[V8] V8 kickdown
RockinV8Q at aol.com
Wed Aug 24 01:12:46 EDT 2005
In a message dated 8/23/05 10:47:15 P.M. Eastern Daylight Time,
sdewitt at stx.rr.com writes:
I guess the Audi Master Mechanic I got the info from was wrong. I am curious
as to why my 94 V8 has lower cruise rpms than my 90 V8.
If the transmissions are all the same then why does Audi have a different
part number for each gearbox, torque converter, and valve body?
I don't know where your Master Mech is getting his info but it does appear
to be incorrect.
I can make a guess that the difference between your cars is related to
VDO's notoriously inaccurate gauges (speedo and tach in this case), although one
of them may have a defective convertor lockup solenoid....if there is a
difference of several hundred RPM its possible one car could be stuck in
"Sport"...as happened to Shawn Head two years ago.
I didn't say the transmissions are all the same, my statement was.....
"All V8 automatics have the same ratios in all gears and the final drive.
There is no difference electrically between the transmissions for any year
There are many possible internal changes that can make the different
sub-assemblies of a transmission incompatible with sub-variants of the same
The ZF HP-24A variant has three basic sub-variants...ATU, AYU, and AGZ. A
confirmed fact is the AGZ has revised lubrication to one of the thrust
bearings...which happens to correspond to the same change made in HP-24E and H
variants used in Jags and Rovers respectively. I suspect but haven't been able to
confirm that the AYU has an early attempt at revised lubrication of the
bearing in question..and that the same revision occurred in the E and H variants
at the same time.
I suspect that as is common practice with nearly every automatic ever built
there were changes in the clutch drum assembly, valve body fluid routing,
check valve springs, and check valve sizes. If so its entirely plausible that
some changes made one sub-variant valve body incompatable with the main gearbox
assembly of the other two sub-variants. The same goes for the torque
My comments were limited to the interchange of complete transmission
assemblies into different year cars, the external differences of each, and the
matching of harnesses and TCU's.
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