shift on the fly....oops?

07Latitude · **Posted:** Sun Mar 18, 2007 7:10 pm

I had some trouble the other day w/my street freezing (darn dustings of snow and cold overnight temps). Well, my KJ didn't want to go up the hill w/just 2wd (and the traction light blinking like a madman). I decided to put it in 4HI. Well, I guess my headcold got the better of me and I had the rear wheels spinning too fast, as when i pulled the 4wd lever, all I got was a nice grinding.

Now, I know I've had the rears spinning before while engaging 4HI in exactly the same spot. Is there a certain mph "tolerance" the Liberty has to engage 4wd, or did I get lucky the first couple times with it meshing fine, and this last time maybe the wheels were spinning too quickly? Obviously this isn't going to hurt the transfercase just once, but I am now kind of curious about what kind of syncros/etc the TC has.

crash87 · **Posted:** Sun Mar 18, 2007 7:18 pm

Your RPM's were probably too high.

Jeepjeepster · **Posted:** Sun Mar 18, 2007 7:24 pm

You just got lucky. :shock:

I would never try to put the Jeep into 4wheeldrive of any kind with the rear tires spinning. Thats just asking to break something.

renegadekj · **Posted:** Sun Mar 18, 2007 8:00 pm

Check your owners manunal for the exact mph's that you can engage 4HI, I think it is around 80 KM/ph, but by no means should you try to engage it when your wheels are spinning, The grinding noise was probbaly the best thing that could have happend. Be thankful that 4 wheel drive didnt engage and the front tires instantly find hard traction...thats when you look for a new front differential!!! :shock:

Skyjump136 · **Joined:** Tue Jul 05, 2005 6:50 pm **Posts:** 1633

All four wheels need to be spinning at the same speed. Putting the Jeep into 4 wheel drive locks the front and rear wheels together...obviously if the rear wheels are spinning and front wheels are sitting still this would result in bad things happening. :shock:

If the wheels were spinning at the same speed there shouldn't be any problems engaging. I think the manual says up to 55 mph in 4 high.

KJTom · **Joined:** Thu Nov 03, 2005 8:37 pm **Posts:** 18

Exactly. The t-case does not have synchros that will compensate for both axles turning at different speeds from one another. To force one axle to speed up or the other axle to slow down instantly will cause a lot of grinding in the t-case. It’s like trying to slam a manual transmission into gear, while stopped, and with no partial clutch engagement. The engine is turning but the rest of the driveline is not. When speeds aren’t matched within the driveline, you need to slip the clutch in order to match them up before you can have a solid link. To link up both axles, make sure they’re turning at the same speed. It’s usually a good idea to shift the t-case without any go-pedal during the shift.

sleeve84028 · **Posted:** Mon Mar 19, 2007 7:43 am

KJTom wrote:

The t-case does not have synchros

Just incase it was missed - all 4 tires need to be turning at the same speed

07Latitude · **Posted:** Mon Mar 19, 2007 8:40 am

Yeah, the more I think about it, I backed off the throttle the times in the past while engaging 4HI. This time, I know I wasn't thinking straight w/my darned headcold (same time every year I get it :roll:

).

I didn't know the tcase didn't have any syncros. Good to know. I'll be more careful next time.

DarbyWalters · **Posted:** Mon Mar 19, 2007 10:10 am

I am guessing that you have Command-Trac and not Selec-Trac? Definitely not the way to go with Command-Trac...but...interesting ? when it comes to SelecTrac...still probably not a great idea. Even with Selec Trac I never shift into Part-Time of Full-Time unless I am going in a straight line and under 50 mph...I think the book says 55 mph.

07Latitude · **Posted:** Mon Mar 19, 2007 10:14 am

Command Trac = 2HI, 4HI, N, 4LO, correct? If so, thats what I have.

Jeepjeepster · **Posted:** Mon Mar 19, 2007 10:46 am

07Latitude wrote:

Command Trac = 2HI, 4HI, N, 4LO, correct? If so, thats what I have.

Yup, thats command-Trac.

shift on the fly....oops?

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