Mlord

So I've searched this as well as several other Jeep forums and got a bunch of mixed opinions regarding putting 37"s on a non-rubicon. I understand that moderate/hard wheeling with 37"s will for sure stress out and eventually break something on the front Dana-30. But to be honest, my Jeep is my daily driver and I live 30mins from the concrete jungle of D.C. There's so much traffic around here that during the week I don't even really break 40mph. I take a seldom trip to West VA for a wheeling event but have kept to 5 or less rated trails to have more steady fun than worry about breaking things.

I currently have a 3" lift on 35"s and am enjoying it very much. But I've been itching to throw an even beefier set of wheels/tires on. I run a 16x8 wheel with 315/75/16 right now. I wanted to go up to a 17x9 wheel on 37x12.5R17. I know the dangers of the weak points it creates on the front axle, gusset, knuckles, ball-joints etc.. but like I said I'm not going to do any aggressive wheeling until I buy a daily driver later this year or early next year and can make my Jeep my "Weekend Warrior".

I also understand that re-gearing is pretty necessary soon after changing to 37"s to mitigate the sluggish performance due to the increased diameter and weight of the new tires/wheels. I do plan on having air-lockers very soon and will re-gear with them.

Anyway, any other opinions or possible validation of my thoughts is welcome.

Thanks fam!

resharp001

You'll be fine on 37s for your use. There's going to be more danger in locking the D30 up front than there is from running 37s, but if you use your head and don't do stupid $hit, you'll be ok. 37s are just going to add to the normal wear and tear items. Regearing is the biggest thing. Plan on paying up for good ball joints. Synergy, TF, Alloy and such won't be enough unless you just love doing that labor over and over. Look at the Rare Parts model if not familiar with them.

BoraBora

resharp is correct: do NOT lock that D30. I honestly wouldn't even spend the money on re-gearing that D30 if I were you, unless you know a guy that can do it on the low. You'll break something eventually (probably a few teeth off the pinion gear), then once you upgrade you'll regret having spent that $$$.

At a minimum I'd weld an Artec armor kit on. All the shops in this area are crooks, so regardless you're going to get bent over on labor. Check the local forums/Facebook groups such as Element Offroad and Nova Jeep, one of us can burn the axle armor on during a weekend. I just did a guy's c-gussets a few weekends ago for $100 and a case of beer. Keep in mind when you're welding the gussets on, you'll need to do the ball joints in the same sitting. I'd also recommend the Rare Parts, as I just had one of my Teraflex BJ's fail after 3,000 miles. Granted it was 3,000 miles of hard wheeling (Corum at the Cove, Windrock Trail 15, 21, etc, Rausch Creek's Rock Creek) and while Teraflex is sending me a new ball joint under the lifetime warranty...doing this over and over is a PITA. I've read the same complaints about the Synergy BJ's.

Really the biggest worry is, if you drive into D.C. everyday like I do, the roads are atrocious. I mean really, I wouldn't feel comfortable driving the pot-hole ridden washboard roads with anything less than a truss and upper/lower gussets on 37's.

Good luck with whatever you decide, and feel free to send me a private message if you need any pointers in choosing a shop or if you have anymore questions.

jjjmm56

resharp001

"good power" is all relative to perspective. Throw 5th gear out the window. It's kinda one of those things you get used to how sluggish your ride is for a while....it becomes your new norm......until you get in a jeep that is geared properly and remember what it's supposed to be like. I made it for bout a year on 4.10's and 37s. Wasn't bad at first, bearable. Then it was a slow decline of satisfaction. Trying to maintain speeds on the interstate in to a headwind or up hill got aggravating. Then it got to the point of even low end grinding on my nerves. Fuel economy might be 15-16mpg, cuz you're on the interstate at like 2k rpm.....but good luck if you gotta put your foot down and shift to 3rd to muster any effort to pass. Regearing is definitely not something you have to do on day 1 in order to run 37s, but it's nice to have a jeep that has some guts back when geared properly.

BoraBora

lol, you ever driven a car with power? You know the amount of stress you're putting on the trans and t-case (and clutch if you have a 6 speed)?

There are also a ton of guys on here who will say their 3.21's with 35's run 'great with no real power loss' but in reality we all know that's not true. Ignorance is bliss.

Edit: Damn, Resharp beat me to it!

Mlord

So on a side note that brings up a good point, I have stock gearing currently in my 2017 Unlimited and it really hasn't been terrible when I put the 35's on. But I'm sure i'll notice it when i switch to 37"s. What is the preference of gearing for a 37" tire?

BoraBora

For you I'd probably go 4.56.

Others will probably chime in and say 4.88, but in my opinion that's just too deep for the streets with the 3.6L Pentastar. With 35's and 4.56 and in 6th gear, I'm right around 2600 RPM on the highway @ 70mph. Who actually goes 70 mph though? When I'm going 75-80mph I'm right around 3k RPM, and I'm not a fan of staying that high in the RPM range (especially on longer drives). If I had a truck and trailer? I'd go 4.88.

Crawling wise, you won't see a drastic change in crawl speed from 4.56 to 4.88. Rubicon transfer case makes it crawl sloowwwwww as hell regardless (I'd recommend picking one up).

wharthog69

I ran 37's for a year on a D30 with stock 3.73 gearing and the 3.8/auto. While it wasn't great, I didn't break anything (I did wheel it, but no lockers so...) and drove it to work every day. I regeared to 5.38 when I put the Prorock in the front and the Rubi 44 in the back. Much better, but you can live with it.

Don't do anything to the D30 but replace it. One of the guys in the club put a locker in and destroyed it the second time he went out. I know everyone is going to say "it depends on how you drive" but IMO it just isn't worth the risk.

nthinuf

If you keep the D30, and if you decide to add traction to it, there are cheaper options than thousand dollar selectables. Lots of people are quite happy with lunchbox lockers. And you could do a lot worse than a Detroit TrueTrac - excellent way to go for the less hard-core crowd.

But with a 10k budget : rather than building the hell out of a d30, you might look into selling it and either searching for a cheap take-off 44 to build, or pricing out the aftermarket selections. Work up a comparison something like this.
https://www.jk-forum.com/forums/modi...-build-274896/


err, what happened to the table?