I’ve decided to regear

[Robbyreneeward]

I want my diesel feeling like it actually has pep in its step since I went to 37s. So I’m regearing. Plus I want to be able to tow my camper with no issues. Who else has regeared, what ratio, what brand, what was cost, and what fuel mileage did you end up with after? Was running 28-29 stock, and I’m at 21.5-22 mpg now. I’m thinking fuel mileage should improve some, right? Thanks

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[MARSHMELLA]

I want my diesel feeling like it actually has pep in its step since I went to 37s. So I’m regearing. Plus I want to be able to tow my camper with no issues. Who else has regeared, what ratio, what brand, what was cost, and what fuel mileage did you end up with after? Was running 28-29 stock, and I’m at 21.5-22 mpg now. I’m thinking fuel mileage should improve some, right? Thanks

21-22? Ouch. My 2.0 gets 19-20 with 37s.

 

[BuffaloBill]

I just finished (about 3 hours ago actually) putting in 4.10s. So have no data on mpg change. I’m running 35s and occasionally tow a small camping trailer. I believe the 10% increase in rpm at 60mph will keep it in 8th gear a much greater percentage of time.

It certainly wasn’t bad with the 3.73, but drove it this winter with the stock 33s, and appreciated the difference in shifting behavior. It was sort of a bucket list thing for me. I turn 60 soon and had never regeared before. I like doing my own stuff and found it rewarding.

I bought used Dana/Spicer gears for $215**
Spicer master install kits about $230 and $245.

So that would have been about $700 with lube. However I found a problem with the used front gear set, where the pinion did not run concentrically. Backlash would vary .020” or more. So I bought a new Dana/Spicer front gear set ($289). My carrier does have about .003” runout, which I understand is at the spec limit. With the new gear set the backlash now varies only about .0025”.

And I wasn’t happy with the amount of carrier bearing preload I was able to obtain while trying to smack in a stack of thin shims. So was either going to make or buy a housing spreader. I wound up buying one for $97 that works great. I think to buy similar chunks of steel would have been more than half that amount.

I want to mention that the backlash of the factory front axle measured .019 to .022”. Way sloppy! The Jeep only has 5300 miles on it and I barely used the front drive. (Covid kept us home mostly).

For 37s, I bet 4.56 would the ticket.

 

[BuffaloBill]

21-22? Ouch. My 2.0 gets 19-20 with 37s.

That is very impressive for a gas engine. My wife’s JK 2 door Recon with 3.6 will not average 19 with stock tires.

My diesel JL with 35s has averaged about 26. On a highway trip, summer temps, 60-65mph, it will do a couple higher. If it’s like our Ram EcoDiesel, mpg will improve over the first 30-50k miles.

 

[MARSHMELLA]

That is very impressive for a gas engine. My wife’s JK 2 door Recon with 3.6 will not average 19 with stock tires.

My diesel JL with 35s has averaged about 26. On a highway trip, summer temps, 60-65mph, it will do a couple higher. If it’s like our Ram EcoDiesel, mpg will improve over the first 30-50k miles.

Sure, but with comparing a gas engine to a diesel, the diesel maintenance cost is about 3 times more, paying for DEF, paid on average $6,500 more in initial purchase price, everything is more expensive for a diesel including parts, oil, fuel, etc.
You would prob have to own that diesel for 250 years to make up for cost with the extra 8 mpg.

 

[BuffaloBill]

Sure, but with comparing a gas engine to a diesel, the diesel maintenance cost is about 3 times more, paying for DEF, paid on average $6,500 more in initial purchase price, everything is more expensive for a diesel including parts, oil, fuel, etc.
You would prob have to own that diesel for 250 years to make up for cost with the extra 8 mpg.

I don’t doubt your analysis, but like most diesel owners I didn’t buy it to save money.

 

[Compression-Ignition]

I want my diesel feeling like it actually has pep in its step since I went to 37s. So I’m regearing. Plus I want to be able to tow my camper with no issues. Who else has regeared, what ratio, what brand, what was cost, and what fuel mileage did you end up with after? Was running 28-29 stock, and I’m at 21.5-22 mpg now. I’m thinking fuel mileage should improve some, right? Thanks

Just put my 37/13.5r17 Toyo MT's back on after the winter. Mostly highway trip yesterday hand calculated out to 24.7 mpg. I don't think I ever saw more than 27-28 mpg on the stock 285's.

So I guess what I'm saying is who can tell, seeing as how everyone's vehicles, driving styles, and terrain they drive on are so different. Conventional wisdom says you should gain some mpg's back, but I wouldn't expect much.

Unlike many of the folks on the board here, I would also like to regear. I'm not one that thinks it drives the same on 37's. It still feels good and has plenty of power, but IMO it's nowhere near where it was. Mine ripped on the little 33's.

I'll go 4.56 whenever I get around to a gear swap.

 

[Compression-Ignition]

I don’t doubt your analysis, but like most diesel owners I didn’t buy it to save money.

LOL I do, 250 years? Guy has ecodiesel envy or is bored. My oil changes cost me maybe $75 with a quality synthetic and a Mopar filter including the stupid DEF.

How many 3.0L people go troll threads in other engine sections to tell them that their engine choice was ill advised? It's annoying, yet somewhat comical.

 

[BuffaloBill]

LOL I do, 250 years? Guy has ecodiesel envy or is bored. My oil changes cost me maybe $75 with a quality synthetic and a Mopar filter including the stupid DEF.

How many 3.0L people go troll threads in other engine sections to tell them that their engine choice was ill advised? It's annoying, yet somewhat comical.

Yeah I know. We hear it so often, sometimes it’s fun to just humor them. The initial cost comparisons often overlook the transmission part of the equation, and the fact that we don’t pay sticker price on the engine difference.

I truly am impressed with that reported 2.0 mileage, and didn’t mean to provoke with the “for a gas engine”. But I can see looking back, how that may have done so.

 

[rickinAZ]

I've noticed that the cost of DEF is sometimes trotted out when making an economic case against the diesel. [but...how do you place a financial value on torque?]

In the big scheme of things, it seems like the cost of DEF (best case $25 for 10K miles) is barely worth mentioning. Am I missing something?

 

[Plongson]

My oil changes cost me maybe $75 with a quality synthetic and a Mopar filter including the stupid DEF.

Sounds like there may NOT be MS-12991 in your crankcase...or am I misreading something here

 

[BDinTX]

Can’t forget diesels smell good.

 

[Compression-Ignition]

Sounds like there may NOT be MS-12991 in your crankcase...or am I misreading something here

You are absolutely correct. I am using an 5W-40 API SN low ash oil designed for diesels with exhaust after treatment.

Engine Oil With Filter 3.0L Turbo Diesel Engine (SAE 5W-40 Synthetic, API SN) 9 Quarts 8.5 Liters

^^^That's what I'm going to pay attention to. If I find a deal on this oil they talk about here, I'll run it;

We recommend you use 5W-40 synthetic engine oil such as Mopar or Pennzoil Platinum Euro that meets FCA Material Standard MS-12991 and the API SN engine oil category is required

But I'm not going to pay a ridiculous premium for it. I'll stick with an API SN oil that will work in all of my rigs. And as they update and change certifications and engine oil requirements I'll keep going for the oil that will work in the majority of my rigs.

And currently while I still have one more 5 gallon bucket left that is Mobil Delvac 1 ESP.

 

[Plongson]

Good for you...And...me too...if you get my drift.

I've researched the crap 'outta this whole Low Ash, MS-12991 thing and what I'm finding out is, the low ash is to save the DPF...and to some limited extent, sacrifice engine lubrication properties in the process (less additives).

If you think about it, it's a catch-22. Blow-by the rings means oil with ash pollutes the DPF that will not burn off (semi-metallic residue), damaging the DPF...OR Use a low ash oil that will reduces ash in the DPF but sacrifices wear additives, increasing wear in the engine, and more blow-by.

I don't want to hijack this thread anymore than I already have, but I've made a choice, and it appears you have too...

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