Posted by Ben on May 20, 04 at 14:07:11:
In Reply to: Gear Ratio and Tire Wear Question posted by snoel on May 20, 04 at 13:37:23:
Length of string taped to drive shaft. Mark datum for starting point and note it's orientation for counting.
Roll vehicle one tire rev.
Count whole turns. That is the first diff ratio number. If 3, then it's a 3.x and if 4, then it's a 4.x
Fraction of whole turn is second part of diff ratio. About 3/4 turn, then it's x.73, etc.
Glove box label will have the codes of all options as it left the factory. Do a search at #1 Son's place and you'll find the RPO code links. That will tell you which diff ratio it left the factory with. Reason for the string thing is that if your not original owner, previous may have changed the diff gears.
Note that 33" dia tires will reduce the effective diff ratio by same percentage difference from OEM tire dia. Stock on 3/4 ton Sub is 30" tire, so your's is 10% taller, so diff ratio is lesser by 10% (lesser in capacity). Plus lift reduces effective lever arms in suspension, etc. "Reduces" meaning lesser in strength unless the drop brackets are designed right. Also the U-Joint angles have been increased, so less HP being delivered to rear wheels and higher stress on rotating stuff on drive train, and shorter U-Joint life. If body lift, then okay.
Trucks and 4x4's cup the front tires. Must rotate'm often. 3K-5K-7K miles like clock work.
Picture is worst tire cupping ever seen. Over in dad's neighborhood and just had to take a picture of it.
Alignment, shocks, suspension condition, etc all play. Mainly trucks just do this.
Now if it's not cupping, and wearing outside rib, then it's alignment. Most likely too much camber (positive).
Lifted trucks have all kinds of alignment, tire wear, balance (tire, wheel, rotating stuff) and vibration problems. Worse when off road a lot and in compound low lots.
Not to say all lifts are bad. Must chose/engineer to the individual's driving style and terrain and rig's setup.