Rear Suspension Rebuild/Bent Trailing Arm

So I finally got around to dealing with the apparent bent rear suspension on my 85 300TD - the main symptom was extremely rapid tire wear on the outside edge of both rear tires. I measured toe-in of the rear w/ a tape measure and found approx 3/4" of toe-in.

I decided to remove the entire rear subframe since I wasn't sure exactly what was wrong, though posts here had led me to suspect a bent trailing arm. As may have been posted here before, it is indeed possible to remove the rear subframe without a spring compressor - also, it's pretty easy.

I did the following:

(1) This is a SLS wagon, so I disconnected the fittings for the shocks from above and unbolted the shock from the top.
(2) Raise the car, block the front wheels, support the rear on jack stands
(3) Remove the shocks
(4) Remove brake calipers from the trailing arm
(5) Disconnect sway bar links
(6) Disconnect e-brake cables at the lever-type thing
(7) Disconnect driveshaft at differential
(8) Remove the exhaust hangers at the muffler and at the tailpipe, lay the exhaust on the ground
(9) Put a jack under the differential, raise it just a hair, and remove the four bolts holding the differential mount to the body
(10) Slowly lower the jack under the differential - the whole works will hang back on the subframe bushings, the springs didn't fall out in my case, but only because the rubber spring seat on top was holding onto them - just a slight pull and they come right out.
(11) Unbolt both subframe mounts
and finally
(12) Drag the whole business out from under the car

This really isn't as bad as it sounds, though the whole thing is fairly heavy and its good to have help when moving it around. It seems to me that it would be fairly annoying trying to unbolt the trailing arms while under the car. Then again, if you're not replacing everything, its probably not worth the effort to get the whole works off the car.

I measured the trailing arms by using a 4 ft straight edge - I placed it flat on the hub, projecting it forward, and measured the perpendicular distance from my straight edge to the outer arm of each trailing arm. The distance on the left trailing arm was 7/16" less than that of the right trailing arm - a used left trailing arm I located measured the same as the right - sweet! I can't see any signs of bending, and the paint on the bad trailing arm doesn't even seem to be cracked anywhere.

Now the strange thing - I was installing new bushings into the trailing arms and about the bolt them back onto the subframe when I noticed that one of them is not nearly as stiff as the rest - I can move the bolt around about as much as I could on my old bushings (200k on those, apparently) - I'm getting another new one and will replace the odd one - anyone ever seen a bushing be too soft right out of the box?

Also, I think I recall reading somewhere in the archives that it is a real pain to get the axle seals out of the differential - this is indeed true. Until I tried this: Grab the seal with a vice-grip, stick something over the end of the vice grip to use as an extension, and give a few sharp pulls on it - both of mine popped right out. A screwdriver was useless, as somebody has noted.

Also, the remainder of one of my old subframe bushings has secured itself nicely to the huge pointed bolt. Any ideas how to get it off there? I was thinking I'd put it in a vice and heat up the bolt with a torch...

So, one more replacement bushing on the way, rebuilt axles from CVJ to arrive next week, hopefully it'll all go back together easily too

[signalredcoupe]

I had to do the same thing when one of my control arms rotted & almost broke in half on my coupe. Good thing my sedan's suspension was like new. Also had the same thing happen with both of the pointed subframe bolts. The torch thing didn't work. I had to cut the sleeve off of the bolt without touching the bolt. The whole system is much harder to install without a spring compressor, but it can be done. Setting the rear wheel bearings is a lot of fun also. Paul.

[bro frank]

i have a 78 300d

have a bad rear wheel bearing.

also have an extra trailing arm with a good bearing. it's already off the parts car

would it be easier to swap arms then to replace the bearing?

[mobetta]

^^^ i cut my old subframe bushings off with an angle grinder, dremel tool and cold chisel. cut most of the way thru, lengthwise, and then take the 3 lb hammer and chisel to it.

^ it just may be cheaper to switch trailing arms. prolly about the same amount of time, but you wont need any special sockets, pullers, etc. bearings are deffinatly easier out of the car, too

I did both t-arms, on the car, as 1 had rusted thru, and the other was close behind. not a terribly difficult job, the worst part was deffinatly dealing with those pionted bolts seized to the bushings- easy 6 hours of a 11 hour project...

make sure to remove the fitting to the shock on sls cars, as it will break off when you drop the shock if not. I had to get one overnited from FL, for $56 its a $11 part. only 2 were in the US at dealers at that time.

[bro frank]

so the bigger of the three bolts is not going to spin out freely?

is it going to come out using a ratchet or a hammer??

and

i got the benz as a wvo test platform.

how long have you been using wvo? do you blend and if so how and with what?

how well does the cummings do?

[bro frank]

so the bigger of the three bolts is not going to spin out freely?

is it going to come out using a ratchet or a hammer??

and

i got the benz as a wvo test platform.

how long have you been using wvo? do you blend and if so how and with what?

how well does the cummings do?

[mobetta]

the large pointed bolt on the subfrme bushings were a PITA on my MN car. you may get lucky. my compressor is small, so I ended up usin a breaker bar. and lots of time.

Ive got only 13K on the benz, one tank w/ gloplug heater, Injector line heaters, and a filter wrap I did yesterday.

I blend w/ ULSD now. rate depends on temps.

the cummins runs great. 2 tanked.