35" vs 37" - Need some advice!

[Rubi SoHo]

yes, the 4.5 required a new front driveshaft but the rear is still fine… until I can afford to replace it haha. I think the cut-off for the front driveshaft is 3 or 3.5 inches.

Might be product dependent, but MetalCloak advises a front shaft replacement on even their 2.5” kits. The articulation will cause issues with the stock one. I’m sure some 2-2.5” kits are fine though.

Sponsored

 

[Themistocles]

Might be product dependent, but MetalCloak advises a front shaft replacement on even their 2.5” kits. The articulation will cause issues with the stock one. I’m sure some 2-2.5” kits are fine though.

When I talked to Clayton as I put in my 2.5, they also recommended a front driveshaft. They were not adamant about it but were clear that it was a should do.

 

[Jtphoto]

The diesel has the 8HP75, the gas has the 850RE. I believe the gearing is the same, but the rating is not. 3.73 was the only gearing offered for the diesel. Because either we didn’t need it.. or Jeep didn’t want to warranty it, lol.

3.73 on 33 = 3.95 on 35 = 4.18 on 37.

On my old JK I had 5.13s, which was perfect, but 4.88s or 5.13s would be insane on the diesel. Unless I’m missing something(totally possible).. SUPER hard pass.



Oh wow. I did not know that was for both. Very interesting. It made sense for the diesel.. but why with the gassers? They need all the help they can get!

That makes sense. The diesel won’t rev as high so it’s more economical at lower rpm then gas, hence it doesn’t need as much gear.

I guess the gassers have more than enough torque to start in 2nd so they don’t need 1st.
I think it’s more about getting wheel speed. 1st Lo would be the crawler gear.

 

[Rubi SoHo]

When I talked to Clayton as I put in my 2.5, they also recommended a front driveshaft. They were not adamant about it but were clear that it was a should do.

Yeah, MetalCloak will sell you a kit without the driveshaft, but that option is labeled “I’m a JL expert; no driveshaft”. Which I believe was written in a fairly sarcastic tone.

This is what you get when ordering a 2.5” gamechanger (mid-arm) kit.

Their rationale: Stock driveshaft will contact other components when flexed out and wear quickly. They also point out that the stock backspacing on the JLURD wheels won’t work, and a different wheel is advised.

 

[BDinTX]

Is that a Mopar tailgate reinforcement I see? Is it a matter of form or function? Have you upgraded your steering yet on 37's?

Ya I do have the tailgate reinforcement but the factory hinges are squeaking pretty good when I open and close it. I have not upgraded my steering, there have been a few times I've been unable to turn them so I had to move a little forward or back. But my thinking is that it's not turning for a reason. if I put a stronger pump or hydro assist it'll just break something.

 

[CableDaddy]

Might be product dependent, but MetalCloak advises a front shaft replacement on even their 2.5” kits. The articulation will cause issues with the stock one. I’m sure some 2-2.5” kits are fine though.

Could be! My memory isn’t the best.. but I remember a verbiage difference. Like recommended @ 2.5, required @ 3.5 ?‍?

That makes sense. The diesel won’t rev as high so it’s more economical at lower rpm then gas, hence it doesn’t need as much gear.

I guess the gassers have more than enough torque to start in 2nd so they don’t need 1st.
I think it’s more about getting wheel speed. 1st Lo would be the crawler gear.

I didnt even know about it when I went to test my vehicle at truckhaven one random weekend to ensure I don’t have any clearance issues, binding, unforeseen issues, etc.. and when going up some stuff I was like… “wait… THIS is all this can do?? This can’t possibly be 442ftlbs.”

turned out I was in 2nd gear which was something I didn’t even think about in my old manual jk, or the friends auto JKs I drove. Wheel speed makes a heck of a lot of sense. Program for the masses/general off-roading.. not rocks as the default.

 

[Rubi SoHo]

Could be! My memory isn’t the best.. but I remember a verbiage difference. Like recommended @ 2.5, required @ 3.5 ?‍?

Yep, probably product dependent. Doubt you need new shaft for a Mopar kit for example.

In other news, anyone need a factory front shaft? I’ve got a takeoff that I’ll let go on the cheap. ?

 

[Jtphoto]

Articulation is the key. Especially with the front if you disconnect. High flex suspension joints will tax your factory driveshafts ability to flex without blowing apart.
Leaving your swaybar links connected and using a bit shorter shock will protect the factory driveshaft.
Those RockSport Shocks are of the longest travel shocks you can buy without going coil over. They are also valved differently then most.

 

[Maverick909]

No issues in the Dana 44 axles so far. I have not trussed the axle or upgraded the C’s. Year into 37’s on the Jeep and wouldn’t go back to 35’s or smaller. 37 is a sweet spot for on and off road manners. I do run moderate to hard trails. I also run overland gear for multi day trips which has me running on the heavy side. But I keep the trails to easy to moderate when loaded down. It all comes down to driver pedal control.

 

[C.Sco]

Not sure if this helps but I don't think anyone has gone 37s and regretted it.

I did 37's and I regret not doing 38's

 

[Grayhound]

So, I will present a very slightly different perspective.

I also have a JLURD with Clayton 2.5. I have Reid knuckles, Dynatrac ball joints, and an Adams front drive shaft, but haven't trussed / gusseted...yet. And haven't switched to RCVs ...yet. I am also still on 3.73 gears, through will likely go to 4.10s soon.

I started with 35s back in the summer of '20 then soon after went with the Clayton 2.5 suspension, then 2.5" Fox shocks. And...I loved that set-up. The 35s looked just a bit small in the wheel wells, especially as I stripped the inner fenders and liners. But the performance was great. I commute about 100 miles (round trip) in my jeep 3 or 4 times a week. It got 22 - 23mpg, handled great, and when I took it off road (once a month or so) plus summer trips to places like Moab it worked well. So, I was happy with the 35s.

But...I was also interested in 37s. So, when it came time to replace my 35s this year (60k miles), I replaced them with 37s. The 37s fit, no extra bump stop needed (because of no inner fenders and no liners). They ride great, look way better than the 35s on the vehicle, and even with 3.73 gearing I still have plenty of power. The one big downside is they took my MPG down to about 18.7. I am not exceptionally happy with that.

Lots more detail on my build thread: Diesel Build - 2020 Sting-Gray JLURD | Jeep Wrangler Forums (JL / JLU) -- Rubicon, 4xe, 392, Sahara, Sport - JLwranglerforums.com

Overall, I think the choice is in your use case. Are you mostly going to use it off-road and want the best capability and not so concerned about cost? ... 37s (and lots of other parts). Are you mostly on road and need comfortable easy driving and good mileage? ... 35s (and limited additional changes) Do you want something that looks good to drive to the mall? ... 37s (and limited additional stuff).

Bottomline, I personally was never unhappy with 35s. I was a little frustrated on some the bigger obstacles as I watched 37 equipped jeeps have an easy time than I did. Will I go back to 35s...probably not. But the switch to 37s will in the end probably end up costing me about $8k in additional stuff (regear, RCVs, truss and gusset, tie rod and drag link, etc), not counting the lost mileage.

Worth it...maybe. Probably. On most days.

This is the most real review of 37s I think I have ever read.

I definitely wish I could justify more than a 35, but the 35s do so well for a DD

 

[kah.mun.rah]

If you are building a dedicated off road rig I’d suggest 5.13.

Unless you daily drive a lot of hills or plan to add 40s, I would stick to 4.88 for off-roading with 37s on a D44. The ring gear tooth on a D44 5.13 is pretty small and breaking one off-roading is a slow ride home.

 

[kah.mun.rah]

Last chance canyon? I don't have the cojones to drive my JL in the notch until it is paid off. Great job!

 

[Pig-Pen]

Lowly base sport here on 37s. Moderately aggressive wheeling on them for about two years at least with no issues. I do plan to do upgardes over time but thats for precautionary measures. So far so good.
I also run lightweight wheels and tires (Patagonias). I can lift my tire onto my tailgate without much struggle.

if youre still unsure, you can get the best of both worlds. 37” K02s

 

[gonzoflick]

Go 38s

Sponsored