W124 1991 300D auto box a bit snatchy when cold

[tedious]

Hi I have read a previous post regards an older W123 300D auto box changing problems...not sure if the same applies to my version regarding vaccum pump connections?

I have adjusted the auto cable linkage so that it changes when it should...for the first mile or so, gear changes are a little snatchy going from 2nd to 3rd - and if 1st is used quite noticeably so.
Seems smooth enough when warmed up. When changing from D to R, and sometimes when stopping in D, can hear a 'clunk' sound from under the car - not too loud...while driving you can just hear a slight buzzy whine which I think is coming from the transmission and seems to change note with the engine revs.....
Is it worth me changing the gearbox oil and filter? If so can I use any Dexron II oil or does it absolutely have to be supplied by MB please?

 

[Andy]

Hi

Most of the diesels auto I have driven suffer with a little snatchiness when cold. There is a valve on the side of the injection pump which controls the vacuum to the gearbox modulating pressure valve. This vavle gives the quality of change or smoothness to the box. There could a number of problems ranging from this control box on the injection pump incorrectly adjusted or worn out. Poor vacuum, which could be a worn out vacuum pump. If its really bugging you get it checked out by your stealership or specialist.

You could also try not accelerating so hard when cold and see if the changes improve as with less throttle there will be more vacuum operating on the modulating pressure valve.

Regards

Andy @ www.mercedesservicing.com

PS. Any oil which has Dextron II as its type will do. Although with the problem you have I doubt it will make a difference. The buzzy noise could be one of your pulley bearings making a noise.

 

[tedious]

Thanks Andy for the reply. If I ease up on the acceleration, the box seems to shift a lot smoother. I was wondering about the tweak I read about in another post regards adjusting something - can I ask is this actually on the Diesel fuel injection pump body or on the vaccum pump body please? ( dont want to be making any rash adjustments on the injector pump )

The Haynes manual only covers the diesel vaccum pump in a couple of small paragraphs with no diagrams or functionality description...does anyone have a diagram of the pump or know of any servicing procedures for it - is a service kit available for it? I am not afraid of stripping it down for an overhaul if it is possible.

Any help - as always - gratefully received.

 

[tedious]

Turns out the flexible prop shaft coupling was wearing, gearbox end - started making a definite clunking noise when stopping - I took it to an independant Merc specialist, thinking he was gonna tell me the torque converter was knackared - he took it for a test drive and diagnosed it straight away.

So no more snatchiness wit new prop shaft couplings!

Thanks