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Unread 01-30-2014, 03:43 AM   #1
ZJ98IEN
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Join Date: Jan 2014
Location: Chetek, Wisconsin
Posts: 4
1998 ZJ Trans Issues

Hello everyone, new member to the forum so please bare with me. I've been having some issues with my ZJ the past couple weeks. It hasn't been shifting into overdrive. Mind you I live in Northern Wisconsin and it is freakishly cold up here this year, but I always let it warm up to temp before I take off anywhere. It wasn't until that lovely -40 f day that we had that it started doing this and the problem has persisted. I even drove 72 miles the other day without it ever going into overdrive. I didn't like it but I hadn't the option. I have replaced the trans filter with a new kit along with new fluid. No evidence of any destruction in the pan. I've checked the temp of the fluid after run time fulling expecting to burn my fingers but it was hardly even warm. What is going on here?

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Unread 01-30-2014, 06:19 AM   #2
shaban
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1996 ZJ 
 
Join Date: May 2012
Location: Yarraville, VIC, AU
Posts: 571
As far as I know, the computer won't let it go into overdrive when tranny oil is cold.

Quote from FSM: "The PCM prevents engagement of the converter
clutch and overdrive clutch, when fluid temperature
is below approximately 10°C (50°F)"
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Unread 01-30-2014, 01:54 PM   #3
ZJ98IEN
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Location: Chetek, Wisconsin
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any idea as to why it wouldn't be warming up on long drives. i.e. 72 miles
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Unread 01-30-2014, 02:28 PM   #4
shaban
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1996 ZJ 
 
Join Date: May 2012
Location: Yarraville, VIC, AU
Posts: 571
Maybe, because its -40?

Try sticking some cardboard in front of the grille, it'll prevent the radiator running too cold and over-cooling the tranny fluid via oil cooler that's in the radiator.
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Unread 01-31-2014, 12:53 AM   #5
Chris_W_2k5
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1996 ZJ 
 
Join Date: Nov 2005
Location: Saskabush
Posts: 269
I had this problem before. Long drive on the highway in OD, slow down going through a city then it wouldn't go back into OD.

Definitely block the grill with cardboard or something. It'll help out keeping the engine and transmission warm. I blocked off 6 of the openings for the warm days (because here, it'll be -25*f one day and 32*f the next).
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'96 stock ZJ

Quote:
Originally Posted by Crashnburn80
...so assuming your Jeep is right-side-up you should be ok.
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Unread 02-02-2014, 01:19 AM   #6
Candymancan
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1998 ZJ 
 
Join Date: Aug 2010
Location: Virginia
Posts: 3,852
if its that cold.. you need to block some of the grill with something... Have you ever noticed how you see 18 wheelers on the road in the winter sometimes have like half there grills blocked off ?
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2013 6.2 V8 Camaro SS 4k miles
1998 5.9 V8 ZJ 160k miles
1998 4.0 I6 Laredo ZJ 210k miles
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Unread 02-02-2014, 01:53 AM   #7
JasonStebbins
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1997 ZJ 
 
Join Date: Jan 2009
Posts: 3,138
Besides the cold weather, check the condition and level of the transmission fluid while running warm in neutral.

Shift solenoids, governor pressure sensor, 3-4 accumulator spring, broken seal on the overdrive unit, TCC, and even a bad TPS can also cause this.
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Unread 02-03-2014, 10:22 AM   #8
ZJ98IEN
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Location: Chetek, Wisconsin
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Thank you all for your suggestions. I've blocked off the grille with some cardboard, left one slot open, and so far so good!
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Unread 02-09-2014, 01:52 AM   #9
Candymancan
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1998 ZJ 
 
Join Date: Aug 2010
Location: Virginia
Posts: 3,852
Block off the grill where the trans lines meet in the main radiator.. assuming you use only the main radiator and your not going directly off a aux cooler like I am.
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2013 6.2 V8 Camaro SS 4k miles
1998 5.9 V8 ZJ 160k miles
1998 4.0 I6 Laredo ZJ 210k miles
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