no fear

I
Have a 1998 GC 4.0L
On the dash there is an Over Drive button. When I press the button while I drive at 100km/h on the highway when hitting an uphill, it goes to 4th gear, holds the speed and on top I press the button again and it goes back to 5th gear. My question is, is it ok if I do this or will I damage something?
If I don’t use the button she kicks down to 3rd gear get over the hill she will go 4th and than 5th.

Thanks

ol"blue

I believe your '98 ZJ w/ the 4.0L I-6 only has a 4 speed auto., 4th being OD. My '97 w/the 5.2L V8 is also a 4 spd auto. The 5 spd. auto came out in '99 on the WJ w/the 4.7L V8, with 4th and 5th being OD. The WJ w/the 6 still had a 4 spd.
Pressing the OD button as you describe won't hurt anything, and is actually recommended in hilly terrain, city driving, or when towing to prevent trans overheating/slippage.

ol"blue

As a test, try the following:
With the OD switch pressed (switch light on, OD dis-engaged), take off from a stop normally and count the times it shifts. It leaves in 1st obviously, then goes to 2nd, then 3rd, then around 45-47 MPH the torque converter will lock up lowering the RPMs. That's not a shift.
Repeat this with the OD switch engaged (switch un-lit). You'll feel the shift into 2nd, then 3rd, then 4th (OD), followed by the torque converter locking up. Again, that's not a shift.
Hope this is helpful.
And by the way, Welcome to CF!

no fear

Thanks ol"blue
I will try that test and see what it does. Just to be clear it is ok to switch the O/D on and off even at high speeds.

ol"blue

Yes it's okay. No different than the Jeep doing it on its own, other than it's less strain on the transmission when you do it with the switch. It can also prevent slippage when the trans doesn't shift out of OD by itself.