riskywhiskey

What gears are you running and what's your mpg? Currently stock 355s looking at either 373 or 410(ad I cannot find 391 for 30/35 Dana's)

jon-d

I have 4:56 gears on 33's and to me that seems right on the edge. Could be that my motor is getting tired but they work. Milage? Difficult to answer. I generally do some paved roads on the way to the trails so I dont have a true milage. Also, the change in ratio changes the speedometer reading, further complicating the answer you are looking for.

keep in mind that 4:56 is as low as you would want to go due to the decreasing pinion gear contact with the ring.

jon-d

You can also do a ratio calc to compare stock tires/gears to 33's and the ratio you are considering.

riskywhiskey

Tried the whole mph x gear x336/tire x final drive it doesn't make any sense what so ever because on the stock 28.5 inch tire says I would be running 1925 rpms at 65 and on 32s I'd be running 2190 at 65 but I run 1800ish at 65 with 32s I was getting 1600ish stock I'm getting 19.5 highway now after head work was at 17.6 before head work and I was getting 24.5 before lift and tires yes I know it's a brick on wheels no I'm not looking for 29-32 mpg I'm looking at a happy medium of torque and 21-22mpg I'd be happy with 22-23 mpg I had an 89 5speed 373 gears 31s 3.5 inch lift and a **** ton of engine work (stroked bored cammed harlandsharp roller rockers 1.7 highlift rods big valve modified head ported 7120 head "stayed with the old HO intake because the horseshoe actually decreases hp by 5-10 and fuel economy by 5mpg on the older HO engines" 3 degree timing advance msd hotwire ignition system 4hole injectors high pressure fuel pump ran 91octane all the time) with a stage 2 street strip clutch pack in an ax 15 I got 25mpg highway out of it

00t444e

The math is set in stone accurate, you may have put the wrong numbers in somewhere, 32s at 65 mph with an automatic and 3.55 gears would put you at 1817 rpm. 4.10 or 4.56 gears would be fine, however I would advise swapping the Dana 35 out for a Chrysler 8.25 and regear that, the Dana 35 is a weak axle and I wouldn't spend the money to regear it.

SatiricalHen

I had 4.56 with 31s, 33s, and 35s. I would go with 4.56 and swap in a Chrysler 8.25.

jon-d

I just used a ratio to get close to the stock setup but with bigger tires. Easier math, provided you liked the feel of the stock set up. formula: (stock gears/stock tires)=(? gears/new tire size). Using public math skills, just solve for ? and select the closest gear ratio.

riskywhiskey

I've ran 30/35 with truss in my 89 for 4 year and never had an issue I jumped it bashed it banged it scraped it and even ratcheded it down by them never twisted or bent them these ones will be trussed soon as well if it's built right you can beat the hell out of anything but when I did 65x355x336/32x.98 I got 2019.17 rpms which is not what I run at what so ever I run roughly 1850 due the force from the ratio

SatiricalHen

The 8.25 tubes are much larger as are the axle shafts and ring and pinion. You can't truss axle shafts or ring and pinions. With how cheap an 8.25 is and with how expensive gears are it's a cheap upgrade in the long run. If you are basing your speed and rpm off of your speedometer and tach it may be incorrect. The speedometers aren't very accurate. There is a website called jeepers creepers that can do all of the gear ratio calculations for you.

SatiricalHen

Just saw that you have a WJ which is even more weight for the 35 and the 89 also had a non c clip dana 35. I'm not sure what is a common swap for WJs though.

riskywhiskey

My dash tach and the obd2 PC read the same as well as the speedometer and is calibrated to the tire size I know they are accurate within acceptable parameters and if I was to throw anything under it it would be a Chrysler axle I'd be putting 40/44 Dana's or 60 series with cut tubes I like my 30/35s they are already chromos I'm doing g2 internals sorry but talking someone out of what they are comfortable with is like a Ford owner telling a jeeper that jeeps suck buy a ford

riskywhiskey

What I looking for is not you should change to Chrysler axles or the 30/35 Is weak I'm looking for basically a graph of I have 373s with 32s and get xmpg or I have 410 and 32s and get xmpg

00t444e

The formula is rpm=speed x transmission gear ratio x axle gear ratio x 336 divided by tire diameter. This whole gear calculator is based off of that formula. http://www.grimmjeeper.com/gears.html

riskywhiskey

That still sets it above 2k rpms I don't hit 2k rpms in od until 70

riskywhiskey

42rle final gear is .96 so the formula can't be exact because even at 65 when I'm reading 1800 rpms the obd2 PC is reading 1798-1815rpms