Rubicon Re-Gearing Advice

[J.Cain]

With the input so far, 4.88 is what I feel would be best for my current use and even possible future upgrade to 35's. Once I find someone to either install them or help me install them I will get them on order. Takers in the Parker, CO area??? I'll do all the dirty work

 

[jjvw]

With the input so far, 4.88 is what I feel would be best for my current use and even possible future upgrade to 35's. Once I find someone to either install them or help me install them I will get them on order. Takers in the Parker, CO area??? I'll do all the dirty work

Again, I will tell you from experience that 4.88 is not quite deep enough for 35s. It was great for 33s.

 

[tworley]

X2. Go deeper.

 

[J.Cain]

X2. Go deeper.

Are you guys telling me 5.13 would be better choice? I thought 5.13 would be for the real rock crawlers, not the mall crawlers like me!

 

[jjvw]

Are you guys telling me 5.13 would be better choice? I thought 5.13 would be for the real rock crawlers, not the mall crawlers like me!

Both of us spent many years daily driving our Jeeps. That is where the recommendation comes from.

 

[97TJNM]

Both of spent many years daily driving our Jeeps. That is where the recommendation comes from.

I'll say this, I have an AX-15, so it's an apples to oranges comparison. That said, I have 4.88s now, and when I was contemplating what direction to go with my build, I was really leaning towards 4 10's. When I went with 4.88's, I thought I'd never need all that gearing, but on 35's and living in the mountains at 7k feet, I now wish I went with 5.13 or 5.38.

 

[jjvw]

I'll say this, I have an AX-15, so it's an apples to oranges comparison. That said, I have 4.88s now, and when I was contemplating what direction to go with my build, I was really leaning towards 4 10's. When I went with 4.88's, I thought I'd never need all that gearing, but on 35's and living in the mountains at 7k feet, I now wish I went with 5.13 or 5.38.

No. The nv3550 gearing is nearly identical to the AX15.

 

[tworley]

Are you guys telling me 5.13 would be better choice? I thought 5.13 would be for the real rock crawlers, not the mall crawlers like me!

Both of spent many years daily driving our Jeeps. That is where the recommendation comes from.

Yes-5.13s or even 5.38. As @jjvw said, our jeeps were our daily drivers for years. I travel all over the state for work and have driven thousands of miles along I70. With 5.13s and my AX15, I can crest the Eisenhower hill and maintain 60 mph the whole way. On flat interstate, maintaining 75 mph is easy. Around town, I can zip thru traffic and its a pleasant experience. Just last week I did almost 500 miles to the western slope and back. At 75 mph on the interstate, I still was able to achieve 15.7 mpg. I am limited to 5.13s in my dana30, but if I had the option, 5.38 would be installed for the couple hundred more RPM at 75 mph

 

[97TJNM]

No. The nv3550 gearing is nearly identical to the AX15.

In that case, the 4.88 is okay-ish on 35's. It was pretty decent on 33's.

 

[RINC]

RPM calculations for a 35" tire...

NV3550/33.875"/4.88=2832rpm @ 75mph
NV3550/33.875"/5.13=2977rpm @ 75mph
NV3550/33.875"/5.38=3122rpm @ 75mph

All of these are lower rpm than a stock TJ with the 3 speed automatic fresh off the assembly line.

I was told there would be no math.

 

[RINC]

Yes-5.13s or even 5.38. As @jjvw said, our jeeps were our daily drivers for years. I travel all over the state for work and have driven thousands of miles along I70. With 5.13s and my AX15, I can crest the nhoEisewer hill and maintain 60 mph the whole way. On flat interstate, maintaining 75 mph is easy. Around town, I can zip thru traffic and its a pleasant experience. Just last week I did almost 500 miles to the western slope and back. At 75 mph on the interstate, I still was able to achieve 15.7 mpg. I am limited to 5.13s in my dana30, but if I had the option, 5.38 would be installed for the couple hundred more RPM at 75 mph
View attachment 462777

Eisenhower, never been through that stretch of I-70 in anythang other than a big truck. Would love to tackle it now in my regeared Jeep.

 

[97TJNM]

In that case, the 4.88 is okay-ish on 35's. It was pretty decent on 33's.

To clarify, what I mean by this is that when I was running 33's I didn't mind the 4.88s on the road. Now that I'm running 35's, they are fine most of the time, but on the highway or interstate pulling steep grades, you will actually lose speed at full throttle in 5th, and in 4th, your RPMs are high, and you can only maintain speed, not gain speed. There's a particularly steep hill on the highway near my town that I frequently have to downshift to 3rd to climb. That's why I said if I had to do it over again, I'd go with 5.13's or 5.38's.

 

[jjvw]

I was told there would be no math.

Copy/paste, thankfully!

 

[jjvw]

To clarify, what I mean by this is that when I was running 33's I didn't mind the 4.88s on the road. Now that I'm running 35's, they are fine most of the time, but on the highway or interstate pulling steep grades, you will actually lose speed at full throttle in 5th, and in 4th, your RPMs are high, and you can only maintain speed, not gain speed. There's a particularly steep hill on the highway near my town that I frequently have to downshift to 3rd to climb. That's why I said if I had to do it over again, I'd go with 5.13's or 5.38's.

Overall, including slow city driving, the best gearing and tire combo the Jeep has ever had was 33s and 4.88. Prior to the auto swap, the plan was to regear to 5.13 and potentially 5.38. Now it is definitely 5.38, which still isn't low enough for the 42rle.

 

[tworley]

Eisenhower, never been through that stretch of I-70 in anythang other than a big truck. Would love to tackle it now in my regeared Jeep.

Heading west from Georgetown its at least 12 miles with 6% grades.

 

[PNW_LJ]

Overall, including slow city driving, the best gearing and tire combo the Jeep has ever had was 33s and 4.88. Prior to the auto swap, the plan was to regear to 5.13 and potentially 5.38. Now it is definitely 5.38, which still isn't low enough for the 42rle.

There’s still the chance to go lower..

 

[jjvw]

There’s still the chance to go lower..

The only way I know to do 5.89 on these axles is to replace both lockers and use standard cut gears. That isn't happening. And I still haven't seen any real world examples of anyone having done it. I don't care to be the guinea pig for this one.

 

[RINC]

The only way I know to do 5.89 on these axles is to replace both lockers and use standard cut gears. That isn't happening. And I still haven't seen any real world examples of anyone having done it. I don't care to be the guinea pig for this one.

I would be in the gallery cheering you on.

 

[PNW_LJ]

I don't care to be the guinea pig for this one.

One small step for jj, one giant leap for
jeepkind.

 

[jjvw]

I would be in the gallery cheering you on.

One small step for jj, one giant leap for
jeepkind.

You two can be my adoring sponsors and send me a couple new ARB rd116 lockers and RGA 5.89 gear sets!