[V8] V8 kickdown

[RockinV8Q@aol.com]

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  
either."
 
 There are many possible internal changes that can make the different  
sub-assemblies of a transmission incompatible with sub-variants of the same  
transmission.
 
 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  
convertor.
 
 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. 
 
KT