I have a 2005 GMC Sierra 1500 SLE, 2WD, 5.3L (LM7), 3 speed auto w/OD, standard cab, short bed with towing option. I'm not sure what running gear it has. I know there would be options but what would be most likely? 3.42?

 

check glove box sticker for gear code.

 

Look up the RPO codes in your glove box, that will tell you what you have.

Could be 3.23, 3.42 or 3.73's. Side note, the 4L60e means 4 speed auto that has overdrive (4th is overdrive).

https://www.performancetrucks.net/fo...-codes-502933/

 

Thanks guys. Is it easy to swap out gears to convert to 4.10 Posi or better just to buy a used one?

 

Pay a reputable person to do it. Buy a Detroit Trutrac for the diff and whatever brand Ring and pinion you preffer. You'll be better off having fresh bearings when its done anyway, these axles eat them.

 

The cam I'll be installing is the 54-600-11 Comp Cams Thumpr. Is a gas guzzling 4.10 gear really necessary? This truck won't be making any trips through the 1/4 mile and I won't be getting on it hard with the stock transmission. More for improved performance and sound.

 

Guys who know better than me, chime in but, that looks like a lot of cam. What have you already done to the truck to support it? who specked that for it?
I'd definitely go to 4.10s. What stall are you running? it looks like its gonna want one.

 

410s really arent that bad of a gear depending on your tire size

 

I agree. I have to be a little easier on the highway but can't imagine driving it with less gear now. Just like a higher stall (have a Yank TT3000 waiting in the garage) LS engines like to rev.

 

There are a lot of Sierra 1500's with stock 5.3L motors running this same cam. They recommend running blue ls6/ls9 valve springs and suggest a 2000 stall but not absolutely necessary. Everything else is stock.