Truck Gear Ratio's For Towing

[ChiliPepperGarage]

My truck is a 2008 Silverado 2500 Duramax (LMM) that has been tuned and DPF deleted. It has a ton of power and I really love the truck. It is on 34" tall tires, also with 3.73's. It has the 6 speed Allison trans with manual shift mode. I pretty much always have it in manual mode and down shift to 5 or 4 on steep grades even when not towing, usually only going to 5th.. This keeps the pyrometer below 1200. When towing heavy I do the same but might have to slow down to 55 or 60 on really big long grades which is really no big deal.

I got thinking though, should I change my gears? I think that I'm working it harder with the 3.73s on 34's and a gear change would be easier on the engine (for longevity as I want to keep this truck forever). A 4.10 or 4.30 would be more efficient and easier on the engine. The question is, which one to go with. Would there be that much difference between the current 3.73 and a 4.10 or should I just go to the 4.30s? I might go to a slightly larger tire (maybe 35") as some point so I'm leaning to the 4.30s.

A lot of you might say to just leave it as is and it does seem to be perfectly capable as it is but as I said, I love this truck and want to keep it until I can no longer drive so I don't mind spending money on it. I've done a lot of mods to it already so I don't mind a few more.

Over the winter I'm building a custom flat bed with side boxes and a new front bumper. Here's a photo just because.

 

[outboard_256]

Do some calcs on each of the gear sets. It's all mechanical so you can calculate the gear ratio, tire size, etc to get your RPM's at different speeds. But you know your truck so you know what RPM range it does best at. If you tell us you want to cruise 65 mph at 1500 rpm on 34" tires we can tell you what gear ratio is close to that.

 

[CLdrinker]

I re geared my 2018 6.4 Hemi from 4:10-4:88. It gained performance but it was not worth 3k. Obviously I didn’t have EGT issues to deal with but just trying to help you set expectations.

If I were you I would either live with what you got. Drop tire size or sell the truck and buy something else. In that order. I wouldn’t even consider regearing.

 

[ChiliPepperGarage]

I re geared my 2018 6.4 Hemi from 4:10-4:88. It gained performance but it was not worth 3k. Obviously I didn’t have EGT issues to deal with but just trying to help you set expectations.

If I were you I would either live with what you got. Drop tire size or sell the truck and buy something else. In that order. I wouldn’t even consider regearing.

I don't want to drop tire size (any smaller than what I have now will look goofy) and I don't want to sell the truck. Replacing it would be ridiculously expensive. $3K to regear is waaaaaaayyyyy cheaper than a new truck.

 

[oldman]

With the 6 speed your better to just gear down than do a swap, running the numbers do they make a gear to get you back to stock?

Tire Size Change Gear Ratio Calculator | Interco Tire

Calculate the proper gear ratio for a tire size change.

www.intercotire.com

Run it through this

 

[sintax]

gonna be honest here... something seems up.

While I dont use the manual mode much, if ever, I can def tow going up the Cajon pass in 6th, where it will drop to 5th at the steeper grade. Unloaded it'll stay in 6th the whole time, assuming I keep the speed at 6th gear speed. Whats this hill i guess?

I'm wondering if you maybe have some boost leak?

Mine is a 07 LBZ Classic on 35" Toyo muds

 

[oldman]

My 06 on a 33's with 3.73 Tuned pulls my 13k double car hauler fine if I pull it down a gear or two, Running a banks tuner intercooler intake setup, and I tow in level 3 or 4

Water temps 210*
Exhaust 1150 or less.

 

[ChrisV]

I recently just did this.

Originally was 3.73 on 35s with my duramax. Changed it to 4.10 and it’s perfect. I wanted to go with 4.30 but I’m glad I didn’t. I drive the truck a lot to havasu so didn’t want it to be ringed out.


Took it to J&s gears in Huntington Beach. Got it done in one day at $1900.

I highly recommend it. Taking off red light doesn’t seem to struggle anymore.

 

[rivermobster]

My truck is a 2008 Silverado 2500 Duramax (LMM) that has been tuned and DPF deleted. It has a ton of power and I really love the truck. It is on 34" tall tires, also with 3.73's. It has the 6 speed Allison trans with manual shift mode. I pretty much always have it in manual mode and down shift to 5 or 4 on steep grades even when not towing, usually only going to 5th.. This keeps the pyrometer below 1200. When towing heavy I do the same but might have to slow down to 55 or 60 on really big long grades which is really no big deal.

I got thinking though, should I change my gears? I think that I'm working it harder with the 3.73s on 34's and a gear change would be easier on the engine (for longevity as I want to keep this truck forever). A 4.10 or 4.30 would be more efficient and easier on the engine. The question is, which one to go with. Would there be that much difference between the current 3.73 and a 4.10 or should I just go to the 4.30s? I might go to a slightly larger tire (maybe 35") as some point so I'm leaning to the 4.30s.

A lot of you might say to just leave it as is and it does seem to be perfectly capable as it is but as I said, I love this truck and want to keep it until I can no longer drive so I don't mind spending money on it. I've done a lot of mods to it already so I don't mind a few more.

Over the winter I'm building a custom flat bed with side boxes and a new front bumper. Here's a photo just because.

View attachment 1426854

WTF are you towing???

 

[rivermobster]

This keeps the pyrometer below 1200.

Does this seem high to anyone else?

I know it Greatly depends where the sensor is though.

Mines in the down pipe, and I never let it get over 8-900.

 

[oldman]

Does this seem high to anyone else?

I know it Greatly depends where the sensor is though.

Mines in the down pipe, and I never let it get over 8-900.

1200 on the exhaust manifold is not high, measuring right at the exhaust port.

 

[oldman]

My old 7.3 never saw over 900 but that was down the line, My LBZ routinely sees 1100+

 

[braindead]

Does this seem high to anyone else?

I know it Greatly depends where the sensor is though.

Mines in the down pipe, and I never let it get over 8-900.

Yep, it shouldn’t get that hot unloaded.
too much fuel?

 

[braindead]

My old 7.3 never saw over 900 but that was down the line, My LBZ routinely sees 1100+

Is that empty or loaded?

 

[Good Stuff]

I don't want to drop tire size (any smaller than what I have now will look goofy) and I don't want to sell the truck. Replacing it would be ridiculously expensive. $3K to regear is waaaaaaayyyyy cheaper than a new truck.

Have you looked at an over/underdrive? Might be a better option than losing economy at cruising speeds when you aren’t towing.

 

[oldman]

Loaded pulling the grade out of Needles 13k trailer weight (3500 lb trailer and two 5k toyotas), on tuner level 3 or 4 I can pull 60mph holding 1100 or less. 4th or 5th gear. Water pushes up to 216.
1100 does not worry me at all.
Pyro is drilled direct into the exhaust manifold. Pass side rear cyl. Directly in line with the port.

 

[rivermobster]

Yep, it shouldn’t get that hot unloaded.
too much fuel?

Loaded to the gills and NOT on the tow safe tune!

 

[CLdrinker]

I don't want to drop tire size (any smaller than what I have now will look goofy) and I don't want to sell the truck. Replacing it would be ridiculously expensive. $3K to regear is waaaaaaayyyyy cheaper than a new truck.

I did the re gear and then bought a new truck.

If I can’t tell the difference on a gasser by much a truck that has way more torque will feel less difference which will lead to minor’s reduction in egt.

I stand by my statement. Ditch the lift and tires or live with it.

 

[CLdrinker]

I recently just did this.

Originally was 3.73 on 35s with my duramax. Changed it to 4.10 and it’s perfect. I wanted to go with 4.30 but I’m glad I didn’t. I drive the truck a lot to havasu so didn’t want it to be ringed out.


Took it to J&s gears in Huntington Beach. Got it done in one day at $1900.

I highly recommend it. Taking off red light doesn’t seem to struggle anymore.

$1900 is what I was being quoted per axle.

That’s suspiciously cheap.

 

[ChiliPepperGarage]

WTF are you towing???

I have a 14K equipment trailer and I haul tractors and other heavy stuff occasionally. I'm also looking at getting another bigger boat like maybe Cafe Racer and they're pretty hefty.

It's not that my truck can't do it in its current configuration but that I'd just like to do it a little easier on the truck. Or I guess I could just slow down a little.

 

[OC Daytona]

I recently just did this.

Originally was 3.73 on 35s with my duramax. Changed it to 4.10 and it’s perfect. I wanted to go with 4.30 but I’m glad I didn’t. I drive the truck a lot to havasu so didn’t want it to be ringed out.


Took it to J&s gears in Huntington Beach. Got it done in one day at $1900.

I highly recommend it. Taking off red light doesn’t seem to struggle anymore.

J&S Gear does good work....is the Aussie owner still there?

They did my 67 Camaro 12 bolt posi and ring & pinion setup a few years back. Good price and great work

 

[ChiliPepperGarage]

Does this seem high to anyone else?

I know it Greatly depends where the sensor is though.

Mines in the down pipe, and I never let it get over 8-900.

I'm not sure where my sensor is located. I'll have to check it out. My local diesel shop that has done the work on it said the gauge could be wonky too as it shouldn't be that high. I guess I should probably just bring it in to him and see what he thinks rather than guessing or going by all our resident "experts" here. No offence to the experts.

 

[mash on it]

Does this seem high to anyone else?

I know it Greatly depends where the sensor is though.

Mines in the down pipe, and I never let it get over 8-900.

Mine are pre turbo, and I'll run it to 1150°. But mine are mechanical pyro's. Aluminum conveniently melts at 1221°. How accurate is your pyrometer? I don't know either.

Dan'l

 

[2Driver]

With the 6 speed your better to just gear down than do a swap, running the numbers do they make a gear to get you back to stock?

Tire Size Change Gear Ratio Calculator | Interco Tire

Calculate the proper gear ratio for a tire size change.

www.intercotire.com

Run it through this

I couldnt get it to work.

 

[rivermobster]

I have a 14K equipment trailer and I haul tractors and other heavy stuff occasionally. I'm also looking at getting another bigger boat like maybe Cafe Racer and they're pretty hefty.

It's not that my truck can't do it in its current configuration but that I'd just like to do it a little easier on the truck. Or I guess I could just slow down a little.

Sounds hefty for sure.

Have you ever had the fully loaded rig, with the fully loaded trailer, on a scale?

Do you know what the GCVWR for that truck is?

 

[ChrisV]

J&S Gear does good work....is the Aussie owner still there?

They did my 67 Camaro 12 bolt posi and ring & pinion setup a few years back. Good price and great work

Yes. Kind of an asshole but he’s legit.

 

[Bpracing1127]

I’m just gonna say it. Buy a ford or dodge if you want to tow

Honestly a re gear isn’t worth it. You are damn close to stock tire size anyway. Jump to a 37” like the rest of us

 

[ChiliPepperGarage]

I’m just gonna say it. Buy a ford or dodge if you want to tow

Honestly a re gear isn’t worth it. You are damn close to stock tire size anyway. Jump to a 37” like the rest of us

I'll probably just leave it as is until I get another boat. Then I'll see how it does. I have zero need for 37" tires. Not buying another truck. Besides, just got back from LOTO towing my buddy's 34' Hallett with his 7.3 Ford. My truck will out tow the shit out of his!

 

[wallnutz]

Look into a gearvendors. I put one on my old gasser MH, god what a difference.

 

[oldman]

I couldnt get it to work.

are the tire metric, you need to convert to inches.

 

[oldman]

I couldnt get it to work.

 

[Mototrig]

$1900 is what I was being quoted per axle.

That’s suspiciously cheap.

I went to J&S 8 years ago for a single Dana 60 regear and was only charged $1100. A lot has changed since then

 

[evantwheeler]

$1900 is what I was being quoted per axle.

That’s suspiciously cheap.

2WD....

 

[eand28]

My truck is a 2008 Silverado 2500 Duramax (LMM) that has been tuned and DPF deleted. It has a ton of power and I really love the truck. It is on 34" tall tires, also with 3.73's. It has the 6 speed Allison trans with manual shift mode. I pretty much always have it in manual mode and down shift to 5 or 4 on steep grades even when not towing, usually only going to 5th.. This keeps the pyrometer below 1200. When towing heavy I do the same but might have to slow down to 55 or 60 on really big long grades which is really no big deal.

I got thinking though, should I change my gears? I think that I'm working it harder with the 3.73s on 34's and a gear change would be easier on the engine (for longevity as I want to keep this truck forever). A 4.10 or 4.30 would be more efficient and easier on the engine. The question is, which one to go with. Would there be that much difference between the current 3.73 and a 4.10 or should I just go to the 4.30s? I might go to a slightly larger tire (maybe 35") as some point so I'm leaning to the 4.30s.

A lot of you might say to just leave it as is and it does seem to be perfectly capable as it is but as I said, I love this truck and want to keep it until I can no longer drive so I don't mind spending money on it. I've done a lot of mods to it already so I don't mind a few more.

Over the winter I'm building a custom flat bed with side boxes and a new front bumper. Here's a photo just because.

View attachment 1426854

If you’re towing, lock out 6th gear and run it in 5th. They like the rpm when towing

 

[Cooter01]

Going from 3.73 to 4.10 to me is not worth the money, spend the money on a better converter, valve body, upgraded clutch packs first. Will chance the way power is delivered and be lower temps.

 

[oldman]

Mine are pre turbo, and I'll run it to 1150°. But mine are mechanical pyro's. Aluminum conveniently melts at 1221°. How accurate is your pyrometer? I don't know either.

Dan'l

I've been over 1250 for a breath or two, And it still runs, I was told 1450 is death.

 

[oldman]

If you’re towing, lock out 6th gear and run it in 5th. They like the rpm when towing

Especially on 35's 4th gear may even put it closer to where stock would be,

 

[BajaMike]

I remember when Chevy first introduced the Duramax, they said the 4:10 put too much torque to the drive wheels, hence 3:73. I’d leave it alone, sounds to me you have the perfect setup.

 

[Eliminator21vdrive]

Look at percentage of change in tire dia and go to the higher numeric # because you are adding frontal area .

MPH x 336 x gear ratio divide x dire dia = rpm

Yes I did this for a living

 

[2Driver]

are the tire metric, you need to convert to inches.

I tried 33 to 37 and a 4:30 ratio and it came back Nan

 

[oldman]

I tried 33 to 37 and a 4:30 ratio and it came back Nan

Is this what your trying to do???

 

[2Driver]

View attachment 1427329


Is this what your trying to do???

Yes thank you I couldn't get it to work. Ipad maybe?

So Ill have a 3:84 when Im done. Maybe Ill get better mileage but doubt it

 

[oldman]

Mine are pre turbo, and I'll run it to 1150°. But mine are mechanical pyro's. Aluminum conveniently melts at 1221°. How accurate is your pyrometer? I don't know either.

Dan'l

Sensor location, and I have seen 1250*at that location. Not towing, and not sustained.