Diff lock vs inter axle lock

Interlock gets one wheel on both axles pulling, diff. lock gets both wheels of same axle(s) pulling, and will only want to go straight, will be fighting steering.

 

What sort of bad things? I accidentally did this while trying to get a frozen trailer out of the ice. I hear hissing now that I dont think was there before. How badly have I just ruined this truck?

 

There is no safety on the rear axles .
If a wheel is spinning and you through the switch to lock that axle it Will force the gear to lock the shaft. Then either the gear teeth will break or the axle shaft will.
It would be like having a manual transmission and trying to put it in gear with the engine running while stopped and not stepping on the clutch.

 

I have an example of why you can use both...

I had a trainee father and son team w/ one of the last years they made cab-over Pete's.

Scaled light at x-rail and pulled forward slowly through a huge water filled hole. Once the drives were centered in the pothole, he lost traction with one set of wheels spinning.

After stopping he put in the power divider interlock which made the opposite wheel of the other axle spin with the original.

A Diff lock would have made both wheels on one axle spin and would have driven him out of the pothole.

We had another driver back his trailer against the struck unit's trailer and give just enough of a nudge to get his wheels to bite...tying up the narrow approach to the scale the whole time.

 

So it’s okay to be going 35-60 mph and activating interaxle as long as I’m not in a spin out while turning it on? Does it help to maybe pull it out of gear, engage it as the truck coasts in neutral, then put it back in gear?

 

As long as you don’t have a whee spinning you can engage at any speed. Lots of modern trucks use electric over air solenoids that the computer controls. The computer can be programmed to not allow the power divider over certain speeds. Which sucks. If I see a big hill that’s snow covered I want my power divider locked in.

 

Another point to consider is if you're one of those guys that only changes tires on one axle. Brand new tires on 1 axle and very worn tires on the other will create a small difference in speed between the 2 axles. On snow or even gravel its not a big deal. On dry pavement you'll be loading up the diffs and causing binding in the interaxle components.