Engine brake

Two types of locks, neither should be engaged/disengaged if there is wheel-spin:

1. Inter-axle, aka, Power Divider
2. Differential lock(s) (less common, usually controlled separately for each axle, required on each axle to have four-way/full lockers)

Inter-axle can be engaged/disengaged and used at any speed. Use anytime traction is less than ideal; wet (extreme--not "damp"), snow, ice, mud, sand, etc. Will still allow differential speed between wheels on the same axle. Very common up here (especially with oilfield/off highway/heavy haul) to leave the inter-axle locked almost the entire winter. Shouldn't be used under high-traction conditions, but if you're driving on pavement that is patchy with snow/ice/gravel it is okay to leave it locked.

Differential can be engaged/disengaged (one or all axles) at any speed up to the maximum recommended by the manufacturer--typically about 50 km/h (30 mph). Most new trucks are set up to disengage the differential locks once the truck exceeds the maximum. This speed can typically be adjusted by the dealer and may need to be (as I have had done) depending on the type of driving you do. Believe me, there's nothing worse than delivering a Super-B load of rig mats to a right-of-way in the Swan Hills where you have to gain speed going downhill in order to get up the other side and your diff locks disengage. Also, for this type of system, the re-engagement speed is really low, so it can screw you up.

Differential locks will push the truck straight when turning corners because the dive wheels can't turn at different speeds. In moderate traction and/or higher speeds this isn't usually a problem. In low speed, very low traction or banked turns like you find where two lease roads meet (and the uphill steer tire gets unloaded), you may need to disengage one or all differential locks. I have never encountered the same issue with just the inter-axle lock engaged and often only disengage the rear differential lock.

Traction control should be disengaged when driving in mud or deep snow as (limited) wheel-spin is desireable in those conditions. Wheel spin when inter-axle or differential locks are engaged is okay, but you break stuff if you engage or disengage them while there is wheel-spin... so get good at reading the road ahead.

 

Well... kind of. It was the momentum of the entire unit. Spinning/sliding wheels will always lead; therefore, if the drive wheels were spinning they will want to lead and will kick out to one side or the other.

 

then the inexperienced driver wont be able to get back into a gear and end up in messican overdrive

 

Interesting. Thank you all for the info

 

I have had a trailer start to jackknife. I applied light trailer brake and a little throttle to straighten it out.

 

Ok. When it's dark n crappy out. Mirrors n windows dirty. HOW do you tell if you're starting to jack? I try to watch my trailer lights, can you FEEL it jacking?

 

You see it dog tracking and you can feel it too.

 

You know you are in a jackknife when your trailer is trying to make delivery sooner than you do.

But seriously, the times I have started to jackknife always begin with a "yaw" of the tractor. It always happened when I did not have the IAD Lock (power divider) engaged when pulling a slight hill.

A yaw is when the right rear drives encounter no resistance, spin out, and causes your tractor to move forward angled to the left. Every time this happened I simply EASED off the throttle and steered to the right to straighten it out. Nothing sudden, just take it in stride.

These days I simply leave the IAD Lock engaged if I THINK I MIGHT encounter slick patches. As our brother from the Great White North pointed out, you can run with the IAD Lock engaged at highway speeds for extended periods of time. Use it. Practice with it.

 

Nobody has taught me anything about it. Yes I understand difference between the inter-axle, and an axle locker. The truck I'm in now just has an inter-axle

I will ask my boss his input, as he owns it. I will try running it more to learn.

Thanks

 

YOU 100% FEEL IT