I have a 1997 C180 (UK spec) with 170,000 miles on the clock 5-Speed Auto (722.6 Gearbox). It use to struggle up hill (I live on a hill
The car would be struggling to reach 35mph with the Rev up to 3.5-4k RPM. It would concern me so I made the mistake of letting another garage other than my usual indi (he was away on leave) to change the gearbox oil. They either used cheap oil or did not not connect the cooler pipe properly as after a few weeks the gearbox made a whining noise and started to slip! Went back to them but the B*****d said the brass bushing in the gearbox had gone and typical of a car of that mileage, the cheaky B*****d! Anyway got myself a second hand gearbox (722.6) from a reliable Merc specialist, had it installed by my regular mechanic and also used Febi Bilstien AFT (They use the exact same oil as the Merc dealers).
However they did not have the right dipstick and over-filled the gearbox, no alot but enough to make the gearbox not function smoothly as I would want, i.e stick in 1st or 2nd when moving off, a bit longer than I would like and change on about 3-3.5 RPM. Anyway, I was glad to have a the car functioning again and drove the car like this for about a couple of months until I got around from removing the excess AFT. I invested in the special dipstick and managed to get the AFT on the right level last week yet still get the sticky shift and struggle up hill? Not all the time mind you but at least a few times on every journey?
Therefore, I have another gearbox fitted, the correct ATF and now at the right level, so what else have I missed? I bit the bullet and went to the Local Merc dealer, they used the STAR machine and said the olny thing they could find was a few gearbox error codes which they think was caused by the old gearbox and they cleared those codes, but could not find anything else wrong??
It is really bothering me and I wish I knew what else I can do as I am attached to the car, and can live with infrequent episodes but dont wish to spend much more than I already have