On my '82 300 SD I have some flaring between 3-4. I have been told by my dealer that the tranny is toast and needs replacement. Is this true? How long can I drive it and if and when it fails will it leave me stranded?

Any info is appreciated.

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82 300SD 100K
91 Caprice SS
92 Jetta TD

100K miles, quite possable. Usally the LB3 clutches go first (reverse). To do a quick test to guage wear. Move gear shift lever from R to P quickly and observe severity and delay of engagement. If delayed into D and then clunks, usally means B2 band/drum worn. If reverse delay/clunk, worn clutches (LB3), however you could replace the spring for accumulator 3-4 shift. If a different spring is installed, it may improve the flare. Also keep in mind 3-4 flare is K2 and K3 clutches being applied and damage may have already been done.
Good luck.


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Mercedes-Benz Master Guild - 2 years
Shop Foreman - 20 + years - dealer.
Part owner - MBZ Transmission remanufacture
2000 SL500
1995 E320
1989 300SE

Oh yeh, forgot to mention. Make sure the vacuum is OK. If too high vacuum during shift, that will also cause flare.


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Mercedes-Benz Master Guild - 2 years
Shop Foreman - 20 + years - dealer.
Part owner - MBZ Transmission remanufacture
2000 SL500
1995 E320
1989 300SE

Ian

Thanks for your reply. Will the tranny fail completely or will I just lose a gear? Also, when you say check the vacuum, where should I check and what should it be?

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82 300SD 100K
91 Caprice SS
92 Jetta TD

Eventually it can fail, however that usally is when B2 band breaks or the pin falls out.
Af for checking the vacuum, there are several things to check and several vacuum components involved in the system.
The first thing is to "T" a vacuum guage to the black line that goes to the transmission. At idle depending on the model, about 14" of vacuum and bacically upon full throttle should drop off to or near zero (basic check only).


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Mercedes-Benz Master Guild - 2 years
Shop Foreman - 20 + years - dealer.
Part owner - MBZ Transmission remanufacture
2000 SL500
1995 E320
1989 300SE

Ian;

Thanks. One more question. If the B2 band is toast shouldn't I see clutch material in the oil? As it is now the oil is absolutly perfect and not a hint of clutch material or anything in the oil? Just seems strange that there is nothing in the oil if one set of clutches is worn out.

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82 300SD 100K
91 Caprice SS
92 Jetta TD

The early 722.3 trannies were full of problems that caused 3-4 flaring. They were originally installed with too much clutch pack end play, the 2nd gear band had too high a friction coefficient and the B2 servo piston which is released to go into 4th caused leaking.

All these problems were repaired with technique or improved parts. A tranny as old as yours would have every reason to have leakage in its 4th gear clutch pack lipseals anyway.

As it turns out most problems such as yours can be covered up by adjusting the modulator pressure higher and finessing the shift point/vac relationship. As Ian points out the vacuum must go from 10-14inches to zero at full throttle, but there are three considerations that affect the actual vac during shift. First is the actual shift point as determined by the control pressure cable. For any given 3-4 shift the modulator pressure will be higher if the throttle is further depressed; thus if you make the shift earlier it will be done with more throttle (i.e. if you are releasing the throttle as the shift is made - due to speed - the vac goes up and pressure decreases tremendously).

The relationship of vacuum to throttle is also adjustable at the proportioning valve on injection pump. Some of the proportioning valves (probably yours) can be adjusted for the overall range (i.e. 14" to zero vrs 10" to zero).

While schmoozing the controls are an easy alternative (if you find someone who can do it - sorta like playing music by ear)the real repairs are inside with proper clutch end play, new non-leaking seals, low friction band (this allows more overall shift pressure without 2nd gear taking your teeth out) and a modified B2 servo piston which improves the shift timing.

BTW unless you brutalize the shift it will continue doing this shifting indefinitely. They did it new if set-up wrong and it doesn't hurt anything if you can adjust your shift style and let up till fully engaged.

Thanks fella's for your help. I will just drive and enjoy. I never have liked making full power shifts so it will be second nature to backoff on the throttle and let it shift.
From reading through the service that had been done on this car it sounds like the tranny has been like this for a long time so it should last a long time. Again I do thank you for your help, it always pays to get a second/third/fourth opinion on these things.

Kind regards
Mark


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82 300SD 100K
91 Caprice SS
92 Jetta TD