Regearing duramax

[Rbcconst]

Anyone regear there 2500? Thought about doing mine. With the lift and 35’s the mpg sucks ass.


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[sczagurs]

What gearing does it currently have and do you plan on ever going bigger?

 

[Rbcconst]

What gearing does it currently have and do you plan on ever going bigger?

Id like to say it has 373’s. Not sure id go any bigger. 37’s look good but no real reason for it.


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[sczagurs]

How bad is the mileage? I spoke With a local gear shop and he suggested 410/430 depending on what you are towing. I assume you have 4wd diesel?

 

[Rbcconst]

How bad is the mileage? I spoke With a local gear shop and he suggested 410/430 depending on what you are towing. I assume you have 4wd diesel?

Yeah 4x4 diesel. Mixed driving probably 13 and highway 14-15.


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[sczagurs]

A shop out in Irwindale came highly recommended to me and estimate was right around 1800. Would put everything as close back to stock but I’m curious when towing on the freeway if you need to run it with o/d locked out.

 

[NicPaus]

Is it programmed for 35s? You could go 410 but don't think its worth it for 35s. I ran 40s for years and planned to regear it until I towed my toyhauler. With truck programmed for the tires it had plenty of power and never geared it left it 373s. With 35s I was getting 16.5 on highway.

 

[sczagurs]

Another option would be a “legal tune”

 

[Rbcconst]

A shop out in Irwindale came highly recommended to me and estimate was right around 1800. Would put everything as close back to stock but I’m curious when towing on the freeway if you need to run it with o/d locked out.

I always tow with od locked out.

What did the shop say you would gain?


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[Rbcconst]

Is it programmed for 35s? You could go 410 but don't think its worth it for 35s. I ran 40s for years and planned to regear it until I towed my toyhauler. With truck programmed for the tires it had plenty of power and never geared it left it 373s. With 35s I was getting 16.5 on highway.

Yes it is programed. Id have to go 70mph to get 16.5 highway.


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[D19]

I had a Duramax on 37s / 373s. Gearing it won’t help with mpg. Your best option is to tune it. I averaged about 15-16 after tuning and deleting it.

 

[sczagurs]

He said about 2 maybe 3 mph better. If you plan on keeping the truck for a long time might be worth it. Stock it didn’t do much better.

 

[Rbcconst]

I had a Duramax on 37s / 373s. Gearing it won’t help with mpg. Your best option is to tune it. I averaged about 15-16 after tuning and deleting it.

What tuner? I have the banks and dont see that.


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[NicPaus]

Yes it is programed. Id have to go 70mph to get 16.5 highway.


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At 70 it shifted into 6th gear and was best MPG.

 

[Rbcconst]

He said about 2 maybe 3 mph better. If you plan on keeping the truck for a long time might be worth it. Stock it didn’t do much better.

Probably should have done it when i lifted it originally. As much as i drive 3mpg would pay for the gears in the first year.


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[D19]

What tuner? I have the banks and dont see that.


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Qaudzilla Stealth II. Always ran it on the 70hp tune. No dpf or cat.

 

[LargeOrangeFont]

Probably should have done it when i lifted it originally. As much as i drive 3mpg would pay for the gears in the first year.


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Really? 3 MPG would save you $1800 a year?

If you got ~90 miles more per tank, you’d save like 22 dollars per tank. Saving $1800 would take 82 tanks of fuel. That is close to 30k miles.

 

[Rbcconst]

Really? 3 MPG would save you $1800 a year?

If you got ~90 miles more per tank, you’d save like 22 dollars per tank. Saving $1800 would take 82 tanks of fuel. That is close to 30k miles.

Yeah I run about 40k miles a year.


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[LargeOrangeFont]

Yeah I run about 40k miles a year.


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How many miles are on the truck?

 

[Rbcconst]

How many miles are on the truck?

140K. Ive contemplated selling it. I dont need to drive a 3/4 ton truck 75% of the time. But that would mean i need to run 2 trucks. Thought about a new 1/2 ton and buying an older 3/4 ton flatbed.


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[LargeOrangeFont]

140K. Ive contemplated selling it. I dont need to drive a 3/4 ton truck 75% of the time. But that would mean i need to run 2 trucks. Thought about a new 1/2 ton and buying an older 3/4 ton flatbed.


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Was gonna say.. you might be money ahead with another truck. At 140k that still sounds like it has some value in it if sold.

The boring answer is just put it back to stock and get close to 20 MPG.

Get a year or two old half ton to drive around in comfort 75% of the time.

 

[DoughBallin14]

3.73 is factory gearing and i have had 37s and 35s and with the right tuning or even the speedo calibration set right i have always gotten 16 city and up to 24 freeway. Although its been deleted for about 240k miles now. Never even considered a regear even with towing 40’ toy haulers. Save the money and make sure the speedo is set right for the tires and shift points and torque curve will be spot on again

 

[Wizard29]

I just have to ask...if you guys are so concerned with MPG, why not just leave the truck alone? Do you really use it for offroading to the point a lift and bigger tires are really needed?

I've left my duramax alone and am glad I did. Does everything I need it to do and gets maximum MPG doing it...

 

[UHHH SUCKA]

Qaudzilla Stealth II. Always ran it on the 70hp tune. No dpf or cat.

This is the way to go! I've had an '05 2500 short bed on 40's, an '07 2500 long bed on 40's and two '08 3500 Duallys, both on 37's. Always ran stock gears in all trucks with minor tunes and Cat/DPF deletes. Still averaged about 13 MPG's pulling my loaded 15,000lb. 40' 5th wheel with the '07 & '08's. Average about 18 MPG's on the highway w/o towing. Always been told changing gears won't help too much considering the cost and stock gears are pretty bullet proof in GM trucks. Good luck!

 

[Rbcconst]

3.73 is factory gearing and i have had 37s and 35s and with the right tuning or even the speedo calibration set right i have always gotten 16 city and up to 24 freeway. Although its been deleted for about 240k miles now. Never even considered a regear even with towing 40’ toy haulers. Save the money and make sure the speedo is set right for the tires and shift points and torque curve will be spot on again

The delete makes a big difference. Id do it if it was reg in AZ. In ca its not worth the possibilities of smog changes and possible fines.


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[Rbcconst]

This is the way to go! I've had an '05 2500 short bed on 40's, an '07 2500 long bed on 40's and two '08 3500 Duallys, both on 37's. Always ran stock gears in all trucks with minor tunes and Cat/DPF deletes. Still averaged about 13 MPG's pulling my loaded 15,000lb. 40' 5th wheel with the '07 & '08's. Average about 18 MPG's on the highway w/o towing. Always been told changing gears won't help too much considering the cost and stock gears are pretty bullet proof in GM trucks. Good luck!

Maybe its all the new deff stuff. I dont see that or anywhere close. I have the banks tuner and in there tow mode you dont see any mpg increase. In there fuel economy mode the truck goes into regen mode to much.


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[Runs2rch]

PPE hands down for canned Duramax tuning.

Run the 100/160 tune. Trans will live with a nice mpg bump.

 

[NicPaus]

My new loaded 4x4 little half ton and reg cab long bed gas 3/4 ton cost the same as 1 new diesel truck. Half ton can tow 9200lbs 3/4 14,500. A third diesel did not pencil out. The 1500 gets killer freeway MPG.

 

[FROGMAN524]

Got Yukon 4.11s in my truck for the 35.4s. Back to stock RPM, mileage sucks but I never drive less than 80 and the truck has just about every part but new internals. Gears make a big difference in driveability, spool up and passing power even with twin turbos, 100% injectors, 12mm CP3 pump, lift pump and some big tunes.

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[DRYHEAT]

I just have to ask...if you guys are so concerned with MPG, why not just leave the truck alone? Do you really use it for offroading to the point a lift and bigger tires are really needed?

I've left my duramax alone and am glad I did. Does everything I need it to do and gets maximum MPG doing it...

Are you new or something?

 

[D19]

I just have to ask...if you guys are so concerned with MPG, why not just leave the truck alone? Do you really use it for offroading to the point a lift and bigger tires are really needed?

I've left my duramax alone and am glad I did. Does everything I need it to do and gets maximum MPG doing it...

Ya I’d off-road it 20 Ft off Gecko Rd onto the pad. Lol

I wasn’t concerned about mpgs, I wanted more power.

 

[Cdog]

I dont see how it's worth it on 35's. I'm pulling 2000-2200 rpm at 75-85 mph. Getting 17-18 mpg on the dash. I'm on 33's. You should technically get better milage on 35's since the peak tq is around 1800-2000 rpm.

I think you need a better tune.

 

[NicPaus]

Ya I’d off-road it 20 Ft off Gecko Rd onto the pad. Lol

I wasn’t concerned about mpgs, I wanted more power.

On Thanksgiving weekend would do the same. I could show up Wednesday night and get a killer spot. The rest of the crew had to show up 2 weeks before to get Pad 3. It definitely had its benefits of being lifted. I damn near have my tailgate under water to launch my boat at Echo with no lift.

 

[Bigbore500r]

 

[D19]

On Thanksgiving weekend would do the same. I could show up Wednesday night and get a killer spot. The rest of the crew had to show up 2 weeks before to get Pad 3. It definitely had its benefits of being lifted. I damn near have my tailgate under water to launch my boat at Echo with no lift.

I also liked being able to see over all the cars in traffic and pick good lines.

 

[Wizard29]

Are you new or something?

Ha, not new but getting old maybe. It's just funny how the realization of the true cost of being a cool guy sets in on the cool guys after a while.

Even though the most offroading my truck will ever see is the gravel in the gutter at the mall parking lot, I lifted it, put really big tires on it, and now my mileage sucks!

Well...no shit. Did ya think it would get better?

 

[Rbcconst]

View attachment 803228

I like that. Thank you.


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[Rbcconst]

I dont see how it's worth it on 35's. I'm pulling 2000-2200 rpm at 75-85 mph. Getting 17-18 mpg on the dash. I'm on 33's. You should technically get better milage on 35's since the peak tq is around 1800-2000 rpm.

I think you need a better tune.

What year truck is that on? Id love to get that and maybe need a new tune. Mine is a 16, one of my guys has a 17 and gets around 16 but he drives like shit.


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[BajaMike]

I just have to ask...if you guys are so concerned with MPG, why not just leave the truck alone? Do you really use it for offroading to the point a lift and bigger tires are really needed?

I've left my duramax alone and am glad I did. Does everything I need it to do and gets maximum MPG doing it...

Best advice I’ve seen on RiverDaves in a while!

 

[DRYHEAT]

Ha, not new but getting old maybe. It's just funny how the realization of the true cost of being a cool guy sets in on the cool guys after a while.

Even though the most offroading my truck will ever see is the gravel in the gutter at the mall parking lot, I lifted it, put really big tires on it, and now my mileage sucks!

Well...no shit. Did ya think it would get better?

Yeah, I was just funning with you. I have to laugh my neighbor has a 6.0 Ford with 37 inch tires in about an 8 inch lift, he gets kind of pissed that he doesn’t get much better mileage than my old 85 454 cc Dooley. But he does have a shit ton more power.

 

[NicPaus]

When I had my lifted Duramax I would leave it hooked up to the Toyhauler all winter. Glamis every other weekend. Before the lift I had backed my toyhauler in to the sand and kept my front 2 tires on the pavement. I got stuck had to get pulled out. With lift and bigger tires I could pull off into the sand and get a spot even on the holiday weekends. And it got double the fuel mileage towing 3 times the load than my previous stock FI 454 dually lifted on 40s.

 

[Cdog]

What year truck is that on? Id love to get that and maybe need a new tune. Mine is a 16, one of my guys has a 17 and gets around 16 but he drives like shit.


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I have a 06 LBZ. Its basically the same engine but you have the DEF cycle that kills the milage during re gens. I run a old Edge tune that's a race programmer that shuts off the egr.

Talk to my boy Daniel Lee at PPE. He will be able to set you up with a tune that should get your truck right.

 

[Rbcconst]

I have a 06 LBZ. Its basically the same engine but you have the DEF cycle that kills the milage during re gens. I run a old Edge tune that's a race programmer that shuts off the egr.

Talk to my boy Daniel Lee at PPE. He will be able to set you up with a tune that should get your truck right.

I bet the DEF is most of my issue and why all the guys with the 06-07 models get great mileage.

For some reason i think my in town mileage is what kills my over all. And any stretch of highway that has a lot of incline.


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[Cdog]

I bet the DEF is most of my issue and why all the guys with the 06-07 models get great mileage.

For some reason i think my in town mileage is what kills my over all. And any stretch of highway that has a lot of incline.


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Yeah but the right tune should help. Call Daniel, he will know what to do. Tell him Corey from AZ sent you.

 

[Rbcconst]

Yeah but the right tune should help. Call Daniel, he will know what to do. Tell him Corey from AZ sent you.

Thank you. I will call him and see what he thinks.


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[Bowtiepower00]

3.73 and 35’s is not unreasonable, your money would be better spent on a quality dune and possibly delete. If you were wanting to run 37’s I would agree on the regear.

 

[sczagurs]

Are you a 100% sure the truck came with 3:73 gears? I think that ratio was only available on the gas engine 2500.

 

[Rbcconst]

Are you a 100% sure the truck came with 3:73 gears? I think that ratio was only available on the gas engine 2500.

Other way around. The 4:10 was only available with the 6.0 gaser! Not sure what year that started but I know for sure the 16 dmax only came with the 3:73


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[Bowtiepower00]

Are you a 100% sure the truck came with 3:73 gears? I think that ratio was only available on the gas engine 2500.

All diesel chevies are 3.73. Gassers were 3.73 or 4.10.

 

[Bigbore500r]

My 2013 Dmax gained a solid 3-5 MPG per tank (depending on my cruise speed) when my DEF / DPF had that tragic accident and fell off