Transmission slipping in 1/2 gear..
 

Can some one give me some idea as to where to start a search, on my transmission issue?

The culprit is my 84 300TD. last filter and fluid change was 20,000 ago. It has been running well until today. on the way home it started slipping when it would down shif into 2nd. I pulled in to a safe place, and checked the fluid, which was abit low, added about a quart. (first time I have ever added fluid, although I have not checked the level in about 7,000 miles)
the car still slips in first, and in second it slips and shudders a bit. If I can coax it to shift in to third then it runs fine.

BY accelerating and letting off repeatedly.. once the car is rolling it gets slightly better and the transmission will kinda grab hold at 5 mph, then it shifts into second with a thump, but chatters and slips until third.

in fact I drove it home about 35 miles in 3/4 gears with not a problem, but 1//2 slip like mad.

My question is it this a adjustment(some how I doubt it) or a new transmission? The fluid did not seem to be brown, or burned smelling. As I write this may be the only way to find out more is to put a new transmission filter and oil in it? please give me a topic to search under and I will run with it, but I dont really know where to start.
Thanks
Jason

I am no tramsmission expert....but I would start by checking ALL the vaccum conections. On mine just blocking off the EGR vac line with a BB greatly helped the shifting/slipping of the transmission. Replacing a 2" section of hose going to the trans modulator valve really smoothed it out. This won't take long, you may get lucky and fix it for $.15!

That the problem came on quick leads me to think "simple stuff"....of course I am by nature simple-minded!

Check your transmission modulator valve circuit (vacuum, lines, switchover valve etc) and let us know what you find.

If the vac' system checks out...try a 'search' for K1 spring.

.

Drive the car with the vacuum hose to the modulator disconnected, if the shifts feel hard, with no slippage, you no vacuum response to the modulator.

I wonder if that could be the beginning of trouble with the B2 piston.

Exactly what I was thinking too...perhaps the piston cracked and is still allowing some pressure to build (enough for a slippery shift) but not what it would when working normally....

I'd check the B2, my bets are that something happened to it, especially since the problem is in gears 1 and 2, and it happened so suddenly.

I doubt it has much to do with the modulator circuit. If anything happened to it, it would be losing vac and causing harsher shifts.
this is odd considering harsh 1-2 shifts are "normal", I don't think my 1-2 slipped at all when I applied full unregulated vac to the modulator, but the rest did massively.

Clutch Pack
 

I have no experience with MB automatic transmissions YET but I have extensive rebuilding experience in American rear wheel drive cars.

From what you describe it does sound like a servo piston cracked or split or sealing rings broke thus not building enough pressure to actuate the appropriate band.

If this turns out not to be the case it sounds an awful lot like worn clutches and steels in the corresponding clutch pack.

The suddenness of this leads me to believe something broke rather than gradual wear to a clutch but it's really hard to tell what's going on inside an automatic tranny till you get her apart.

Good Luck,

Wayne

mine did that and it was the b2 piston. Easy change from the outside of the tranny. Search this site for info
Steve

Yea its the b2 piston did the same thing on my car not that bad to change, just be carefull when you jack up the car to block it well be safe. Lots of info on the b2 even a write up with pictures and every thing.
Bill