1992 Mercedes Benz 300SL R129 Automatic transmission never ending 5th gear question!
It is a 722.5, 5 speed automatic trans..124K miles.Fluid looks and smells good.Did a pulse test on the trans.controller and got 1 blink (OK).On the highway it does not upshift into 5th,so RPm's at 65 mph are 3500 .So,its got to be in 4th.With my foot On the accelerator I can push the shift lever to the left which is "4" and nothing happens,no down shift car keeps on like I did nothing.If I do the same hing but with my foot Off the accelerator,it does a down shift! Another thing I noticed is when the shift lever is to the right in "4D" (which should be in 5th gear) and I take my foot off the accelerator and coast the tach.drops down as if it where in neutral.When I put my foot back on the accelerator tach goes back up in RPM's and no signs of slipping or anything noticeable like that.I did test the shifter micro switch with a Ohm meter and it worked every test.I also made a jumper for its connector and tried that on the highway with no different results. I also matched the wiring colors on the 3 male and 3 female conns.of the decrepit,breaking itself apart from age plug between the FI and the engine head.That seemed to be the correct thing to do because I had 3 choices not matching the wire colors the trans.did not do the down shift no matter what.Any ideas ? Thanks!!