This is taken from another thread because I didn't want to hijack it. The thread was discussing transmission life extension.

Y2KW57 wrote several good tips for extending your trans life and #5 caught my eye.

5. Change your tires. Don't drop your trans pan... drop your tire size. You're rolling 285s... a 33" tire. If you drop to an OEM factory size 31" tire, you will restore the lower gear ratio originally engineered into the transmission's rated GVWR capacity and service life.

My first tire replacement with my new truck (2002) I wanted a slightly larger tire because it made the truck look better IMO because it filled the wheel well better.

I went up 1 size to 285's and have been running those since. My question is; Would I be better served to switch back to the 275's for trans life?

BTW I have 275K on my truck.
David

 

I am betting there is not hard data to support or disprove this hypothesis.

 

I believe unless you're towing HEAVY, even going to 35" tires isn't going to cost you any trans life...
Dropping the trans out of OD when climbing hills (so it isn't hunting back and forth) and changing the fluid at recommended intervals (or sooner) have worked for me on my other high mileage vehicles.

 

Yep, the trans will live forever with 275 tires, but it's not going to make 100K with 285s.

If there is ANY validity to this, and I don't think there is, you should expect one less mile of life from your trans with the larger tires.

 

It does take more work to turn a larger tire. But not enough for anything to care as far as you or me are concerned. There's still those people out there towing 10,000 pounds on a daily basis that are getting great life out of their trucks.

I'd say once you get to a 37" tall tire or larger then there are some extra steps you need to take for reliability. (gears, trans coolers etc).

Keep on truckin and stay on top of regular maintenance.

 

Thanks guys!