Regearing Truck after lift kit and 35's tire

LongrangeLauber · July 13, 2016

With all that would it not just be easier to like replace the axels / diffs? That sounds like a crazy amount of work.

It's not really that bad. No matter what, they have to be set for the proper tolerances anyways. It's called meshing the gears (proper contact of the teeth). The carrier holds the ring and then mounts into the axle housing. The pinion slides in from the front and the axles pop in from the sides and stay in with a C-clip inside the carrier.

In theory, yes it'd be much easier to just swap the entire housing but if you could find a fully built housing with aftermarket gears (I believe factory only goes to 3.73 or 4.10 in the housings, so if you wanted steeper gears they would have to be aftermarket) it would cost a loy, lot more considering how new these 12 bolt housings are

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Silvern Sentry · July 13, 2016

3.73 is max I believe. At least when I checked builds it was. Of course HD's would be a much bigger diff allowing for a bigger gear with more teeth, do I have that correct? SO would that not also mean squeezing in something like 4.10 would yield very thin gear teeth? And being so thin they would be more fragile?

Edited July 13, 2016 by Silvern Sentry

LongrangeLauber · July 13, 2016

3.73 is max I believe. At least when I checked builds it was. Of course HD's would be a much bigger diff allowing for a bigger gear with more teeth, do I have that correct? SO would that not also mean squeezing in something like 4.10 would yield very thin gear teeth? And being so thin they would be more fragile?

Not necessarily true, but correct to an extent. Because there are fewer teeth to each the ring and pinion they can build them fatter per say. But you are right, that's why the diesels have the huge 11.5" rear end. It is said that the more teeth that make contact at one time (lower numbered gears) are to be stronger because the torque is distributed across more surface area

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Silvern Sentry · July 13, 2016

Not necessarily true, but correct to an extent. Because there are fewer teeth to each the ring and pinion they can build them fatter per say. But you are right, that's why the diesels have the huge 11.5" rear end. It is said that the more teeth that make contact at one time (lower numbered gears) are to be stronger because the torque is distributed across more surface area

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That makes sense to me, thanks for clarifying. Always like to learn.

arcasey · July 14, 2016

The trailer weighs around 7500 pounds loaded. Usually tow it on the weekends when camping.

Honestly, I would go with the 4.10 gears since the majority of your time will be without the trailer and you're not quite at max capacity. That should yield you better mileage when not towing. Plus, a 4.10 ratio is actually over what the equivalent to the stock setup would be so your truck should pull that trailer just fine. With all that said, how does the truck tow the trailer right now?

I ain't so sure about the lift increasing towing capacity. The only way to increase the amount of weight the truck can pull is in the drive line. Raising the body/suspension of the truck shouldn't affect the amount of weight you can tow although this drastically affects the stability of the vehicle which can negatively affect the amount that you can tow "safely".

LongrangeLauber · July 14, 2016

Going up usually means bigger tires, and that WILL decrease your tow capacity bc the final gear ratio will be less than that of a stock truck. Lifting it will not increase your tow capacity, idk where anyone heard that. It will actually decrease, even if you change gears and have the same final gear ratio as a stock truck bc you have a huge wall of air resistance plus you have to turn the heavier, wider tires as well.

My stock 6 speed 5.3L 3.42 gears high country tows way better than my 02 silverado 4 speed 5.3L lifted 10 inches on 37's and 4.88 gears (which was the equivalent of a stock truck with 3.73's). I realize not apples to apples, due to the transmissions, but the trucks, stock to stock, were rated to tow within 1000 pounds of each other. I've had the same load hooked to each and at only 3k pounds or so I couldn't tell it was behind my new truck where as my lifted truck it was struggling lol.

Also, remember that the higher you go up the more you are risking yourself to trailer sway, especially if you don't have trailer brakes. Which on a camper that size I would hope it has brakes haha

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Josh121 · July 15, 2016

Going up usually means bigger tires, and that WILL decrease your tow capacity bc the final gear ratio will be less than that of a stock truck. Lifting it will not increase your tow capacity, idk where anyone heard that. It will actually decrease, even if you change gears and have the same final gear ratio as a stock truck bc you have a huge wall of air resistance plus you have to turn the heavier, wider tires as well.

My stock 6 speed 5.3L 3.42 gears high country tows way better than my 02 silverado 4 speed 5.3L lifted 10 inches on 37's and 4.88 gears (which was the equivalent of a stock truck with 3.73's). I realize not apples to apples, due to the transmissions, but the trucks, stock to stock, were rated to tow within 1000 pounds of each other. I've had the same load hooked to each and at only 3k pounds or so I couldn't tell it was behind my new truck where as my lifted truck it was struggling lol.

Also, remember that the higher you go up the more you are risking yourself to trailer sway, especially if you don't have trailer brakes. Which on a camper that size I would hope it has brakes haha

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Yeah the trailer has trailer brakes. How much more sway do you think i would get with the lifted truck?

Honestly, I would go with the 4.10 gears since the majority of your time will be without the trailer and you're not quite at max capacity. That should yield you better mileage when not towing. Plus, a 4.10 ratio is actually over what the equivalent to the stock setup would be so your truck should pull that trailer just fine. With all that said, how does the truck tow the trailer right now?

I ain't so sure about the lift increasing towing capacity. The only way to increase the amount of weight the truck can pull is in the drive line. Raising the body/suspension of the truck shouldn't affect the amount of weight you can tow although this drastically affects the stability of the vehicle which can negatively affect the amount that you can tow "safely".

Right now the truck pulls the trailer just fine, i did a big trip with a few friends from Canada through Idaho, Utah, Vegas, Southern California. Drove over 8000 kms. Had no problems, drove in all different weather conditions and terrain.

LongrangeLauber · July 15, 2016

Yeah the trailer has trailer brakes. How much more sway do you think i would get with the lifted truck?

At the time my old truck was lifted 6 inches on 35's, no trailer brake controller, so no trailer brakes. Had a 3k pound car on a 2k pound trailer. Was going down a gradual grade about 75 and increasing. Hit the brakes to slow us down and the trailer started swaying so bad I was ending up in the other lane at times, honestly thought I was gonna lose it. If the trailer has brakes you should be fine bc the trailer brakes will pull the trailer back whereas the truck brakes provide stopping power from the front so you still have the weight of the trailer trying to swing on the 2 5/16" ball

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SarahsGMC · July 15, 2016

I have a 7" lift 35s and regeared from 3.42 to 4.10. I also have a mild built trans and tunes. Truck will roast 35s if I want to and tows just fine.

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arcasey · July 15, 2016

Yeah the trailer has trailer brakes. How much more sway do you think i would get with the lifted truck?

Right now the truck pulls the trailer just fine, i did a big trip with a few friends from Canada through Idaho, Utah, Vegas, Southern California. Drove over 8000 kms. Had no problems, drove in all different weather conditions and terrain.

I would say then if you were happy with the way it towed before then 4.10 gears should be just fine for you.

Josh121 · July 15, 2016

I have a 7" lift 35s and regeared from 3.42 to 4.10. I also have a mild built trans and tunes. Truck will roast 35s if I want to and tows just fine.

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Awesome I think I'll just go with the 4.10 gears then. How much did it cost for the parts and labour?

schubee · July 15, 2016

I just switched to 4.10's and love them. I'm running 35s and I tow a couple times a month (toy hauler / enclosed 16').

My RPM is right around 2k at 75mph which I think is perfect. I'm also getting better gas mileage after the gear swap running the 35s versus the 3.42s

I paid just under $2k for both front and rear here in CA which is very reasonable. The shop recommended OEM (US made) gears versus any of the import sets out there (Yukon, G2, etc...).

I have my 3.42s for sale in the classifieds section if anyone is interested: http://www.gm-trucks.com/forums/topic/189664-fs-2015-gmc-sierra-4x4-oem-342-ring-and-pinion/

Cheers,

John

BBChevy2017 · April 7, 2020

On 7/11/2016 at 7:33 PM, Vic15 said:

I haven't felt the need to re-gear. There's plenty of power even with the 6.2, 3.23 & 8 speed. My brother is plenty happy with his as well, 5.3, 3.42 & 6 speed. We both have a 6 inch lift on 35s. Try it before you spend the money to re-gear.

Vic15,

I have been researching online regarding re-gearing and ran across your post.

I just bough a 2017 Silverado 1/2 ton crew cab standard bed Z71 with the 6.2 liter motor, 8 speed transmission and 3.23 gear ratio.

I am going to lift my truck and having a hard time debating between a 4” or 6” BDS. I love the look of 6”, but afraid with my high factory gears, it would require re-gearing. If I go with a 4”, I will run 275/70/18 (33.6”) and if I get a 6” I would go 285/70/18 (34.1”) or 295/70/18 (34.5”). The tire I will be going with is Toyo Open Country has MY. My factory stock tire is 275/55/20 which is (31.9”).

I noticed you have the same motor, trans and gearing as me. On your 6” lift, what size of tire are you running. How is the performance and gas mileage for you currently. Do you plan in re-gearing?

Most shops I talk to say to re-gear, but I don’t want to do lower gears and regret it with my truck sucking gas. So far people are saying 3.73 for the 33” tires and 4.30 for 34”/35” tires.

Look forward to hearing back from you and getting your feedback as you have the setup currently. Thanks man.

Vic15 · April 7, 2020

I'm running Nitto Ridge Grapplers, 35x12.5 20 at generally 48 psi. I see no need to re-gear. Plenty of power. Decent gas mileage for driving pretty fast most of the time, you know, 420hp . 15-16 mpg combined, but mostly short around town driving. I see 18 on the highway if I can stay below 80 mph.

Edited April 7, 2020 by Vic15
Mph instead of mpg