It's a 2005 Mack Granite tandem with a dually lift axle used to transport shingles(with a rear mounted Moffet). Other than raising axle for sharp corners are there any other conditions when axle should be raised.
It's equipped with an Eaton Fuller 9 speed...does that mean a high or low powered engine?


edited for year correction

 

You need to lift or reduce pressure on the lift axle when the pavement is slippery to put more weight on the drives. I think the Granite model(CV713) came out in 2002, so yours is probably a RD model. Most Macks do ok power wise for staight truck applications.

 

Normally you'd lift the axle when unloaded or lightly loaded -assuming you don't exceed the capacity of the drive axle. I have driven a single drive tractor w/ lift axle and I could run with the lift up if I had under 30k in the 53 foot van if it was loaded right. 8) The drive axle was air suspension and the lift axle wheels would touch down if you ran out of capacity on the drive airbags so you'd know to lower the lift axle. I don't know if that forklift on the back puts you over with no load or not? As for the 9 speed, your motor hp could be most anything.

 

that was the 1st year for the granite.