Last night I attempted to back up to my friend's front door to unload some heavy stuff out of my truck. The driveway was full, so he told me to park on the grass.

The back wheels of course made it up fine, but the front wheels were stuck on the curb while the back tires just spun. Now it had just got done raining so this was understandable. No big deal, put it in 4hi and problem solved. WRONG. The back tires still spun while it seemed as if no power was going to the front. Tried 4lo and same thing. I literally could not drive up a curb!

I know my 4wd works and I even rolled forward first to make sure it engaged. Why weren't the front tires just climbing up the curb? If the back tires started to slip shouldn't the power go to the front? Or do I not understand how this system works?

 

Were your hubs engaging?

 

How do I tell? After I put it in 4hi I rolled forward to make sure it engaged and I could "feel" that it was in 4wd

 

The transfer case splits power equally to the front and rear when the transfer case is shifted to 4wd. If you have ESOF it is possible your hubs were not locking or even the t-case was not staying in 4wd. If you have manual 4wd you obvious have to manually lock both hubs and shift the t-case into 4wd.

Even when in 4wd you are still at the mercy of the differential. From the factory the front differential is an open unit which means it can deliver all the power the wheel with the least amount of traction on that axle. Same with the rear if it has an open diff, if the rear diff is limited slip both wheels will turn until the torque reaches a point until the clutch pack cannot hold it any further and one wheel can "unload".

Engage 4wd and see if you can spin the front driveshaft and each axle shaft by hand. If you can spin either by hand (more than 1/4-1/2 turn or so) you are not entirely in 4wd. If the driveshaft does not spin but one or two of the axles shafts spin manually lock the hub and check to see if you can rotate the axle shaft again.

 

most likely your hubs weren't engaged

also, the transfer case splits the transmission output exactly 50/50. front wheels get exactly same power as the rears. they don't "share" power. so even if your rears were spinning, the fronts were only getting 1/2 the power, no transfer occured


so yeah, the front hubs were likely not engaged.



jack up the front of the truck so wheels off the ground. start truck and put into 4x4. get out and attempt to spin front wheels. they should not move because they'll be mechanically locked to transmission. if they move, it means the hub isn't engaging.

also, place your truck into 4x4 while running and turn on the A/C. if it blows out the defrost, you have a vacuum leak

 

That makes sense. So basically if I just gave it more gas it would have spun the rears more and the front would eventually have crawled up. I just didn't want to tear up his grass too bad.

 

yeah, pending traction, the fronts would have eventually climbed the curb


also, when climbing curbs the best route of attack is 1 wheel at a time. hit it at an angle and you can climb most in 2wd even in slippery situations. perpendicular attacks where both tires hit at once are harder to climb and usually result in wheel spin

 

Find a dirt or grassy area, put the truck in 4wd and nail the skinny pedal. Get out and see what was spinning.

 

great advice Tylus. One wheel at a time. or just hammer the damn thing in 2 wd next time and just say sorry bout the grass dude. haha.

 

If I understand correctly, if 1 REAR tire is spinning, 1 FRONT tire has to be spinning.
So if you were spinning your tires on grass, and the front tires were not spinning at the same speed, (at least one) you're hube were not locked, or you were not in 4wd
The transfercase can not uncouple front to back like an older jeep cherokee can.

 

If something like that happened to me, I would never hear the end of it. Not very many of my friends drive Fords.

 

correct. in 4x4 the front and rear axle are mechanically locked together.

you can do traction aids like a locker or limited slip to make both wheel spin, but you will always have at least 1 tire in each axle spinning while in 4x4

 

When I brought my brand new 2007 home from the dealer, I got stuck in a small snow drift in 2WD. No problem, click on the ESOF to 4H and nothing -- rear tires spinning nothing from the front. Got out and manually locked the hubs and drove right out with no issue. The problem turned out to be a vacuum line that controls the front automatic locking hubs. I've never had a problem since. The same vacuum issue also affected the heater, preventing the blend doors that direct heat to the floor from opening.

 

That ESOF is so much grief up here in the land of slush salt and ice that I went for the fully manual (hubs and man-stick) in my latest SD. Now I know if 4wd is in or out because I put it there myself.

 

It gets even simpler than that. Use some common sense and drive forward onto the grass, this way you eliminate the possibility of a rear wheel slip and trashing your friend's grass.

Or recognize the fact that your light rear end would have a tough time pulling that heavy front end over a curb when your grabbing grass instead of pavement and putting it in 4WD in advance. Of course there is something wrong here, but there are better ways to get this done. Or maybe I'm just crabby from lack of sleep...

I agree with the majority here, it sounds like one or both hubs weren't engaging. Did you try manually locking them?