Wrangler 2002 Auto Transmission Problems

I have a wrangler 2002 4WD w/auto transmission. When I haul my trailer,
less that 2000 lbs, on long steep grades, the transmission doesn't
downshift. The car will drop from 65 to 45 mph and not downshift with
constant pressure on the pedal. When I floor it, it still won't. Or when I
let off the throttle and then floor it still doesn't. Car operates fine
around town without trailer, and on level ground with the trailer.

The manual says a throttle valve linkage could be the problem, but gives no
guidelines on how much to adjust it or in what direction.
I have also noticed some vacuum problems, as the damper door on the AC
doesn't seem to work right all the time, but that could be another problem.
Is there any vacuum switch for the tranny?

My auto shop said to try downshifting manually to see if it would and what
changed, but declined to make any adjustments until they could reproduce the
problem.

Any suggestions.

I have a wrangler 2002 4WD w/auto transmission. When I haul my trailer,
less that 2000 lbs, on long steep grades, the transmission doesn't
downshift. The car will drop from 65 to 45 mph and not downshift with
constant pressure on the pedal. When I floor it, it still won't. Or when I
let off the throttle and then floor it still doesn't. Car operates fine
around town without trailer, and on level ground with the trailer.

The manual says a throttle valve linkage could be the problem, but gives no
guidelines on how much to adjust it or in what direction.
I have also noticed some vacuum problems, as the damper door on the AC
doesn't seem to work right all the time, but that could be another problem.
Is there any vacuum switch for the tranny?

My auto shop said to try downshifting manually to see if it would and what
changed, but declined to make any adjustments until they could reproduce the
problem.

Any suggestions.

Theres a cable that runs from the throttle body to the transmission (TV cable). It attaches to the throttle body right beside the throttle cable coming from the acc. pedal. That cable tells the transmision when to down shift based on throttle position. There is an adjustment for that cable right at the throttle body. Im not sure exactly how it adjusts on an 02 but I can go through the procedure for a 99. Hopefully you can fill in the blanks.
Theres a clip where the cable passes through the mount. Push that clip down to release the cable. Open the throttle all the way by hand. You will hear clicking as the cable is pushed through a series of teeth. With the throttle completely open, release the clip. The teeth will grab it and hold the cable in adjustment. You're done. Go see if it downshifts as it should. This adjustment has to be done occationally as the cable stretches over time.
DISCLAIMER: What I discribed is for a 99. The specifics of how to release the cable changes from year to year and Im not sure how it works for an 02 but I think all autos have the TV cable and I think all have an adjustment. They are all adjusted by allowing the cable to move freely either by pushing a clip down or pulling it up, opening the throttle all the way then locking the cable in. You may have to fiddle with it to figure out exactly how the release clip works.

The vacuum is a seperate problem.

While the adjustment is probably contributing to the problem, remember that your transmission will stay in the higher gear when you coast down a hill or on flat without a load. You'll have to manually downshift to get the engine braking you desire.