. I agree 4.56or4.88 would work good. 
5.38s too much????
Thread Starter
Launching!
Joined: Jan 2004
Posts: 227
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From: clovis ca
i have 5.13s in it right now and the guy who set the rear end up messed up my gears so hes replacing my gears and redoing my rear. i get about 14 miles to the gallon right now. im at about 2400rpm at 70 right now, anyone knwo what rpm illbet at with 5.38s??
On The Tree
Joined: May 2004
Posts: 157
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From: Rome,Ga
I seriously wouldn't go that tall unless you have a 9.5" ring gear or larger. I thought a 4.56 was a small gear for a 8.5" 
But for your question, a 4.56 is all you need for up to a 36" and still retain close the the factory ratio if your truck originally had 3.73's. BTW, somebody asked this before....but why do you only have 36's on a 15" lift? A 2wd could still easily fit a 38" with no rubbing. My friend has a 12.5" on a 2500HD and he's running 40's everyday and can clear 44's for shows.
To be honest.....i think my 35's look a little goofy with the 9" lift, but im stickin with them so i wont loose my gear until i swap out a 10.5" 14 bolt and then i might go up to 5.13's when i go to 36's. But if you have to have the extra gear, keep the 5.13's and go easy on your 10 bolt. If you see how small your pinion is with a 5.13 ratio in a 8.5" you'll see what im talking about. I feel your pain on the 14 mpg highway though....2200-2400 rpm's suck!
But for your question, a 4.56 is all you need for up to a 36" and still retain close the the factory ratio if your truck originally had 3.73's. BTW, somebody asked this before....but why do you only have 36's on a 15" lift? A 2wd could still easily fit a 38" with no rubbing. My friend has a 12.5" on a 2500HD and he's running 40's everyday and can clear 44's for shows.
To be honest.....i think my 35's look a little goofy with the 9" lift, but im stickin with them so i wont loose my gear until i swap out a 10.5" 14 bolt and then i might go up to 5.13's when i go to 36's. But if you have to have the extra gear, keep the 5.13's and go easy on your 10 bolt. If you see how small your pinion is with a 5.13 ratio in a 8.5" you'll see what im talking about. I feel your pain on the 14 mpg highway though....2200-2400 rpm's suck!
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Launching!
Joined: Oct 2004
Posts: 251
Likes: 0
From: Ohio
Originally Posted by Hawkeye2
I had 5:38's in an old Jeep. Top cruising speed 62MPH! Careful if you drive the
highways at all.
highways at all.
As a further note, 5.38 is not tall it is deep and you can get up to a 5.13 for the 8.25 IFS and a 5.38 for the 9.25 IFS. As far as gearing for 36's. A 4.56 would be marginal as it ould be equal to 3.73's with 30's before you factor in extra rolling resitance and wind drag from tires and taller truck. A 4.88 to 5.13 would be a better match if you want good performance on and off road too and a 5.38 would not be too bad either. Remember you do have OD. A lot off people stick with stock tall gears and big tires and have power overall performance and then blame tranny design when it fails not the tire gear mismatch. Also do not throw in the better MPG arguement with taller gears and big tires as it takes power to turn them things and if you are really worried about MPG, you would never put those things on to begin with.
