92 trooper AT harsh up-shifting 2nd to 3rd only


Dang it! à i just knew if i started lurking around here again, and even chiming in on a post or two, something would pop up (or off). <img src="/forums/images/graemlins/lol.gif" alt="" />
And so it has. . . any help greatly appreciated.

This started ôall-of-a-suddenö, after driving 5 miles in hot weather, parking in the shade, and then when driving back within a mile or so. So, hereÆs the info:


PROBLEM:
auto transmission up-shifting harsh from 2nd to 3rd *only*. . .(apparently)

WHEN:
only during regular non-aggressive around-town driving.
***** (if i push it at higher rpmÆs, both in full automatic mode and when manually shifting, with and without power switch on, it does seem perfectly OK.) mmmmmà

other checks
No Check Trans light
Fluid check:
Level: Hot level at Min mark (so not real low)
Color: light brown (not new pink color, æcause it is not new; and not dark brown or burnt color)
Odor: no burnt aroma at all
Not aware of any slipping

My isuzu service manual supplement for this trans isnÆt a whole lot of help because it mainly is concerned with using the Tech-1 diagnostic tool to troubleshoot.

Any ideas? I was thinking low fluid level because of higher rpmÆs seemed to fix the problem, but the level seems ok, though not perfect.

Plus, iÆm surprised itÆs only the upshift from 2 to 3 and not paired with any other up-shift points.

IÆm going to try adding a little trans fluid on the off chance thatÆs it (but i doubt it).

Btw, æsearchÆ hasnÆt helped so far.
Thanks in advance

1992 isuzu trooper, automatic transmission 4L30-E