How many driven wheels?

[Drivetrain]

Ok, on your typical tandem axle tractor that has 4 sets of two wheels, how many are driven. It's been a while since I've been on a rig, but I remember an axle lock switch and also remember peeking underneath the rear and seeing two differentials. If you get stuck and start spinning, do both F and R and L and R all spin?

Thanks

[classictruckman]

Ask Mackman

It depends on the setup of the truck, if it has differential locks on both axles and an interaxle lock then yes all will spin. Without a diff. lock one side left or right will spin and without an interaxle lock one axle could spin.

[Windwalker]

Ask Mackman

It depends on the setup of the truck, if it has differential locks on both axles and an interaxle lock then yes all will spin. Without a diff. lock one side left or right will spin and without an interaxle lock one axle could spin.

I agree with you except for one point. Anytime I've found myself spinning, it's been in trying to take off. Nearly always at very low speeds. And, when I did, it was most generally opposite corners that would spin. Front left and rear right, or front right and rear left. One more note.

Absolutely, never, NEVER, NEVER lock the interaxle differential when one wheel is spinning. Not while any wheels are spinning. If you have one set of duals hanging over a pothole and spinning, hold the brake for a good 20 to 30 seconds to make sure that no wheels are turning when you engage the differential lock. If you still have a wheel spinning when you flip the switch, you will generate multiple fragments inside the differential housings, and the repair will cost thousands. If you're moving, release the throttle, press in the clutch, and flip the switch. Then let the clutch out and apply throttle.

[mike in idaho]

Summer before last I was leaving the local paper mill and came by this brand new pair of drivers in a bobtail swift tractor, they had missed the turn into the yard and had pulled into a pot-holed wide spot to flip a u-turn. The truck was parked with two opposite rear wheels high and dry, over two potholes. One of the guys was outside watching his partner, trying this gear and that, spinning the two sets of airborne duals. I should have stopped to show them what to do, but I was laughing so hard I just couldn't.

[Copperhead]

Good case for lockers on the drive axle. Of course, there are few company drivers like those at the mega carriers that would be able to use them properly without destroying a drive axle. But you won't hang up and not have any traction!

[willismith]

Hi Windwalker, I am agree, and thanks for sharing it. It is helpful to me also.

I agree with you except for one point. Anytime I've found myself spinning, it's been in trying to take off. Nearly always at very low speeds. And, when I did, it was most generally opposite corners that would spin. Front left and rear right, or front right and rear left. One more note.

Absolutely, never, NEVER, NEVER lock the interaxle differential when one wheel is spinning. Not while any wheels are spinning. If you have one set of duals hanging over a pothole and spinning, hold the brake for a good 20 to 30 seconds to make sure that no wheels are turning when you engage the differential lock. If you still have a wheel spinning when you flip the switch, you will generate multiple fragments inside the differential housings, and the repair will cost thousands. If you're moving, release the throttle, press in the clutch, and flip the switch. Then let the clutch out and apply throttle.