[T3] "Built" Transmissions

[Jim Adney]

On 30 Sep 2018 at 22:16, Keith Park wrote:

> I put it back in with the 2056 this year and its MUCH better, but I
> still get alot of gear whine.  I was always of the opinion that nobody
> builds these like the Germans and spends the time to get them as quiet
> as they did but should I be worried about the gear whine?  Or is that
> Normal for a built unit? 

>From the feedback we've hear from you and others, I'm guessing that 
the aftermarket builders mix and match ring and pinion gears 
randomly, to get as many good pairs as they can, without spending all 
the time that a careful rebuild would actually require.

Anyone who has read thru the MT section of the Bentley manual must 
realize how much time and effort it takes to do this job right, and 
how much tooling is required. It's a massive effort.

My guess, and it's only a guess, is that the vast majority of rebuild 
trannys go into vehicles that will never see another 10k miles. 
They're dune buggys and rat rods that are hobby cars and they'll be 
driven occasionally, never more than 100 miles at a time, and usually 
with the loudest possible exhausts, so there's no chance of noticing 
a tranny while, and no chance of ever realizing that the R/P is 
wearing itself out.

R/Ps are matched at the factory with very specific specs as to how 
they are to be mounted with respect to each other. The location is 
done with shims that have to be installed, then measurements taken, 
then adjusted and remeasured. I doubt if ANYONE outside an official 
VW service station does that correctly any more.

On old style US cars, with a rear "solid" axle, those measurement 
checks could be made with a Sharpie, or Dykem, or Prussian Blue. 
Corrections are easily done until the gear mesh is right, then the 
differential cover is bolted on. This is SO much easier than the VW 
system; anyone can do it.

I wonder how VW did it at the factory, when making so many per day. 
They MUST have had different tooling that enabled them to measure all 
the parts up front and select the proper shims before the first 
assembly. (Note that the factory shims were installed in different 
locations than the repair shims, indicating that the factory process 
must have been different.) There's just no other way this could have 
been done economically. Has anyone ever seen anything about how this 
was done?

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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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