1994 Ford Explorer Automatic Overdrive not Locking in

AWILLIAMS

MEMBER
1994 FORD EXPLORER
6 CYL
4WD
AUTOMATIC
145,000 MILES

The automatic overdrive is not locking in consistently and when it occasionally does, it will drop out after a few miles. Have had a new transmission put in with solenoid replacement, vacuum checks etc. But problem persists after 4 revisits to the shop. This model does not have the OD selector button- fully automatic system. Lack of OD results in rpm's being 250-300 rpm higher than normal at 65 to 70 mph. Mechanical? Electronic? Vacuum problem?

3 Replies

BLUELIGHTNIN6

MECHANIC
16,542 POSTS

Hello
Thanks for the donation.

It sounds more like a sensor then anything mechanical. Are there any illuminated lights in the instrument panel such as O/D off, check engine etc.?

Was this issue the reason for the tranny swap?

The shop probably used the same sensors and elec. Hook ups. I suggest checking out all wiring to ensure it is properly tightened and no bare spots on wires.

Hope this helps.
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Wednesday, December 24th, 2008 AT 1:08 AM

AWILLIAMS

MEMBER
2 POSTS

Vehicle doesn't have an O/D light indicator but the "check engine" light is on and has been diagnosed as an EGR issue- not tranny related. Yes the original visit to the mechanic was to correct this O/D problem and the solution was to first rebuild the tranny which ultimately lead to a new transmission. I have since replaced the engine temp sensor but no luck. Any particular sensors to check related to the O/D system?

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Wednesday, December 24th, 2008 AT 2:11 PM

BLUELIGHTNIN6

MECHANIC
16,542 POSTS

The VSS (Vehicle Speed Sensor) is the one that comes to my mind and it is located on the transmission itself.

Although your issue is that the OD doesn't engage, or will not stay engaged, this doesn't mean that it is necessarily the OD itself. No OD is the safe mode that a transmission goes into when the computer senses a problem with the tranny. Usually, it is electrical if you aren't having problems with slipping, clunking, etc.

Hope this helps.
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Wednesday, December 24th, 2008 AT 3:06 PM