This is weird........(tranny prob)

Hi,
a couple of months ago i purchased a 91 laredo 4.0 in excellent condition with 110,000 miles on it.....It runs great but i doesnt want to downshift when going up a hill to give u more power. The wierd thing is i found that if when going up a hill and the engine starts to bog down and wont downshift, all i have to do it just tap the brake pedal and it downshifts right away to a lower gear like it should! whats up with that?????????

TPS?

I'm sure it's your Throttle Position Sensor (TPS). Do you have any sort of service manual? A Factory Serviced Manual (FSM) is the best to have, but if you're strapped for cash pick up a Chilton's manual, that does tell you how to adjust the sensor. It's possible the sensor is just bad (happens a lot), but it's also possible that it just needs to be adjusted...take a look in a manual. All you need to adjust it is a Torx Driver (I forget the size), a calculator, and an ohmeter.

Sequoia

Don't know if the '91 is set up the same way as my '88... There's a transmission "kick down" cable hooked up to the throttle. It's easy to adjust and that may be your problem too. Check it out before you spring the cash for the TPS. Procedure to adjust is in the Haynes or Chiltons. The brake thing does make me think that it may be your TPS but give this a shot, might save you some bucks.

I'd first check the TVS (that cable) adjustment -- adjust it with your floor mats insitu -- you'd be surprized how often a floor mat drops the last 3/16 of pedal travel and boogers that setting up!

The brake thing does kinda talk about the TCU not seeing the "correct" data to drop the Torque Converter lock -- If your rpms change more than a few hundred (like you're really dropping a gear and not just unlocking the torque converter, you may wanna look at the condition and fill-lkevel of your ATF (foamed or too high)

Thanks for the replies, yeah i already changer the TPS and it still does it! i have to check the fluid now it seemd to be a bit overfilled, hard to think that would cause the problem though......

When you changed the TPS did you adjust it with a digital meter? Just a little bit off can cause havoc, it takes some time and calculation to get it just right, but 85% is where you want it. If you don't have access to the info on adjustment let me know, I can dig it up for you.

Hi, thanks for the help, but i thought the 91 tps was non adjustable?