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1987-1991 Torque Tube - Thrust Bearing

Transmission

Vehicle Information: Year: 1987 S4; Engine (size, modifications): 5.0L V-8 stock; Total Mileage: 82,XXX; Transmission type: Autotomatic;

The torque tube ("TT") bearings in my car started complaining last summer, so I had the TT replaced last week. The rebuilt TT that I bought from a supplier in California had a longer drive shaft than the TT removed from my car. But the supplier told the mechanic that the part was interchangeable and explained to me that the longer drive shaft and some washers were used to add preload even though Porsche says not to use the system anymore. The TT was installed and I put on 25 miles of local driving over the weekend. On Monday, I took the car back in for an oil change and the mechanic said it sounded like the hot engine was straining at start-up, as if the battery were weak (I just installed a new battery last month), compared to how it sounded when the engine was cooler after the oil change. In the mechanic's mind, this was a possible sign of a thrust-bearing problem. So now I'm worried, and the next step will be to loosen the pinch bolt at the front flex plate and see whether the hub moves to the rear (and how much), and to measure the crankshaft endplay. Do you have any knowledge or experience with an "updated" TT with a longer drive shaft? Isn't added preload bad, i.e. the likely cause of thrust bearing failure?

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