w124 300TD differential years of compatibility.....
 

Good morning Team -

Looks like the differential in my 87 300TD is bad - terrible growling noise from the rear of the car, not effected by turning or application of breaks, sporadic severe scraping noise that went away with some speed, yadda, yadda, yadda. I've been under the car a bunch, nothing is hot, nothing looks out of place. Car has over 300K miles (estimated).

So, this weekend I'm going to have it on a lift - for another job - and will check the fluid and change if needed, just to see if that helps. If not, then I'm pretty sure I need a replacement differential - which brings me to this question;

Are all the w124 series differentials compatible? I have a line on one from a 92 300TE locally, but I haven't been able to determine if it is a straight fit.

Anyone know for sure?

As always - thank you all for the help !

Pretty much all W124 differentials will bolt into the suframe BUT there are 2 limitations. One is the size of the imput flange. The diesel used a larger imput flange than most of the 300e variations except for the 24valve. You can swap your input flange onto any W124 diff but you will need a special 12 point 30mm (i think) socket.
The second limitation is the differential ratio. You have a 2.64 differential and most of the gasoline diffs are much shorter (aka higher numerical ratio). If you were to use that 300te (2.87) diff which would give you better acceleration at the expense of more noise on the highway. The differential and speedometer are also paired so you would also have to chance the speedo in order to keep it accurate.


http://mbturbo.com/gear-ratios/
Scroll down to W124. Going from 2.64 (300td) to 2.87 (300te) is not a huge difference and you might enjoy the improved acceleration. I would go for it. Don't forget to also swap the speedometer.

Rats....
 

That's exactly the info I needed - and was also dreading. Seems I really need to find a 300D differential - I have a 50 mile one-way commute everyday on I95 - so being able to spend quiet time at 75mph is important to me. Guess I'll post in the Parts Wanted section should I find out that I need a differential. I'm not feeling like rebuilding a diff.

Thank you again !

I've found and purchased a used differential on this site:

Car-Part.com--Used Auto Parts Market

The secret to finding one is to look for "axle carrier" instead of differential.

Call the yards that advertise they have one, confirm via VIN that the donor vehicle is correct. Expect to pay a little extra for shipping.

I had to replace the ASD differential on my '95 sedan, I think I found one for $200 or $300, had the yard verify it was still full of oil and turned easily before shipping. It's been in my car for a couple years now no problems.