No, you can't use the r+p set from a 4 speed in a 5 speed or the other
way around for that matter. You also can't use either of those in a
Syncro tranny or the other way around. Also you can't use the early
aircooled and diesel 4 speed r+p sets in a waterboxer 4 speed or the
other way around. Machining can be done to allow some mixing between 4
speed types, or so I was told.

The r+p set in Vanagon trannys uses a pinion shaft which runs the full
length of the tranny. One side of each of the other gears fits onto
machined locations on this shaft. A complete tranny rebuild is involved
to change the r+p. Tranny rebuilders have access to various r+p ratios
that were never used in North American models so it is likely that you
can get the gearing combination you desire but not by simply mixing r+p
sets  from different tranny families.

Mark

Kim Springer wrote:

>Hi,
>
>For inquiring minds:
>
>http://www.t3-infos.de/images/T3-Getriebe.pdf
>
>I have the AAP transmission in my Tristar.  Has anyone ever considered (or done) a conversion/hybrid with a diesel 5 speed gearbox and a 4 speed ring and pinion?
>
>Would this work to make a "freeway flyer" 5 speed?
>
>Kim Springer
>'89 Tristar
>
>ps. glad to see the John Wallace, email generating, hacking, exchanges, die off!
>
>
>