Alexf7019

K I know there are many threads on this but I have 33s on my jk right now with auto trans I am going to upgrade the first of the month to a bigger tires I don't want to get a regear right now but if I go to a 37 will I absolutely have to? Will it be unbearable and put too much stress on the front Dana 30?

Ryan0260

I wouldn't go over 35's with the D30, and yes, 37's will be miserable on an auto without a regear.

nthinuf

No, you don't "absolutely have to" do anything. It's your jeep. If you can deal with less oomph out of the engine, go for it.

But, if you want some better opinions, you might start by filling in some info, like: What year/engine/transmission. Current gears. Location (elevation with hills/mountains, flat roads at sea level). Normal usage (mostly in-town, mostly high speed freeway, bunch of crawling, etc) With no info, hard to get opinions on how 'you' will feel about the performance.

Chapman89

I have a 2011 JKU on 35's and 3.73's. The only reason it's tolerable in my opinion is the fact it's a 6 speed. I think with an auto it would suck.

I wouldn't worry too much, some people have a shorter tolerance for what's acceptable. I'm not too hard on my jeep. I will be adding c gussets to my d30 but that's it. Not worth dumping money into it in my opinion.

tarpon4me

I have 4.56 gears with 33's and it's just right. If I did more highway i'd go with 4.10's. I couldn't imagine an auto with 37's and stock gears.

TheDirtman

I would not worry about the axles with factory gearing and 37's the rest of your drivetrain will be really stressed mainly the driveshafts but you are going to really overwork the transmission and will have no torque for climbing anything. If you have a 07-11 with the 3.8 I would stop at 35" tires and run 5.13 gears.

stefel22

I was driving with 35s and 373 for years, which on the 3.8 really sucked power wise. Over the course of the past few years I installed sleeves ,gussets ( Christmas present from the wife ) and recently Chromolloy axles and Synergy ball joints, a little breakage on my last rausch trip . I really had no intentions to go to 37s ...Well needless to say I had the opportunity to purchase some 37 " MTRs for a good price , so with that I regeared to 513s . I must say that with the 37s and 513s the ride is sooo much better than the 35s with 373s. Now I don't go crazy wheeling, mainly greens and blues , so Im hoping that the D30 holds up.

Jersey_Devil

Ran 37" km2 tires on my last rig, factory d30 and 373s sure it was sluggish but I rolled it before I could really wheel it hard

Punisher

I currently have 37 km2 on my 08, 3.73 and an auto, it's ok on flat roads and can't use overdrive.
I have only done gussets an sleeves, made my appointment to get gears 5.13 and an arb air locker

ricon

I have 08 auto with 3.73 gears. Ran 37s on d30 for about 4 months. Also had the flash cal. It did ok around town, and sluggish on the freeway, on any incline. Took OD off and it helped slightly. Very lite wheeling. Like previously stated, it absolutely can be done and you do not have to regear right away but it will cause additional stress on the transmission and Cs. For me, the cost of repairing/replacing my tranny wasn't worth it. I downsized to 35s.

Hope this helps.