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Old November 2nd, 2019, 19:39
JungleJames JungleJames is offline
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AW4 Transmission flares in overdrive?

Hey Y'all, first post!

I just picked up a 2000 2door XJ and love it.

When driving at highway speed in the final "overdrive" gear I notice that when I coast (off throttle) and then get back on the gas, the RPM's flare up to about 2500 then drop back to 1500 or 2000ish depending on speed. Is this normal behavior of the transmission or is something wrong?

Any help is appreciated, thanks!
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Old November 3rd, 2019, 00:44
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devildog0 devildog0 is offline
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AW4 Transmission flares in overdrive?

Normal. When you release the throttle and coast the torque converter is unlocking. When you get back on the gas it takes a second for the converter to lock backup up so you are seeing the spike in engine speed right before it locks.

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Old November 3rd, 2019, 06:58
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ehall ehall is offline
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Re: AW4 Transmission flares in overdrive?

The torque converter clutch should stay engaged in coast, only release when brake switch is applied or speed drops below 40ish MPH.
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Old November 3rd, 2019, 07:49
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Tim_MN Tim_MN is offline
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Re: AW4 Transmission flares in overdrive?

What type of ATF is being used, and what is the condition of the fluid ?
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Old November 3rd, 2019, 07:53
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devildog0 devildog0 is offline
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Re: AW4 Transmission flares in overdrive?

Quote:
Originally Posted by ehall View Post
The torque converter clutch should stay engaged in coast, only release when brake switch is applied or speed drops below 40ish MPH.
Across 3 different XJs with AW4s ive experienced exactly what the OP is describing. Whether its the TC unlocking and unlocking or some other function within the trans (im not an auto trans expert by any means) that is the result of coasting then getting back on the gas in my experience. The way the vehicles behaved was exactly like taping the brake to unlock the conveter then having it locked back up.

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Old November 3rd, 2019, 08:58
JungleJames JungleJames is offline
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Re: AW4 Transmission flares in overdrive?

Excellent, thank you!

I just wanted to make sure it was normal behavior.
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Old November 3rd, 2019, 13:04
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Re: AW4 Transmission flares in overdrive?

Quote:
Originally Posted by JungleJames View Post
Hey Y'all, first post!

I just picked up a 2000 2door XJ and love it.

When driving at highway speed in the final "overdrive" gear I notice that when I coast (off throttle) and then get back on the gas, the RPM's flare up to about 2500 then drop back to 1500 or 2000ish depending on speed. Is this normal behavior of the transmission or is something wrong?

Any help is appreciated, thanks!
I have not checked the RPM but my XJ have done that all its life when driving around town i.e. 45 MPH or lower. At highway speeds it do not unlock.
While you are at it, check the fluid quality and level. A preventive maintenance check.
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Old November 3rd, 2019, 13:56
Black1990jeep Black1990jeep is offline
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Re: AW4 Transmission flares in overdrive?

for me all used vehicle purchased get fluid changes unless there is written proof that it was done by prior owner within prescribed intervals. coolant, tranny, differentials, motor, and brake fluid. Alos the inline six is notorious for trapping dirt around the sparkplug threads, before removing the plugs, blast that area clean, else dirt can fall into the sparkplug hole!

also check the airfilter. Note if assembled wrong, the filter can fall out of its retaining groove, and slump into the airfilter box, causing the filter to be bypassed. Mine was like that when purchased! I also had water in the front diff, and filthy brakefluid and motor oil.

Also grease all fittings, there can be many grease fittings on the jeep.
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