Trans/Diff Fluids

["Al Powell" <APOWELL@agcom.tamu.edu>]

Vikram sent: 

> I've been thinking about doing the same thing... using synthetic trans.
> fluid along with the synthetic diff. fluid that's already in there.
> 
> BTW, what are the symptoms of a failing transmission ? My transmission
> shifts smoothly (fingers crossed) except that on start it builds momentum
> slowly. Reverse engagement is also fine.

>From what I've heard, the first thing to show up is hesitation in 
engaging reverse gear when the selector's moved to R.  Tends to be 
more noticeable when tranny fluid is warm, as it's thinner then.  
Ours started with less than 1 sec. hesitation - now it's 1-2 secs 
when cold, NEVER engages when hot unless we rev it to @1500 rpm, 
which is death on the drivetrain.  (Ours is in death throes, tho..) 
Next stage of symptoms is sticking in Second gear, not wanting to 
upshift into Third after road speed is reached.  (When ours is warm, 
it won't even go into 3rd...toast, I tell you!!!! Toast!!!)

(Fluid in trans & diff mixing may be a bogus issue...)
> 
> Hmmm, interesting... if this is true, then why are all of changing or 
> looking at getting the damn seals changed ? Also, if the seals are ok
> why did we have to change to synthetic diff. fluid ? The explanation that
> I had is that it mixed with auto. trans. fluid and then evaporated !

I'll try to explain more of what I THINK I understand.  The 
differential assembly has no direct connection to the tranny thru 
which fluid should be able to flow.  They're bolted together, but 
there's a mechanical space in between and a weep hole so that 
leaks should just run out, not mix.

The reason for the synthetic diff. fluid is ANOTHER reason that 
synthetics are better.  Starting with the 5K series, the differential 
fluid's check-plug is in such an obscure place that no one ever 
checks it (other than a few canny techs known by folks on this 
list...) and over time, the differential fluid got low in the 5K 
series.  I think part of this was evaporation of the volatile 
elements, which is more common in petro-oils than in synthetics, and 
part of it may have been simple mechanical wear.  At any rate, the 
diff. fluids got low and the assemblies FRIED.  Audi solved this by 
putting a factory recall on all the drive assemblies some time in the 
last 80's - the fix was to replace the petro-oil with synthetic 
lubricant.  To this day, Audi uses synthetic in the differential 
aeesmblies...and you can bet they will continue to do so.

BTW, if anyone on this list has an Audi which has NOT been retro-
fitted to synthetic, call your dealer and have it done.  I do not 
think there is any time or mileage limit on the service!!

My read on the stories circulating is that the fluids did not 
actually mix, but the situation was not well understood.  If I have 
this wrong and others on this list have personal experience that is 
more specific, please post...and I'll listen.

I will NEVER use anything but synthetics in my Audi drivetrain again, 
in engine, differential or tranny.  Reasons:

1)  It is better lubricant and reduces wear between mechanical parts.
2)  It reduces the resistance of parts to motion, sometimes 
providing better mileage.
3)  It is better at transferring heat from assemblies, therefore, 
allowing engines (in particular) to run cooler.  This is a well-
documented capability.
4)  It does not break down nearly as fasst as petro-oil under heat, 
mechanical wear or contamination, providing better protection to the 
assemblies in which it's used.
5)  Because of the above, I expect fewer breakdowns and extended 
service from all assemblies so lubricated.  (Since I now believe that 
my 1990 200T is under-engineered in the tranny, this becomes 
critically important.)

Note that I do not use brand names - this is true of ALL synthetics.

I'm not sure that changing to synthetics  when we bought our Audi at 
39K could have averted transmission trouble - but if I had it to do 
over, I'd have changed the transmission fluid immediately, just as I 
did the engine oil - to synthetics.

Lordy, look at all that stuff I spouted!!  I need to get off my 
soapbox and have a brewski or twoski........





********** A Washington State Cougar in Aggieland (aTm) **********

Al Powell                           Voice:  409/845-2807
Ag Communications                   Fax:    409/862-1202
Texas A&M University                Email:  a-powell1@tamu.edu 
W3 page - http://agcomwww.tamu.edu/agcom/rpe/alpage.htm

         "This is the silliest stuff that ever I heard..." 
            (Shakespeare, A Midsummer Night's Dream)
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