Differential Swap
 

I have a 1984 300SD with a 3.07 diff. and want to change it for one in the 2.xx range but I can't find the data on the ones that would be a direct drop in. Can anyone help with this info? Thanks

the most
 

obvious is the 288 from the 85 123s. others will work too but some need extra adapting.

tom w

Just did this on my 1984 300SD. Here are the cars that will fit:

1985 300SD 2.88
380, 420, 500, 560 SE, SEL, SEC 2.47

You need one of these from 1981-1985. The 1986- cars had a different mounting style that will not work with your car. Make sure you grab the speedometer too. Some cars have an ABS sensor in the rear diff - the ABS diffs will still work (but you won't have ABS).

Read and understand how to remove the diff before you start. You can kill yourself if you make a mistake. I almost let a shop do it for me.

I ended up putting the back of my car on ramps. Make sure you have a floor jack tall enough to reach the diff.

You will need to swap the differential yokes as the gas 126 have a larger bolt pattern on the yoke. Buy a pinion seal and a new locking nut ahead of time.

This is a great time to change the rear flex disc.

When you remove the exhaust system, make sure you support the end of the front downpipe so it does not hang at any awkward angle. I let mine hang, and I also got to replace it this weekend too. :)

Here's my BTDT tip - make sure you put the locking clips on the end of the driveshaft before you bolt the new diff in. If the shims need to be changed, you will have to drop the diff again.

I can't offer any advice on the 2.88, but I do like the 2.47. Below 50mph I leave the transmission in 3rd, which gives me plenty of power for passing. On the highway in D, I turn about 2400rpm @ 65mph. Very quiet, very smooth. My wife even commented about how quiet the car seemed.

Just What I was looking for
 

Thanks Thorsen, I will try to locate a 2.47. You don't have a line on another one
do you? What do you think I should be able to pick up one for? BTW which one did you use?
Thanks for taking the time to reply it really helped me alot.

that should
 

be one of the easiest to locate. there were a lot of those cars sold and the yards must have scads of them.

tom w

I used the 2.47 from a 1984 380SE, I paid $75 for it on eBay. I also picked up a 2.47 from a 1985 500SEL for $125 from this forum. I think anything under $150-$200 is a deal. I wouldn't go any higher than that unless it was recently rebuilt.

Also, search on my ID and 2.47 as I posted some other useful information in another thread.