92 300te-trans slip (update)
 

(Please see latest post)We had heavy rain for 2 days, and I don't know if it's related or not, but my trans just started slipping. I noticed it with a rythmic slipping sensation in 1rst, and 2nd, and I turned around and went back home. Noticed it in reverse too. Fluid looks clean and correct. Previous owner told me trans was rebuilt about 12k ago.
I am wondering what if anything I can adjust. I assume there are vaccuum lines to check. A few years ago I had a 300sd that had a B2 piston I replaced and fixed that car, so please someone tell me there is something I can check myself.
Thanks in eager anticipation, Michael

How many miles are on the car now? Do you have records for what was done when the transmission was rebuilt? Does the fluid smell okay ie. not burnt?

Car has 148k. My buddy who I bought it from travels out of the country frequently and that must explain why he hasn't returned my calls. Among the many reciepts in the car, this trans rebuild is NOT among them. The fluid has vurtually no odor and looks amazingly clear and clean.
I am a DIYer, but don't want to do anything that could possible affect a potential warranty. This is driving me crazy! (er)
I just took it for a drive this morning. First I tried it cold, then warmed it up-no difference. While parked and foot on brake, I can feel the thunk when put in drive, but slip is immediate. (barely made it up my diy ramps) It will shift solidly into each gear but any rev's will induce slippage. I just drove it about 10 city miles this way very slowly. 3rd and 4th seemed to slip less but still there. rechecked fluid is fine.

Confirmed rebuild at 2 1/2 years and 40k miles ago. No warranty, shop says based on description of problem it needs another rebuild.

There has to be something I can adjust or check,... anyone?

Sounds like a control pressure issue.

The transmission is mechanical/hydraulic. Hydraulic pressure is used for shifting and for compressing the clutches to maintain friction, if the hydraulic pressure is inadequate the clutches and bands will slip.

A competent shop can test the working pressure of the transmission, which IMO is the next step. Since the problem seems to be affecting all directions and gears, it is not a single clutch-pack, piston, or brake band (the pistons operate the brake bands and have nothing to do with reverse).

Thanks. I changed the filter andfluid today just to check things out, and a mechanic frend suggested I disconnect an electrical plug from the left rear side of the trans, which is supposed to change hydraulic pressure. Ever heard of that?
Either way, it's going to a transshop tomorrow to have the pressures checked.
Michael

The downshift solenoid? Won't change pressures. The other electrical connector is the start-interlock (AKA: neutral-start switch)/reverse-light switch.

Correct on the start-interlock as I found out. The only other plug I could find (1 pin) was on the very tail right side of trans., no difference unplugged.

Well a trans shop tested line pressures and said they were normal, indicating the problem is internal. The clutches are slipping and it will require a rebuild.
Now I am weighing wether to buy a used 4matic trans or ditch 4matic and swap in a 5 spd automatic.
Any comments appreciated.
Michael

I've not studied up on the 5speed, but believe that it requires a control module that runs it, and being that it is on a '94-up chassis I'd guess that it needs communication with the CANbus which your '92 doesn't have.

Ok, I want to try to repair this myself. I have found several places that sell overhaul kits witch include clutch dics, and b2 and modulator bands. My questions: Is there ANYWHERE to find detailed instructions or diagrams for the transmission, and are there special tools required?

Anyone?

magical trans fluid?
 

So I removed the pan, B2 piston and valva body only to find no evidence of broken or sticking parts. My conclusion is that I need to replace the entire trans with a reman unit.
My question is, has anyone had luck with a different fluid or fluid additive which might work even if only temporarily?

Well today I re-examined the valvebody and B2 and could find no faults, so I put it back together with new fluid. I continued to check vacuum lines, bowden cable, kickdown wire, anything I could see or think of.
I had not driven the car more than 50 miles since this it has started slipping and have changed the fluid for the 3rd time now. I have lost my borrowed car so today I had no choice but to start driving it again.
It slips/shudders at take of, but if done very gently it will make it to any speed I want to go, but again, any sudden throttle increase will induce slip/shudder.
Considering the complete lack of fiber, silt ,chunks or even a burned smell, I am not convinced this 39k trans is shot.

Comments are welcomed

So I just drained the trans fluid with the "Lucas" , and refilled with DexIII, and I have adjusted the modulator.
One question about the modulator, does the flat tab have to be pulled out to adjust it? Because I was able to turn it without pulling it out-I went 1 and 1/2 turn clockwise with no change in trans operation.
Thanks, Michael

Today I replaced the modulator. Weird thing is that absolutly nothing is different, how can this be? I have read that modulator adjustment is very tricky but just popping this thing in and driving has produced NO change at all, I then turned it up a full turn and still absolutly the same. (has strong vacuum to mod.)
I then drained 3 qrts and refilled with B&M trick shift, again, no change.
Somebody please give me a tip here.
Is this just a worn out set of clutches? or possible an adjustable issue?

Today I turned the mod up 7 turns until it stopped, absolutly no change in trans slip or shifting. What gives? I have read that at this point it should be slamming into gear but it is unchanged.
Also, has anyone read of a bulletin to shim the shaft to reduce clearance in the modulator?

Well I appreciate your replies, but today pulled off the vacuum line from the modulator and the trans still is unchanged! I expected it to just slam into gear but still thunks nicely into each gear and doesn't slip until significant throttle is applied. And now that it's real cold out it slips even less.Weird. A call to the local MB dealer informs me that if it slips with the vac disconnected that the problem is definately internal. Anyhow this car is now parked and you will soon find it in the classifieds.
Thanks all.

the trans was not re done correctly we have seen this many times

the 2 main drums in the unit one being the foward clutch it has a riverted plate in the clutch drum, shops that do not do enough of this type of unit have no idea that the O Rings the factory put under the plate in the drum can be replaced ,

when we buy a rebuild kit we ask for this Special O ring kit as well as the re program valve body KIT They do not come in the regular OH major OH Kit -- all together its pricy but you need to do it all not just at the time what is worn,

and thats what i think they did, if they do it again they may even mis it again and end up charging you twice for what they dont know < we have had many sent to us from other shops to be fixed -- jz