Manual trans help please!
 

I have a 91 w124 with 270 000 Km and the 5 gear trans, shifting (only while the car is in motion) between 1rst and second was never smooth, I decided to change both trans and differancial lube last saturday, the guys at the shop told me that the trans lub looked as if it was neglected too long, as I suspected since I bouth this car, last year. My trouble: I expected an improvement in shifting and got the oposite 1 and 2 are harder as ever to use 2nd is only to be engaged coming from 2000 rpm from 1rst or real pressure (force) is needed on the stick, it doesn't feel right
What's going on???

Difficult to explain why it would get worse. Did you put in thick gear oil? These gearboxes take a thin oil.

Before condemning the internals, consider the shifter mechanism itself. Mine was binding horribly mostly for want of a clean and lube.

See this thread for more details.

the synchronizers need some friction to work properly, so better lubrication would reduce their performance.

not an expert in this area, but maybe the synchros from 1-2 are worn already?

i envy you guys in Europe - you have lots of manual 124s.

I forgot to mention the shifter linkage bushings. These are easy to replace, and can make a big difference on their own.

What lubricant did they put in the trans?

The spec for my '88 five-speed is Type A Suffix A ATF. That's the old original GM ATF that has a small dose of whale oil to prevent clutch chatter and hasn't been available in this country since the early seventies!

An acceptable alternative should be the current Dexron III. Mercedes also lists 20W non-detergent motor oil as an alternative, but I wouldn't recommend it unless you live in a tropical climate.

I use Redline MTL, which is a specially formulated synthetic base 70W-75 GL 4 gear oil designed for boxes that specify ATF.

Duke

The shop used a 70w/80 Motul formulated for manual trans, I don't see anything outlandish there, after a few Kms the shifting ease as the trany warms up, it has just become more finiky or touchy, downgrading from 3rd to second I have to apply pressure on the stick t'il 2nd engages sort of itself witch can take up to 5 second, or I can force it while double clutching. Could an overfill cause hard shifting? they filled the tranny t'il lube spiled out of the fill hole, I have no idea if that amout to the specified oil content.
As for the shifter mechanism, I had a look at it, it seems to be made of a lot of different materials, metals, plastiques, teflon coated rollers maybe? I droped some light oil in it, would lube maybe not be recomended? there was no sign of grease or oil left over. I suspesct that the shifter linkage bushings are sealed and can't get greased am I right?
Thanks for your imput guys.

Putting 70/80 in a trans designed for 10/20 will definitely make it shift harder. After a while you will stretch the syncros and it may seem better, but a while later they won't work at all.

Because the syncros were probably poor to start with, you may be better off with a higher straight weight motor oil like 20w or 30w.

Well, that explains why it got worse.

Try the right oil, and go from there. I like the Redline MTL, if that is available over there.

The linkage bushings I am talking about are under the car, on the ends of the metal rods that actuate the 3 gearbox levers.

I had the oil changed and What a difference!!!
The shop an I assumed that regular manual trans oil would do but You guys were absolutly right on the money, we switched to oil I bouth at the MB dealer and I now shift smooth and only with a slight hand pressure, the way it was ment to be.

Thank you!!

What lubricant did you install?

BTW gear lubricant viscosity numbers are different than motor oils. For example, ATF is usually about a 70 "weight" gear oil, which has a similar viscosity range to 10 weight motor oil.

Further information on motor and gear oils is at:

www.api.org

Duke

Get synthetic tranny oil. Seriously.

My dad had an 93 BMW 3.6 M5 and had sythetic tranny oil put in and it shifted much better; much smoother. In fact, it kept on getting better.

MB gave me a Metabo Dexron III ATF. This oil is the replacement that is used in their shop. The back label specified that it is for Automatique and SOME manual transmitions. It was 16 Euros for two quarts I didn't check if it was syntetic or not. sorry