37 vs 38 Ridge Grappler

[trace_A_face]

I’ve been super happy with the 38” RGs. They are quiet and smooth on road and have good traction offroad, especially for a non-MT tire.

I’m still running the stock 4.56 gears that come with the XR package. While still plenty of power, there was a noticeable difference in resposiveness when going from the stock 35” tire to the 38” tire. I feel it could use a slightly taller gear, however I’m eventually going to go up to UD60s so I’m not going to regear and will just deal with it for now.

I also had to trim about an inch and a half off of the rear pinch seam on the body to keep the tires from rubbing at full flex off-road (see pics below). Not a big deal. That’s with the 3.5” Clayton lift.

This is sooo incredibly helpful as we essentially have close to the same stock setup correct?

What engine do you have and with our wheels we need wheel spacers correct? If so, what size are you running? Would that help with not having to trim anything?

I am new to all of this and want to ensure I purchase all of the essential parts needed in one swoop as my buddy is going to install my lift.

I feel like I have so many questions for you! Are you on instagram by chance?

Things I am considering and wondering if I need:

- New tire carrier? Considering Teraflex
- Pedal Commander? Is this needed?
- Also wondering if I should re-gear down the line but not sure how that differs from swapping from the Dana 44’s to the 60’s?? I have so much to learn! Ha!

Thank you for all of your help in advance!

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[trace_A_face]

I’ve been super happy with the 38” RGs. They are quiet and smooth on road and have good traction offroad, especially for a non-MT tire.

I’m still running the stock 4.56 gears that come with the XR package. While still plenty of power, there was a noticeable difference in resposiveness when going from the stock 35” tire to the 38” tire. I feel it could use a slightly taller gear, however I’m eventually going to go up to UD60s so I’m not going to regear and will just deal with it for now.

I also had to trim about an inch and a half off of the rear pinch seam on the body to keep the tires from rubbing at full flex off-road (see pics below). Not a big deal. That’s with the 3.5” Clayton lift.

I should also ask…is this your daily driver as well? If so, just curious what your mpg’s are sitting at now? Haha

 

[sinisterj]

I should also ask…is this your daily driver as well? If so, just curious what your mpg’s are sitting at now? Haha

I am running 38" RG on my JLUR with a Clayton 3.5 3.6L and 4.10 gears. I am averaging around 16.4 MPG. The 4.10 gears are tolerable around town but you really notice when on the highway I seldomly see 8th gear. I am planning to regear eventually to 4.88. You will definitely want to beef your tire carrier up. I have the teraflex alpha HD.

 

[trace_A_face]

I am running 38" RG on my JLUR with a Clayton 3.5 3.6L and 4.10 gears. I am averaging around 16.4 MPG. The 4.10 gears are tolerable around town but you really notice when on the highway I seldomly see 8th gear. I am planning to regear eventually to 4.88. You will definitely want to beef your tire carrier up. I have the teraflex alpha HD.

This is great info! Thank you for this! My jeep is my daily and I definitely drive highway often. It’s so hard to know if 4.88 or 5.13 would be best? I’m guessing it’s best for me to see how it feels with the 4.56 but then that’s where I’m clueless on what exactly the gears do and how each size truly makes the difference to know which would be best ya know? The currently have the reinforced Mopar carrier but the teraflex alpha HD is what I have on my list to upgrade to. Do you like it a lot?? It sure is pricey!??

 

[sinisterj]

This is great info! Thank you for this! My jeep is my daily and I definitely drive highway often. It’s so hard to know if 4.88 or 5.13 would be best? I’m guessing it’s best for me to see how it feels with the 4.56 but then that’s where I’m clueless on what exactly the gears do and how each size truly makes the difference to know which would be best ya know? The currently have the reinforced Mopar carrier but the teraflex alpha HD is what I have on my list to upgrade to. Do you like it a lot?? It sure is pricey!??

You may be ok with the 4.56 I would try it first. From my reaserch 4.88 is closer to stock gearing with 33's (35 in your case) and 5.13 will have a little more pickup than stock. The teeth on a 4.88 is larger than 5.13. I have not heard to many complain that got either. I love the teraflex carrier it is super strong with the 38 on it and it does not move at all. The price is fairly high but for me the peace of mind and possibility of damage to the tailgate without it is worth it. Im not sure the mopar reinforced carrier does a whole lot to be honest

 

[trace_A_face]

You may be ok with the 4.56 I would try it first. From my reaserch 4.88 is closer to stock gearing with 33's (35 in your case) and 5.13 will have a little more pickup than stock. The teeth on a 4.88 is larger than 5.13. I have not heard to many complain that got either. I love the teraflex carrier it is super strong with the 38 on it and it does not move at all. The price is fairly high but for me the peace of mind and possibility of damage to the tailgate without it is worth it. Im not sure the mopar reinforced carrier does a whole lot to be honest

Yes! I completely agree. If I’m going to do this massive build, I want to ensure I do it right from the start. I don’t mind paying the price for the quality and peace of mind either. Also, good to know on the 4.88 & 5.13. With the added cost I will definitely feel it out to start and then go from there. But for my understanding, adjusting sizes gives you more “throttle?” The higher you go does that also lower your mpgs? Thanks to all for the help! Now I just need discounts!?

 

[Zandcwhite]

Yes! I completely agree. If I’m going to do this massive build, I want to ensure I do it right from the start. I don’t mind paying the price for the quality and peace of mind either. Also, good to know on the 4.88 & 5.13. With the added cost I will definitely feel it out to start and then go from there. But for my understanding, adjusting sizes gives you more “throttle?” The higher you go does that also lower your mpgs? Thanks to all for the help! Now I just need discounts!?

With the 8 speed auto, people make way too much out of gears. The only place the gears give any kind of additional leverage is 1st Gear. After that the transmission will decide what gear it needs to be in for the required output. If you do a lot of freeway driving at 75+mph you'll likely see a drop in mileage from going to lower gears. When we went to 5.38s with 39s vs the stock 4.10s the jeep didn't improve at all 0-60 and we lost 3 mpg on long road trips where the cruise control was set at 80mph. Sure we saw 8th gear a lot more, as it was usually in 8th gear by about 50mph. In my opinion is rather only see 8th under low load scenarios where it can actually save me fuel. I am very happy in our 2022 on the stock 4.56s and 39s personally.

 

[trace_A_face]

With the 8 speed auto, people make way too much out of gears. The only place the gears give any kind of additional leverage is 1st Gear. After that the transmission will decide what gear it needs to be in for the required output. If you do a lot of freeway driving at 75+mph you'll likely see a drop in mileage from going to lower gears. When we went to 5.38s with 39s vs the stock 4.10s the jeep didn't improve at all 0-60 and we lost 3 mpg on long road trips where the cruise control was set at 80mph. Sure we saw 8th gear a lot more, as it was usually in 8th gear by about 50mph. In my opinion is rather only see 8th under low load scenarios where it can actually save me fuel. I am very happy in our 2022 on the stock 4.56s and 39s personally.

Oh this is so awesome to know! I have seen a lot of charts which appears that my gears would be just fine at 4.56 and I have been considering 38’s or 39’s (BF Goodrich KO2’s A/T). It’s good to know that I should be ok with either 38 or 39? The KO2’s are A LOT lighter so I don’t know if that would help at all either?

 

[trace_A_face]

With the 8 speed auto, people make way too much out of gears. The only place the gears give any kind of additional leverage is 1st Gear. After that the transmission will decide what gear it needs to be in for the required output. If you do a lot of freeway driving at 75+mph you'll likely see a drop in mileage from going to lower gears. When we went to 5.38s with 39s vs the stock 4.10s the jeep didn't improve at all 0-60 and we lost 3 mpg on long road trips where the cruise control was set at 80mph. Sure we saw 8th gear a lot more, as it was usually in 8th gear by about 50mph. In my opinion is rather only see 8th under low load scenarios where it can actually save me fuel. I am very happy in our 2022 on the stock 4.56s and 39s personally.

Also, any insight on the pedal commander and if that helps with the “giddy up” and is worth looking into?

 

[7.62x392]

This is sooo incredibly helpful as we essentially have close to the same stock setup correct?

What engine do you have and with our wheels we need wheel spacers correct? If so, what size are you running? Would that help with not having to trim anything?

I am new to all of this and want to ensure I purchase all of the essential parts needed in one swoop as my buddy is going to install my lift.

I feel like I have so many questions for you! Are you on instagram by chance?

Things I am considering and wondering if I need:

- New tire carrier? Considering Teraflex
- Pedal Commander? Is this needed?
- Also wondering if I should re-gear down the line but not sure how that differs from swapping from the Dana 44’s to the 60’s?? I have so much to learn! Ha!

Thank you for all of your help in advance!

It’s a 2022 392 with the XR package. I’m still running the XR stock wheels (which have since changed for the 2024 MY), which I believe are a -12mm offset. I am not running any spacers which may have contributed to the need to trim the body despite the 4” of bump and a 3.5” lift.

I am running the Teraflex carrier and hinge gate. It’s very stout and has the fit and finish that I think is better than the stock Mopar reinforcement. No rattling.

I’d say without the 392 engine you’d need to regear on 38s. The 392 provides enough power and torque for me to get away with the 4.56 gears.

Unless you plan to take off-road often, I would not recommend an axle swap. It’s very expensive (around $25k installed, give or take a few grand) and you run the risk of issues down the road that your warranty won’t cover. There are some unique issues with the 392 transfer case and axles that is driving me to consider the swap.

This is my daily driver for now, however in the market for a daily as I want to keep the mileage on my 392 low and Turn it into a dedicated trail rig. I’m currently getting about 12MPG, which isn’t bad for 6.4L of displacement and 38” tires, especially given most of my driving is local around town.

Hope this helps answer some of your questions. Full details on my build are in the link below.

https://www.jeep392.com/threads/matts-392-build.2114/

 

[GATORB8]

I’m still running the XR stock wheels (which have since changed for the 2024 MY), which I believe are a -12mm offset.

I believe it's the flip, +12mm offset/5 inch BS.

 

[trace_A_face]

I believe it's the flip, +12mm offset/5 inch BS.

My understanding was that I would need to get wheel spacers to accommodate my stock wheels with the new lift, etc. Fo I not need wheel spacers for the XR wheels?

 

[GATORB8]

My understanding was that I would need to get wheel spacers to accommodate my stock wheels with the new lift, etc. Fo I not need wheel spacers for the XR wheels?

Im sure it depends on the lift to some point.

Most manufacturer backspace requirements are universal, and don’t take into account that the Rubi axles themselves are already .75” wider per side.

I can verify that running 37” KO2s on a MC Gamechanger, the only issue I have running +18mm is at stuff/lock I can touch the tire to the front sway bar link.

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