Wanna run 40s-thoughts?

[Deezus]

Looking for input, ideas and thoughts on how to run 40s. I'm running 37s now on an 2018 JLUR with stock axles.
I wanna run 40s but it might be a process as not only do you need 60s but there's also new rims as well. Looking for ideas you guys might have who are considering going to 40s in the future. One idea I had was to get a ProRock 44 in the front and a Dana 60 in the rear. I might have to run wheel adapters in the back or just get 2 new rims. My concern is front pinion seal damage but I'm easy on the skinny pedal and I don't go fast over ruts. Mostly wanna run 40s to lowspeed crawl. I'm trying to do this more on the legit side
What do you guys think?

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[spies]

Low speed crawling is actually what grenades axles because of the massive torque multiplication from low gearing. If you had said you wanted to bomb down fire roads at 50mph in 4-hi on 40s and stock axles you’d actually be better off.

The only way to do this legit and actually be able to wheel the thing is with one ton axles. I would not run a pro rock 44 on 40s either. Deepest gear you can run is 5.13 and those 5.13 Dana 44 pinions are tooth picks.

 

[UKCATS]

With 40’s, I would run a 60 front, and a full float 60 rear. Breakin’ ain’t fun.

 

[Deezus]

Yea that's what it keeps coming back to if you wanna do it legit. If I do it that's how I'm going, legit.
For me, I'm staying with 4.10s even if I go 40s. I'm not down with 2800 rpms at 70 plus mph, I don't care how much better it is for crawling.
Thanks for the info.

 

[gsxr310]

Here’s my setup

 

[Crawdad1028]

Yea that's what it keeps coming back to if you wanna do it legit. If I do it that's how I'm going, legit.
For me, I'm staying with 4.10s even if I go 40s. I'm not down with 2800 rpms at 70 plus mph, I don't care how much better it is for crawling.
Thanks for the info.

The JL handles deeper gears extremely well. I have 5.13 and run about 2400 at 70 on 6th. (6speed) I would have gone 4.88 but I live in the mountains and tow regularly and I love this setup. Still getting about 17.5 mpg hwy and close to 20 at 55 in the country. Running 37s.

 

[spies]

5.38s would put you at 2100 rpm in 8th gear with 40s.

You don't want to run 4.10s for a couple reasons. One, resale, anyone buying those will need to regear. Two, you move a lot of drivetrain load upstream. 5.38s will let you do most obstacles in 2nd or 3rd gear which takes a ton of load off the Tcase and driveshafts. The 8 speed has a 4.71 first gear which is just ridiculously low and should probably avoid using it as much as possible if you've got 40s and a 4:1 transfer case. Personally I would switch to a sport transfer case.

 

[5280Sapper]

I've been wheeling 38's and 40's now for a year no issues...

 

[Shenanigans]

5.38s would put you at 2100 rpm in 8th gear with 40s.

You don't want to run 4.10s for a couple reasons. One, resale, anyone buying those will need to regear. Two, you move a lot of drivetrain load upstream. 5.38s will let you do most obstacles in 2nd or 3rd gear which takes a ton of load off the Tcase and driveshafts. The 8 speed has a 4.71 first gear which is just ridiculously low and should probably avoid using it as much as possible if you've got 40s and a 4:1 transfer case. Personally I would switch to a sport transfer case.

Yea, let’s go to a taller geared t-case?????

If you have concerns regarding the strength of the 241OR and the guy you are trying to give you advice to is talking about 40”s and d60’s, better advice would be a stronger aftermarket t-case. I would probably go to a 5:1 t case myself and I too only play with rocks.

 

[spies]

Yea, let’s go to a taller geared t-case?????

If you have concerns regarding the strength of the 241OR and the guy you are trying to give you advice to is talking about 40”s and d60’s, better advice would be a stronger aftermarket t-case. I would probably go to a 5:1 t case myself and I too only play with rocks.

A lot of people switch to a sport T-case or a 3:1 atlas... but if a 100:1 crawl in an automatic suits you then that’s great, I can’t argue your subjective preference. Just giving mine and the majority of other trucks I see. Only people I know going 100:1 and over intentionally are manuals.

 

[Shenanigans]

A lot of people switch to a sport T-case or a 3:1 atlas... but if a 100:1 crawl in an automatic suits you then that’s great, I can’t argue your subjective preference. Just giving mine and the majority of other trucks I see. Only people I know going 100:1 and over intentionally are manuals.

With old school non selectable automatic transmission, it made a little more sense to rely on the torque converter a little more. With a deep crawl ratio you were stuck with very little wheel speed. This was the main focus of multiple speed t cases. With a selectable transmission, no need to sacrifice an awesome crawl ratio.

With 5:38’s, the 8 speed, and a 4:1 t case, first gear would net you a crawl ratio of about 101:1, 2nd 67:1, 3rd 45:1. With the roll out of a 40” tire, this is perfect for hardcore crawling.

 

[spies]

With old school non selectable automatic transmission, it made a little more sense to rely on the torque converter a little more.

Well manual valve bodies were a thing back then and are still quite popular. And leaning on the torque converter is what makes autos so much better offroad in my opinion. You have this variable crawl ratio that you control entirely with your right foot without any shifting. You can keep the converter in stall and crawl as slow as you want, and then when you need to bump an obstacle just give it some gas and the wheel speed will be there for you. If you want to keep your converter coupled and get all your crawl from gearing, why not just get a stick shift?

Ultimately you're right though, if first gear is too low, then you don't have to use it. But personally, instead of completely writing off a gear, I would just get a case that I thought was more appropriate for my application. And if you're happy with 100:1 in an auto, there's nothing wrong with that either.

 

[LunchBoxFab]

no lift, portals on 40's all day

 

[pokey02]

Here’s my setup

Purdy axles. What suspension are you running? How tall of a lift?

 

[Crusifix]

If I can't make it where I'm going with 37's then I am probably drunk.

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