I just bought a 1981 300SD which is being shipped to me. The PO describes a transmission problem as follows;

1st to 2nd gear flare - if you let off the accelerator petal, it switches to second immediately. 2nd to 3rd to 4th - no problem.

I searched the forum and found info on K1 spring, B2 Piston and vacuum adjustments. The info I found relates to 2-3 and 3-4 flare regarding the K1 and B2 problems.

Do you think the 1 to 2 flare is also K1 or B2 related? Your advice would be greatly appreciated, since I hope to do the repairs myself.

Thanks

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1961 220SB Hydrak
1966 230S - Too Good for Parts
1981 300SD - now in Oakville

Could be B2 related, but not K1.... Or it could be as simple as some vacuum or modulator adjustments. You'll just have to get your hands on it and start tuning..

it could just be that you have some vacuum leaks, and maybe need to adjust the bowden cable on the throttle linkage...

but also, the B2 affects 1-2 gears, but i think if it were busted it would slip really badly, more than just flaring...im only going by my single experience, though...my B2 piston went out and made my transmission slip really bad when in 1st or 2nd gear...when i got up into 3rd and 4th i had no problems at all, it seemed....the B2 piston job would be a major pain to go through and not have to...id check the vac system and do some adjusting on the bowden cable before anything else

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1985 300SD 192,000miles...Astral silver/ Grey MbTex

1983 300D 194,000miles...White/Tan MbTex...my newest addiction

Thanks -

What actualy happens to the B2 piston when it has a problem - Does it actually break or does it jam up and fails to move? Can you tell by looking at it if it is gone? Can it be fixed or just replaced? The part is over $100.

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1961 220SB Hydrak
1966 230S - Too Good for Parts
1981 300SD - now in Oakville

when it fails, it breaks up into about 5 or 6 pieces....heres a pic of a broken one, and one of a new one....i got these pics from www.mbz.org ...if you go there and click on "articles", and then look for the B2 article listed under transmissions, theres a whole writeup about symptoms as well as instructions for repair

Attached Thumbnails

 

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1985 300SD 192,000miles...Astral silver/ Grey MbTex

1983 300D 194,000miles...White/Tan MbTex...my newest addiction

http://www.peachparts.com/shopforum/attachments/tech-help/23407-need-some-help-quick-w126-b2-piston-replacement-intact.jpg


copy and paste

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1985 300SD 192,000miles...Astral silver/ Grey MbTex

1983 300D 194,000miles...White/Tan MbTex...my newest addiction

Hey Wally!
Sounds like a vac prob to me. There is a lot of tuning that you can do on the vac system on one of these. The modulator is the best! Adj, drop off jack, test drive. Jack, adj, drop, test drive... etc... There is plenty of info on here, but I have some links if you have any trouble finding it. You will know way more than you ever wanted to know about diesel vac systems by the time yr done.
Cheers, and happy dieseling!
-Matt-

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Currently:
1972 350SL Euro 4spd
1973 BMW R75/5
1981 BMW R80GS
1995 FZJ80 with OM606 Conversion In Progress

1984 300d Turbo
Found Vacuum Leak Very Slow, Fuel Door Lock Actuator Leaking Locking And Unlocking It Is Spring Load Open, Pull Panel Right Side
Remove Plug At Rear And Bend Top, 2=nuts Turn 1 Turn Ccw And Slide Up 2 Vacuum Connectors And Do Not Loose Spring On Shaft

Brakes, Trans, A/c Vacuum Controls Improvement Great Results Of
Trans Shifting If You Lock Doors Overnight And Push Or Pull The
Fuel Cover Open 8 Hrs Later Its Leaking, Check By Using Vac Tester

1984 300d Turbo
Transmission Shift Adjusted Modulator Cw 1/2 Turn And Adjust
Bowden Cable It Was Slipping In 3 Gear 1000 Rpm After Adjustment Ok
Also Replace Valve Seals And Springs 6 Hrs Diy Power Is Like New Engine, Seal Kit Is Mercedessoure.com $74.00 With Push On Tool And Instructions Plus Push On Thread Stem Covers, Oil All New Seals Overnight