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  #1  
Old 04-12-2010, 01:46 PM
Richard Howard
 
Join Date: Nov 2008
Location: Western NC Mountains
Posts: 69
Soft & Slow 3rd to 4th Shift - 722.303

With some luck I've found and bought a 2nd W126 300SD, a very good 1984 from Texas without any rust, and have been working through the few neglected issues that came with the car.

Transmission shifts from 1 to 2 and 2 to 3 are quick, firm, and without any flaring after setting the line pressure to 41PSI and modulator vacuum at idle to 9 inches. The shift from 3rd to 4th is however slow and soft.

From reading the posts I found in the forum archives, it appears that the B2 piston, its fit in its bore/sleeve, and the piston's link to the band are considered the probable culprits with poor 3rd to 4th shifts.

Is the B2 piston and its related parts the primary and likely cause of slow and soft shifts into 4th gear?

I'm wondering about this given the fact that all other shifts are very good. It would seem that the B2 band clamping would also occur during other functions in addition to the 3rd to 4th shift.

What else could be checked? Any comments will be appreciated very much.

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Respect, protect, and maintain complex systems - whether natural or of German design, to benefit from their full potential.

1982 300SD W126.120 with an OM617.950 from a W116.120
1984 300SD W126.120 with an OM617.951
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  #2  
Old 04-12-2010, 03:45 PM
Registered User
 
Join Date: Apr 2007
Posts: 342
If you don't have any trouble moving off from a stop your B2 is OK, unless it really bangs on a 4-3 downshift; then the internal seal is suspect.

Probably you just need a "shift kit," exhaustively discussed previously. Only add the spring which corrects your particular issue--3-4 flare, in this case--not the entire kit.
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James Marriott
2003 Buick Regal
1983 300D (228k, frau Auto)
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1987 300SDL junker 170k
1982 300SD junker, 265k
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  #3  
Old 04-12-2010, 08:44 PM
Richard Howard
 
Join Date: Nov 2008
Location: Western NC Mountains
Posts: 69
bump...

Thanks Jim, but I'd like to hear some additional comments in addition to yours.

__________________
Respect, protect, and maintain complex systems - whether natural or of German design, to benefit from their full potential.

1982 300SD W126.120 with an OM617.950 from a W116.120
1984 300SD W126.120 with an OM617.951
Reply With Quote
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