Ive got a 2005 Silverado 5.3l with bolts ons and a cam. Ive got 323 GU5 and G80 in the rear right now. future mods are a stall and gears. going with a 2600 or 2800 stall.
I'm wanting to put a 3:73 or 3:90 gear in. which one would be best?
whats the best gear and install kit to get? a buddy said summit racing gears,usa standard ,or Yukon????
ive got a local guy to do the work for me. thanks for the help.

 

What kind of driving will you be doing?

Is this an everyday truck or just a weekend fun toy??

Do you care about fuel mileage at all?

If I wanted an all around gear without going crazy and still wanted to bum around at 70mph on the freeway at a decent rpm, I would install 3.90's with a tru-trac. Yukon gears I've heard and read are just fine.

I know people will comment and say go 4.10's or 4.56's yadda yadda but it comes down to what you want to use it for. And I know people say they get such and such mpg doing whatever speed but in the end they are never always driving like a grandma going to the grocery store.

 

Either ratio will be a night and day difference over the 3.42s you have now, difference between 3.73/3.90 is really not enough to really be noticable, id agree with FFDP on the 3.90, personally have had good luck with 3.73s but at times wanted a bit more!!!

 

As far as a gear manufacture I would go with Richmond or Yukon, I currently have a set of Usa gears in my truck and the backlash variance was way out of factory spec I went ahead and ran them and they are a little noisy

 

I think im going to go with the 390 gear. i just feel like it will be better suited for me. i drive my truck about twice a week. maybe 750 miles a month. so gas mileage is not a factor. i have a worktruck for work and daily driving.
it is the 10 bolt. GU5/G80 which i looked up and it says 3:23 gears.
so i think it would be a big difference.

when i order i order for the 8.6 right?

 

also do i use syntheic fluid for break in?

 

Use what eaton says to with the trutrac.... My eaton posi called for mineral oil... Which i need to look up exactly what again i need to chnge my fluid...

 

my parts guy ran my vin # and he said I had 2.73 gears. but my RPO code says GU5.
so I guess im going to pull the cover and do the math. lol

 

The RPO code is right.

They never offered that gear ratio in your truck. 3.23, 3.42, 3.73's and 4.10's are the standard gears.

 

kind of what I was thinking?? im just going to order a set of gears and a install kit. new seals and fresh fluid and go with it. lol