33s with 3.31s

[Rande]

Anyone running this combo?
I'm about to get the new J10 on the road and thinking of using 33" tires. The truck has 3.31 gears and an automatic tranny. I know the take-off from a stop will suffer but how does this combo do in everyday driving?

[Robber80]

I am going fine with 35s and 331s. I doesnt' really effect me that much at all. I am suffering from low comperssion and burning lots of oil too. You will be fine with 33s.

[CowKiller]

blah, i got 33's with 3.05/3.07 gears. acceleration DOES suck. but it loves to cruise at 55. could go all day.

[maxrad]

I was thinking of the same combo myself.

[Stuka]

it will screw over your crawl ratio if you do any wheeling. You should get metter HWy milage as you will be running lower rpm's, but your acceleration and hauling/towing power will suffer.

[1980chief]

i'm about to be running 33's on my cherokee thats also geared 3.31 so i'm glad to know thats not a problem. i might eventually go a little lower for better offroad though

[Michael]

I am running that combo for about a week. I also have a much larger cam which has helped. But I notice little diffrence between the 31's and 33's. Stuka is correct. It will affect your towing and wheelin' if you do any.

[derf]

3.31's and 33" tires will run a lot like stock tires with 2.73 gears. Not great off the line but not too bad for highway driving.

[CowKiller]

i havent had any probs wheeling, but i guess the low range and an auto helps alot.

[TexasJ10]

Derf makes a good point. My 31X10.5 inche tires are actually only 29.5" in diameter. Using the handy dandy gear ratio chart shows that at 60 I should be running 2,250 rpm with 3.31 gears. If I had 2.73 gears I would be running only 1,850 RPM.

I think the stock tires were about 27.5" in diameter which would require 2000 RPM to reach 60 using 2.73 gears whereas if you had true 33" tires you would be going 60 at 2025 rpm using 3.31 gears. As Derf indicated, you would be running within the orignal doggy factory acceptable levels.

I think that the only vehicles that got 3.31 gears as an option in the 80's, also got tires which were approximately 1" greater in diameter. A 28.5" tire with 3.31 gears requires 2325 rpm. Assuming the stated 33" tires you buy are actually 32" in diameter, your rpms will be 2075. That is a pretty good drop that you will feel.

Is everyone completely confused yet? Then my job is done!

[Tad]

Originally posted by TexasJ10:
...Is everyone completely confused yet?...LOL, Nope, made perfect sense to me.
Have 33's that measure out at 32.
Started with 31's that measured out at 29.
I notice very little difference between 29's and 32's but betcha it's a big difference between the 32's and stock. Having the low compression Buick 350 and the TH400 seems to help.
Running in sand is fine, gets right up on top fast and stays there.

[Mavawreck]

how much lift woud you need for 33's?

[will e]

I noticed a differenece between stock and 31" (really 29 inch) tires. I have 3.31. It runs okay so I have no complaints. I would regear if I went to 33's but not 32's. JMO.

[BIG BAD JON]

BobthaBuilder- Think of it this way, you are prolly running 27"s, if you upgrade to 33"s thats 6" taller. Thats 3" more clearance you will have to create. Anyways, thats how I figure it. ;)

[Stuka]

My 31x10.50's measure out to 30.50 inches tall. I noticed a differance from the stock 235/75R15's too the 31x10.50's. When I had the 235's it would really jump off the line, and had traction problems (although thats partially because they where street tires) They also looked small with my lift. So I put on the 31x10.50's and I got better traction, but I also lost some acceleration. The 235's measure out to 27.9 inches tall. So there is almost a 3 inch differance in hight. BTW: I have 3.54 gears. If I went to 33's I think I would want to gear down to 3.73's.

[Maynard]

i have been running 33's with 3.54 gears, to me i notice a deffenite lack of gumption, i am going to either 4.56 or 4.27, but it will not be seeing much highway driving.

[scotty]

i used to run 3.31s with 38s smile.gif wasnt my daily driver but in those days i did drive it up to 75 miles each way to the trails. this was with a 904 tranny. it was certainly not quick,but it wasnt undriveable either. the auto tranny help alot. it was fine off road with the auto and the 2.61(219,208,d300) or 2.71(207) low range of the xfer cases i used with it.

i once drove all the way from dayton to middletown(15 miles or so) on the highway in 2nd gear,and didnt really notice :eek: cruise rpm was about the same as 235s in 3rd gear ;)

[Baldy]

I used to run 36s with 3.07s. YUCK!! It was still drivable, but even with the 401 off the line she was a slug. Currently I've got 3.73 gears in and she's doing well with a healthy 360. The 4.10s are sitting on a shelf waiting installation....

[maxrad]

The problem I have with going to 33s..er..32s is that the tire will get wider (12.5" normally), therefore, creating more rolling resistance that may cancel out any final drive ratio gains in the mpg arena.

Right now my surface area (actual tire/street contact width) is 9.5 inches with my Pirelli Norseman tires.

What say you?

[Stuka]

maxrad: that is correct, with a wider tire there is more rolling resistance, add aggresive mud terrain type tread or the like and it takes more power too turn them. I know of people who ran BFG MT's in like a 35x12.50 size and drove fine, then went to boggers of th same size or even smaller annd turned their jeepp into a gutless pig. Because of the super high traction boggers give. I noticed a differance in going from street tread to MT style tread.

[maxrad]

Thanks Stuka,

You confirm my fears. I will no longer do an "improvement" on my rig without taking mpg into account. I'm on a quest to see how good a mpg number I can get without going to fuel injection or making drastic (i.e. expensive) modifications.

"Ein, swo, drei, vier, funf-un-dreisig Russische bier!" (I probably misspelled it. Just remember it was written by drunk Bavarian soldiers)

[bigfodee]

should be fine. i ran 35s with 3.55 gears for a while. it sucked, but my 4.0 doesnt quite match the awesome power of a 360 :D

[Dude23455]

what gears is my rig running. 89 GW, 727, np229, D44's

thanks
Cullen

[Chero77]

Originally posted by maxrad:
I'm on a quest to see how good a mpg number I can get without going to fuel injection or making drastic (i.e. expensive) modifications.
This is my philosophy also. Every "improvement" should increase MGP, albiet not at the expense of accelleration. To a certain extent, you can achieve this with alloy wheels, free flow exhuast (3" single, or dual 2 1/4), electric fan, and perhaps with a new cam. Comp Cams claims their 260H will produce more power and better highway milage (haven't tried it yet, so can't say). My goals for my truck have changed, its now meant to be road-trip vehicle and off-road use is a secondary consideration.

[Stuka]

Dude23455: You should have 2.73 gears unless you have the trailor package, in which case you would then have 3.31's. There should be little tags on your front and rear dif's saying what gears are in them.

[Panther]

For what it's worth, I run 3.31s with 33s, works out great. I do have a T18 that helps out with the start up.