Answer to "single axle with lift axle in front or rear"I am specing out a new truck for Canada, will be going from Vancouver, BC to Winnipeg, MB. About 600 miles of mountains one way.Just spoke to people at Meritor, they said one diff can't handle 90,000 lbs????!!!! And I see so many people here pulling 80k+ with one. I am looking at ordering a Volvo 670 (high rise cab) with D13 and IShift (AMT). Would you recommend a different setup? and why? What other fuel saving options can I get? All input is appreciated.