Quote:
Originally Posted by Orangetxguy
Power Dividers today are far and away superior to the power dividers of the 60's, 70's and early 80's. Technology ...go figure.
Now...the Wheel Differential Lock..that is sweet, if you are chained up, pulling 105,000 pounds, and climbing a mountain. It makes it tough though, if you have it engaged and try to turn a 90 degree corner. Lot's of crow hopping, even at slow crawl.
If you're always (or most of the time) on pavement ALL of the above apply. If you're on slippery stuff, whether mud, sand, ice or snow the cautions about engaging while spinning are absolutely correct - you can blow up a differential by engaging any one of them with literally any difference in speed of the wheels. And, once you've engaged, as soon as you get back onto tractive surface you'd better disengage something.
However, at least in Alaska during the winter when there is a shoulder-to-shoulder sheet of ice or compacted snow, it's not unheard of to run at 55-65 300 miles and more with the Inter-Axle Lock engaged. It's also not that uncommon to drive with one Wheel Differential Lock engaged. Sometimes, during the worst of conditions, you can run for a few hundred miles with both the Inter-Axle and one (JUST ONE) Diff Lock.
A tandem-axle truck or tractor has One-Wheel-Drive - maybe the front, maybe the rear axle, but only one side of one axle. Usually the side with the least traction will start to spin causing loss of traction and forward motion. Engaging the Inter-Axle Lock will give you one wheel on EACH axle because it engages a gear that passes the power to each axle - that would give you Two-Wheels driving; again, one on each axle. Engaging the Diff Lock will give you Two-Wheel drive also, but only on one axle; both axles don't have power to them so only one will drive. Engaging the Inter-Axle Lock AND one Diff Lock will give you Three-Wheel drive; both axles, and both wheels on the 'locked' axle. It is also possible, with 'triple lockers,' to lock the Inter Axle and BOTH Diff Locks giving you Four-Wheel drive; both axles and both wheels on each axle. I've never seen a truck set up with Diff Locks on both axles but no Inter-Axle lock so I didn't discuss the possibility of both wheels on one axle driving and the other axle simply tagging along.
The remarks on understeer are very accurate and true. The Inter-Axle lock doesn't really affect your steering too much. However, with the Diff Lock engaged there is a tendency of the truck to run straight. The puny steer tires simply don't have the traction to overcome the tendency of the drive tires to go straight. And with BOTH Diff Locks engaged it's nearly impossible to turn the truck because all of the drive tires want to go straight and the puny steer tires don't have the traction to overcome them.
I can't emphasize two most important facts enough: NEVER engage any of the locks when there is a difference in wheel speed - NOT WHEN SPINNING, and; if everything is locked up (Inter-Axle and both Differentials) you're in a dangerous condition because steering is severely compromised. At any speed and/or for any distance this is simply deadly.
If there are any doubters next time you're stuck take a close look at which wheels ARE or ARE NOT turning/spinning. I've been stuck on glare ice on flat-level ground and had more than enough opportunities to observe this step-by-step. I've had all four drive wheels spinning - and everything locked up - and not been able to move but put a chain on a single tire and gotten moving. I've also had one wheel spinning and not been able to move. I chained it and the other wheel on the same axle started to spin. I locked the axle and got moving again. I've used the Diff lock and had one wheel on each axle spinning - chained one of the 'spinners' and had the other wheel on that axle spin along with the original spinner.