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Unread 09-21-2012, 03:01 PM   #1
89jeepers
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89 jeep won't shift out of 1st... Help!

I have seen a few posts on the web but no direct answers so I'm hoping to get to the bottom of this. Jeep info: 1989 jeep cherokee loredo 4x4 4.0 liter in line 6. Issue: when driving the jeep (regardless of rpm) will not shift out of first gear. It goes into park, reverse, and first fine (no slipping) but when in drive the engine revs way up and won't exceed 20 mph. History: never had a problem before. I bought the jeep used in 2010, it has 158000 mi on it, it was on non op for a year and I've been driving it for about two weeks until yesterday. I did pressure wash the engine yesterday before leaving and about 2 miles down the road at about 45 the engine revved up to about 4000 rpm for about 2 seconds and then switched into great. I went about 3 more miles with no issues, stopped at a stop sign and when I went to accelerate it wouldn't shift out of first. I checked the trany fluid and all is good there. Solution: ????. Any help would be GREATLY appreciated.

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Unread 09-22-2012, 10:26 PM   #2
jnicewan
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The most notorious problem with the AW4 is probably the neutral safety switch (NSS) at this point I would probably disconnect every sensor and connector you see that related to the trans and clean/dry them out. It would be good to squeeze some die-electric grease on the pins inside the connector before putting them back together. Other than that see if you can find a scanner to pull codes out of the Jeep for possible trans concerns.
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Unread 09-23-2012, 06:50 AM   #3
cruiser54
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Cruiser’s Trans Plug Refreshing


Over near the transmission dipstick tube are 2 rather large connectors. One is black and the other gray. These 2 connectors carry all the info between TPS, TCU, NSS, speed sensor, and transmission solenoids.
Unplug each one, visually inspect for corrosion or bent pins, spray them out with electrical contact cleaner and plug them back in.


Additionally, if your Jeep is an 87 to 90 Renix, it’s always a good idea to reach up under the glovebox area and unplug the connector to the TCU and spray it out along with the receptacle of the TCU. While you’re there, find the fuse right in that area for the TCU. Remove it and spray out it’s receptacle and clean any corrosion from the fuse.

Revised 9-10-2012
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Unread 09-26-2012, 08:26 PM   #4
89jeepers
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Thanks guys for the info. After hours of research, I narrowed it down to the TCU/TCM. I unplugged the fuse (red 10AMP) from under the dash on the passenger side and took it for a test drive. Sure enough, I have to manually shift gears but all is good which told me the TCU/TCM is bad. Not to find one :-(.
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Unread 09-26-2012, 08:36 PM   #5
cruiser54
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88 to 90 would be fine. Did you do the trans plug refreshing?
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Unread 10-28-2012, 01:01 AM   #6
89jeepers
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Quote:
Originally Posted by cruiser54 View Post
88 to 90 would be fine. Did you do the trans plug refreshing?
whats the trans plug refreshing
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Unread 10-28-2012, 08:34 AM   #7
cruiser54
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Quote:
Originally Posted by 89jeepers View Post
whats the trans plug refreshing


Cruiserís Trans Plug Refreshing


Over near the transmission dipstick tube are 2 rather large connectors. One is black and the other gray. These 2 connectors carry all the info between TPS, TCU, NSS, speed sensor, and transmission solenoids.
Unplug each one, visually inspect for corrosion or bent pins, spray them out with electrical contact cleaner and plug them back in.


Additionally, if your Jeep is an 87 to 90 Renix, itís always a good idea to reach up under the glovebox area and unplug the connector to the TCU and spray it out along with the receptacle of the TCU. While youíre there, find the fuse right in that area for the TCU. Remove it and spray out itís receptacle and clean any corrosion from the fuse.

Revised 9-10-2012
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