I have a 92 400E 124k miles. Under medium to hard throttle the shift from 1-2 and 2-3 is fairly hard. Sometimes when this shift occurs there is also a belt squeak which also kills the AC for a while. I recently had some kind of rpm sensor??? replaced in order to get the AC working. What can be done aboout the hard shifting and the belt slip? (belt was replaced about 1yr. ago)

Thanks,
Alan


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Your monobelt tensioner is either out of adjustment or done...quite common on M119 motors it would seem. And when the belt's slipping, it'll shut down the A/C every time. Start there and hopefully you'll need go no further. I consider the tensioner a maintenance item and plan to replace it every 50-75k mi. Mine died at 43k mi. on my 500E, and that's essentially the same motor.

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All the best, Michael
500E
300TE