Removing differential
 

I am in the process of removing the differential on my 1984 300SD. I am down to the four main bolts that hold the diff to the sub-frame. I can get my 19mm box end wrench on the nuts, but I can't enough leverage to break them free. Not enough room for my breaker bar. They are soaking in Busty tonight while I think about it some more.

Are there any hints/tips/tricks to removing these four nuts???

Slip a helper wrench over the other one?

Its tricky to explain...but you use the boxed in end of one wrench (an extra) and put it on the open end of the wrench you are trying to turn with in such a way you can get way more leverage. The only downside is...non-quality tools will break :)

What's Busty?

If it's like Liquid Wrench, then that should do it. But in like 10 miuntes or so...

Busty is a penetrating oil.
http://www.hogwash.com/Busty%20Penetrating%20Oil.htm

Heating up the part that the bolts are threaded into will tend to expand it, make penetrating oil soak in faster, and make removal easier. It's best if heating is done quickly to minimize heating of the bolts.

At this point I'm going to presume you have the driveshaft off and the rear differential mount removed (the one that is attached to the rear cover of the differential.

You should have the back end of the car up on jackstands, being held by the frame - I think I did this either at the subframe mount points or further back near the rear sway bar mounts. Make darned sure the car is stable at this point, because you have little crush protection as the differential comes out, because that helps hold the subframe in place which in turn holds the rear wheels.

The problem you are having with clearance has to do with the subframe position. With the frame up on jackstands, as you push the wheel ends of the subframe upward, the differential will drop down, allowing you more access to the bolts. You can figure out your own method of holding the wheels up - I think I used a bottle jack somehow.

A lot of times I use extra wheels (lying on their sides) as crush protection by putting them under the frame. You really have to get pretty far under the car for the differential work and I fear not only for myself but others. I seem to remember spending a lot of time completely under the car in the vicinity of the front of the differential to get the front two bolts off.

Please be careful.

Ken300D

Ken,

You have me second guessing myself now...

The back of the car is sitting on ramps, with jackstands under the rear subframe mounts. I have removed the exhaust and loosened up the driveshaft. I elected to leave the drive shafts in; I will slide those out of the diff as I lower it.

I understand how the diff helps tie the subframe to the frame, but I thought the subframe mounts would prevent it from falling. Is this incorrect?

Thanks,
Thorsen

I did the exact same job on the exact same vehicle and pulled the diff with the axles, so, follow carefully:

1) You are going to have to get the car off the ramps. The trailing arms need to be unloaded and hanging down if you wish to get the axles out of the hubs. So, jack it up via the differential, block the body at the jacking points, and remove the wheels.

2) Now, the vehicle is fully supported by the body with the trailing arms and hubs hanging downward on the shocks.

3) Put the jack under the differential and support it.

4) Remove the differential mount at the back of the differential. Two large cap screws hold it to the mount and four smaller screws hold the mount to the body. Usually, now is a good time to throw the old mount away and get a new one.

5) Carefully lower the differential about three inches. The subframe will come down with it. Don't go too far because the subframe is still held at the two front mounting points and you don't want to bend or distort those mounts too badly.

6) With the subframe/differential down a bit, you can now get a breaker bar up on those nuts above the subframe. Break them loose but don't remove them just yet.

7) Jack the differential back up to the normal operating position (approx.)

8) Block the subframe in one place to prevent it from coming downward. The springs want to send it to China, so do this safely and carefully.

9) Remove the four nuts and bolts that hold the differential to the subframe.

10) Lower the differential about two inches, with the jack, and push it forward toward the front of the vehicle about two inches.

11) Presumably you have removed the screws inside the hubs that hold the axles to the hubs. At this point, the axles can easily be removed from the hubs.

12) Pull the jack rearward and manipulate the axle shafts past the brake lines........a bit of a problem.........but doable.

13) Pull the jack all the way rearward with the diff and the axles attached.

Blocking the subframe....
 

Brian,

I'm going a bit different - the axles are staying with the car. The rear wheels are on the ramps with jackstands under the control arms.

I was able to break loose the four main bolts holding the diff to the subframe. I am using a length of 3x4 - one end wedged against the ground, the other end against the subframe near the diff. Do you think this is adequate? Do you have a better suggestion? It's probably a good 24"-30" from the ground to the subframe - too much distance to use a jackstand.

If you have safely blocked the trailing arms, and you have managed to break those nuts and bolts loose, then you can lower the diff.

But, if you intend to leave the axles in the hubs, then you must open the rear cover of the diff, while it is underneath the vehicle, and pull the C-clips that hold the axles in place. If the vehicle is high enough, you might be able to maneuver the diff so that you can pull the axles from the diff while leaving the axles installed in the hubs.

I have not done it this way because I wanted to reverse the axles. After 180K, it's better to switch loading within the axles for the next 180K.;)

Thanks Brian. Good idea about swapping the axles.

I put jackstands on the subframe where the trailing arms attach. I took off the rear cover of the diff to remove the C clips but realized ----- the 2.47 differential I have is too large. It looks to be about 1.25" to 1.5" too wide. I buttoned everything back up and am now back at the drawing board.

Thanks for your help.

How is this possible? Is the bolt pattern different? I was under the assumption that all of the S class diffs were interchangeable. What vehicle did it come from?

I recently purchased a 2.47 (hopefully) but have not received it and it was from an older SEL. Now I'm wondering too...................:confused:



Anytime.

Brian,

I just email the seller and asked him to confirm the year it came from. I thought it was a 1985 SE/SEL when I bought it, but the one I picked up had an ABS sensor in the case, just aft of the yoke. I think ABS was from 1987 on? The biggest problem for me was that the case was too wide - I would have had to shorten the driveshafts (NOT!).

In case you don't know already, you'll need a deep 30mm twelve point socket to remove the yoke.

I believe the ABS started in 1985. My 2.88 from a 1985 SD had the ABS sensor on the case, just aft of the yoke.

It does not seem possible that the case would be "too wide". If the diff will bolt up to the subframe, the axles should fit the diff.

Granted, the case I have now has no lateral caps, while the 2.47 has the lateral caps secured with eight bolts. Even still, there is an extra inch or so of case width.

Did you ever try fiting the 2.88 with ABS into your 84?