So you want to run 35" tires on your TJ?

This was a very informative thread. I'm resurrecting it from the grave to ask for some opinions.

I was talking to someone from East Coast Gear the other day and we built out an axle with 4.88's for me on the computer. My ultimate goal is to run 35's. My thought/question is... why not gear lower? Would 5.13's be intolerable on the highway? I very rarely drive on the highway, but when I do I never go much faster than 60. I've got a 6-speed and I never use 6th gear.

Basically, I figure gearing lower = better, so long as I can go 60 in 6th at a reasonable amount of RPMs.

What do you guys think? Is there a way to reasonably accurately calculate what my RPMs would be with x size tires at x speed?
 
RipSteakface said:
This was a very informative thread. I'm resurrecting it from the grave to ask for some opinions.

I was talking to someone from East Coast Gear the other day and we built out an axle with 4.88's for me on the computer. My ultimate goal is to run 35's. My thought/question is... why not gear lower? Would 5.13's be intolerable on the highway? I very rarely drive on the highway, but when I do I never go much faster than 60. I've got a 6-speed and I never use 6th gear.

Basically, I figure gearing lower = better, so long as I can go 60 in 6th at a reasonable amount of RPMs.

What do you guys think? Is there a way to reasonably accurately calculate what my RPMs would be with x size tires at x speed?
Click to expand...

If you’re going to spend the coin on some axles from ECGS, I’d highly recommend going heavier duty than you need for 35s. Im not sure what axles you’re considering, but I’d consider stepping up to 1 tons. I don’t imagine the cost difference would be outrageous compared to the cost of say a Dana 44, but you’d never have to worry if you wanted to move up to 37s or 40s.
 
  • Like
Reactions: Mikester86
RipSteakface said:
This was a very informative thread. I'm resurrecting it from the grave to ask for some opinions.

I was talking to someone from East Coast Gear the other day and we built out an axle with 4.88's for me on the computer. My ultimate goal is to run 35's. My thought/question is... why not gear lower? Would 5.13's be intolerable on the highway? I very rarely drive on the highway, but when I do I never go much faster than 60. I've got a 6-speed and I never use 6th gear.

Basically, I figure gearing lower = better, so long as I can go 60 in 6th at a reasonable amount of RPMs.

What do you guys think? Is there a way to reasonably accurately calculate what my RPMs would be with x size tires at x speed?
Click to expand...
The pic below is your NSG370 tranny with NP231 T Case and 35’s

Left column is with 4.88 gears and right is 5.13
A391F890-8E82-4120-8668-4D14358FD269.png
 
  • Like
Reactions: EzPeezy, RipSteakface and Alex01
Until you realize it's all in the power band of the engine. In my case, I have the 46RE/V8 and with it's O.D. gearing I went with 5.13's. If I were still running a 4.0L motor, I'd have gone with the 5.39's if I had the 42re/rle in it. The 6-Speed NSG is a little different animal but I would at least run 5.13's and if you EVER go with 37's in the future, you'll kick yourself if you stay on 4.88's FWIW. This way your 6th gear O.D. will actually be usable on the street.
 
RangerRick said:
Until you realize it's all in the power band of the engine. In my case, I have the 46RE/V8 and with it's O.D. gearing I went with 5.13's. If I were still running a 4.0L motor, I'd have gone with the 5.39's if I had the 42re/rle in it. The 6-Speed NSG is a little different animal but I would at least run 5.13's and if you EVER go with 37's in the future, you'll kick yourself if you stay on 4.88's FWIW. This way your 6th gear O.D. will actually be usable on the street.
Click to expand...

If 37s are a possibility, let's hope a different set of axles are a part of that plan.
 
  • Like
Reactions: MaloStapalo and RangerRick
jjvw said:
If 37s are a possibility, let's hope a different set of axles are a part of that plan.
Click to expand...
Well there's always that..... Hey I ran on 37's for 7 years before axle failure. Unfortunately it was epic where it happened and described on my build page.

Now there's RJ60 in residence where that stuff was.....
Nuff said!
 
  • Like
Reactions: JMT
The ECG guy and I were looking at the Dana 489. I admit I don't know exactly what that is, or where it falls in relation to the Dana 44 or the Dana 60, but I got the impression it was a beefed up Dana 44? All my mechanical experience is with early 80's Toyota pickups.

What I meant by '150 RPMs NBD' was me looking at highway RPM at 70mph and determining that going down to 5.13's or even 5.39's seems totally doable, and that it is a negligible rise in RPMs, especially since I don't really go above 60.
 
  • Like
Reactions: RangerRick
RipSteakface said:
Would 5.13's be intolerable on the highway? I very rarely drive on the highway, but when I do I never go much faster than 60. I've got a 6-speed and I never use 6th gear.
Click to expand...

I drive on the freeway a lot and I'm going with 5.13s on my 6-speed LJ on 35s.

RipSteakface said:
Is there a way to reasonably accurately calculate what my RPMs would be with x size tires at x speed?
Click to expand...

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


JMT said:
The pic below is your NSG370 tranny with NP231 T Case and 35’s

Left column is with 4.88 gears and right is 5.13
View attachment 95318
Click to expand...

I got slightly higher numbers but I enter 34" as the tire diameter to compensate for the actual rolling diameter:

4.88s/5.13s
488513.png
 
  • Like
Reactions: jjvw and RipSteakface
Effective rolling diameter will be the hub center from the ground x2. Measure from the ground to the center on the axle tube. Where the tape touches the tube is the height. Then double that number. For the purposes of the calculator, both the sidewall and manufacturer's website are incorrect.
 
Unfortunately tires are measured like monitors & TV's used to be. They fudge the actual sizes between rated & rolling height. Very common but at least the larger the tire, the smaller the discrepancy difference is percentage of overall diameter wise.
 
I have a 04 Rubicon with 35. Figured I was fine because it's a Rubicon...it stays in the desert so no highway speeds. I don't do any crazy off roading mainly established pole roads and stuff. Am I good or will I need to re gear?
 
LakeBeard said:
I have a 04 Rubicon with 35. Figured I was fine because it's a Rubicon...it stays in the desert so no highway speeds. I don't do any crazy off roading mainly established pole roads and stuff. Am I good or will I need to re gear?
Click to expand...

You don't "need" to re-gear, but it will be 15 times better if you do.
 
  • Like
Reactions: LakeBeard and Starrs
I just got a 4.0 with automatic it has 4in lift with 35s but 3.05 gears it really hates the 35s and previous owner also welded the rear gears but he gave me 2 8.8 rears one with 4.11 gears drum brakes and one with 3.55 disc breaks to make a disc break 4.11 and kit to put the 8.8 in my thing is if i have to buy gears for the front are 4.11 really enough i was thinking 4.56 gears and just build the 30 and 35 it will be on highway and dirt roads hit some mud holes in it and hunt out of it no rock climbing but some slick ass red clay gumbo and post oak mud
 
Cgcrock said:
I just got a 4.0 with automatic it has 4in lift with 35s but 3.05 gears it really hates the 35s and previous owner also welded the rear gears but he gave me 2 8.8 rears one with 4.11 gears drum brakes and one with 3.55 disc breaks to make a disc break 4.11 and kit to put the 8.8 in my thing is if i have to buy gears for the front are 4.11 really enough i was thinking 4.56 gears and just build the 30 and 35 it will be on highway and dirt roads hit some mud holes in it and hunt out of it no rock climbing but some slick ass red clay gumbo and post oak mud
Click to expand...

That was really hard to read without punctuation. Sorry I don’t have any more helpful input.
 
  • Haha
Reactions: MaloStapalo
Bababooey said:
That was really hard to read without punctuation. Sorry I don’t have any more helpful input.
Click to expand...
Im sorry everything has to be perfect for you to understand it i didn’t learn everything i should in english because it didn’t intrest me i have to read things im interested in 3 times before they stick so things i was not interested in i didn’t put in the effort at the time i was a dumb kid that thought i would never need it but i know alot of really smart people that i make look ignorant at times because they lack common sense and i will take that over book smarts any day
 
I just got a 4.0 with automatic (what year or transmission?) it has 4in lift with 35s. It has 3.05 gears and it really hates the 35s.

Previous owner didnt do any real research and welded the rear gears.
He gave me 2 Ford 8.8 rears, one with 4.11 gears and drum brakes, and one with 3.55 gearing and disc brakes. Disc kit is with 3.55 gearing for the 8.8.

If i have to buy 4.11 gears for the front to match possible 4.11 gesring in the 8.8 axle, i was thinking 4.56 gears instead front - rear, and just build the 30 and 35.

It will be on highway and dirt roads, hit some mud holes, and hunt. I will not be rock climbing, occasionally some slick ass red clay and post oak mud.




Instead of making a smart ass comment, I decided to see if anyone can help answer your question. Welcome to the board.

Cgcrock said:
Im sorry everything has to be perfect for you to understand it i didn’t learn everything i should in english
Click to expand...
 
Last edited:
  • Like
Reactions: Alex01, Cgcrock and Leakey
Top Bottom
Back