I recently bought a 91 300TE with 4-Matic and 120 K miles. The differential was noisy under load, quiet otherwise. Took it to the leading rear end shop in N. CA (Rearend Specialties) and they diagnosed it as bad pinion bearings. They installed MBZ factory bearings and said it was done properly. Now there is a constant howl at about 40 mph and another at 55-80. Over 45, under 55 it is relatively quiet. Don't know about over 80. Howl is there now with or without load (pressing on gas pedal).

Shop says that this happens sometimes. I'd greatly appreciate some advice as to whether this problem can be fixed and how to approach it with the shop. Hopefully I won't have to resort to the old "sawdust in the grease" trick. Many thanks.

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