R129 Auto gearbox

[nevilledoreen]

Hi I am a new member ,I have a 1993 R129 ,300SL 24 valve.
Recently the automatic gearbox has been flaring on the change from first to second gear it only does this at certain engine revs ,when I drive it slowly it is OK and when I drive it hard it is OK At times it will also thump into gear on the first to second change.
Can anyone tell me what the problem is?
The car has only done 100000 kilometres and the transmission oil is full and replaced recently.
Regards
Neville

[CraigB]

I don't know your model but it sounds possible that it could be the modulator on the auto. This is a vacuum operated thing so vac leaks or the diaphragm can be the problem - but lots more people on here know more about this than me!

[Ivanerrol]

Depending on the market and where your R129 originated from it may have a 4 speed or a 5 speed auto transmission.

The 4 speed will be the common 722.3 transmission used in many cars of the period.
The 5 speed is the not so common 722.5.

Flaring between first to second is a very common problem.
Can be as simple as the transmission vacuum modulator or valve springs in the valve body.

I would take your car to an Independent Mercedes specialist to get an opinion.
Worst case scenario is that an overhaul is required.
4 speed overhauls are in the region of between 2 and 3 thousand dollars
5 speed more $$$$

[nevilledoreen]

Thanks fellas much appreciated
Regards
Neville

[Greg in Oz]

Just approved your post and moved your topic to the R129 forum where it is more likely to receive helpful replies.

[AMG]

If it wasn't a problem before you had the transmission fluid changed, the first thing to check is that the fluid is the correct type and the level is correct. check when engine is HOT and on level surface in P or N.
dipstick has a max mark to tell.
do not use any paper towels to wipe it. introducing any debris will cause issues.

having said that, if the trans is now slipping, you have a couple of possibilities, other than above.

1. debris in valve body causing a blockage.
2. modulator failing or vacuum leak. (adjustment needed or replace modulator)
3. K1 & k2 piston seals worn.

If the trans fluid change included the pan gasket and a new filter, along with the correct fluid, and it was done cleanly, then the possibility of introducing foreign object debris into the transmission should be minimal. Not to say that it is not possible though.

If the fluid level is correct, there should be an improvement in shifting, and not the opposite.

If you have the 5 speed, you may be needing to reset the adaptive-shift parameters. There is a how-to on this Adaptive Shift reset Video

[Ivanerrol]

If you have the 5 speed, you may be needing to reset the adaptive-shift parameters. There is a how-to on this Adaptive Shift reset Video

The 722.6 didn't come in until '96 and the O.P. has a '93 model.

Some of the six cylinder W129's were provided with the 722.5 - 5 speed which in essence is the 722.3 with an electrically controlled overdrive tacked on.

[Greg in Oz]

If it has the 5 speed 722.5, overhaul can be expensive. This transmission was also used in the Australian delivered 124 coupes and cabriolets with the 24 valve 6 cylinder (M104) engines (300CE-24, 320CE and E320) and has a reputation for being fragile. The four speed 722.3 (used with both 6 cyl and V8 engines) by comparison is more reliable and less costly to repair.

I don't know how much truth is in it, but I have heard that the life of the 722.5 can be extended by selecting "4" rather than "D" for running around town (lower speed and stop-start driving). This prevents the transmission frequently shifting between 4th and 5th. The use of "D" can be reserved for the highway when overdrive 5th is needed. So far it has worked for my father with his 124 E320 coupe.

[AMG]

If you have the 5 speed, you may be needing to reset the adaptive-shift parameters. There is a how-to on this Adaptive Shift reset Video

The 722.6 didn't come in until '96 and the O.P. has a '93 model.

Some of the six cylinder W129's were provided with the 722.5 - 5 speed which in essence is the 722.3 with an electrically controlled overdrive tacked on.

Didn't see that it was a 93 when I initially read the post. the 93 M104 24v SL's should have the 5 speed if not manual. (92 mechanical update- HFM)

However all the same rules apply except for resetting the adaptive shift.

check oil. check modulator & vacuum line, check bowden cable, check kickdown solenoid operation, then move on to more serious investigation.

Trans service manuals are in the reference library.

Trans will likely be a 722.50x, which means making sure that valve body passages, springs and ball bearings are spotless clean, pump is working properly and the reverse clutch pack & piston are not slow to engage also, as well as the points I mentioned previously.

If the trans does croak and it's a 5 speed auto, you're looking at big $$$$ bill for a complete overhaul. Taking shortcuts on the 722.5 is a big no-no and will cost more in the long run.

For the OP's sake I hope it's a vacuum leak.

[nevilledoreen]

Thanks for your replies they have been helpfull.
The gearbox is a 4 speed automatic with the switch for economy and speed mounted next to the gear lever, also the gearbox was flairing prior to the oilchange.
I think I will start looking for loss of vacume first and go from there.
Thanks again any further info will be appreciated
Regards
Neville