# Changing diff gear ratio?



## DallanC (Jan 13, 2009)

Thinking about swapping out my 3.42 gear set to a 4.10 for towing. Anyone done this? Its a older GMC 4x4 which means both ends need to be done. Should give me alot more "oomph" on the hills (that pull up Fairview canyon really brings that truck to its knees). According to the manual, 4.10's would also give me another 1000lbs of trailer towing capacity (7400 to 8400lbs).

Can't really find any info on costs or local shops that specialize in differential work. I probably should get the factory rear limited slip clutch pads replaced at the same time.


-DallanC


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## ZEKESMAN (Sep 14, 2007)

You will need to change the carrier to a 4 series carrier. so you will get new clutches with it. you will be around 2500.00 3000.00 for the job.


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## legacy (Sep 30, 2007)

Check out Advanced 4WD Systems. They're on 1102 S 200 W in Salt Lake. They used to do all sorts of custom 4 wheel drive work and we used to deal with them quite a bit. I think they mostly do conversions now but they may be able to help you out. You could call Six States as well.


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## 2full (Apr 8, 2010)

I switched my 3.23's to 4.10's years ago. 

But it was in my '68 Road Runner. 
I can only do about 105 now. 
But, can pretty much do it between stop lights.......;-)

Sorry, I couldn't resist. :mrgreen:


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## DallanC (Jan 13, 2009)

ZEKESMAN said:


> You will need to change the carrier to a 4 series carrier. so you will get new clutches with it. you will be around 2500.00 3000.00 for the job.


I'll gladly bow to those with more knowledge, I'd always heard you didnt need a new carrier unless you go lower than 4.10

I'll make a few calls and see what its going to run. If it really is in the 3k range I'll punt and just put up with people giving me the finger as I grind up the steep grades in 1st gear. 8)

-DallanC


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## weaversamuel76 (Feb 16, 2017)

I had six states in Orem put the gears in my Rubicon. I called around and wanted a quality shop to install around the electric lockers. Tons of people recommend them and they came in at a very competitive price. I'm very happy to also recommend thier work

Sent from my moto z3 using Tapatalk


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## weaversamuel76 (Feb 16, 2017)

I do think you'll be around 1800 but I'm not sure if you'll need a carrier or not.

Sent from my moto z3 using Tapatalk


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## taxidermist (Sep 11, 2007)

DallanC said:


> I'll gladly bow to those with more knowledge, I'd always heard you didnt need a new carrier unless you go lower than 4.10
> 
> I'll make a few calls and see what its going to run. If it really is in the 3k range I'll punt and just put up with people giving me the finger as I grind up the steep grades in 1st gear. 8)
> 
> -DallanC


Dallan, You still get to where you need to go, correct? I've got a 5.9 Cummins in front of a 6 speed manual. (Bone stock, no mods.) My Nephews have Duramax's (Chipped, big cans) and they ask me, "what took ya so long"? I tell them "I'm here aren't I"?

Guess what I'm getting at, is...&#8230;&#8230;&#8230; Who cares how long it takes to get to the top of the hill? As long as you make it. Keep flying the bird, kick back and enjoy the ride.8)


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## BPturkeys (Sep 13, 2007)

Just for fun...if your truck, as is, can pull Fairview Canyon(about 10 miles) at 30MPH, that's about 20 minutes drive time...if by some miracle those new gears double your speed to 60MPH, you're going to save 10 minutes.
How many minutes do you really expect them new gears to gain you? Oh, what about gas mileage and normal freeway driving?


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## DallanC (Jan 13, 2009)

All good points. Thanks for the feedback. I am more worried about stress on the transmission than milage or ETA issues. Our new trailer is much heavier than the old one.

Next truck (if I ever get to that point), will be a GMC 3/4 ton w/ the 6.0 engine. Those come with 4.10 gears. My current truck is a '05 and I haven't cracked 100k miles yet.


-DallanC


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## kdog (May 4, 2015)

I am not sure on current prices but i habve regared two trucks so far, one chevy and one ford, Ford went from 3.55 to 4.10s when i moved to 35 inch tires. that cost me 700 bucks or so but i did much of the work myself. the second was a 3/4 ton chevy that I went from 4.10 to 4.56 when running 38s. that one was done at advanced 4wd, i think it costs me 1200 or so. both were 18 ans then 10 years ago so labor may have gone up. I would think adanced 4wd would be a good option, they regear all the time. my first one was done by six states ( just the front removable diff ) and they did a great job. but they changed ownership a number of years ago also.


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## shaner (Nov 30, 2007)

Try Paul's 4x4 in Sandy.


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## CAExpat (Oct 27, 2013)

Automatic or manual? What are your RPMs while pulling the hill?


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## DallanC (Jan 13, 2009)

CAExpat said:


> Automatic or manual? What are your RPMs while pulling the hill?


Automatic. On a steep climb like fairview canyon 4500'ish RPM in 1st gear. 24-26mph. Ditto that same steep pull near fish lake. Got the GMC 5.3ltr engine

-DallanC


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## Raptorman (Aug 18, 2009)

6 States is a good option, they do good solid work.


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## CAExpat (Oct 27, 2013)

It's not going to be an easy answer Dallan. After running some quick numbers and making general assumptions as to powertrain (5.3L/4L60E), you're in a tough spot. Swapping gears may bump you out of first gear (even if you lock out) purely because of RPMs. Your power curve, assuming the 5.3, peaks at approximately 4100. With the 4.10s in there it should compensate and allow for slightly lower RPMs under load but it won't negate your torque to the wheels is still what it is, mild as a half-ton gasser. 

Gears may help, but it's going to realistically be around $6-700 per axle. You'll have to decide if it's worth the cost to offset the few times a year you pull. I've done gear swaps on the last three trucks i've owned, always looking for that perfect ratio. Your truck will be MUCH happier, but will you?

How heavy are you towing?


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## legacy (Sep 30, 2007)

Here's the deal, quit screwing around! The new GM trucks come out in 2020...I'm thinking you need a new truck. Don't buy the new Silverado (Ugly beyond belief) and don't buy a 2020 (First year). Do what I want to do...buy a 2021 GMC Sierra 2500HD with the new 6.6L GASSER in it. :smile: I know the current gassers with the 6.0L have 4.10's. I'm assuming the 2020 gassers with have 4.10's as well? 
BTW, I'll never buy a diesel. I currently have a 2012 Sierra 2500HD with the 6.0L gasser and it has 3.73's. It pulls my 10,000 lb toy hauler as good as I could ever expect. BUT, 4.10's sure would make it a little nicer for sure!
(Ford is also going to put a 7.3L gasser in their new trucks)


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## DallanC (Jan 13, 2009)

CAExpat said:


> It's not going to be an easy answer Dallan. After running some quick numbers and making general assumptions as to powertrain (5.3L/4L60E), you're in a tough spot. Swapping gears may bump you out of first gear (even if you lock out) purely because of RPMs. Your power curve, assuming the 5.3, peaks at approximately 4100. With the 4.10s in there it should compensate and allow for slightly lower RPMs under load but it won't negate your torque to the wheels is still what it is, mild as a half-ton gasser.
> 
> Gears may help, but it's going to realistically be around $6-700 per axle. You'll have to decide if it's worth the cost to offset the few times a year you pull. I've done gear swaps on the last three trucks i've owned, always looking for that perfect ratio. Your truck will be MUCH happier, but will you?


Hmmm good points.



> How heavy are you towing?


Last trailer fully loaded (we'd actually double trailer, with a snowmobile trailer +2 atvs on that) was around 7500lbs. New trailer w/ 3 atvs is between 7680 with no fluids (water / gas), or up to 8800 fully loaded. So between 200lbs more on the low end or as much as 1800lbs over the old trailer (full load of water and fuel is 1132lbs). New one has a max GVWR of 9900 but no way we'll ever get that much weight on board.

New one has a 100gal water tank (vs old one at 30gal). Most places we go have water sources so we can fill up when we arrive. I doubt we'll ever travel very far with it full.

So yea, probably around 8000lbs ... around half a ton more than the last one.

-DallanC


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## CAExpat (Oct 27, 2013)

> So yea, probably around 8000lbs ... around half a ton more than the last one.


I'm sure you already have, but call around and talk to the professionals that deal with it all the time. I have nothing but anecdotal evidence, I've always had diesels so my re-gear experiences were always because I was stupid and putting bigger tires on. My next truck will be left alone! New trucks are insanely expensive, beyond belief honestly. The used market is fair, but you have to go back MANY years and sort through tired and abused trucks. There are some really good ones out there around the $15000 mark that are pre-emissions and stock but they sell quickly. The most economical choice would be to keep what you have and re-gear. When you hit the grade, just get in the right lane and throw the flashers on


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## DallanC (Jan 13, 2009)

Current plan is to load'er up the first reasonably warm weekend we get and make a run to the dunes. Give'er a test on that pull up out of Eureka. Then I'll know better if I need to get serious about regearing.

My truck is a 2005. Sounds like from some research they changed something after 2007, and the pre-2007 trucks of that era had a better power curve... so post-2007 alot of guys need to regear, but previous to 2007 (I dont know how early) the trucks had more "oomph". I know my brother in law with a 2010 GMC 1/2 ton had frequent overheating issues pulling his trailer (same model as we just got) and had to regear... but my truck with a little less load never has come close to over heating when pulling the same hills).

Maybe I'm overthinking this. The obvious solution is to buy a winning lotto ticket, then go pick up a new Denali Duramax. 


-DallanC


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## DallanC (Jan 13, 2009)

With the nice weather today I went out and attempted resetting the equalizer hitch for the new trailer. Its 3" too low from the last trailer. Well... come to find out my shank isnt tall enough so I'll have to order up one of those... then I noticed I cant move the snapup brackets far enough back to center on the trunion bars as the battery holder / generator mount bracket is in the way. Soooo I'll have to work that out with the MFG and see what they recommend.

P I T A :x

But... as we were that far into it, and it was still a nice day, we test fit / loaded the 3 atvs into it then loaded it up with a full 100gal of water then went for a joy ride up and over Suncrest drive and back. Not a super steep hill but its a pretty good climb with 2 lanes so we wouldnt hold up traffic. The trunk took it in stride, about the same speeds as the last trailer... 1st gear running 30-35mph @ 3500-3700rpm (coulda gone a little faster but no real reason to do so... engine sounds good at that rpm). Good enough I guess without jumping to a new truck with a 6ltr.

So I'll run it as is for the moment, just get a good set of sunglasses so I dont make eye contact with the guys / girls flipping us off when they pass is on steep grades 8)


-DallanC


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## stimmie78 (Dec 8, 2007)

My 2005 Crew Cab 1/2T Chevy has 3.42 gears. Great on the highway when empty (25mpg). But she struggles going from home in Roosevelt to Uinta Canyon pulling a 1965 12ft camp trailer. Granted my truck is at 235k . My brother had an 06 with 4.10 gears. He got low 20s on the highway on a good day. But he sure could out pull my truck. I would rather do 3.73s just so I get a little umph but don't kill my mileage.


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## DallanC (Jan 13, 2009)

stimmie78 said:


> My 2005 Crew Cab 1/2T Chevy has 3.42 gears. Great on the highway when empty (25mpg). But she struggles going from home in Roosevelt to Uinta Canyon pulling a 1965 12ft camp trailer. Granted my truck is at 235k . My brother had an 06 with 4.10 gears. He got low 20s on the highway on a good day. But he sure could out pull my truck. I would rather do 3.73s just so I get a little umph but don't kill my mileage.


What engine you have in that? I have the 5.3 and the best highway mileage I've ever gotten was 19.5, set on cruse control over long highway trips. IMO I'm not sure its worth the expense to go from 3.42 to 3.73, I dont think the "oomph" will increase as much as you would think it would (according to gear ratio charts I've read).

Currently I'm still planning on limping through on the current truck for a while yet, maybe when the next recession hits and people start turning over their existing trucks like happened in '09, I'll pick up a 3/4ton with the 6.0ltr for a steal of a deal.

-DallanC


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## stimmie78 (Dec 8, 2007)

I have the 5.3L in it. Crew cab with a camper shell on it. Easy mid 20s going from Roosevelt to the Wasatch Front. I try to keep it around the speed limit as much as I can. Lately I haven't taken trips out that way so I really could be getting less now. I also run synthetic blend engine oil and keep up on the maintenance.


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