Cruse control is shifting transmission into too low of a gear - JeepForum.com
 
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post #1 of 7 Old 09-10-2021, 08:37 PM Thread Starter
Rapidrob
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Cruse control is shifting transmission into too low of a gear

1998 GCL 4.0 automatic.
When driving with the cruse control on and climbing a hill, the transmission shifts into too low of a gear,and then cycles from low to high back and forth. This is unnerving and creating very high RPM as the transmission down shifts.
The transmission shifts normally during everyday driving with the cruse control off. It shifts at about 2,400 RPM from 1st to second when cold. From 3rd to Over Drive I some times have to back off of the throttle and it will shift into O.D, the shifts are abrupt but not violent.
I've read that the shifts should not be butter smooth as this can cause band slippage.

Is this a throttle cable misalignment/adjustment? Your ideas?


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post #2 of 7 Old 09-10-2021, 08:46 PM
PolkaPower
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Cruse control is shifting transmission into too low of a gear

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Originally Posted by Rapidrob View Post
1998 GCL 4.0 automatic.
When driving with the cruse control on and climbing a hill, the transmission shifts into too low of a gear,and then cycles from low to high back and forth. This is unnerving and creating very high RPM as the transmission down shifts.
The transmission shifts normally during everyday driving with the cruse control off. It shifts at about 2,400 RPM from 1st to second when cold. From 3rd to Over Drive I some times have to back off of the throttle and it will shift into O.D, the shifts are abrupt but not violent.
I've read that the shifts should not be butter smooth as this can cause band slippage.

Is this a throttle cable misalignment/adjustment? Your ideas?

You can try adjusting the TV cable. Can't hurt. Are you running larger than factory tires?

For TV cable adjustment if I remember correctly pulling it out = later more firm shift point.
Pushing it in = earlier softer shift point.

Correct me if I'm wrong.

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post #3 of 7 Old 09-10-2021, 09:56 PM Thread Starter
Rapidrob
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Yes,one size larger than normal tires.

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post #4 of 7 Old 09-10-2021, 10:11 PM
PolkaPower
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Cruse control is shifting transmission into too low of a gear

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Yes,one size larger than normal tires.

It'll be off a bit then. Definitely do the TV cable adjustment and see if it helps.
Stuff like this is more noticeable with the 4.0 because of the smaller displacement and less gearing to start.

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post #5 of 7 Old 09-11-2021, 01:55 AM
Timo_90xj
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Engine has redline for a reason, that is the safe limit where the engine is designed to operate. In other words, there is no such thing as "too high RPM" on a rev- limited engine.

As for gear hunting on hills, that definitely happens with the 4.0 on stock 3.55 gears and tires larger than stock. Transmission shifts into lower gear when certain parameters order it to do so. You might not be experiencing gear hunting with the cruise control off because you can modulate the amount of throttle the way you want to do it, you're probably loosing some speed but the transmission won't shift.

Cruise control tries to maintain speed, so it opens the throttle as much as required -> downshift occurs. This usually happens the most at around 50mph range, when engine RPMs are fairly low and there's not enough torque on the 4.0 to maintain speed on inclines in OD. Try OD off if it still does this?

Like PolkaPower mentioned, you can try adjusting TV cable, but the thing is if it's too loose, your transmission will NOT downshift early enough and it will also cause slipping.
If you adjust it tighter-than-stock, shifts will be firmer BUT it will also downshift with less throttle input. So you will get even more gear hunting with the cruise control engaged.

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post #6 of 7 Old 09-11-2021, 07:10 AM Thread Starter
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Thanks for the replies.
Right now there is no slack in the TV cable. I could add a little slack and see if that helps.

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post #7 of 7 Old 09-11-2021, 02:27 PM
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I've always cancelled cruise control on the hills. Cruise control tries to keep it right at the set speed and IMHO, causes too much wear and tear. The more a trans shifts, the shorter its life will be.

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