Why pull front driveshaft for highway driving? - JeepForum.com
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post #1 of 15 Old 08-18-2017, 07:34 AM Thread Starter
dnt6972
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Why pull front driveshaft for highway driving?

My son will be driving his 1999 Grand Cherokee from CO to WI next week and someone suggested we pull the front driveshaft and run it in 2WD on the highway. Why?

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post #2 of 15 Old 08-18-2017, 08:12 AM
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MPG savings.

But while it sounds reasonable in theory, I'd hesitate to call it prudent. Physically removing a part that is designed to be there could introduce other issues that will cost more than the modest gas savings. Especially on an older vehicle.


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post #3 of 15 Old 08-18-2017, 08:22 AM
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If I were that concerned with MPG, I would look into borrowing a car.
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post #4 of 15 Old 08-18-2017, 08:42 AM
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If I were that concerned with MPG, I would look into borrowing a car.

^ this is good advice ^


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post #5 of 15 Old 08-18-2017, 08:48 AM Thread Starter
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That's what I thought. The guy said it would "destroy" the front end. I have a hard time believing that one but thought I would ask around.
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post #6 of 15 Old 08-18-2017, 08:51 AM
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Wait... He told you you SHOULD remove the front driveshaft for a long drive to PREVENT the front end from being destroyed?

I wouldn't let him maintain any of your vehicles...

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post #7 of 15 Old 08-18-2017, 08:52 AM
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Why pull front driveshaft for highway driving?

Removing the front drive shaft has zero affect on the drivetrain wear. You can drive without it forever and nothing will happen.
Having said that you also get pretty much zero gas savings.
I had mine off for the entire summer because I need it to get balanced.
And I did at least a dozen 300 mile trips with it off.
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post #8 of 15 Old 08-18-2017, 09:06 AM
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Correct me if I'm wrong, but I was under the impression that 4x4 WJs were designed to run 100% power to the rear wheels by default until slippage starts to occur, and then the Quadra-Trac/Quadra Drive system works it's magic to distribute that power where needed.

I don't know if removing the front drive shaft would harm the engine or not as I've never tried it myself.

However I can't imagine the MPG gains would be terribly significant. The only thing I see it reducing on 100% highway driving is drivetrain friction caused by the moving parts freewheeling while disengaged. But you'd still get some even then...

Again, I could be totally wrong here. Please do correct me if I am.

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post #9 of 15 Old 08-18-2017, 09:57 AM
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Quote:
Originally Posted by TheDashingRogue View Post
Correct me if I'm wrong, but I was under the impression that 4x4 WJs were designed to run 100% power to the rear wheels by default until slippage starts to occur, and then the Quadra-Trac/Quadra Drive system works it's magic to distribute that power where needed.
Correct.

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Originally Posted by TheDashingRogue View Post
I don't know if removing the front drive shaft would harm the engine or not as I've never tried it myself.
Engine wear is not relative to driveshaft number.

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However I can't imagine the MPG gains would be terribly significant. The only thing I see it reducing on 100% highway driving is drivetrain friction caused by the moving parts freewheeling while disengaged. But you'd still get some even then...
Since WJs don't have lockout hubs, all of the axle parts would still be spinning. The only reduction in friction by removing the driveshaft would be the loss of driveshaft movement itself.

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post #10 of 15 Old 08-18-2017, 10:02 AM
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Quote:
Originally Posted by ChrisHager View Post
Correct.



Engine wear is not relative to driveshaft number.



Since WJs don't have lockout hubs, all of the axle parts would still be spinning. The only reduction in friction by removing the driveshaft would be the loss of driveshaft movement itself.
Awesome! Glad I got that right, and that I wasn't just repeating nonsense.

And about the friction, I figured as much. That's why I didn't think there'd really be any significant difference with the MPGs if you remove the driveshaft or not.

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post #11 of 15 Old 08-18-2017, 04:03 PM
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Quote:
Originally Posted by dnt6972 View Post
My son will be driving his 1999 Grand Cherokee from CO to WI next week and someone suggested we pull the front driveshaft and run it in 2WD on the highway. Why?
"Someone" is an idiot. I think if you have Quadratrac II or Quadradrive, the nv247 transfer case (i.e. progressive coupler) will detect different wheel speeds between front and rear when the front DS is disconnected, thereby engaging 4wd and probably not for the better. If you have SelectTrac (nv242), then I guess you could run it in 2wd and disconnect the front DS, but I'm not sure why. You guys can correct me on the nv247 thing, if I'm wrong.

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post #12 of 15 Old 08-18-2017, 04:15 PM
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Quote:
Originally Posted by Planetcat View Post
"Someone" is an idiot. I think if you have Quadratrac II or Quadradrive, the nv247 transfer case (i.e. progressive coupler) will detect different wheel speeds between front and rear when the front DS is disconnected, thereby engaging 4wd and probably not for the better. If you have SelectTrac (nv242), then I guess you could run it in 2wd and disconnect the front DS, but I'm not sure why. You guys can correct me on the nv247 thing, if I'm wrong.


247 or 242. Makes no difference. You can remove the front DS and drive forever and you'll be just fine.
You just won't have a 4WD Jeep.
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post #13 of 15 Old 08-19-2017, 07:31 AM
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Quote:
Originally Posted by grayWJ4x4 View Post
You just won't have a 4WD Jeep.
I'm sad that this exists from the factory.

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Quote:
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Quote:
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post #14 of 15 Old 08-21-2017, 02:45 PM
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the viscous coupler in the tcase doesnt care that its locked up with no load. key being no load. it will spin the output but the actual torque transfer is virtually nothing so the fluid wont get destroyed. the driveshaft is like nothing in energy to spin, if you could unlock the hubs thats a different story because you are dealing with the ring and pinion friction. i wouldnt bother, literally might save 5 bucks over a thousand miles. youre better served checking alignment and tire pressures lol.
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post #15 of 15 Old 08-28-2017, 07:06 PM
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Quote:
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My son will be driving his 1999 Grand Cherokee from CO to WI next week and someone suggested we pull the front driveshaft and run it in 2WD on the highway. Why?
I pulled mine due to a joint going bad. Didn't notice any difference in mpg, and I lost my holeshot superpower in the rain. Drifting on/off ramps was fun, though. It went back in when I got a repair kit.
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