How 'bad' is it to use the transfer case for front-wheel-drive?

[Lynn]

I heard years ago that running a t/c in 4x4, with the rear drive line removed (effectively creating fwd), or running the t/c in 4x4 with front hubs unlocked, would 'eat' the t/c due to unequal loading.

However, I believe one of the selling points of the Atlas T/C is that it can be used fwd in a pinch, and have been told that other t/cs (with dual stick conversion) can be used this way, as well.

However, on another thread (here, to be exact) I mentioned a wrecker I saw that basically used a transfer case in a 'front-wheel-drive-only' application, and was told by ntsqd that there were other wreckers built this way.

I also used to know a guy who had a '70s Blazer that he had run for years in a fwd mode because he couldn't seem to get around to replacing his failed rear u-joints.

So, I know it probably depends on the t/c, but what's a general rule-of-thumb regarding using a t/c this way?

1. In an emergency (twisted rear drive line), do what you have to do to get back to civilization.

2. Don't worry 'bout it, ya ain't gonna hurt it.

3. Can't answer without knowing the exact t/c in question.

 

[kodiak1232003]

I heard years ago that running a t/c in 4x4, with the rear drive line removed (effectively creating fwd), or running the t/c in 4x4 with front hubs unlocked, would 'eat' the t/c due to unequal loading.

However, I believe one of the selling points of the Atlas T/C is that it can be used fwd in a pinch, and have been told that other t/cs (with dual stick conversion) can be used this way, as well.

However, on another thread (here, to be exact) I mentioned a wrecker I saw that basically used a transfer case in a 'front-wheel-drive-only' application, and was told by ntsqd that there were other wreckers built this way.

I also used to know a guy who had a '70s Blazer that he had run for years in a fwd mode because he couldn't seem to get around to replacing his failed rear u-joints.

So, I know it probably depends on the t/c, but what's a general rule-of-thumb regarding using a t/c this way?

1. In an emergency (twisted rear drive line), do what you have to do to get back to civilization.

2. Don't worry 'bout it, ya ain't gonna hurt it.

3. Can't answer without knowing the exact t/c in question.

i have heard of several stories of trucks with t/cases that had FIXED REAR YOKES(i.e. not slip yokes) that pulled the rear shaft and drove off the trail.

one actually drove about 40 miles (at low speeds) back home.

these we're in magazines, or on a websites with pics of the pulled shaft and the truck heading down the trail/highway..so i think they're pretty reliable...

seems to me a toyota tcase would do fine, as would a suzuki, as i think they have rear fixed yokes...

my np231 probably wouldn't fare to well due to the slip yoke (but I'm not sure)

 

[Digger]

I bent my rear drive shaft once and drove the truck home 200 miles @ 60+mph in FWD. This was with the stock chain driven transfer case. It got very hot and understandably so. However, it did get me home. I now have an Atlas transfercase, and I would feel more comfortable doing that with the Atlas because it is a heavy-duty gear drive unit. It will still get hot though because in RWD, the transfer case sends power directly through, while in FWD, power travels through the gears which generates heat from friction. I seriously doubt you could hurt that transfer case, but you will be putting extra miles on the gear set.

I would not recommond driving around if FWD often with a chain drive t-case. It will wear the chain out much more quickly. Emergencies only.

EDIT: Yes if you pull the rear driveshaft from a slip yoke t-case, you will lose your gear lube and ruin the t-case.

 

[goodtimes]

I have done this on a number of occasions. Usually due to rear driveshaft problems.

On my old '72 blazer, I drove for several weeks this way while saving $$$ for a new driveshaft.

On my 2000 chevy zr2, I tried it after a spotter failed to see the rock that my aluminum driveshaft got up close and personal...but the IFS didn't really like it, and it was really scary to drive due to the way it handled.

On my '03 TJ, I have done it when my rear driveshaft was being made (after I installed a lift), and again when the driveshaft was being rebuilt (worn DC joint).

I have seen no ill effects. If you have a slip yolk, be prepared to leak a bunch of oil...so you'll be stopping alot to check the level and fill it up. Also expect some contamination (dirt) in the t-case.

Also, any t'case that is designed to act as a differential (can have different output speeds between front and rear driveshafts) must be equipped with a locking mechanism of sorts (like the "center diff lock" used on toyota land cruisers).

 

[efuentes]

We just did 500 miles on a Jeep Rubicon with a busted rear yoke, it did drive a little weird, but was ok.

So far the transfer case feels normal.

 

[BigAl]

Just to muddy the waters further, I think tc's that use a viscuous coupler (like a clutch) can be damaged in fwd only mode. My plain jane 231 with sye has been run that way several times with no issues.

 

[kodiak1232003]

We just did 500 miles on a Jeep Rubicon with a busted rear yoke, it did drive a little weird, but was ok.

So far the transfer case feels normal.

see there's the exception..the NV241 (rocktrac) has a slip-yoke from the factory...

jeep tj's would need to have a slip yoke eliminator kit put in.
(about $2-300ish, i think)

not sure what older jeeps have installed...


EDIT:hehe, just saw your post, AL...

 

[goodtimes]

see there's the exception..the NV241 (rocktrac) has a slip-yoke from the factory...

jeep tj's would need to have a slip yoke eliminator kit put in.
(about $2-300ish, i think)

not sure what older jeeps have installed...


EDIT:hehe, just saw your post, AL...

Actually, the NP241 has a fixed yolk, no slip yolk eliminator needed.

Al, you are correct, if the front and rear output shafts are not locked together, you are going to have trouble. This is why the toyotas (and others that use a center differential) without the center diff lock shouldn't be driven without the rear driveshaft.

 

[adventureduo]

Drove in front wheel drive (NP231) many times with no problems. Just remembered my rig driving funny... when i gave it gas pulled left, when i let off it settled right. Was fun. Just keep your speed down and you'll be just fine.

 

[evldave]

If you have a slip-yolk go to Napa/Shucks/etc and get a $5 tranny cap. On my XJ I mangled the U-joint offroad, slipped on the cap and drove it out & home (25 miles maybe) - it didn't leak a drop of gear oil. You can also use a cut-up 2 liter bottle and duct tape (trust me I know ) - but $5 is cheap insurance...

 

[kodiak1232003]

Actually, the NP241 has a fixed yolk, no slip yolk eliminator needed.

Al, you are correct, if the front and rear output shafts are not locked together, you are going to have trouble. This is why the toyotas (and others that use a center differential) without the center diff lock shouldn't be driven without the rear driveshaft.

derr, thats what I meant...nv241's have a fixed yoke....231's need the kit...

i must be tired...lol.

 

[cruiser guy]

This is why the toyotas (and others that use a center differential) without the center diff lock shouldn't be driven without the rear driveshaft.

This would only apply to the newer full time 4wd Toyotas. Older ones like the '40's, '55's and '60's do not use a center diff and are all gear driven.

 

[DaveInDenver]

This would only apply to the newer full time 4wd Toyotas. Older ones like the '40's, '55's and '60's do not use a center diff and are all gear driven.

Yup, any Toyota without a center diff would be fine and locking the center diff should also be fine. This includes the Cruiser that you mention as well as most mini trucks and Tacomas. I've driven mine around in front drive only with the rear propeller shaft removed for maintenance and the like. The t-case can get a little hotter than normal 2WD because there's more stuff engaged and I get fairly bad torque steer. But you're not hurting anything and it's something you can certainly keep as an option during recovery. For example, having the same length front and rear drive shaft means you have a built in spare.