Upgrade to 3.73 or 4.10 gears with 31" tires?

[mots]

Using the grimmjeeper calculator, I want to make sure I’m entering correct info. I have 2003 x 4.0 manual. So transmission is NV3550 wide ratio, transfer case is NP200, not sure what my underdrive is. Would this be correct? Anyone know the underdrive?

You should have the following, here is some info:
NP231 Transfer case - https://www.novak-adapt.com/knowledge/transfer-cases/np231/
NV3550 Manual Trans - https://www.novak-adapt.com/knowledge/transmissions/manual/nv3550/

Underdrive should be "None", unless you have something extra installed.

 

[jazngab]

You should have the following, here is some info:
NP231 Transfer case - https://www.novak-adapt.com/knowledge/transfer-cases/np231/
NV3550 Manual Trans - https://www.novak-adapt.com/knowledge/transmissions/manual/nv3550/

Underdrive should be "None", unless you have something extra installed.

Ok thanks!

 

[jjvw]

Assuming the drive train is stock...

NP231 or Rubicon NP241

No underdrive

Measure your tire radius from the ground to the hub. Double that number. That is your tire diameter for the purposes of the calculator.

 

[Pcleaners2]

I run 31” with 3.73.
5th gear on freeway sucks bad.
Not kidding. It’s a slug. 4.10 with 31” is it!

 

[SoBadRich]

I am running a Cherokee XJ automatic, 4.0L with 31" tires and the stock 3.55 gears and it did just fine off road the last two years at the Moab Safari. It is a bit sluggish as a daily driver in High Range and the math tells me going to 3.73 would put me back close to stock overall drive ratio and give me a little help around town (and they fit in my carriers). My calculations say I will be OK to go with 33" with the 3.73 gears off road and be back where I started with 3.55 and 31's around town. I understand why most recommendations go higher ratios but mine is mostly a daily driver so I let the automatic trans to the extra work the few times a year I am off road and keep close to the original overall ratio on the road.

 

[Jerry Bransford]

@Jerry Bransford always approves of 1 size up in gearing if you don't care about highway speeds

I just saw this bullshit reply. Every gearing recommendation I make is ALWAYS made with highway driving speeds as the major and most important consideration. 4Lo takes care of the offroad gearing needs.

 

[chino1969]

If I re-gear from 3.73 to 4.56, 33" tires with a 4.0 5 speed manual in a 2004 TJ what can I expect? How will it handle off road and on the highway comparing 3.73 vs. 4.56?

 

[Jerry Bransford]

If I re-gear from 3.73 to 4.56, 33" tires with a 4.0 5 speed manual in a 2004 TJ what can I expect? How will it handle off road and on the highway comparing 3.73 vs. 4.56?

4.56 is the overall optimal ratio for 33's with the 5-speed and 4.0 engine. That ratio works well extremely well for both the highway and offroad. It'll restore the power lost when those larger tires were installed and don't be surprised if your mpg goes up a little with the engine operating at a more efficient rpm.

 

[Alex01]

I just saw this bullshit reply.

You have seen it before... just like at the time it was in good fun based off a jeep that would never see the highway.

No, all of my ratio recommendations are always made with highway speeds in mind. Even when I recommend 1 size lower ratio, like 5.13 over 4.88, it's always made with highway rpms in mind as well.

Edit: I just re-read what you said for the third time and think I know what you were getting at. If a Jeep will never be driven on the highway, you can gear to a lower ratio than you'd want if it were also driven on the highway.

 

[chino1969]

4.56 is the overall optimal ratio for 33's with the 5-speed and 4.0 engine. That ratio works well extremely well for both the highway and offroad. It'll restore the power lost when those larger tires were installed and don't be surprised if your mpg goes up a little with the engine operating at a more efficient rpm.

Thanks Jerry. I'm considering one of two possible paths to take. 1) Drop to 31" tires and keep the 3.73 gears or 2) Keep the 33" tires and re-gear to 4.56.

 

[Pcleaners2]

If keeping 31s go 4.10
3.73 no good on freeway

 

[Alex01]

If you're running a 30/35 combo you may be able to find axles geared in 4.10 fairly cheap. I had 3.07 and swapped in rubicon axles. With the 5 speed and 33s the 4.10 ratio was liveable. But I was running the 33s with 3.07 prior so anything at the time was a major improvement.

 

[drcomf22]

Picking the ideal gear ratio depends on a number of variables:

1) Tire Size
2) Manual or Automatic Transmission
3) Engine (4 cylinder or 6 cylinder)
4) What year is your TJ? (this is to determine which automatic or manual transmission you have)

Before we can give you an ideal gear ratio, you have to answer those questions.

What would you recommend for 2000 Wrangler TJ 4.0 6 cylinder automatic transmission with 31 inch tires driving 50% of the time on dirt roads with decent grade. Currently it has Dana 35 rear with 3.07 gear ratio. It feels weak to me. Does one always change the front and rears together?

 

[Chris]

What would you recommend for 2000 Wrangler TJ 4.0 6 cylinder automatic transmission with 31 inch tires driving 50% of the time on dirt roads with decent grade. Currently it has Dana 35 rear with 3.07 gear ratio. It feels weak to me. Does one always change the front and rears together?

The kind of driving you do makes no difference.

See this thread:

https://wranglertjforum.com/threads...angler-tj-lj-and-other-re-gearing-faqs.17063/
Per that thread 3.73 would be idea for your setup.

You will want to change the front and rear gears together, yes.

 

[drcomf22]

The kind of driving you do makes no difference.

See this thread:

https://wranglertjforum.com/threads...angler-tj-lj-and-other-re-gearing-faqs.17063/
Per that thread 3.73 would be idea for your setup.

You will want to change the front and rear gears together, yes.

Wow...That thread was perfect!!!! Thank you!.

 

[Chris]

Wow...That thread was perfect!!!! Thank you!.

You’re welcome

 

[S.McArthur]

Wow...That thread was perfect!!!! Thank you!.

Go deeper, use the 4.10, I had 3.73 on 31 and it was decent, I wanted more though.

 

[RMETeeJay]

Go deeper, use the 4.10, I had 3.73 on 31 and it was decent, I wanted more though.

Same here. It's not terrible, but it's rare that I can use NV3550 5th gear with 31s and 3.73 (flats and downhills)

 

[drcomf22]

Go deeper, use the 4.10, I had 3.73 on 31 and it was decent, I wanted more though.

I

Go deeper, use the 4.10, I had 3.73 on 31 and it was decent, I wanted more though.

curious if you had a 5 speed or Auto and whether that matters. I have 3 speed Auto.

 

[S.McArthur]

I

curious if you had a 5 speed or Auto and whether that matters. I have 3 speed Auto.

42RLE 4 speed.