sloppy tachometer?

djlarroc · Dec 16, 2011

Been noticing that the tach on my 97 w/AW4 seems sloppy.

I can be coasting at 1100 RPMs, and if I accelerate (not downshift), RPMs increase to past 2000. Is that common? Is in an automatic thing?

My Tahoe, BMW, and every other car I've owned, I don't remember noticing that.. I know it's Jeep, but still..

heyhar · Dec 16, 2011

Coasting at 1100 RPM at what speed? Depending on what gear you're in, a 900 rise in revs might not be unusual. If you're driving at 65 MPH, as on an Interstate, if you back off the gas and allow the torque converter to unlock, the revs will go down to 11-1200. Is the tranny operating correctly otherwise? All four of ours will be turning right about 2000 RPM at 65 MPH, and I guess yours should too, assuming you have the normal 3.55 diff gears.

djlarroc · Dec 16, 2011

Well, I have noticed it a different speeds. I AM having a CEL for tranny code, but have been working on it, and not sure if it's ultimately the indicated TCC or TCM. I have the PITA '97 so it's been hard to nail down, and don't want to just throw parts at it.

Thought it was causing the RPM to be so sloppy, but sounds like it's not? I'm pretty sure, accelerating (just to keep the speed constant) to stay at 65, my RPMs are about 2300-2500. Stock w/3:55s.

old_man · Dec 16, 2011

Sounds like your torque converter isn't locking up.

heyhar · Dec 17, 2011

Yeah, revs are too high. CEL for tranny may be trying to indicate a lockup problem.

djlarroc · Dec 17, 2011

well a member from here helped me trouble shoot it.

used a test light into the tcm harness and it appeared the tc was working perfectly. would turn test light on and off at appropriate times.

i have checked the harness and it seems fine. have not bought a tcm to test yet, but i guess if the code is pointing to the tcc, i will have to trust that and replace the part..

djlarroc · Dec 21, 2011

drove on the highway for a while and my rpms were right around 2150 @ 65mph.

drove my brothers xj w/ax15 and his tach does not move much when accel/decel in the same gear. he also gets much better mpg than i do on stock 3:07s, and 31s.. i dunno..

Flyfisher · Dec 21, 2011

With a stick (AX15) there will not be any change in RPM's without a corresponding change in MPH (unless clutch is slipping), so that's not a good comparrison.

djlarroc · Dec 22, 2011

ok.. i was wondering about that. thanks.

sloppy tachometer?

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