biggest tires with the 2.9, gearing

[89DANGERANGER]

what are some of the biggest tires ran with factory 2.9 motors on bronco 2's? factory gearing im guessing is 3:73. and if alot of people are re gearing with 33 or 35+ sizes what gears are most popular?

 

[The Jester Race]

I'm at 5.13 with 37"s. Engine turning every bit of 4K in 5th gear to do 70mph.

-Jester

 

[b2rich]

I run 235s with 373s. I think my rig would like it more with 410s. if i went any bigger with tires (31s) i would say that 456s would be ideal. JMO

 

[Surrey]

I run some crappy 31" ATs with stock gearing.
Im sure the truck would love lower gears, but I wouldn't waste the money on re-gearing a dana 28 front/7.5" rear.

Still had enough guts to pull my friends toyota outta the mud, and drove on the roads better than my '86 diesel VW Golf. ('course that badboy had like 46hp...)

 

[86freebie]

32's

i run 32's with stock 373, and the dane 28 up front. it has 241,000 miles on it now.
it does fine for the hills and mud i play on and in. on the street it could use more power but does fine for me.

 

[91rangerxlt]

i ran 30'' mud grips and it did just fine

 

[Hahnsb2]

I'm at 5.13 with 37"s. Engine turning every bit of 4K in 5th gear to do 70mph.

-Jester

Your tach is very wrong. Try 2700.

 

[adsm08]

Your tach is very wrong. Try 2700.

More likely his speedo is very wrong.

 

[Hahnsb2]

More likely his speedo is very wrong.

That too.

 

[baddis]

i have run 31's and 32's with 3.73 and now running 35's with 4.10 and a d28

 

[The Jester Race]

Your tach is very wrong. Try 2700.

It could be off some, but its definitely turning quite a bit faster then 3k.

More likely his speedo is very wrong.

I know my speedo is wrong but the CHP's radar gun is pretty damn accurate

-Jester

 

[Hahnsb2]

It could be off some, but its definitely turning quite a bit faster then 3k.

I know my speedo is wrong but the CHP's radar gun is pretty damn accurate

-Jester

The calculations don't lie. You'd have have 25" tires to turn 4K with 5.13s in 5th gear at 70

 

[The Jester Race]

The calculations don't lie. You'd have have 25" tires to turn 4K with 5.13s in 5th gear at 70

Tell you what, come on down and drive my truck and tell me I'm wrong.

-Jester

 

[Hahnsb2]

Tell you what, come on down and drive my truck and tell me I'm wrong.

-Jester

I don't have to drive anything to tell you you're wrong. It's simple math.

 

[4x4junkie]

5.13s and 35" tires here. Seems perfect dead-on to me, wouldn't want it geared any lower or higher (at 65MPH tach shows about 2900).

 

[feellnfroggy]

His clutch may be slippig, or he has a different gearing inside his trans, dont ask me how. But I can educatedly guess that maybe he meant 4th gear, even with 5.13's I dont see the 2.9 having the torque to push 37's 70 mph.

 

[The Jester Race]

His clutch may be slippig, or he has a different gearing inside his trans, dont ask me how. But I can educatedly guess that maybe he meant 4th gear, even with 5.13's I dont see the 2.9 having the torque to push 37's 70 mph.

It'll do it but the engine is spinning pretty high(about 4000). I took the GPS out and tried to get a picture of speed and RPM. You have to take my word for it that it is in 5th. I can't get a picture of the Tach, GPS and shifter while driving. There was a head stiffwind and it would not get up to 70mph or 4K in any gear.
[Jeremy Clarkson]I need more POWER!!![/Jeremy Clarkson]

I don't know if you can see that but it says 64mph @ 2900RPM and it is in 5th.

-Jester

 

[lethal-threat-b288]

33"s 3.73"s just fine in 4low and ok in 2wd in mud. Street driving is average with 18 miles per gallon

 

[tmaxxman]

i have 2.9 with 410 and 33s is that good or bad ????

 

[88Bronco2EB]

Math

I found a formula on some 4x4 site(can't remember the name) but it will give you your RPM at a given speed depending on what gears and tire size you run.

here it it!!

speed x gear ratio x 336 / tire size

I'm not sure were the 336 comes from it is just part of the formula, and the gear ratio would be your diff gears in a 1:1 ratio or 4th gear in a manual, 3rd gear in an auto. But you could just multiply your diff gears by your over drive gear ratio.

Ex. (60mph)

60 x 3.73 x 336 = 75,196.8

75,196.8 / 27 = 2,785 RPM

This would be my RPMs in 3rd gear with stock tires NOT over drive

Ex. (60mph in OD) Diff gears x OD gear ratio in A4LD auto trans

3.73 x 0.75 = 2.7975

60 x 2.7975 x 336 = 56,397.6

56,397.6 / 27 = 2,088.8 RPM

I think its pretty damn cool