4X4 vs 4X2 fuel mileage

[CDW6212R]

Joe, this thread isn't about the BWM, it's the OP who has pulled his front shaft and not touched the brown wire.

 

[RetiredWrench]

I'm returning to this thread just to report that I have not had any damage to the 4wd sysytem from disconnecting the front shaft. I installed the front shaft several months ago with a new u-joint. The 4wd system has been working fine every since. I have driven through snow and ice so far this winter with no problems. I intend to remove the front shaft in the spring.

 

[chris's2005]

I'm returning to this thread just to report that I have not had any damage to the 4wd sysytem from disconnecting the front shaft. I installed the front shaft several months ago with a new u-joint. The 4wd system has been working fine every since. I have driven through snow and ice so far this winter with no problems. I intend to remove the front shaft in the spring.

i may have to try this, i currently get 10 mpg with my 2005xlt (its bad mpg is based on the suspension and large tires ive added to it)

 

[HahnsB2]

I'm returning to this thread just to report that I have not had any damage to the 4wd sysytem from disconnecting the front shaft. I installed the front shaft several months ago with a new u-joint. The 4wd system has been working fine every since. I have driven through snow and ice so far this winter with no problems. I intend to remove the front shaft in the spring.

Unless you have some SERIOUS binding in the front driveshaft u joints, you didn't see 5MPG increase by removing it, it's just not physically possible. The axles and gears are still spinning in the front diff anyways.

 

[RetiredWrench]

Perhaps you could enlighten us as to what is physically possible to achive in this situation?

 

[HahnsB2]

Perhaps you could enlighten us as to what is physically possible to achive in this situation?

There is simply no way to gain 5MPG by removing a 15Lb spinning object from the drivetrain, especially since all the other crap in the diff is still spinning

 

[RetiredWrench]

You're kinda missing the point here Einstien. Even if it wasn't exactly 5mpg, it was significant. It was enough that myself and other drivers could feel a difference in coast down. As I stated before, some of the difference was from the tight u-joint. The rest was probably from elimininating the drag of the transfer case. If there is such little to be gained from reducing the friction of a front axle, why do some people run lock out hubs?

 

[HahnsB2]

If there is such little to be gained from reducing the friction of a front axle, why do some people run lock out hubs?

Like I said, there is no 5MPG worth of drag in turning the front axle and driveshaft, otherwise car companies wouldn't use live axles if they cut fuel economy 25+% when they're constantly trying to make cars more efficient. Sure there is .5 maybe 1MPG you could gain, I've never seen any drop in fuel economy by keeping my hubs locked in.

 

[chris's2005]

You're kinda missing the point here Einstien. Even if it wasn't exactly 5mpg, it was significant. It was enough that myself and other drivers could feel a difference in coast down. As I stated before, some of the difference was from the tight u-joint. The rest was probably from elimininating the drag of the transfer case. If there is such little to be gained from reducing the friction of a front axle, why do some people run lock out hubs?

I trust you, in fact once it gets into pring weather i will be trying this. nice idea

Chris

 

[Aero540T]

Hey Retired, I'm wondering has the mileage gone back down since you've replaced the ujoint and shaft?
Thanks for your info so far

 

[RetiredWrench]

I haven't accurately checked the mileage since I put the shaft back in. The drag on the vehicle does not feel as bad as it did before. Replacing the u-joint appears to have made a pronounced difference. The old one had about 40,000 miles on it. It didn't have any slop in it at all. After I removed the shaft, I could feel the joint was binding. The caps had full range of motion, but they got tight at some spots. I replaced it with a greaseable Spicer. The original was a non-greaseable Spicer. I plan on keeping the new one well lubed. My recommendation to anyone with a similar vehicle, would be to check the front u-joint.

 

[IZwack]

You wont see any damage from removing the front driveshaft or the BWM on the 4.0L v6s (not the v8s) as long as you dont do burnouts. Its the burnouts that kills the transfer case when one axle is not moving and the other is at 3k RPMs. As for "friction" in the clutches made during a turn, its almost insignificant because the difference in the arc length during a turn between the two axles is very little.

But as far as the MPG gain figures, I'm going to have to go with HahnsB2. I think there is some human error in this and an ideal test would be a long drive with cruise control on the same road and relatively the same environment (temps and precip).

 

[helmsa]

i may have to try this, i currently get 10 mpg with my 2005xlt (its bad mpg is based on the suspension and large tires ive added to it)

Chris, what type of driving are you getting 10 MPG from? I got about 16.563 with mixed driving (between tire sizes & hwy vs city). I will let you know what I get on the tank I'm running right now (mountains & snow). I should be filling up this weekend or early next week as I really only drive on the weekends.

 

[RetiredWrench]

If the only consideration of two axles in a turn was arc length, we all could drive around in four wheel drive all the time. I think there is some human error in this.