Nevadasmith
Full Member
Ok so 1971 bronco zf5 d20, d44/f9" 250 i6(Boss170)
35" tires(on there now), and or 32" tires...
I had a weak 250, and 4.11r/4.09f gears, and I couldn't really use 5th much, any hill would be down shifting to 4th or 3rd. I found out the 4.09 gears in the front end were roasted from a previous bad install when I put the tru-trac in...not wanting to run metal through the tru-trac, I needed new gears...I found a set of 5.38/5.42 gears at a swap meet for Penny's on the dollar! So that's what I'm running now, with the old motor they were working ok. Just ok..., Old motor ran out of go all together at 2600rpm. I could get to about 65 on flat ground.
I built and installed a new warmed up 250 that makes 200+ ft/lbs torque from idle to 2600 rpm. Actully pulls hard to 3000 rpm. Now I leave stop lights in 3rd high range and in 5th by 25-30 mph top out at about 72-73 on flat ground, ...I'm getting 16mpg regularly...but I have a goal of 18 mpg.
After A lot of math I have decided 4.88 would be great, but....and here is my problem, I love the way it pulls straight in mud and snow and ice with 5.38f 5.42r.....the only listings I can find is 4.88f 4.86r my fear is that the rear will be pushing the front....and I would have to drive my but off to keep it straight on low traction situations, so question 1 has any one found a better ratio combination????in that range?
Questions 2 is if not I'm looking at 4.55f 4.57r, or 5.12f 5.14r, Keeping in mind I want to run 32"(235-85r16) tall skinnys in the winter, and 35-12.50's summer, which would you choose??. Usage is 60% commuting, 40% hard to difficult trails, light to medium rock crawling, lots of rescue missions!!!!!
Thanks for the input!!!
35" tires(on there now), and or 32" tires...
I had a weak 250, and 4.11r/4.09f gears, and I couldn't really use 5th much, any hill would be down shifting to 4th or 3rd. I found out the 4.09 gears in the front end were roasted from a previous bad install when I put the tru-trac in...not wanting to run metal through the tru-trac, I needed new gears...I found a set of 5.38/5.42 gears at a swap meet for Penny's on the dollar! So that's what I'm running now, with the old motor they were working ok. Just ok..., Old motor ran out of go all together at 2600rpm. I could get to about 65 on flat ground.
I built and installed a new warmed up 250 that makes 200+ ft/lbs torque from idle to 2600 rpm. Actully pulls hard to 3000 rpm. Now I leave stop lights in 3rd high range and in 5th by 25-30 mph top out at about 72-73 on flat ground, ...I'm getting 16mpg regularly...but I have a goal of 18 mpg.
After A lot of math I have decided 4.88 would be great, but....and here is my problem, I love the way it pulls straight in mud and snow and ice with 5.38f 5.42r.....the only listings I can find is 4.88f 4.86r my fear is that the rear will be pushing the front....and I would have to drive my but off to keep it straight on low traction situations, so question 1 has any one found a better ratio combination????in that range?
Questions 2 is if not I'm looking at 4.55f 4.57r, or 5.12f 5.14r, Keeping in mind I want to run 32"(235-85r16) tall skinnys in the winter, and 35-12.50's summer, which would you choose??. Usage is 60% commuting, 40% hard to difficult trails, light to medium rock crawling, lots of rescue missions!!!!!
Thanks for the input!!!