I can not decide on what gear to run in my 99 silverado.

I have a 6.0 lq4 (stock) with long tube headers backed by a GTO t56. My tires are 29 inches tall. They are 275 45's on 20's. I do spray a 125 shot on the 6 liter.

What gear do you think would be good.

The 4.56 would give me the same run out as the stock wheel and tire combo with a 5 speed.

I do alot of highway driving with a weekend tow of a chevelle and or boat.

What would you do?

 

1 / 2/ 3/ 4/ 5/ R
3.49/ 2.16/ 1.40/ 1.00/ 0.73/ 3.55

that is the 5 speed (nv3500) gearing

1 / 2 / 3 / 4 / 5 / 6
2.97:1 / 2.07:1 /1.43:1 /1.00:1 / 0.84:1 /0.57:1

that is the M12 t56 gearing

To be honest, i would to the 4.30's if not the 4.56's That way you have the torque when pulling the trailer.

 

Right. That is about what I was thinking.

 

of the three I would go with 4.56s. If it were me though I'd go with 4.88s. With that overdrive you'll have the same gear ratio(actually slightly higher) as a 4l60e and 4.10s.

 

4.30 means 2130 in 6th going 75

4.56 means 2259 in 6th going 75

4.88 means 2417 in 6th going 75

SO i would go with 4.56's OR 4.88's cruising with a little more rpm is nicer when passing

 

i'd say 4.56s look about right.

 

definately 4.56's....

 

I vote 4.56's

 

in the GM Drivetrain section there is a sticky at the top with an MPG calculator in it. Use it to see where you're rpms will fall with each. This will let you have a good idea of your shift points and speed alike so you can go with the one you want.

Edit: nevermind, it's only the auto's listed in that.

 

4.56 sounds good to me. great for towing and getting out of the hole