35" vs 37" - Need some advice!

[Grayhound]

The desert climate and altitude must have something to do with it!

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[kah.mun.rah]

I went with 35s and instantly regrated not going right to 37s. I have been running 37s for about 4 years now and zero regrets. IMO, 35s look too small on a lifted JLUR. My evolution:

https://www.jlwranglerforums.com/forum/threads/35’s-on-2021-rubicon-questions.110581/post-2296084

 

[Ryan long]

The desert climate and altitude must have something to do with it!

Hot shot’s claimed you’ll get better fuel mileage and less regens with their products. Maybe?

 

[Grayhound]

Hot shot’s claimed you’ll get better fuel mileage and less regens with their products. Maybe?

I used EDT until the hpfp was replaced under recall . I don’t feel like I see a lot of regens because I do quite a bit of highway driving. I do not see any kind of bump in miles per gallon with EDT. I am hesitant to use it now because other former members who have had problems with their diesels claim to use it every Fill up. I guess I just didn’t see the benefits of using it beyond having higher lubrication in the fuel pump.

 

[Grayhound]

I went with 35s and instantly regrated not going right to 37s. I have been running 37s for about 4 years now and zero regrets. IMO, 35s look too small on a lifted JLUR. My evolution:

https://www.jlwranglerforums.com/forum/threads/35’s-on-2021-rubicon-questions.110581/post-2296084

Nice rig, why did you change lift kits from Mopar to TeraFlex?

 

[kah.mun.rah]

Nice rig, why did you change lift kits from Mopar to TeraFlex?

Thanks. They are both great lifts. It was a matter of changing Jeeps...not lifts:

 

[grimmjeeper]

I have a 21 Rubicon Diesel. I went with 35s when picked it up from the dealer. I did the Clayton 2.5" kit and ran it that way for a while. I've been slowly upgrading it for a while. I did a truss, steel knuckles, RCV shafts, HD tie rod, HD drag link, and ball joints in the front in one shot. Swapped out the front driveshaft a while back. Went to 37s almost a year ago. Ended up needing a little bump stop extension in the rear. I have a truss, rear driveshaft, and rear axle shafts ready to go in when I get back from EJS.

I would say you should upgrade everything but you don't need to do it all right away. One step at a time as time and budget allow is fine.

 

[Grayhound]

Thanks. They are both great lifts. It was a matter of changing Jeeps...not lifts:

What a nightmare!

 

[Jtphoto]

.

i haven’t regeared yet but I want to. I did notice a difference but it’s not that large. Going to 37s, to match stock “feel” I would need 4.10s. That’s only one “step” up. Not a big deal. Still have torque for days (big note, just incase you didn’t know: when going into 4L the auto with your diesel shifts into 2nd gear, not 1st, unlike the 2.0 or 3.6). However.. as I intend to only use my diesel for off-roading.. I’m going to go with 4.56s. Going up the mountainside angers the transmission if you don’t regear, from what I can tell. Went into limp mode so now I just go up slow and steady (at or within 5-10mph below) and it hasn’t caused me an issue since.

Interesting comment about the gears. The gearing for the gas engines should be the same as the both run the same ZF 8 speed. 4.10 gear is the standard for a Rubicon with 33” tires. If you want a factory matched feel then 4.56 is the perfect match for 35s (rubicon Xtreme Recon factory package), 4.88 for 37s, 5.13 for 40s. If you are building a dedicated off road rig I’d suggest 5.13.
I run 4.56 (Xtreme Recon) with 37s and it needs more gear. 4.88 would be perfect.

The gas engines also start in 2nd gear in 4Lo

 

[Nicarague Joe]

I think it really depends what you want to do. The first pic is on 38's with 3 1/2 MC lift, trussed, gusset, 2 ton steering, apex hd ball joints , Reid knuckles, PSC Hydro assist ( which is the best upgrade you will ever do)

This picture is on Anaconda trail in Table Mesa AZ. We did collateral Damage after which was over my head. This is on 37's with same set up but no Hydro. I think the key for you is figure out your end game and start there. You live in UTAH so one trip to Trail Hero in Sand Hollow, Ut and it's over and if you aren't on at least 37's you won't be happy. I would also start with a 3 1/2 ' lift. 2 1/2 won't cut it unless it will be a pavement princess.

My suggestion is hook up with a group and go on a trail and talk to he group. see how your jeep does and what you don't like. Get some real life advice and go from there. But I can tell you from experience that you will not be happy with a 2.5 lift and 35's because I did the same thing first. Good luck

 

[Ryan long]

I used EDT until the hpfp was replaced under recall . I don’t feel like I see a lot of regens because I do quite a bit of highway driving. I do not see any kind of bump in miles per gallon with EDT. I am hesitant to use it now because other former members who have had problems with their diesels claim to use it every Fill up. I guess I just didn’t see the benefits of using it beyond having higher lubrication in the fuel pump.

I also got my hpfp replaced in December. These fuel pumps need a lubricant the pressures are too high. I don’t understand why it would cause any problems using edt? My F250 service truck is a 2020 6.7 diesel that I got in 2019 and it has 120k miles and I double dose it with edt every fill up. That truck has never been in the shop. I’m a heavy equipment mechanic and I’ve seen farm equipment with these pumps go to 32,000 psi. Water, air or improper fuel filter changes will cause these pumps to fail. I have a hpfp from green diesel for my JL I’m gonna put on it pretty soon.

 

[Grayhound]

I also got my hpfp replaced in December. These fuel pumps need a lubricant the pressures are too high. I don’t understand why it would cause any problems using edt? My F250 service truck is a 2020 6.7 diesel that I got in 2019 and it has 120k miles and I double dose it with edt every fill up. That truck has never been in the shop. I’m a heavy equipment mechanic and I’ve seen farm equipment with these pumps go to 32,000 psi. Water, air or improper fuel filter changes will cause these pumps to fail. I have a hpfp from green diesel for my JL I’m gonna put on it pretty soon.

I was really considering GDE tune. But in reading the ram 1500 forums one of the guys has a couple of trucks that he’s run with GDE. When he did used oil analysis, he found a high presence of fuel in the oil with the GDE tune when he de tuned it is Used oil analysis went back to normal. So that’s left me a little cautious of going GDE.

 

[Ryan long]

I was really considering GDE tune. But in reading the ram 1500 forums one of the guys has a couple of trucks that he’s run with GDE. When he did used oil analysis, he found a high presence of fuel in the oil with the GDE tune when he de tuned it is Used oil analysis went back to normal. So that’s left me a little cautious of going GDE.

Yea I’m just using the pump. No tune. I’d rather do a gear change than try to add more power to that motor

 

[Themistocles]

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.

 

[CableDaddy]

Interesting comment about the gears. The gearing for the gas engines should be the same as the both run the same ZF 8 speed. 4.10 gear is the standard for a Rubicon with 33” tires.

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.

If you want a factory matched feel then 4.56 is the perfect match for 35s (rubicon Xtreme Recon factory package), 4.88 for 37s, 5.13 for 40s. If you are building a dedicated off road rig I’d suggest 5.13.
I run 4.56 (Xtreme Recon) with 37s and it needs more gear. 4.88 would be perfect.

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.

The gas engines also start in 2nd gear in 4Lo

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!

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