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Old 10-26-2006, 05:10 AM   #1
SOLITUDE
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Default Front Driveshaft Removal Myths

Ok, once and for all, please explain plainly for everyone why it is not good to remove the front driveshaft off of a 249(AWD) transfer case. And please explain for everyone what happens inside the case if you remove it. I found this:

Quote:
Originally Posted by AndyZJ
My whole thing with removing the front driveshaft is that it causes uneven load on the chain and output shafts. I've known a few cases where the Tcase has basically self distructed as it is still sending load to the front output yoke where there is nothing there. It binds up and then the chain becomes floppy. I'm pretty sure that its also not good for the VC since since it is always then sensing a variance in load from the front end. If you plan on using the 249 again, then its really not good for the Tcase.
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Old 10-26-2006, 07:09 AM   #2
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From what I understand it's bad to remove the front shaft from 93-95. I believe it's bad for the VC not the TC itself. From 96 - 98 it seems they used a different pump or something.....might have something to do with those years having an actual low lock. I'm not an expert. The only other bad thing about removing the front shaft is when you park...the pump will lose pressure and release the driveline and your rig could roll away.
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Old 10-26-2006, 07:59 AM   #3
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This is what I've found while overhauling my '98 249:
In a nutshell, The '96-'98 249 has essentially a straight shaft (made up of two seperate shafts) from the input side to the rear output yoke. These two shafts are "locked" together when the transfercase is in high range and the VC takes care of any speed differential between the front driveshaft and the rear one. In low range the VC itself is locked and taken out of the equation.
It is on this "main" shaft that the VC resides. The ID of the VC is splined to the shaft and the outside of the VC is connected to the front output shaft by the chain.
Keep in mind that the VC is very stiff and is very difficult to turn by hand. If the front driveshaft is out, the VC simply turns on it's shaft and easily turns the chain driving the front output yoke. It never locks up because there is no shearing action to heat up the fluid. It just spins because there is not enough resistance to make it slip. You have to have both driveshafts in and turning at relatively different rpm's in order to get the shearing action in the VC which heats up the fluid and causes it to lock up.
This is only for the '96-'98 249. In high range all the torque to the front wheels is transferred through the VC.
On the '93-'95 249 the VC acts on a planetary gearset which transfers the torque. The input shaft and the rear output shaft are not locked together. That's why these tend to burn up the VC and will roll if left in "park" when the front driveshaft is out.

This is just my opinion from first hand experience at taking a 249 apart.
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Old 10-26-2006, 10:49 AM   #4
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Quote:
Originally Posted by 85IrocZ-28
All time 4x4. Think of it this way...If you park on a hill with a 2 wheel drive car and the right tire is in the gutter on ice, it can roll backwards. While the left tire on dry pavement is rolling backwards, the right tire is actually rolling forward and pilling out on the ice.
Now apply this to the jeep...When the front driveshaft is out, tires can spin independently. The front tires are not going to prevent rolling at all because the driveshaft is gone.
If the VC is going out, when it cools down it will allow the front driveshaft output to slip with respect to the rear driveshaft output. So the rear tires can roll on the pavement while the front output shaft spins freely in the air because the stationary front axle is not connected and cannot prevent the front output shaft from spinning.
I have not only seen this happen to others, but it has also happened on my ZJ. It isn't fun to come out of the store and find the jeep in the middle of the road.
I really don't think that this will net much benefit on mpg. Unless you have changed your front axle and have locking/unlocking hubs... while you are driving down the road, both axle shafts are still spinning. The diff is still spinning as well. The only thing in your drivetrain that is no longer sucking gas milage is a rotating front driveshaft that doesn't weigh that much. I think a better solution to milage is to take it easy on the throttle.
If you are set on running without it, I recommend setting your park break very tight. I share my experiences so that others don't have to see the same crazy things that I have. I would hate for someone's jeep damaged from rolling while parked. Luckily mine didn't hit anything.
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Old 10-26-2006, 06:23 PM   #5
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Default Simply put.

It is a diff, if one tire spins on a open diff the other doesn't go anywhere. Yes it will burn it up if you try to do it, I have learnt this from experience.
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Old 10-26-2006, 09:44 PM   #6
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i have had no issues at all with my front driveshaft out of my 5.9. the only issue i do have is that the rear tires spin real easy on dry and wet roads. its fun.
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Old 10-29-2006, 04:55 PM   #7
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its bad. jeep had a recall cause grands with the 5.2 and 249 came with a space saver spare. so when you had a flat tire, you put on the spare and you could get about 50 miles before you needed a tire repaired and a new viscous coupler. i dont believe anyone that says they run without a driveshaft without issue.
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Old 10-29-2006, 06:15 PM   #8
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Geez i sure hope i wasn't talking out my arse on this one. All i have ever heard is that if it is designed to run 4 wheels, don't re-invent the wheel.
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Old 10-29-2006, 09:58 PM   #9
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think about this, when you put your transmission in park you are in a sence locking it from moving correct? well, when you lock it from moving how in the heck is the driveshaft going to move. on the 249 the front and rear turn together, when you remove the front driveshaft the front output will still spin like as if the driveshaft is still there. the rear will spin also, but when you put your tranny into park it cannot move. just cause the fronts not there doesnt mean the rear isnt going to lock. i have been running my 5.9 for almost 9 months without a front driveshaft with absolutely no problems. i have smoked my tires off in 1st thru 3rd gear and still have no issues. a good friend of mine has a 5.2 he removed the fornt driveshaft on his for awhile also had no issues.
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Old 10-30-2006, 08:05 AM   #10
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with the front driveshaft out, the vc is constantly slipping. i wonder if you were to reinstall the front driveshaft if the vc would be locked up and chatter like mad on turns.
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