4WD questions

[dr jazz]

I understand from some posts here and talking to others that it is generally not a good idea to engage 4WD Auto at speed (Ihave 2WD-4WD Auto-4WD Low). I can see that with spinning driveshafts engaging non-moving parts some problems could happen. I wonder why Ford says this is okay at any speed??

What is the consensus here about leaving the switch in 4WD Auto, let's say during the winter months? Manual says no problem, just a slight increase in fuel usage. Salesman at dealer says something about there being an extra tooth in the front differential that can cause tire scrubbing over time. He kind of lost me on that one.

What is the truth, the whole truth, and nothing but the truth?

 

[Jason_25]

Here's the truth for you:

You can engage 4-auto at any reasonable speed.

You can also keep it on all the time. The only thing it will do is slightly increase front end companent wear and decrease gas mileage slightly.

 

[dr jazz]

Thanks, Jason. That is pretty much what I thought. By reasonable speed I assume maybe under 30? Some say stop altogether.

Any other truths out there, particularly about problems leaving 4WD Auto on for long periods?

Thanks

 

[Jason_25]

Well I've actually turned mine on at 75 before, no harm done. The only thing that actually happens at speed is that the vacuum coupling in the front end engages, once you get below 30 or so, the t-case clutch engages when needed.