Easiest (Safe) Way to Drop Rear Subframe? - PeachParts Mercedes-Benz Forum

rs899 · #1 02-13-2008, 11:43 AM

My pal and I are parting a rusty old 240D stick (don't bother to ask

) and we soon will be dropping the rear subframe for good. What's the easiest way? I have a Klaan clone, but I would think some other creative means using jacks would be easier.

Ideas?

Rick

TheDon · #2 02-13-2008, 11:45 AM

remove the rear seat.. unbolt the top bolts for the shocks.. then unbolt the bolt from the subframe bushing mount( one on each side).. I think a jack would be neccessary to hold the whole thing up then gently lower once the bolts are removed

R Leo · #3 02-13-2008, 11:57 AM

The subframe bushing that's located underneath each rear door has some SIGNIFICANT downward pressure exerted on it from the rear springs. Be careful!!

The safest way to remove the subframe would be to use a spring compressor and remove the springs first. To remove it using only jacks, I believe you'd need to support the body separately from the subframe then use three jacks to support the subframe assembly: one at each side and one under the differential. Only then could you unbolt the subframe mounts, shocks, brake lines, e-brakes and driveshaft and lower the assy by dropping the three jacks more or less simultaneously.

JimFreeh · #4 02-13-2008, 12:35 PM

You can pull the shocks and relieve enough pressure on the coil springs to avoid using a compressor.

Place a jack under the trailing edge of the trailing arm and unbolt the top of the shock. Do a controlled release and the the spring will extend and loosen. Remove spring.

Jim

babymog · #5 02-13-2008, 12:37 PM

On the 124 (different animal I'm sure) I pulled the upper shock nut off first with a floor-jack under the hub, then lowered the floor-jack to allow the spring to extend/relax. Next the other side, same thing. Unhooked all of the lines/wires/cables/driveshaft, put a floor-jack under the diff-housing, and unbolted the four isolators holding the subframe in place.

Now just the floor-jack is holding it tight against the car, and (on the 124) the sway-bar is still attached for a safety. I lowered the jack under the diff and controlled the rotation of the asssembly as it lowered (better for two people, I did with just one), when it was on the ground, I pulled the sway-bar loose.

Bajaman · #6 02-13-2008, 12:40 PM

You can do this safely using two floor jacks. One under the front portion of the subframe and one under the a-arm. Undo the subframe bolt and slowly let them both down to relieve the force in the spring. Without two jacks the subframe will try and twist do to the moment created by the spring/a-arm. In the end, the spring compressor is the best way.
bb

johninva · #7 02-13-2008, 04:56 PM

just dropped one off an 85td at the pick n pull 2 days ago, jack the rear from the jack points. undo the shocks at the top, the differential had a bracket on the rear of it attached to the body, remove those bolts. cut yer brake lines. undo the 26mm bolts attaching the subframe on each side (while your on the side not underneath the vehicle ) needed a very long breaker bar for these. the rear subframe drops off the vehicle, it may need some assistance from your foot.

johninva · #8 02-13-2008, 04:58 PM

what are your plans for the manual transmission ?

rs899 · #9 02-13-2008, 05:59 PM

re the transmission:

Quote:

(don't bother to ask

)

-that was the whole point of this car.

It's really my buddy's car- he may convert a 300D that he has or wait for a 240D auto to come up.

so..johninva you are saying the springs weren't an issue at all? I am leaning toward putting a jack under each trailing arm in turn and removing the subframe bolts, then slowly let down each jack.

Brian Carlton · #10 02-13-2008, 06:14 PM

Quote:

Originally Posted by rs899

r I am leaning toward putting a jack under each trailing arm in turn and removing the subframe bolts, then slowly let down each jack.

That's dangerous. The load on the rear diff mount could be positive or negative.

Just block up the body sufficiently high.

Then support the diff with a suitable hydraulic jack.

Proceed to the left side subframe mount and support it with another hydraulic jack. Remove the bolt and lower the jack.

Proceed to the right side subframe mount and support it with the same jack used for the left. Remove the bolt and lower the jack.

The subframe will fall slightly in the front. Shove some wood under the two forward points so it doesn't fall further.

Now proceed to the rear diff mount. Remove the two bolts and lower the diff and subframe together.

rs899 · #11 02-13-2008, 07:47 PM

Thanks Brian.

But are you saying that the diff, even though bolted securely with its mount, could drop if unsupported by a jack? I hadn't considered this, and I'm not sure I understand it. Certainly can't hurt anything and there will be jacks available, but I don't see why this would be a concern.

Rick

Brian Carlton · #12 02-13-2008, 08:24 PM

Quote:

Originally Posted by rs899

Thanks Brian.

But are you saying that the diff, even though bolted securely with its mount, could drop if unsupported by a jack? I hadn't considered this, and I'm not sure I understand it. Certainly can't hurt anything and there will be jacks available, but I don't see why this would be a concern.

Rick

The diff is bolted firmly to the subframe. When you remove the two bolts from the back of the diff, it's going upward into the body.........or downward toward the pavement.........depending on how you've got the body supported. If you support the diff.......but don't support the body.........it's going up. If you support the body and don't support the diff........it's going down. But, you can control the downward movement with a hydraulic jack beneath the diff.

bob_98sr5 · #13 06-08-2008, 08:00 PM

Hey guys,

I spent most of this afternoon working on my rear suspension with a friend. Pretty tough inside a single bay/car garage!

Anyways, so this is what we did:

1) We sprayed the hell out of all the bolts
2) While the vehicle was on the ground, we loosened the 4 major subframe bolts and the top nuts for the rear shocks
3) We jacked up the vehicle and put two stands on the rear rubber supports. We also put jack stands underneath the trailing arms (where the holes are). we also put the jack underneath the differential
4) Removed the exhaust system
5) Unbolted the bolts on the driveshaft that runs through the flex disc that connects to the front of the differential
6) Unhooked the speed sensor to the differential
7) Undid the brake lines
8) Undid the sway bar bolts

So after doing all of the above, we jacked up the vehicle a little higher just to remove the jack stands underneath the trailing arms. We were expecting that the weight of the subframe would lower the entire subframe assembly as all of you guys wrote above. That did not happen. So we knocked on the driveshaft a little bit to see if there was something preventing it (like a bolt or rust bonding) from separating it from the differential, but no luck. However, my thought was that there is some shaft protruding from the differential into the flex disc as I believe the FD has a large hole in the middle:

So gents, help me out because I feel I am close now. I need to drop the rear subframe so I can put in the new one and take care of three spots of rust I need to weld patches

Thanks,
Bob

babymog · #14 06-08-2008, 09:50 PM

You will need to pry them apart. Both of mine were a little stubborn, once all six bolts were out, still took some prying to get them apart.

bob_98sr5 · #15 06-08-2008, 11:02 PM

Jeff,

So as shown in my picture, is there a green shaft coming from the differential that goes through the flex disc? Or i just need to pry apart as you said? We first tried a stout screwdriver, then a chisel, and gave up after that.

Did you disconnect the front part of the driveshaft right above the heat shield? Perhaps thats why mine is not coming off?

Thanks,
Bob