Quote:
Originally Posted by crosive
The slip tables, as they are, allow a degree of slip (5-10 I believe). once it sees it, the car switches from the low pressure to the high pressure pump. The slip disappears, high pump off, low pump on. This is the shudder you (and I) feel, as it happens many times per minute.
Zeroing out the slip tables basically makes the high pressure pump stay on all the time.
That slipping is what kills the tc friction material, so once it starts, it won't stop, it can just be hidden by either zeroing out the tables, or forcing the car into v8 mode. V4 mode, and the transition to and from is where the tcm allows the most slip, so that the pulsing from that mode aren't felt so prominently.
The flushes are to remove that friction material from the transmission as they will cause premature wear on the clutch packs.
bottom line, if you have the shudder, your tc is toast. you can bandaid the situation at best and perhaps make the shuddering not felt so often or so much. The only way we know of to actually fix the problem is a decent tc that doesn't have a shit-ass paper friction material that is flat, and not warped because of the way it was manufactured. Then you need a proper friction fluid. Then you need to remove the slip tables so that the high pressure pump won't allow any slip (thus degrade the tc friction plates). That, should in theory, solve the problem once and for all.
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This is about the most theoretically-right statements made about this issue. The only thing I am not sure about is the "low" and "high" pressure pumps. I was under the impression the A8 had a typical gerotor setup, driven off the torque converter and used the pressure solenoids and valving to control pressure.
Edit: A8 pump is a vane-type run off the torque converter , but not directly; it is run via a chain connected to the inputshaft. Only this one pump; pressure control is via pressure solenoids and valves. The basic theory, above, is still right.