pug Posted March 15, 2012 Share Posted March 15, 2012 Went to drop truck off monday for gear install. Mechanic said he would not use 4:88 he would use 4:56. I have 8.8 with 4:10 now don't know about front. I have a 1990 2.5 ax5 and 31x10.50 15 not going any bigger tire size.Just use as work truck sometimes pull a trailer with mower and mild trail rides. Any help thanks Link to comment Share on other sites More sharing options...
mvusse Posted March 15, 2012 Share Posted March 15, 2012 With 4.56 you will lose a bit of power, but highway mileage should be a bit better. 4.88 will overshoot the 31" tires. My 2.5 has 3.55 gears (originally had an ax4), which gives me the same final drive ratio as an ax5 with 4.10 gears. Great mileage at 60mpg (27mpg), but only got 19 at 75. Installed an ax5 but kept the 3.55 gears and mileage at 60 is still 27 mpg, but at 75 I now get 24. With 4.56 gears your final drive ratio on 31" tires will fall somewhere in between my current and your current on stock tires. Link to comment Share on other sites More sharing options...
86customanche Posted March 15, 2012 Share Posted March 15, 2012 IMO 4.10 is a perfect ratio for 31s if you are driving it on and off the road. Not sure what your work entails but might want to consider leaving the 4.10s in the 8.8 and regearing the front to match. Link to comment Share on other sites More sharing options...
pug Posted March 18, 2012 Author Share Posted March 18, 2012 Just got home from fishing trip branson mo. 4:10 and a 4cyl not very good for going up hills had to downshift to 3rd gear. Good thing i wasnt pulling a boat. Gas milage was getting 18.3 mpg doing 65-70 mph on 18 gallon tank if thats what size tank i have.For work pull a small 4x8 trailer with walkbehind mower not much weight just no power going up hills and sometimes mulch.thanks Link to comment Share on other sites More sharing options...
Pete M Posted March 18, 2012 Share Posted March 18, 2012 that's a tough call. re-gearing is so expensive that it's hard to justify doing it. but a deeper gear will certainly help the truck get back its power. Link to comment Share on other sites More sharing options...
Jeep Driver Posted March 19, 2012 Share Posted March 19, 2012 Just got home from fishing trip branson mo. 4.10 and a 4cyl not very good for going up hills had to downshift to 3rd gear. Good thing i wasnt pulling a boat. Gas milage was getting 18.3 mpg doing 65-70 mph on 18 gallon tank if thats what size tank i have.For work pull a small 4x8 trailer with walkbehind mower not much weight just no power going up hills and sometimes mulch.thanks I had the very same problem and I live here in E TN. 2.5 with AX5 and 4.10s just as you. Get you engine to run right and keep your gearing. When I first got he truck I had to down shift to 3 and rag it out up long inclines............same inclines now in 4th gear and smooth. Running 30s Link to comment Share on other sites More sharing options...
pug Posted March 19, 2012 Author Share Posted March 19, 2012 Motor has only 1200 miles on rebuild. So motor is good. It has power just not going up hills or pulling the trailer. I have the gears just don't know what ratio to use 4:10 or 4:88 Link to comment Share on other sites More sharing options...
Eagle Posted March 19, 2012 Share Posted March 19, 2012 Motor has only 1200 miles on rebuild. So motor is good. It has power just not going up hills or pulling the trailer. I have the gears just don't know what ratio to use 4.10 or 4:88 The STOCK gearing with the 2.5L and the 5-speed was 4.10, and 2.5L MJs typically came with 205/75-15 tires. Jumping up to 31s means a change of approximately 11 percent, so you need at least a 10 percent increase in gear ratio just to stay even. Since 31x10.50s are so much heavier, you really want to do a bit more than just stay even. So ==> 4.10 + 10% = 4.51. So the 4.56 gearing is going to be about the same as stock gearing and stock tires. I think with the 2.5L and 31s you really need the 4.88s. Link to comment Share on other sites More sharing options...
pug Posted March 19, 2012 Author Share Posted March 19, 2012 The mechanic didnt say he wouldnt put them. He just said he thought it was to low of a gear.I just want something with a little more power and mpg. Link to comment Share on other sites More sharing options...
btm24 Posted March 19, 2012 Share Posted March 19, 2012 Its hard to get both tho :( are you ever planing to upgrade the the tire size? Brandon Link to comment Share on other sites More sharing options...
pug Posted March 19, 2012 Author Share Posted March 19, 2012 No keeping bfg 31x10.50 15 Link to comment Share on other sites More sharing options...
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