MB Trans. Problems (Please Help)
 

My '86 560SEL is driving awfully. After 55 mph the transmission starts shaking terribly and doesn't want to go any higher in gear. I think I am at the 3-4 upshift, but lately I've only been feeling 1 shift, that being the 1-2, so is it possibly the 2-3 shift. The tranny leaks from the Vac. Modulator (see my last post) , but I know that it is full of fluid when I check it. I changed the tranny fluid a few months ago, and I am wondering if I overfilled it. The dipstick is showing anywhere from a 1 & 1/2" over the highest mark to 2" over the mark. Also, if it is the modulator, where can I find some instructions on how to replace it. To top it off, the passenger valve cover gasket just won't stop leaking. I've replaced it twice, and it still leaks at the back. I know that it is on right, (The second time I used a MB gasket, whereas the first time I got one from Advance Auto and it split after install, this one is ok, but still leaks. I live in eastern NC, and None of the local shops know anything about a Mercedes. I would have to go 50 miles + to get to a MB specialist, and, well I dont think my car will make it. I like the old car, and I want to work on it myself, but I am at a dead end. I do not have a manual (always used MB Braingears until they disappeared:( ) so I guess I need to get one, but where from. Also, what is a good source of Quality MB parts. And finally, honestly, do you guys think that a person who mostly has worked on older American Cars, (Corvette, Continental, Seville, Skylark, Grand Caravan) is, to put it into the words of the nearest MB Independent," Uneducated persons such as yourselves should NEVER even open the hood of a fine motorcar such as a Mercedes-Benz."
Thanks for your help,
Dave

Seeing that the car is 20 years old, I would look for a good reman trans OR possibly a good used one.

a great source for repair information is alldatadiy.com. You can purchase an annual membership for your MB for $19.95 (I think that's the rate). It has TONS of valuable information for service and repair of your MB.

When checking the fluid on your transmission, the car should be at operating temp, on LEVEL ground and the motor should be running. If you're seeing fluid levels above the highest mark on the stick, hopefully the engine wasn't running - if it was - the tranny is severely over-full and needs to be drained of some of it's extra fluid.

When checking the fluid in a cold transmission, at least on my '92 300SE, a full transmission will show a level below the lowest mark on the stick.

Sorry for the rant on the previous post, just having a bad day.:dizzy2: Anyway, will the alldata cover any info on the transmission? I know that the M-B CD version used by Braingears did not seem to have any transmission info, and I know that mercedes used to make transmission manuals, but finding one is hard. I have been thinking that I might be best off to replace the transmission, where is a good source, (possibly adsit company?), I want to get out fairly inexpensively, but I also want a good unit. How hard is it to replace the transmission? I've never replaced a tranny before, (mostly have done engine repairs, i.e. head gaskets, intake gaskets, exhaust manifolds, fuel injection, sensor and sending units, and electrical, like starters, alternators, distributors, etc.), and I want to know if it something that I can do or that I need to budget for a shop to do it. What is a good price for a used tranny for a W126 like mine with the 722.4 I believe.
Thanks for all of your help,
Dave

I've done several transmission R&R's in my time. The most recent was on my MB to replace the rear main seal on the engine. On a V8 car, which yours is, the work is harder, you've got exhaust system piping on both sides of the transmission - mine is a L6, so only on one side for me.

This recent job I had a lift to do the work, and taking my time, it was about 10 hours work all-in-all. I wouldn't want to do it on this car without a lift.

The work isn't hard, just tedious. You do need a good set of tools - long extensions with swivels, etc. Preferrably swivel-sockets, where the swivel mechanism is integrated into the socket. On my car, the transmission-engine block bolts were 17mm heads.

AllData will provide instructions on changing the modulator, I remember reading about that on my car.

As for the leaking cam cover - I'd again recommend AllData - it provides good information on the proper torque values for fasteners - seals like the one you describe will leak if under tightened (duh), but may also leak if over tightened. I have both a 1/2" click-style torque wrench, and a 3/8" click-style torque wrench (needed when the torque values are less than 30 or 40 nm).

Before you call in the calvary for the tranny replacement, I'd make sure that all of the externally replaceable items - like that leaking modulator, are in working order and that the transmission isn't over-full.

I have no idea what a good used transmission would cost, nor where you would find one, although others on the board I'm sure do know.

What worrys me is that I will misadjust the modulator, making a bad situation worse. Is this possible? Also, would some Lubegard Red help or hurt the situation?
Thanks, Dave.

The modulator isnt too bad or hard of job to do yourself. When you get the new modulator, install it back in the hole and then drive it and adjust it accordingly after each drive to find the correct setting for you. Be carefull as not to break the plastic shaft when removing it. Pull it out at a slight angle above horizontal to remove it straight out.

The V8's also have exhaust on the right side of the trans. Depending on model there is a crossover pipe above (SEL/SEC) or below (SL) the engine.

These transmissions are fairly easy to remove as well, but that said I havent attempted one on my back in the driveway at home. It could be done, but I've always had a lift available to use.

Well, I'm going to try and order a modulator tomorrow, and install it as soon as it comes in. I'm also going to drain a little trans fluid tomorrow and see if I can get it down to the correct level. Thanks for all of you guys help, and Merry Christmas.
Dave

I believe these guys have some valuable books concerning transmissions for mercedes.

http://www.atsg.biz/oldsite/about.html

Wouldn't it be advisable to adjust the fluid level in the tranny first before ordering that modulator?