Just to amuse you guys:

Ever since I did some extensive maintenance on my ’65 daily driver P130 I had some very weird vibrations while driving at speeds higher then about 50 mph. The vibrations were not speed nor engine rpm related and seemed to be a very weird harmonics problem.

I had quite a number of desperate threads while trying to get it solved. Here’s the summary of this adventure:

-did some extensive maintenance (welding, painting, engine, fitted a tilted M46).
-had weird vibrations ONLY at 80 mph (not at 79 nor at 81 mph), differntial and support bearing got extremely hot.
-checked complete drive line, replaced lots of stuff.
-got frustrated and concluded the M46 didn’t like sitting tilted.
-fitted a tilted M47 (thinking it would work ok tilted since it only has round parts in it).
-again weird vibrations at around 80 mph, and a hot dif (and again frustrated)
-fitted an other M47 right up (with rare 240series B20 bellhousing).
-again similar vibrations (even more frustated).
-went completely nuts and replaced all rotating parts on the complete car. (2 rear axles, 4 trannys, 4 drive shafts, 4 support bearings and rubbers, 2 flywheels, 3 clutches, 3 camshafts, 2 camgears, wheels, tires, etc., etc.)
-again similar vibrations and hot dif and support bearing.
-got depressed and just drove the bugger around for half a year annoyed by the vibrations.

But then:

-for maintenance purpose I replaced the front wheel bearings on the drivers side (with car on jacks you could *just* hear them while spinning the wheel)
-went for a test drive and a big smile appeared on my face: no vibrations!

Aparently the rumbling form the the front wheel (no play on the bearing, it was just winning a bit, not noticable inside the car) and some vibes from the driveline and/or engine created some harmonic or resonance vibrations. These vibrations travelled trough the drive line and created a very hot dif and support bearing. Now, after replacing the front wheel bearing, things are smooth as, and the dif doen not turn hot anymore…

I find it incredible to believe that an only slightly worn front wheel bearing can cause a differential to overheat. If I hadn’t seen it with my own two eyes I would not have believed it, but believe you me!

Cheers, Ben

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Daily driver: P130, '65, B18+M47. In the proces of restoring: P131, '69, B20+AW71L. (www.knutselsmurf.web1000.com)