Should I Be Re-gearing?

BrettB91 · July 26, 2011

Just aquired a 2007 Sierra 1500 2wd Crew Cab. It has a 6" supsension lift with 33 inch tires.

My questions:

1. How can I tell if its already been re-geared? I dont think it has, but you never know.

2. Should I re-gear it? And what should I put in it?

3. What temp range should my trans be operating at?

Im a newbie to the whole lift scene, Thanks for any help.

Mckenzie · July 26, 2011

1. Find someone with a stock truck similar to yours and have them go say 60 mph and see what they are tack'ing and then if your rpm's are the same then it is stock

2. I wouldn't regear with 33's, but if you jumped to some 35's or a little bigger i would personally go with some 4.56 gears. Also i see it is a 2WD if you re geared it would be much cheaper than doing a 4x4

3. I don't know

SouthCo · July 27, 2011

33" tires shouldn't require a re-gear and the lift has no effect on gearing. I guess if the stock diameter is alot smaller than 33" than maybe. My 2010 seirra 4wd had a stock tire diameter of about 32". I don't know what diameter 2wd's had if different than the 4wds.

Trans temp when not towing will depend on how hot is outside. I'm not sure what the upper limit is. IE, when it's really cold it should be lower than hot summer months. I think mine is usually a little over 100 degrees while not towing but can check if you really need me to.

Stevens03 · July 27, 2011

Just aquired a 2007 Sierra 1500 2wd Crew Cab. It has a 6" supsension lift with 33 inch tires.

My questions:

1. How can I tell if its already been re-geared? I dont think it has, but you never know.

2. Should I re-gear it? And what should I put in it?

3. What temp range should my trans be operating at?

Im a newbie to the whole lift scene, Thanks for any help.

Since your trucks a 2wd, gearing could/maybe an issue depending on what you have stock. Lets take the "if" out of the equation and post what gears came stock. You can find that in the glove box by looking at the RPO codes. GU4 = 3.08, GU5 = 3.23, GU6 = 3.42, GT4 = 3.73, GT5 = 4.10

For 33" tires, 3.42's would be about as low as I would consider. For the most part, you really don't need to regear for 33" tires, but if you want near stock power, near stock mileage, and near stock "getty-up", then you need to match the gears to the tire size. IF you have 3.23's, then I'd certainly consider it.. and if you do, then I'd look at nothing less than 3.73's and maybe 4.10's

As far as tranny temp, normal operating temps would be in the low 100's. Even mid 150-160's would be a decent number for not towing anything. The next question you need answered is... what size tire came stock on your truck? Bumping to 33" tires will throw off your mileage, shift points and speedo depending on the differences in stock tire size to the 33" tires if your truck hasn't been programmed for them. Since your trucks a 2wd, most likely the tire size was a 245...The tire size would be (if they were) 30.5" over all and a 285 would be 32.8". This will throw off the speedo by approximately 5mph. Not that much but it's enough to throw your mileage and speedo off.

You can get a Custom tune or handheld tuner to adjust for the tire size and get you a little more power before considering a gear swap.

Post back what you find out and that will helps us help you

And Congrats on the new truck.

SouthCo · July 27, 2011

Handheld tuner or custom tune by Blackbear would be a good option as stevens11 suggested. Regrearing for less than 3" difference in diameter isn't necessary.

BrettB91 · July 27, 2011

Thanks guys. Ill look at the RPO codes tonight when I get home. I bought the truck from a Chevrolet dealership and it already had the lift on it. It has I believe 31 inch tires on it at the moment, 285/something something. Im asking about 33's becuase thats what I want to put on it in the very near future. Ill get back to you with answers to your questions. Thanks again!

BrettB91 · July 27, 2011

I forgot to add it has the 4.8L and i DONT plan on doing any offroading.

BrettB91 · July 28, 2011

Its got the 3.23's in it stock.

Stevens03 · July 28, 2011

With those gears, I'd consider a swap if your going to run 33" tires. It will bring the truck back to near stock with RPM's and power. Do you have to..... No.... but it would make the truck more enjoyable to drive and help the life of the transmission.

BrettB91 · July 29, 2011

thanks for the help man. Ballpark what can I be expecting for gears/labor on a 2wd truck?

Mckenzie · July 29, 2011

thanks for the help man. Ballpark what can I be expecting for gears/labor on a 2wd truck?

gears installed for a 4wd varies depending on location and shop doing it etc. 1200-1400 for a 4wd truck is fair, so i'd say maybe 600ish for a 2wd

Prokopchuk_9 · July 29, 2011

I forgot to add it has the 4.8L and i DONT plan on doing any offroading.

4:10's would do you fine....i wouldnt pay over 500 bucks to do a gear swap in a 2x4

Doug_Scott · July 29, 2011

You say you have the 4.8, that also means you have the 4 speed trans. Go with the 4.10 gears. The truck will drive so much better with them. With the 3.23 and the 4 speed, it is a combination that you need to plan for passing someone, or to merge onto the highway. Put the 4.10 in, and get a tune from BlackBear, and you will think it is a different truck. I have that combination in my 2010 Ext Cab.

Stevens03 · July 29, 2011

You say you have the 4.8, that also means you have the 4 speed trans. Go with the 4.10 gears. The truck will drive so much better with them. With the 3.23 and the 4 speed, it is a combination that you need to plan for passing someone, or to merge onto the highway. Put the 4.10 in, and get a tune from BlackBear, and you will think it is a different truck. I have that combination in my 2010 Ext Cab.

I agree