some1 good w/math

[blazin_blazer]

i would like to figure out what gear ratios would be 1:1 at transfercase...while i have 44''s all the way around on 12'' front springs/8'' rears w/4'' blocks....(all in parts now)..if i ditch the blocks and put a 54'' bogger on the rear, a 54'' will raise the rear 5'' more than a 44''....use zero rates up front for 1'' w/44's up front to clear stuff and a 54'' in the rear and it should be level...but what ratio gear w/54'' tire and what ratio for the 44'' front, so it will be same at transfer....a baby quaqmire!

 

[rwright07]

well that depends on your gearing in front, the only math you would need to do is to make (front tire size/front gear ratio) = (rear tire size/rear gear ratio)

so simplified your new rear gear ratio = 1.227*(current front ratio)

plus, do you think a 14bff will stand up to 54" boggers?

 

[4X4HIGH]

The closest you're gonna get is a 44" tire up front with 4.10 gears at 65mph will be 2035rpm while a 54" tire out back with 5.13 gears at 65mph will be 2075rpm's. That's about a 2% difference and from what i've heard a 1% difference is acceptable.

 

[longbedder]

Yer cruisin for trouble with tire sizes differing in 4WD. You will, at the very least, eat tires like chips and salsa.

 

[muddermilitia]

Actually you will be bigger than quagmire, he was only running 38s in the front

 

[Blue85]

I don't think you can get lower than 5.38 with the 14B axle. That makes the ideal ratio for the front diff 4.38, but 4.11 and 4.56 are both pretty far from that. Plus, those ratios are too high for those tires (front and back). EDIT: I think you can get 4.30 for the Dana 60, but possibly only for high pinion. Still, people use lower gears than that for their 35" tires.

If you swap to a D70 rear axle you can get gear ratios of more than 7:1

7.17 and 5.86 would be a good match

With 6.17 rear, you want 5.02 up front. I think the closest thing is 5.13, which is more than 2% off.

4WD would be used off-road only, right?

Are you set on using 44's up front? Is there a 46-47" tire that would work?

 

[blazin_blazer]

heres what i had on my mind

Actually you will be bigger than quagmire, he was only running 38s in the front

yes that is correct, but he had bigger than 54's on the rear, iirc

this is/was the plan ...set the truck up with the 12'' lift and 44's all the way around, rear is 8'' springs/4''blocks....not sure of the gear'n yet haven't popped a diff cover off to see, what ever was stock in a 86 k30, prolly what i will run until it breaks....i have a sm465 trans so i can get the gearing pretty low w/4.56's(granny is 6.12:1..iirc, t/c is 1.96:1, rear diff 4.56:1=54.7 final crawl,4.11's=49.3?) in mud really steep gears are not all that necessary and 50-54:1 would be plenty low, i believe..

i use the truck w/ 44's as my toy..i.e. trails, mud, gravel rd, camp grounds..

but once a month when they have the mud pit open for competition, i would have another axle, set up with just 8'' springs and 54'' boggers(no blocks),.. geared to match the front w/ tire difference. 2-3 days before the event, just swap out the rear, springs and all...6 bolts. 2 shackles and 2 leaf eyes, and 2 shocks...i am going to go by an industrial supply and see if i can't find a way to put a quick dico in the brakeline. go run the pit, then swap the springs back out to driveable 44's all around.

since this is just a toy, it would only be in 4x w/54''s, in the pit and i doubt very seriously it would ever see 65 mph, 45 would be fine. so, now that you know what i'm thinking...tell me what am i forgetting?

edit: emergency brakes on axle w/44's will be disk w/eldo calipers(unhook the cables) or a line lock for emergency brake, 54'' axle, don't need no stinking brakes!

 

[blazin_blazer]

3.73/front...4.56/rear....is pretty close using the # supplied and mutiplying 3.73x1.227=4.57671

3.73 w/44'' tsl seems a little hi, even with the 6.12 granny and 1.96 transfer??

 

[4X4HIGH]

MPH doesn't matter, 65mph just happens to be on a chart that i have to figure out gearing versus tire size. The % difference is what matters. Just for your info the math is

MPH x gear ratio x 336
________________________
divided by tire diameter

 

[muddermilitia]

ok well if these mismatched gear sets will only be used for mud pits, than thats fine. Actually most of the professionals run a numerically lower gearset in the front and a smaller tire in the front so that the front will spin faster and keep the front up, out of the mud.

I have a friend with a 92 dodge 3500, mopar big block (562ci I think) d60 in the front with 4.10 gear and 38.5 skinny boggers. In the back he's running a 14bff with 5.38s and 44" boggers

 

[zero cool]

My calculator only goes up to 53" tires. I'll try to update it for 54's when I get home from work.

But you can do a side by side comparison of 44's and 53's and see how things work out:

http://www.grimmjeeper.com/gears.html

But a rule of thumb is to figure out what gears you want to run for your 44. Say it's 5.13's. Then multiply that by 54 and divide by 44. So 5.13 * 54 / 44 = 6.30. So find the ratio that comes closest to 6.30 and that's what you need.

 

[muddermilitia]

But a rule of thumb is to figure out what gears you want to run for your 44. Say it's 5.13's. Then multiply that by 54 and divide by 44. So 5.13 * 54 / 44 = 6.30. So find the ratio that comes closest to 6.30 and that's what you need.

using that theory, the closest I could find would be 3.73 in the front axle and 4.56 in the rear

 

[zero cool]

using that theory, the closest I could find would be 3.73 in the front axle and 4.56 in the rear

Sure, those would be closest but that's not as critical as you may think. Differences in tire pressure can amount to a much bigger difference than that. The rule of thumb is to be within 3%.

So, for 3.73, you'd want 4.56's. 3.93's match with 4.88's. 4.10's with 5.13's, 4.27's with 5.36's, 4.56 doesn't have a great match but 4.88's match with 6.17.

 

[blazin_blazer]

i mph doesnt matter..i.e if only 40mph capable with 54's then so be it, that kind of don't matter...how fast it will go...so, i need to find a d70 rear for the 54's, so i can get steep enuff gears for it to match decent gears for the 44'' tire axle

 

[6.2Blazer]

I'm pretty sure that Quagmire had 40x17 Ground Hawgs on the front, and 48x24 Ag tires on the back. Anyway......

Different tires front and rear are fine as long as the gearing is adjusted accordingly. There are tons of farm and construction equipment that are 4wd with different size front and rear tires.

I would have no problem running 3% or more difference in overall gearing in this type of setup. Not like you are going to be using 4wd on the highway at 65 mph. Any time you would actually need 4wd there would be more than enough slip to compensate for any differences.

My recommendation would be to start by putting the lowest possible gears in the back, and then just get as close as possible to matching with the front.