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transmission problem

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1995 jeep cherokee xj 4wd 4.0. trans shifts at very high rpms. check engine light working but not showing. replaced iac,tps, and trans output speed sensor. any suggestions. only about 101,000 mi. fluid ok.
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Adjusted the kick down/throttle valve cable ? Considered a good used Transmission Control Unit from the junkyard ?
 

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1/2 qt shouldn't make any difference.
 

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Discussion Starter · #6 ·
checked connectors cleaned and sprayed, no tcu inline fuse under dash.did vacuum test. had trans flushed w/ conditioner and new fluid. no luck. still no engine light warning,bulb is working. can't find a obd1 anywhere to check. any way to test tcu?
 

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Have you checked the line pressure at the test port on the trannie? At wide open throttle should be 170-210 psi.

If it is not you have a faulty pump, a faulty valve or dirt.
 

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Discussion Starter · #9 ·
battery and alt volts fine. what does brake light switch contacts have to do with trans not shifting until high rpms are achieved ? shifts from 1st to 2nd about 3500 rpms. shifts into reverse or forward gear no problem. does not shift manually shifts great no clunks no slippage. no off road or towing.
 

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Does not shift manually?

If you disconnect the TCU can you get it to move from gear to gear with the shifter? From memory I think it will go R, 1, 3 and 4 on the shifter. This is the first test in the FSM.
 

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battery and alt volts fine. what does brake light switch contacts have to do with trans not shifting until high rpms are achieved ? shifts from 1st to 2nd about 3500 rpms. shifts into reverse or forward gear no problem. does not shift manually shifts great no clunks no slippage. no off road or towing.
I'd have to look as to what the brake light switch specifically affects. It is part of the loop in this system. Also, the selector switch on the passenger side of the trans. Blanking on what it is really called.
 

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I'd have to look as to what the brake light switch specifically affects. It is part of the loop in this system. Also, the selector switch on the passenger side of the trans. Blanking on what it is really called.
A defective Brake Lamp Switch may prevent the trans from going into overdrive, not what the OP is seeing.

The selector switch on the passenger side of the trans is the Transmission Range Sensor, aka NSS.
 

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battery and alt volts fine. what does brake light switch contacts have to do with trans not shifting until high rpms are achieved ? shifts from 1st to 2nd about 3500 rpms. shifts into reverse or forward gear no problem. does not shift manually shifts great no clunks no slippage. no off road or towing.
Is shifting from 1 to 2 your only problem? Or is there a problem going from 2 to 3 as well?
 

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"Not shifting manually" - we need more info on this. Does it not shift manually at all, and only shifts in "D" from 1st to 2nd at 3500rpms? Or shifts fine in "D", but in manual mode shifts from 1st to 2nd at higher rpms?

As was asked, is the only problem the 1-2 gearchanges, and 2-3 and 3-OD are fine? When/ how does it shift into lower gears in D? Can you manually select lower gears if tranny is in higher gear?
 

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"Not shifting manually" - we need more info on this. Does it not shift manually at all, and only shifts in "D" from 1st to 2nd at 3500rpms? Or shifts fine in "D", but in manual mode shifts from 1st to 2nd at higher rpms?

As was asked, is the only problem the 1-2 gearchanges, and 2-3 and 3-OD are fine? When/ how does it shift into lower gears in D? Can you manually select lower gears if tranny is in higher gear?
Save your breath (key strokes).
 

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^ well, that sure is one answer :D
 
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