shiftin problems

I have a 1991 Jeep Cherokee Laredo it has the v6 4.0 motor automatic. When I am driving it will shift up and down all the time. What is the problem.

When you say "all the time" is it literally all the time, or every once and awhile it does it, then returns to normal? What speeds and what gears are affected?

First thing to do is check your fluid level. If it's ok, then change it. You may also have a bad sensor, and a bit more information will help us narrow it down.

Yes it does it at any speed all the time. the fluid is fine it was change about a month ago. My father brought it to a garage and they told him that the tranny was strong in it. then check engine light is also on. I checked the code thing and the light blinked 20 times.

If there were any pauses between blinks, go back and have another look..Count the flashes between pauses.

Since it does it all the time, I'm thinking it might be a speed sensor. Do a search in this forum for speed sensor and see if that describes your problem.

Also when I stop and it is in drive. The back passager side tire will spin. does that mean it is the speed sensor

What do you mean, the back passenger tire will spin? While you're stopped?

HUH?? Bad brake cylinder in the right rear??

I had that actually...only found out when it was on the Smog dyno....(Callifornia...test only station).

like if I stop on snow or dirt that one tire spins

If you're pressing the brake pedal when that happens, AlohaBra has your solution.

ok I got a new speed sensor and it still does the same thing. Could it be the trottle position sensor? And is that the sensor right under the speed sensor on the transfer case?

ok I got a new speed sensor and it still does the same thing. Could it be the trottle position sensor? And is that the sensor right under the speed sensor on the transfer case?

Hi there jnco. (lol, I used to wear those when they 1st came out many years ago... haha!)

Anyway, sure the TPS could cause the auto-trans to shift funny. It has 2 wiring harnesses coming off of it. One's for the tranny.

It's located on the throttle-body. Do a search for "TPS adjusting / adjustment".

~Good Luck