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Unread 05-31-2003, 04:46 PM   #1
spichman510
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Overdrive QUE?!?!?!

Ok, i am starting to actually get some knowledge about jeeps here, but heres a normal car question. What exactly does overdrive do? And was it causing my trans to shift up then down real fast and jerk so much that i lose power when i am accelorating pretty fast? I turned OD off but i havent floored it yet to see if its the same, will do that tongiht.

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Unread 05-31-2003, 06:50 PM   #2
Ryan2son
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OD decreases your RPMs ~500 and gives you better gas mileage. I turn mine off in the mountains because the tranny will shift, shift shift (did I mention shift - hehehe).
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Unread 05-31-2003, 11:43 PM   #3
Zaphod
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I believe overdrive allows you to engage and disengage the highest gear. so when overdrive is on in a 4-speed AT, you have all 4 gears. when it is off, you have only the first 3.

the reason your jeep was shifting up and down rapidly with overdrive on is that the car is at an angle on the hill that your present speed and engine RPM kept the computer right on the line of when to up/down-shift. it couldn't decide which to do, so it did both, over and over. turning off overdrive disables that fourth gear, keeping the jeep in the 3rd gear and smoothly rolling up the mountain with less abuse to your tranny.

correct me if i'm wrong, y'all. i hate spreading mis-information.

Oh, and for spichman:
Don't think overdrive would do that with your tranny, especially if it is on level ground. That sounds like a different (and very nasty) tranny problem.
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Unread 06-01-2003, 08:49 AM   #4
spichman510
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mmmmmmmmm, i like very nasty tranny problems,...alot. Ill take it in and check it out, thanks for all the info.
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Unread 06-02-2003, 05:46 PM   #5
Stocker
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Ryan2son & Sonar have it right...

OD is simply your highest gear, by definition higher than a 1:1 direct ratio. Fourth in a 4 speed, fifth in a 5 speed etc. The OD lockout just, well, locks out the highest gear. If conditions cause your tranny to constantly hunt in & out of OD, lock it out - it's less stressful to the tranny & driveline. If you floor the throttle, the tranny should shift down - out of OD.
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Unread 06-02-2003, 09:21 PM   #6
ZR7 Ken
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Spicher,

When you take your ZJ in for service, have them check for a service bulletin about "bucking at wide-open-throttle". There were some governor pressure sensors that would allow the vehicle to hit the rev limiter before upshifting. Rev limiter causes jerking/bucking due to fuel shutoff. Sound like your problem??
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Unread 06-02-2003, 09:35 PM   #7
spichman510
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ken,
that sounds EXACLTY like my problem. Thats prob what it is, if not ill be one unhappy camper. thank you for that one.
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