tmoney12

Hello everyone.
I have a 1999 Cherokee sport 4.0 aw4 4x4. I am just curious about the part throttle unlock on my transmission. When I am at hwy speeds in 4th gear with converter locked, the torque converter will not unlock as I press the throttle but will unlock if I tap the brakes. When I get enough throttle, the transmission downshifts to 3rd, and skips the 4th gear unlock mode. Any ideas on what would cause this? I have a brand new mopar tps installed and all other aspects of shifting work normal. I have no codes as well. Any help would be greatly appreciated. Thank you.

lawsoncl

The trans computer through the years changed the shifting patterns, and I think this is normal for a 99.

00t444e

Normal operation, they aren't programmed to run in 4th gear with the converter unlocked. Most 4 speed autos are that way.

dave1123

You will find if you run in 3rd gear that the converter will lock up after reducing the load of accelerating or climbing hills. This too is normal. It will lock and unlock as power is needed, but 4th gear is overdrive so the theory is if power is needed it's better to drop down a gear than load the engine in overdrive. The area that I live in has many country roads that twist and have small hills that average 40 to 45 mph. I run in 3rd gear most of the time on those roads because I get better throttle response and less load on the engine. It shifts in and out of lockup a lot.

My WJ has the 42re Chrysler transmission in it and that one sometimes can't make up it's mind what gear it wants to be in. It's frustrating sometimes when pulling onto a highway and trying to accelerate into traffic. Give it some throttle and it won't shift, give it some more and it might go down to 2nd! I got into the habit of pushing the button to eliminate O/D as I come onto the ramp thus keeping it in 3rd and it accelerates fine, then shifting into O/D. Each transmission has it's quirks and you have to learn what to expect.

tmoney12

Thank you all for your comments! I also have a 2003 tacoma 3.4l auto and it will unlock the converter before downshifting to 3rd and i thought the cherokee would also. I appreciate your time.
-tmoney12

dave1123

If that's got an AW4 in it, it may be a difference in the TCM programming.