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Unread 09-20-2012, 05:04 PM   #1
papadon99
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1998 FSJ Cherokee 
 
Join Date: Sep 2012
Location: Drumright, OK
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HELP What causing downshifting?

98 Grand cherokee Laredo, 4.0l engine and auto transmission (42RE)

When going down highway after @ 30miles, will shift down to 3rd and stays there. What could be causing this? Mechanic said Transmission itself is ok. Sensors maybe? Which ones?

HELP!!!
TY ahead of time!!


Last edited by papadon99; 09-20-2012 at 06:42 PM..
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Unread 09-20-2012, 06:41 PM   #2
papadon99
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1998 FSJ Cherokee 
 
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OOps, sorry!
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Unread 09-24-2012, 02:47 AM   #3
seattle_yj
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1993 YJ Wrangler 
 
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Location: Issaquah, WA
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Quote:
Originally Posted by papadon99 View Post
98 Grand cherokee Laredo, 4.0l engine and auto transmission (42RE)

When going down highway after @ 30miles, will shift down to 3rd and stays there. What could be causing this? Mechanic said Transmission itself is ok. Sensors maybe? Which ones?

HELP!!!
TY ahead of time!!
The throttle cable might need adjustment. I would start there.
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Unread 09-24-2012, 10:50 AM   #4
seattle_yj
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1993 YJ Wrangler 
 
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I was reading through my FSM last night and came across this issue in the diagnostics section. When I get back to my computer I will post that info here.
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Unread 09-24-2012, 10:49 PM   #5
jnicewan
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1995 ZJ 
 
Join Date: Dec 2010
Location: Norman, OK
Posts: 2,076
T/V cable adjustment is very important but that shouldnt be an issue for O/D or T/C lock (Torque Converter lock-up).

First off can you verify if its downshifting into 3rd, or is the T/C just unlocking. Also when it happens try hitting the O/D cancel switch a see what happens. If it is in 3rd gear then you should notice the T/C locking in 3rd ( T/C only locks 3rd when O/D is cancelled with the button)

What is probably the heaviest influence in T/C lock up and O/D shifting as far as external trans concerns/sensors is the TP sensor, also if its just T/C lock up problems I would check the brake lamp switch too. If the brake lamp switch is coming on or is real sensitive to come on then it could be unlocking the T/C
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