can't really spin the wrenches like I used to .

I moved way out West in 1970 but for decades every road trip I took Down East I'd fish in salt belt junkyards and find perfectly good low mileage hard parts and interiors dirt cheap, don't loose heart here just yet .

[t walgamuth]

Originally Posted by cleeves

That would be a godsend. Must be 300D though as I believe the 240 and others have a 3.92 diff.

But maybe the other one Frank linked to just now will work (not the old one). It appears to have the right casing.

he 220 Has the 3.90, the 240 has 3.69.

[cleeves]

Mechanic said the original pinion not only had some oxidation but also some strange wear patterns. They were able to get the pinion (and gears?) from the diff with the snap retained bearings swapped into my original casing. I noticed that a whine I previously heard on the highway is now gone, and I experienced less drag when I took my foot off the gas (but the latter I could be wrong).

The main noise I was experiencing on this is still there -- happens during engine load at lower speeds like when the car is coasting downhill at 10mph. It's something on the end of transmission, perhaps the bearing there is going out. Transmission shifts fine, but this means it was a two-fold issue all along! So no wonder there was difficulty troubleshooting it.

Half way there ... drives fine otherwise though.

-Henry

[vwnate1]

That's good to hear .

Are you going to dip into the tranny ? .

[cleeves]

Originally Posted by vwnate1

That's good to hear .

Are you going to dip into the tranny ? .

Maybe next year. I will maybe put another 500 miles on it if that this year, so I'm going to bet things will be OK for at least that much.

-H

[t walgamuth]

Just a comment. The difs are extremely long lived. Replacing one is rarely needed. I would look at your driveshaft and park it so there is not a load on your drivetrain....then try to wiggle the ds. There is the center bearing which is a somewhat frequent problem along with its rubber mount ring, then there are u joints and CV joints which can make various noises.

[cleeves]

Originally Posted by t walgamuth

Just a comment. The difs are extremely long lived. Replacing one is rarely needed. I would look at your driveshaft and park it so there is not a load on your drivetrain....then try to wiggle the ds. There is the center bearing which is a somewhat frequent problem along with its rubber mount ring, then there are u joints and CV joints which can make various noises.

That is a good point that the issue could be in the center mount ring or in the U joint.

That being said, I fully believe the transmission shop of my diff having an excessive / weird wearing pattern, and I know that the whine at highway speed is gone. This may have been caused by driving the car for 5,000 or so miles before I changed the fluid. It had been sitting for 20 years previously, and it's possible it was the original fluid from 1976. The tech who changed it noted that it was a weird color and suspected it was burned, but there were no metal shavings in it.

Also, the driveshaft is rock solid with no sideways play in it. But I also think the U-joint is starting to go bad, from a slight rumble noticed at low speed with my foot on the gas. Deja vu for me it happened on my BMW years ago. But it's not so bad that I want to fork over 500 bucks for a rebuild and then either put it in my self or pay some one another 500 bucks to R&R.

I guess these driveline issues are all to be expected for a car of this age. Almost a half century old.

-Henry

[cleeves]

Follow up note -- I just got back from a trip from the City to Oyster Bay Long Island. About 2 hours each way. I observed that the "main noise", i.e. the high pitched scraping at 4x wheel speed (i.e. driveshaft speed), while still present with foot off the pedal at low speeds, is not as bad as it used to be. So clearly the differential pinion swap is linked to that issue too, and it seems to be a worthwhile repair. The tech did it for a very reasonable cost too.

-Henry

[t walgamuth]

Glad you got some good news!

[vwnate1]

Okay, you may have driven it with low gear oil in the diffy, I did that on my beloved 300CD and after a few (maybe more than ten) thousand miles it began to whine so I checked it and discovered it was very low on gear oil .

So, I snagged a cheap junkyard diffy with the correct ratio, took the old diffy out and spent some time washing the inside of the housing to ensure no SWARF , added a magnet , installed the junkyard diffy, buttoned it up and filled it up with a new filler plug gasket (the old one was weeping) and all was well .

As far as your driveshaft, go find a heavy duty truck repair shop and ask them who does their driveling rebuilding and balancing ~ them go to that place and ask them if they'll do your Mercedes driveshaft, most will for $250 or le$$ .

If the center rubber support is anything less than perfect, by one and hand it to them with your driveshaft .

They'll install greasable U-Joints and press on the center support too , all for $250 or less .

Taking the driveshaft off the car isn't difficult, you just need to either jack it up and block it safely or find some really tall curbstones and drive two wheels up and scrooch underneath the car o access the drive shaft .

It goes without saying this IS NOT A JOB TO DO IF THE PARK BRAKE DOESN'T WORK ! .

[cleeves]

Originally Posted by vwnate1

Okay, you may have driven it with low gear oil in the diffy, I did that on my beloved 300CD and after a few (maybe more than ten) thousand miles it began to whine so I checked it and discovered it was very low on gear oil .

So, I snagged a cheap junkyard diffy with the correct ratio, took the old diffy out and spent some time washing the inside of the housing to ensure no SWARF , added a magnet , installed the junkyard diffy, buttoned it up and filled it up with a new filler plug gasket (the old one was weeping) and all was well .

As far as your driveshaft, go find a heavy duty truck repair shop and ask them who does their driveling rebuilding and balancing ~ them go to that place and ask them if they'll do your Mercedes driveshaft, most will for $250 or le$$ .

If the center rubber support is anything less than perfect, by one and hand it to them with your driveshaft .

They'll install greasable U-Joints and press on the center support too , all for $250 or less .

Taking the driveshaft off the car isn't difficult, you just need to either jack it up and block it safely or find some really tall curbstones and drive two wheels up and scrooch underneath the car o access the drive shaft .

It goes without saying this IS NOT A JOB TO DO IF THE PARK BRAKE DOESN'T WORK ! .

Thanks for the tips. Yes, I did this with my previous car (BMW 635) over a decade ago - it was $450 or so with shipping to have the driveshaft rebuilt and I R&Rd it. Maybe I could find something local for less. I completely agree about the parking brake!

Maybe rebuilding the U-joint will solve the remainder of the issues.

[vwnate1]

That's why I said go to the local big rig shop ~ they're constantly sending driveshafts out for rebuilding and one of the things a driveshaft shop does is balance them after they're done .



I'm sure the price varies depending on location but $450 seems extreme to me.