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Old 03-20-2006, 09:12 PM
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Join Date: Nov 2003
Location: northern VT
Posts: 537
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.

46 WDX Power Wagon

84 300TDT daily driver
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Old 03-20-2006, 09:58 PM
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Join Date: Dec 2005
Location: Texas Hill Country
Posts: 510
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!
1983 300TD Wagon
Even a broken watch is right twice a day
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Old 03-20-2006, 10:12 PM
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Location: Loganville/Atlanta
Posts: 2,156
Check your transmission modulator valve circuit (vacuum, lines, switchover valve etc) and let us know what you find.
1981 300D 147k
1998 VW Jetta Tdi 320k
2001 Dodge Ram 2500 141k
1979 300D 234k (sold)
1984 300D "Astor" 262k(sold)
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Old 03-20-2006, 10:21 PM
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If the vac' system checks out...try a 'search' for K1 spring.

[ ]

"A liberal is someone who feels they owe a great debt to their fellow man, which debt he proposes to pay off with your money."
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Old 03-20-2006, 10:29 PM
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Location: new york/orange county
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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.
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Old 03-20-2006, 11:58 PM
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Location: RI shore
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I wonder if that could be the beginning of trouble with the B2 piston.
'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.
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Old 03-21-2006, 12:14 AM
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Join Date: Oct 2004
Location: Grand Rapids, MI
Posts: 15,429
Originally Posted by Pete Burton
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.
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 102k - mine - (OC-104,600)
'17 Metris(VITO!) - 26k - wifes (OC-25k)
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'13 ML350 Bluetec - 73k - dad's (OC-75k)
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Old 03-21-2006, 06:50 AM
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Location: Rochester Hills, MI
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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.
Adam Lumsden
(83) 300D
Vice-President of the MBCA International Stars Section
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Old 03-21-2006, 07:27 AM
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Join Date: Mar 2006
Posts: 26
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,

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Old 03-21-2006, 07:31 AM
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Join Date: Nov 2005
Location: new bedford Massachusetts
Posts: 179
mine did that and it was the b2 piston. Easy change from the outside of the tranny. Search this site for info
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Old 03-21-2006, 08:41 AM
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Join Date: Mar 2000
Location: cool ca
Posts: 109
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.

94 dodge cummings,86 ford 6.9,75 mbz 240d[ sold], 82 mbz 300sd,83 mbz 300sd
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