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Ecodiesel gearing

JINO

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Will the ecodiesel (3.73) need to be upgraded if going to a larger tire?
Say a 35 or 37"?

I'm getting mixed answers on facebook, many say the 3.73 has enough torque where you won't notice any change with either tire, while others say you need at least 4.10 and a few that say you need much higher gearing.

I won't be rock crawling, mostly deep rutted trails, snow trails, deep sand trails, and mountain terrain.
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I have 37's and stock gearing and it is totally fine. I have considered regearing to 4.56 but at this point it is unnecessary. The diesel is just a torque monster, however if you live in serious mountain terrain for your regular commute, then you may benefit from regearing but again I still don't think it is necessary. So far mine suffers no problems traversing the smokies and surrounding mountains.
 

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I'd say it would absolutely perform differently with larger diameter tires than the OEM gearing. It's probably about weighing the change of performance vs what your on/offroad expectations are.
Personally, I don't like the effects on a non re-geared vehicle that larger tires introduce, regardless of engine.
That's just me...
 

BDinTX

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I think you'll get mixed answers here too but on mine with 315/70r17 in TX I hold 8th gear no problem.
 

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Ok I'll drive a while without regear and sew how I feel about it.
I think that is a good plan given the torque of the 3.0TD:

3.6L = 285 HP and 260 LB-FT
2.0T = 270 HP and 295 LB-FT
3.0TD = 260 HP and 442 LB-FT
392 = 470 HP and 470 LB-FT
 

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It doesn't absolutely "need" to be regeared. The problem with this type of question is there is so much subjectivity involved in it. I know people with 37's on the diesels with stock gears and they run just fine down the road. Not like they stall out going up a hill or have a ton of downshifting all the time.
There is a difference between the stock tires and 37's. The difference on the diesels is not as big as the difference is on the other engines, but it is different. Also, just because it is different doesn't mean it's "bad".
 

CarbonSteel

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It doesn't absolutely "need" to be regeared. The problem with this type of question is there is so much subjectivity involved in it. I know people with 37's on the diesels with stock gears and they run just fine down the road. Not like they stall out going up a hill or have a ton of downshifting all the time.
There is a difference between the stock tires and 37's. The difference on the diesels is not as big as the difference is on the other engines, but it is different. Also, just because it is different doesn't mean it's "bad".
Agree; you rarely hear a 3.0TD or 392 gal/guy complaining about performance after increasing tire sizes and not re-gearing and it is 100% because those engines produce enough torque to compensate for the loss of gearing where as the 3.6L is the worst of the lot.
 

grimmjeeper

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I'm really happy with 3.73s and 35x12.5R17 Duratracs.

Honestly, I think the diesel would have come with 3.45 gears if the front M210 axle had 3.45 gears available. But 3.73 is the tallest gear available. So that's what all the diesel Wranglers and Gladiators come with. Sport, Sahara, Rubicon, they all come with 3.73 gears.

I cruise down the freeway at 75 MPH right around 1,800 RPM. That's just about perfect for the diesel.

37's will drop you to around 1,700 RPM at 75. That's also right there in range of where it needs to be for good performance and fuel economy.

I don't plan on regearing my diesel. Even when I upgrade to 37s.
 
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JINO

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I'm really happy with 3.73s and 35x12.5R17 Duratracs.

Honestly, I think the diesel would have come with 3.45 gears if the front M210 axle had 3.45 gears available. But 3.73 is the tallest gear available. So that's what all the diesel Wranglers and Gladiators come with. Sport, Sahara, Rubicon, they all come with 3.73 gears.

I cruise down the freeway at 75 MPH right around 1,800 RPM. That's just about perfect for the diesel.

37's will drop you to around 1,700 RPM at 75. That's also right there in range of where it needs to be for good performance and fuel economy.

I don't plan on regearing my diesel. Even when I upgrade to 37s.
What size lift do you have?

I'm wondering if 2.5 is enough for 37s on the trails.
Might have to get 35s for now.
 

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grimmjeeper

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What size lift do you have?

I'm wondering if 2.5 is enough for 37s on the trails.
Might have to get 35s for now.
I have a 2.5" lift on a Rubicon. 37s will fit no problem. I just have to buy the tires. But the 35s are working just fine for now.
 
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JINO

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I have a 2.5" lift on a Rubicon. 37s will fit no problem. I just have to buy the tires. But the 35s are working just fine for now.
I know they will fit, but will they rub when articulating, full turn, high speed offroading?
 

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I know they will fit, but will they rub when articulating, full turn, high speed offroading?
I have bump stop extensions up front for clearance with my Artec truss. At full stuff I have more than an inch of clearance with 35s. Same setup as a buddy of mine who's already running 37s with no rubbing.

I might possibly need some bump stop extensions out back.
 

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I have been running 37's on my diesel for about two years without issue. I can cruise at interstate speeds (80 on I-70) in 8th gear, and the rock-climbing performance is amazing. I did add a Bank's Pedal Monster to make up for some of the acceleration lag, but I would have done that even with stock tires. My previous JK was a gasser with 37's and definitely needed re-gearing to 5.13. The diesel torque makes a world of difference.
My lift is a 3.5" Metalcloak GC and did get a bit of rubbing on the rear inner fenders at full flex until I re-shaped them, so you may have some issue with a 2.5" lift, but shouldn't be a problem if you're not rock crawling.
 
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JINO

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I have been running 37's on my diesel for about two years without issue. I can cruise at interstate speeds (80 on I-70) in 8th gear, and the rock-climbing performance is amazing. I did add a Bank's Pedal Monster to make up for some of the acceleration lag, but I would have done that even with stock tires. My previous JK was a gasser with 37's and definitely needed re-gearing to 5.13. The diesel torque makes a world of difference.
My lift is a 3.5" Metalcloak GC and did get a bit of rubbing on the rear inner fenders at full flex until I re-shaped them, so you may have some issue with a 2.5" lift, but shouldn't be a problem if you're not rock crawling.
What kind of extra parts did you need for 3.5"? Any steering components? I'm guessing don't driveshaft for sure.
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