Swapping out a 1982 for an 1985 rear end

Mercedes lowered the ratio on the 85's which gives you lower engine speed and thus better mileage at freeway speeds. It is a direct swap. My axle repair manual only covers removing the axles which you do have to do to change the differential. but it does not cover specific instruction on changing the differential (pumpkin) replacement. I am working on an addendum to that manual which will cover rear end replacement but it won't be done for a few weeks. Check other post on this forum for tips on getting the replacement rear end bolted back in.

If I remember correctly the ratio was lowered form 3.07:1 to 2.88:1. I have cars with both axle ratios and do not see much difference in fuel economy. The higher ratio gives you slightly lower gearing and better acceleration from standing start. Lower gear ratio (=higher gearing) is better for highway cruising.

Yea, I just did that about a month ago, with an 82 TD. The 2:88 made a noticeable difference, I still need to replace the instrument cluster, mine is off now around 5MPH(?) I have the 85 cluster (is 120MPH which is cool) which I still need to change. I drive over 700 miles wk and the highway cruising is better, I just got a speeding ticket, he clocked me at 84 in a 65, car likes 80 now. The swap was not too bad, but the bolts at the top of diff were a pain to get at (tight too) two of the studs came out instead of the nuts. Don't let the car down with the diff out, it will damage the front bushings. ~mark