Shift on the Fly T-case??? - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 04-26-2000, 09:20 PM Thread Starter
 
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Shift on the Fly T-case???

I am just curious to see what your opinions are. On two of my jeeps they have the shift on the fly lever. In both of the owner's manuals they say that you can shift into four wheel drive at any legal road speed. As far as shifting into four wheel low you should be going 2-3 miles per hour for a safe shift. I have friends who say it is better to stop completely before shifting into 4x4 high or 4x4 low. Should I trust what the manual says or should I trust what my friends and father say? Let me know your opinions and thoughts on this topic. Keep riding the rocks.

[img]/wwwthreads_images/icons/cool.gif[/img]'46 CJ 2-A Rusty, but still fun to drive and easy to work on.[img]/wwwthreads_images/icons/cool.gif[/img]
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post #2 of (permalink) Old 04-26-2000, 09:32 PM
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Re: Shift on the Fly T-case???

[img]/wwwthreads_images/icons/tongue.gif[/img] There are SO MANY different cases out there, and some really don't shift very well "on the fly" but most will. The stuff that is behind automatics is a little more of a problem if you don't concentrate and understand what you are doing. I think what gets most folks out of whack is the HUGE difference into Low Range. They just don't realize how far down even 2.5:1 actually is. We used to use our army truck tranny/transfer case combinations as "Oklahoma Seven Speeds", by starting in 2WD low....go through all five speeds in the main box.....pull the t-case into high range....then do 4th and 5th again in the mainbox.[img]/wwwthreads_images/icons/crazy.gif[/img] Man, were we cool[img]/wwwthreads_images/icons/cool.gif[/img]or what?

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Quadra-Trac modified by the crack moonguy[img]/wwwthreads_images/icons/wink.gif[/img][img]/wwwthreads_images/icons/smile.gif[/img][img]/wwwthreads_images/icons/tongue.gif[/img] transfer case team.
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post #3 of (permalink) Old 04-26-2000, 11:32 PM
 
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Re: Shift on the Fly T-case???

I have a 86 XJ with the 2.8L V-6, 904 auto and NP207 transfer case. My owners manual says the very same thing: you can safely shift into 4wdlo at 2-3 MPH as long as the transfer case has COMPLETELY shifted into 4wdhi. When I first attempted this the gears would grind, however (14 years ago). Since then, I have always come to a complete stop to shift into low and I have to put the transmission into neutral in order not to grind gears (to relieve some bind in the drivetrain, I suppose). I've learned to anticipate where I'll need low range and stop to engage it beforehand.[img]/wwwthreads_images/icons/crazy.gif[/img]

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post #4 of (permalink) Old 04-27-2000, 06:45 AM
 
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Re: Shift on the Fly T-case???

It's just kinda hard to get out and lock the hubs above 0 mph ,the faster you go the harder it gets...... LOL [img]/wwwthreads_images/icons/laugh.gif[/img]

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post #5 of (permalink) Old 04-28-2000, 12:18 PM
 
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Re: Shift on the Fly T-case???

I shift to 4H at speeds of 35 mph or slower and come to a complete stop to go into 4L.

[img]/wwwthreads_images/icons/cool.gif[/img] Big Ed
<font color=red>'88 YJ, 4" susp,3" body,33's,283 Chevy V8,TH350,4.11's,D30,D35c</font color=red>
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post #6 of (permalink) Old 04-28-2000, 06:08 PM
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Re: Shift on the Fly T-case???

A good general rule of thumb no matter what the vehicle is is to never shift on the fly unless the front and rear tires are travelling at the same speed...i.e. if you're in 2wd and are spinning the rear tires faster than the front tires, you'd want to equalize the speed of the fronts and rears before shifting into 2wd...so even if your hubs are locked and you're about stuck in 2wd, you'd have to stop spinning the rears to lock in the 4wd. Otherwise, engaging the 4wd will cause quite a jolt to the whole drivetrain... On older vehicles, a good rule of thumb is to never shift on the fly unless the front and rear driveshafts are both turning at the same speed...either both spinning at the same speed or both stopped. This would mean that the hubs (if so equipped) must be locked, and the tires must be revolving at the same rate (once again, no slipping those rear tires). Of course in this world of central axle disconnect and instatrac, this rule is becoming less relevant. As far as the shifting into low-range goes, you could probably do whatever works best. My 77CJ's Dana 20 likes shifting into and out of 4low at a very slow roll with the transmission in neutral...that's the way she shifts easiest, and with the least amount of grinding. My 95 F-150's Borg-Warner t-case likes to shift into 4 low stopped, and shift back out either fully stopped, or going about 4 mph...no where in between. Of course, starting out in low when pullin those loaded gravity wagons out of the field lets that big 300 straight six go to town, and then with the shift into high range at 4 mph, I don't quite have the 7 gears that CJDave had, but I have a rough 5 2 speed...sure beats the snot out of my dad and brother's 350 chevys pulling with instatrac and automatics...[img]/wwwthreads_images/icons/wink.gif[/img]

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