I bought a truck with new virgin tires on the front/rear axle and worn tires on rear

If you are driving a Mack, with Mack rears, this is a BIG no-no....gotta keep the front/rear & side/side pretty close. Mack interaxle differentials are limited slips...even if they have air-assist, they are STILL trying to send power to both axles. If you are mismatched front/rear as you are describing, you'd hear loud pops & clangs as the power divider is trying to lock up.

HOWEVER, on pretty much any other trucks, they recommend keeping the left & right side of each drive axle the same, but since the interaxle differential is open, it doesn't matter if the tires on one axle are more or less worn than the tires on the other.

Years ago, there were trucks with Eaton 3-speed rear tandems. Basically, it was a pair of 2 speed rear axles. Low speed was achieved by having both rear ends in low. You were in high when both rear ends were in high. The middle gear? One rear end was in high, the other in low.

 

With the different sizes, it may not cause immediate damage, but it will cause more wear and will also hurt your fuel milage as the rearends are "fighting" each other, even when not locked together.

 

At least its not worm drive.

 

I feel for you, I was going to do what predictiment you are in now, I decided to wait, shopped around and got a smoking deal on 10 tires for my tractor.......

 

No problem- always match tires on THE SAME AXLE. If tires on the same wheel end are different diameters, the smaller tire will be scrubbed bald until it blows out. If you have a new recap next to a nearly bald virgin tire, the virgin tire will be scrubbed bald and blow out. If you have recaps on one side and virgin tires on the other side of the same axle, the gears in the differential will be spinning as you drive down the road- as if you were turning a corner. It'll cost you in lost fuel mileage and diff wear. It's ok to run tires like that for a week or two but no longer- it'll cost Ya. You can run different sizes on the front and rear drives - as long as the tire sizes match on the same axle. For example, you could run low-pro 22.5's on one axle and low pro 24.5's on another axle. (I can't imagine why you would want to.) But not low pro 22.5's on one side of an axle and 24.5's on the other side of the same axle. The gears in the diff will be spinning like crazy. If you have different size wheels and tires on the drive axles, it's UNWISE to lock the diff's for any reason, it can cause blown tires from scrubbing or overheated rears from the friction. If you look at local delivery trucks and regional tractors you'll sometimes see different tire sizes on the front and rear drives. They only do it to get the last penny's worth of wear out of a tire.