so is there any ill-effects in doing so? i can't think of any but i have never owned a full-time t-case. i am hoping to gain a tad gas milage and less tire/front-end wear.

forget about better mileage and more even wear :shaking:
You won't win anything by removing the ds, unless there's binding because of the vc being shot.

Why not get a 2wd Jeep then? :smokin:

Pull that 249 out of there and put a real case in. If it's a 93-95 you will destroy the VC rather quickly. Regardless of what year it is you won't see a worthwhile improvement in mpg or tire wear.

Pull that 249 out of there and put a real case in. If it's a 93-95 you will destroy the VC rather quickly. Regardless of what year it is you won't see a worthwhile improvement in mpg or tire wear.


what is the VC?
this is my son's DD and he doesn't use 4WD but if there is a potential prob, i will put the driveshaft back on. this is why i am asking.........don't want to fawk up the t-case.

and this is a 96 with V8 laredo

ok, scratch that....i see in the haynes it is the VISCOUS COUPLING.....and why would it go with the front shaft dico'd? can you explain?

thanks

Think of the VC as a limited slip differential. With one wheel spinning freely all the time (no shaft to connect it) the VC has to work overtime to transfer any power to the opposite wheel. It'll be cooked in no time.

If it's the later 249, it's a bit different. if it's locking up, you will see a small difference in driving, and it should be OK to drive with no front shaft.
I think the later ones don't really use the VC to drive the rear shafts. You can drain it, and have 2wd and 4lo (lock)
now mine being a 93 with a 249, it's different. The VC drives both the front and rear

If it's the later 249, it's a bit different. if it's locking up, you will see a small difference in driving, and it should be OK to drive with no front shaft.
I think the later ones don't really use the VC to drive the rear shafts. You can drain it, and have 2wd and 4lo (lock)
now mine being a 93 with a 249, it's different. The VC drives both the front and rear



thanks....i have the 249 J

and i quote from haynes about the 249:

the np249 is a fulltime 4WD transfer case......engine torque is distributed to the front and rear axles through a differential and viscous coupling in the transfer case..........."


now it also states this about the NV247 which i DON"T have:

"......is an on-demand transfer case with two operating ranges and a neutral. under normal conditions, with the t-case in 4-high, the majority of the torque is applied to the rear wheels. when rear wheel slip is sensed, torque is transferred to the front axle, allowing the axle with the best traction to receive the majority of torque..............."


sounds to me like it can't hurt the 249 to be without the front shaft since it is applying torque to both all the time.

and even on the 242, as long as you stay on pavement and don't get the rear slipping, then the front won't be asked to engage.

this is interesting.



so..........i am still wondering if taking off the front shaft was such a good idea :)

Think of the VC as a limited slip differential. With one wheel spinning freely all the time (no shaft to connect it) the VC has to work overtime to transfer any power to the opposite wheel. It'll be cooked in no time.


could you be thinking of the NV247?

read my post above :)

The 242 uses gears to provide the fulltime action.
Since you have the later model 249, I say take out the front shaft and go for it.
Go to nagca.com and jeepsunlimited.com and start reading about the 249. You'll find all kinds of stuff about them

I've got a 96 V8 5.2 with an NP249 and I've been running without my front shaft for several weeks now. Breaking the rear end loose is SO much fun :laughing:

Oh, and 96+ is fine to run without the front shaft.

I've got a 96 V8 5.2 with an NP249 and I've been running without my front shaft for several weeks now. Breaking the rear end loose is SO much fun :laughing:


that's interesting......and how do you know the VC isn't being "overworked" and wearing out and/or turning toast like some say here? and why 96? what's different with that year and up i assume?

not doubting you........i would like to see you right. my son has been running his off since july 5th and driving 50 miles a day. it operates just fine but i am wondering what would happen if we put the shaft back on some day? would the VC be toast and the front shaft wouldn't transfer torque or maybe "Bind" as someone suggested?

i plan on keeping it off........if the VC were to crap-out it probably has by now......couple thousand miles.


thanks

they redesigned the 249 from 95 to 96 model years.

the earlier cases had no lo lock. This means that the awd properties of the case are still present even when 4lo is engaged. Both the front and rear drive shafts don't have to turn at the same rate. In the 96 and up cases, in 4lo both driveshafts are locked together. As to how they do this not sure.

:cow:

they redesigned the 249 from 95 to 96 model years.

the earlier cases had no lo lock. This means that the awd properties of the case are still present even when 4lo is engaged. Both the front and rear drive shafts don't have to turn at the same rate. In the 96 and up cases, in 4lo both driveshafts are locked together. As to how they do this not sure.


ok, so i read your response 3 times....maybe not enough but.........

so your answer to MY question is what?????????????

will i damage the VC on my 96 NV249 if i run with NO front driveshaft???????

apparently moderator STEVE feels this is just a trivial NEWBIE question :)
so then steve........shed light on this trivial issue with your worldly knowledge :flipoff2: yeah right ..............didn't think so :flipoff2:

Ok, here is a little description of how the VC works. I don't know what years are safe and/or unsafe to run without both driveshafts, but I can try to tell you what the VC does.

Basically, the VC is a center differential between the front and rear axles. It allows the front axle/wheels to run at a different speed than the rear axle/wheels. This eliminates the wheel hopping or binding feeling that occurs with normal locked 4x4's when turning corners in 4wd on dry pavement.

If one of the driveshafts is disconnected, one side of the VC will be getting overworked, therefore overheating the VC and likely eventually locking it up. The older ZJ's with this transfer case are supposedly prone to having the VC lock up and start binding. I know that my buddy has had 2 different early ones and they both started to lock up and not do their job.

If it were me, I would leave well enough alone and just leave the shaft in there. That way you know you won't mess anything up and I honestly don't feel that you will gain any mileage doing it.

Just my $.02

I just bought a 1994 Grand Cherokee Laredo with the 318 V8 at an auction. The rear drive shaft (called a propeller shaft by Chrysler) apparently broke off sometime in the past. I drove it home. About 300 miles using only the front drive shaft. Soooo, I will put new u-joints in it and put the drive shaft in this weekend. Then we will solve this little mystery we seem to have here.

Also, I used to own a 1979 Dodge Power Wagon that had full time 4 wheel drive and THERE WAS NO INCREASE IN MPG WHEN THE FRONT DRIVE SHAFT WAS REMOVED! But like it was mentioned earlier, it was fun. hehehe.

If one of the driveshafts is disconnected, one side of the VC will be getting overworked, therefore overheating the VC and likely eventually locking it up. The older ZJ's with this transfer case are supposedly prone to having the VC lock up and start binding. I know that my buddy has had 2 different early ones and they both started to lock up and not do their job.


Just my $.02If the VC locks up then there is no problem as long as you never ever put the front driveshaft back in. From what I understand the VC is several hundred dollars for a new one.



Also, I used to own a 1979 Dodge Power Wagon that had full time 4 wheel drive and THERE WAS NO INCREASE IN MPG WHEN THE FRONT DRIVE SHAFT WAS REMOVED! But like it was mentioned earlier, it was fun. hehehe.
Keep in mind that while the driveshaft is out and not turning, the entire front end is still turning as there are no lockouts on the hubs.

The 247 will work, although it is has different innards. I don't know that you could go 2wd with it. I had one for awhile, but there is no plug for the speedo.

Fianlly, you can replace the entire tcase with a 241 from an earlier ZJ or XJ. Just be sure of what you are buying as I had a hell of a time trying to explain to the dipshits at a local junkyard what I had and why it didn't match what they wanted to sell me.

OK! The verdict is in... after 300 miles with only the front drive shaft, there seems to be no problem with the transfer case after the rear drive shaft was re-installed. It may be a little low on fluid yet but if it changes anything when I top it off I will post it.

Why would anyone NOT want full-time 4-wheel drive? The purpose of a 4 x 4 is 4 wheel drive...

I have to disagree... if one drive shaft is disconnected, the VC sees the condition as traction loss and will lock. As long as there is a force applied to the VC it will remain locked. When the VC is locked there is no clutch disk slippage, no heat build-up, no problem. It should be safer to do this than have it under normal conditions since when both drive shafts are connected the VC must continually slip during turning to compensate for speed discrepancies between the front and rear wheels. This will cause more heat than with only one drive shaft connected...

The VC is a VISCOUS COUPLER.
A viscous coupling is made up of alternating circular plates. The plates have tabs or perforations in them. The plates are mounted in a sealed drum, and are located very close to each other. The drum is filled with silicone, or some dilatant fluid. When the two sets of plates are rotating in unison, the fluid stays cool and remains in a liquid state. When the plates start rotating at two different speeds, the shear effect of the tabs or perforations on the fluid will cause it to heat up and solidify (Silicone when heated will turn into a near solid; the viscosity of dilatant fluids rapidly increases with shear). The fluid in this state will essentially glue the plates together and transmit power from one set of plates to the other. The size of the tabs or perforations on the plates, along with the number of plates and fluid used will determine the strength and onset of when this mechanical transfer will happen.

The very thing that makes it work (heat) is also the very thing that kills it.


after 300 miles with only the front drive shaft, there seems to be no problem with the transfer case after the rear drive shaft was re-installed. Go do some tight circles in a parking lot and see if the front end binds.