I just bought an 85 300d with a bad tranny. It leaks like a sieve and won't go into any gears except 1st, 2nd and reverse. I want to replace it and understand that the 300sd is a better solution and more bulletproof. I also understand that the plugs are different and the linkage needs some mods. Can anyone help me with this? I want to go to the junkyard armed with what I need to know and retrieve. Also, this is a California model and so smog crap is involved if that makes any difference. Thanks everyone and I hope someone sees and replys to this message before I buy another albatross to hang around my neck because I bought the wrong thing!

Sincerely,

Jimi x 12

I recommend staying with the same tranny you have. The design of your current tranny is just fine and you dont have all the other headaches of a hack job. Just get one that does not leak and slip, or better yet just rebuild your tranny.

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1981 300D 147k
1998 VW Jetta Tdi 320k
2001 Dodge Ram 2500 141k
1979 300D 234k (sold)
1984 300D "Astor" 262k(sold)
Mercedes How-To and Repair Pictorials
I love the smell of diesel smoke in my hair

Save yourself the headache of getting another bad tranny from a wrecking yard. Good chance the car is there because of one. Do a search here on rebuilt trannies and you'll find some places that have reasonable prices in CA.

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

http://mercedesdismantlers.com//usedmercedesparts.html

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

My understanding is that 1985 300D's and 300TD's have a "one year only" transmission. I don't know if the tranny from a 300SD is compatable or not. I think your best and maybe only bet is to have yours rebuilt. You could also find sombody parting out an '85, which happens from time-to-time.
I worry about this also......

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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

Rebuilding a MB trans can be a risky endeavor for those of us without the proper experience and tools. A mechanic told me that even places like AAMCO is a bad idea. They charge like $2,500, and although it is warrantied for a year, there is no riembursement for 'consequential losses' such as not being able to get to work. For what it is worth this mechanic felt any rebuilt trans from a source other than Mercedes is a gamble. Having said that, prior to rebuilding a transmission yourself you should consider how much time and effort is involved, along with the 'what ifs' if it doesn't work right.
I learned the hard way. Bought a trans on ebay that was said to be new and from the dealer. The seller said it would fit my sd (126 chassis), it wasn't his fault that I didn't do my homework and ended up buying a $1,000 trans for a 123 chassis (300d, cd, td). The difference being the signal for the speedo was a mechanical cable on the trans I bought vs. an electronic wire on my car. This was corrected by swapping the tailends of the two transmissions, adding another $250 to the labor. When it was installed, it shifted really hard and the mechanic was quick to point out that it might not be a genuine MB trans but just one that is poorly rebuilt and cleaned up nicely. I now believe it had to do with the vacuum line to the trans-which is getting to my point. Unless you conclusively test the vacuum quantity throughout the throttle range (see the sticky about 123 diy by Boostnbenz)
you don't know for sure whether your trans is bad or not. A new trans might just do the same thing because that is what it is 'being told' to do. The throttle position cable (aka bowden cable) also might be playing a part but vacuum is most likely. A small vacuum leak in the climate control could make it shift bad. As for leaks, mabee it is just the fliter gasket, or a seal-both are cheaper to fix than buying and installing a trans. Verify the vacuum/bowden cable etc. before spending any money on a trans. An exception would be if it shifts o.k. when cold but not hot, which would means leaking clutch packs. The fluid becomes less viscous when hot and the trans will 'flare' or seem to go into neutral instead of 4th gear, etc. As far an SD trans being better-I think it is the exact same except for the tailshaft, not stronger or weaker but the wire vs. cable setup.
As for an '85 being exclusive from earlier years, I thought it had to do with external components like the little modulator on the side where the vac line goes, not the actual transmission. Not really sure about this last statement,
anybody really know?

perhaps the valve body is different to better use the signal from the vacuum amplifier, which was introduced in 85.

For all those seriously contemplating rebuilding a MB transmission yourself (at least something like the 722.3 series), I'd encourage you to give it a try if you are either an experienced DIY or even just really interested. There really isn't anything there which is very difficult, and if you like machines you'll likely have a lot of fun doing it. And don't worry about the special tool issue. Most of the "special tools" just make it easier and the few things you do need can be easily improvised.

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'82 300SD - 361K mi - "Blue"

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

listen, look, .........and duck.

aside from the oil leaks, your transmission problems
are classic b2 piston failure. reverse works without
problems, 1st & 2nd might work, 3rd & 4th wont engage
or hold unless you are very light on the pedal, if you can
get them to engage at all.

if you look up at the passenger side of the transmission,
best with the transmission rear bracket dropped, you will
see two round metal 'portholes'. the rear one holds the b2
piston. if you take the plate off, a broken piston will be in
pieces.

there is much info on the b2 to be found. it, along with its
sleeve is a <$200 parts replacement and an hour(s) or so
work.

the 1985 tranmission is supposedly a superior one to earlier
ones, but the are all interchangeable. the '85 torque converter
is desired.

don
foolishly looking for another car . three aren't enough?

please, no, failure to engage 1st is a classic B2 failure. Failure to engage 3rd is something else. In the 722.3/4 3rd is engaged via DISengagement of the B2 band and application of K1 clutchpack. I'm not sure what trans Jim's 300D has, but he wouldn't be moving in 1st or 2nd without the rear brake band.

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'82 300SD - 361K mi - "Blue"

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

listen, look, .........and duck.

The banjos on the transmission cooler lines of the '85 are smaller than previous models. I dont know about the SDs. If you are replacing it with an older tranny, check the banjos.

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'85 300D Cal 280,000 miles
'14 GLK 350 60000 miles