Dave:
It's pretty rare IMHO to see a worn synchro ring/hub on the 4th gear,
especially since you are never downshifting into it. The 3rd gear side of
the hub, operating sleeve and its synchronizer ring do take some of the
beating.

It is very possible that your shift linkage needs to be adjusted to allow
the sleeve (inside the tranny) to engage further into 4th gear.

When the 3rd/4th hub fractures, you usually cannot shift in or out of
3rd/4th without a lot of pressure, or at all.

Good luck,

TomC
tcarrington@relitech.com
http://www.relitech.com/tomc
http://volksweb.relitech.com
85 Vanagon Crew Cab
82 Westy diesel=>gas conversion
65 Notchback

> the
> transmission
> slipped out of 4th gear to neutral.  Then about a half hour later, it
> did it twice in 5 minutes.  Pulled over to a gas station and looked
> under to see if it looked like it had sprung a gear oil leak or
> something obviuos on the shift linkage.  Nothing visible.
> When in gear,
> it sounded normal.  So I kept going.  It happened about every 2 hours,
> usually twice in a few minutes.
(snip)

>     I figured it was more likely a linkage problem than
> internal, though
> I could be wrong.  I decided to risk doing internal damage since I do
> have a spare on the 87 bus I picked up cheap.
>     So I wonder if anyone has any idea what might cause this
> ?  A month
> ago, I had a dealer work on the linkage (shifter bushing and
> some seals
> - I've got part numbers at work and can post them later if it's
> useful).  So it could be a warranty situation.  On the other
> hand, I've
> read about the defective design on the part for shifting
> between 3rd and
> 4th, but I figure that would more likely disable the vehicle than do
> this, right ?