Differential swap part 2
 

I am attempting to change my differential on my 82 300D from the .344 to the .288...any ideas on what model/year I should look for a used one on?..thanks for your replies

Your 1982 300D (W123) should have a 3.07. I can imagine where you got a 3.44 installed, unless it's Euro.

If you want to go to a 2.88 you'll need a diff from an 85 (W123). !

:D

Gee, I thought only the turbo models had the 3.07
 

and that non-turboes did have something in the 3.44 range, but maybe my information is only correct for wagons.

The labor involved in doing this is pretty excessive unless you really need a new differential. I personally would not undertake a differential swap just to get what I consider a better gear ratio.

However, I recently did change out my differential because the old one was severely worn. I should post a picture sometime of just how badly it was worn (and where, so you can all do an inspection).

If you have to get a replacement differential, by all means get one from a 1985 300D with the 2.88:1 gear ratio.

One thing I should advise you about: On my car with the replacement differential, and 15" wheels vs. the stock 14", the trip odometer indicates 9/10ths of a mile for every mile on the interstate. So the speedometer presumably has a 10% under-indication error.

Keep the gear oil changed!

Ken300D

labor intensive?
 

I have changed my axle shafts on the car...the diff is just the center unit that is only bolted with like 4 bolts in the rear and a few on top..that and removing the axles again..is there something i am missing?..let me know....I drive on an interstate that is 75mph...just wanted to get the rpms down a bit....thats for your replies

diff swap
 

a) go for a 126 body diff with a 2.88 ratio (anything from 1982 -85)
b) piece of cake, 15 min to remove each side axle stub, 40 min or so to remove the center pumpkin (already drained if you got the C-clip off) and another 3 hrs to batten the hatches and fill fluid

GO for it !!!!
email if you're stuck....

pps- If you cannnot get the fill plug (14 mm hex socket) off before you drain the diff, stop and DO not proceed !!!!!!!

Now i find out i do have the 3.07...this might not be that big of ratio change per cost...any comments on that?...3.07 to a 2.88..hmm....that might only be 200 rpm change...I am just concerned about driving this car at 75 mph for long trips..seems like it would be better to drop the rpm to 2800 - 3000 range..let me know what you guys think..thanks for your replies

All of the 1985 (W123 & W126) turbo diesel have a 2.88:1 ratio, b/c they are equipped w/ ABS. :D

diff swap
 

I just swapped my differential not too long ago. I was doing it alone and it took me about a day. The hardest part is getting the new pot into place. I didn't have any means of holding it up there except my dad helping me as I try to bolt it. That thing gets real havey real quick. The axel shafts are just a lot of playing around with a ratchet. Make sure you have a good 12 point bit for the bolts. The bolts tend to strip the bits much quicker then the bit the bolts.

It's a real fun DIY, just take your time and do everything as the manual says since those parts are kind of important.

Clean everything when you get the old pot out and make sure to oil the bolts before reinstalling them. Use threadlock if you are reusing the old bolts, or get new ones.

xp

bottomline
 

Guess what I really need to know now is the change from a 3.07 to 2.88 really worth it....will that make cruising at 75 mph better?..as in engine stress / mpg.... I did some math and it seems it would be around 5 mph difference @ 70 mph.... anyone that has did that exchange have any insight ?..thanks again for all the replies..

seems like a lot of hassle for small gain and you will loose some aceleration. Can't imagine that crusing at 75 or more will do any kind of damage to a well maintained engine ,don't forget to let turbo spool down after long runs.........
William Rogers........