Gearing Question

[08SierraCC]

Ok I have an 08 5.3 with 3.42 gears. Im running 33" tires now. I want to change my rear end gears but Im torn between 3.73 and 4.10s. Anyone have any Idea what my rpms would be at 80mph with these. Do they make 3.96 gears? for our trucks?

[brad519]

I've got a 08 5.3 that had 3.73's stock I used to run 275/70/18's which is 33" tire and it was a tad bit sluggish nothing big but I could tell a difference with the 33's so I would say get the 4.10's the 3.73 wouldn't be worth the cost IMO.

Don't remember what my rpm's were at 80 though but I did get it up to 120 with spare pedal with the 3.73's

[Matt_]

4.10s without a doubt. They're the ideal gear for the 5.3L, 4spd, 33s combo for all around driveability. If you did any towing or wanted to target performance, id even do 4.30s.

 

3.73 would be a waste of money IMO if you currently have 3.42s.

[nickvrebel]

for a 33" tire you will want 4.10's with the 4 speed.

 

I went from 3.42 to 3.73 on my 03 2wd with stock sized tires, it helped a tad, but I did a lot of highway driving and had smaller tires than you. The main reason I swapped them in the first place was to add a limited slip, figured while I was in there getting rid of one wheel peel I'd get a little more gearing for when I added a load.

[chevyman09]

dont mean to thread jack but i also have a 5.3 cc z71 gmc and have the 3.42 and do alot of highway, i have 285/70/17 and tow every now and then, would it be worth upgrading to 4.10s and would any mileage be lost on the highway. i mainly drive 65mph

[Matt_]

dont mean to thread jack but i also have a 5.3 cc z71 gmc and have the 3.42 and do alot of highway, i have 285/70/17 and tow every now and then, would it be worth upgrading to 4.10s and would any mileage be lost on the highway. i mainly drive 65mph

 

depends on the trans. in 08 the 5.3L came with the 4spd. Is yours an 09 like your username implies? if it is, i think you have the 6spd.... in which case no, you dont want to regear; 3.42s are perfectly fine

[Ryan00TJ]

Ok I have an 08 5.3 with 3.42 gears. Im running 33" tires now. I want to change my rear end gears but Im torn between 3.73 and 4.10s. Anyone have any Idea what my rpms would be at 80mph with these. Do they make 3.96 gears? for our trucks?

 

 

4.10's for sure with the 4L60E as others have stated. Don't forget the front diff if it's 4WD. I'm not sure if they make 3.90's for the GM 8.5" 10 bolt? I know they do for the 7.5" 10 bolt in the 4th gen Fbody's.

[nickvrebel]

'm not sure if they make 3.90's for the GM 8.5" 10 bolt? I know they do for the 7.5" 10 bolt in the 4th gen Fbody's.

they make them for the rear, but I have never seen any for the front in a 3.90

[zibzer]

with 33" Diameter tires you will want the 4.10... TRUST ME

 

3.42 would be ~1350RPM @60MPH in 4th OD*

 

3.73 would be ~1500RPM @60MPH in 4th OD*

 

4.10 would be ~1650RPM @60MPH in 4th OD*

 

your 3.42 is lugging as far as im concerned right now. The 3.73 would be adequate.. However, the 4.10 will wake her up and make you smile

 

... *these are all with respect to the 33" wheels and the gearing of a 4l60E transmission

 

EDIT: dont worry about gas mileage.. you will see very little change going from the 3.42 in your setup to a 4.10... you likely will have a drop.. but it'll likely be in the =<1MPG range... hardly worth worrying about

[chevyman09]

thanks for the replys but i dont have a 09 its an 05 gmc, whats the best place to get a set of gears front and rear with master kit.

[hockeypro1411]

thanks for the replys but i dont have a 09 its an 05 gmc, whats the best place to get a set of gears front and rear with master kit.

 

http://www.ronsmachiningservice.net/servlet/StoreFront

[Mckenzie]

my 01 Z71 has got the 3.73's with 285 75 17 MT's, and it can still get up and go when you mash it, but it took a hit in the MPG's...i'd go with the 4.10's

[brainpause]

Your engine revs at 80 mph will be about 20% higher with 4.10's than your current revs at 80 mph with 3.42's.

[fraiolib]

thanks for the replys but i dont have a 09 its an 05 gmc, whats the best place to get a set of gears front and rear with master kit.

 

the tires you have now are only an inch taller than stock. you only tow every once in a while. realisticly its not worth the change.