Another 300SD with a 2.47 differential transplant - success!

[pawoSD]

My dad's '83 300SD (daily workhorse) had ailing axles, differential, differential mount, flex disk, center carrier.....the whole assortment. So, we recently managed to snag an excellent condition (despite 330k on it!!) 2.47 differential and axles off of a euro 500SEL at the junk yard for $112 (for all of it!) The differential had 0 play in it, even the slightest movement of any shaft produced movement on the other side....inside it looked new. It must have been well serviced through its life time.

We put up the car on stands and pulled out the entire drive line, from the front flex disk all the way back.

We recycled the original 3.07 diff and axles, the axles were grinding and clunking, and the differential had a massive amount of play in it, close to 1/4 turn between input and output, plus metal shavings coming out in the fluid when it was changed. It passed on with 305k on it.

The axles that came with the 2.47 looked to be in good shape and moved smoothly, but the boots were beginning to crack, so we just went ahead and rebooted them using the pledge+cone+flex3000 boot method. Its very easy to do once you warm the boots in super hot water....maybe 10 minutes per axle if that. Then you just install one of the clamps (I always did the smaller one first) and then fill the boot with about 1/4 quart of gear oil. (Valvoline Durablend 80w90 was used) Then clamp the larger clamp (this can be annoying, two people is a huge help for the whole procedure.

With the diff all cleaned up, both inside and out, and all seals replaced, (output shafts as well as the pinion seal),I re-inserted the axles/clips and then reinstalled the cover and sealed it with the fancy MB sealant. Also replaced was the input yoke for the flex disc, as the gassers have a bigger yoke/disc. This requires a new 12point 30mm locknut. I installed it and used my impact to torque it to around 75-80lbs, I then peened the nut into the locking tab on the shaft, securing it from ever coming undone. An impact is very helpful for these tasks (both install and removal of the yoke nut as well as the rear 22mm diff mount to cover bolts) I just use my 12V harbor freight digital unit connected to an old computer power supply for endless 12Volts.

We lifted the whole unit into the car in one motion(using a floor jack), and just slipped the axles into the hubs as we lifted it in place....way easier this way. Brake calipers did not have to be removed either....nor did the wheels. In fact aside from drive line parts, all I removed from the car was the exhaust, under shield, and rear wheel center caps. I then reinstalled the axle securing bolts, and we set to work at bolting the diff in place. This can be annoying to line up because its a very snug and precise fit. After a while we got it in, and I put in the diff mount. I then installed the drive shaft (I had previously pulled and replaced the center bearing and carrier), and bolted up the flex discs.

The cover was then reinstalled, and then the exhaust, and it was done.

Driving impressions....off the line feels pretty close to a 3.07....slightly slower, but each gear is held much longer, its an interesting experience....it pulls quite strong up to 85+.....the main loss of power is in 4th gear on the highway, its a bit more gradual to increase speed. Noise is gone, the car feels completely different in that regard, its hard to believe its even a diesel, at 70-80mph its virtually quiet, even quieter than with a 3.07 at 55-60mph. All the clunks in the driveline are now gone, and it rides very smooth. The different ratio also made the trans behave differently....in a good way, it shifts more smoothly and less perceptibly. The 2.47 really smooths everything out. My dad is quite pleased and doesn't mind the slight loss of acceleration....if necessary it can be dropped to 3rd and it will pull strong to 80+mph in the 4000-4500rpm range, then it can be put back in 4th to cruise.....its like the car finally has an over drive!

So the project was a success. I am not sure if I'd do it with a 2.47 to my own car, I like the brisk acceleration of the 3.07.....I would readily do a 2.88 though.....I would still go 2.47 if I managed to obtain a limited slip unit.....I'd love to have that for the winter.

Feel free to ask questions about the project...all in all we probably spent about 40-45 hours on it.


I also replaced the shifter bushings while under there, that is a HORRIBLE job, perhaps the worst part of everything I did! Those nylon bushings are REAL hard to get in and out. For the front one I actually removed the shifter lever from the trans, and used a vice to squeeze the bushing into place. The other one my dad managed to get in after about a 15 minute fight. There's got to be a secret or special too for that....am I right??!