Ring and pinion choice for 4.8 LS

[72LSLB]

My 72 currently has a spool rear end and I'm going to have it changed over to most likely a posi or maybe an open. I was wondering what gear would be best for my setup. Will be a once in a while cruiser to work and to shows.

The engine is a 2007 4.8 LS with a 4l60e trans, controlled by a Mega Squirts MS3 Pro controller. The rear tires will be 28.66 in diameter. I'm not sure what the overdrive ratio is for a 4l60e trans.

Can anyone help me with the formula for figuring this out? I was thinking on going with a 3:55 or 3:73.

Thanks

[72LSLB]

Oh and the motor is a stock 4.8, the trans has a stock stall. Might possibly update that in the near future. May also add a single turbo set up.

[Custom 68]

Im not sure you can get a 3.55 rear gear for these but I note recently looked. For your combo I would go with the 3.73 that is what I had for years. The over drive in the 4l60 is .70.

[Custom 68]

I have tried to include a zipped file that has a spreadsheet inside it. This can be used to calculate the speeds and other info based off tire size, gear ratio and transmission.
Good luck
Dave

[72LSLB]

Originally Posted by Custom 68

I have tried to include a zipped file that has a spreadsheet inside it. This can be used to calculate the speeds and other info based off tire size, gear ratio and transmission.
Good luck
Dave

Thanks Dave!

[69gmcc10]

I would second the 3.73. I have driven many ls powered trucks with various displacements with 3.55, 3.73, and 4.10. The 3.73 seems to be the perfect harmony of cruising speed and excellent response.

[sprint_9]

3.42 or 3.73 are your options in that range, there is no 3.55. I just bought a ring and pinion for mine. You can get a 3.55 for car 12 bolts, but not the truck 12 bolt, this is atleast what I found.

I went with a 3.73 for more get up and go over the 3.42. I guess in my case the small amount of mileage gain wasnt worth it for me on a fun weekend cruiser, I want this thing to move quickly.

[Clyde65]

I have the 4.8/4l60e with 28+" tires, went with the 3.73 rear gears and still get 19-20mpg on the highway.

[72MARIO]

I have 3:42 with 28" 6.0/4L80 It needs 3:73 for my driving preference

[Kainedogg]

I am against the 3.73 in light of your single turbo goals. 3.42 will still be peppy behind the 4l60e. Stock truck ecm really comes to life with a basic tune. Tuned by Frost did my C10 a few years back. Made quite the difference, despite the 2.73's and long 1st gear in the 4l80e. I am going twin turbo on mine so a 3.4# something gear is what I plan to install after.

[sangell]

Originally Posted by Kainedogg

I am against the 3.73 in light of your single turbo goals. 3.42 will still be peppy behind the 4l60e. Stock truck ecm really comes to life with a basic tune. Tuned by Frost did my C10 a few years back. Made quite the difference, despite the 2.73's and long 1st gear in the 4l80e. I am going twin turbo on mine so a 3.4# something gear is what I plan to install after.

I was going to say the same thing. If you are going to turbo it go with 3.42s, if it will say NA then 3.73s.

[1970 CST Short Wide]

I'm running a 5.7 with a T56 six speed, Ford 9' with 350 gears. At 80 mph I'm only tacking 1740 rpm. I'm thinking at least 3;73 range if not 4;11 in the near future.
1st - 4th pull very strong 5 & 6 Freeway only. A LOT of FUN to drive

[Daaaanz67]

I have 4.8 with 4l60e in my 69. Currently 3.08 gears with 255/60/15. Freeway driving is great. In the foot hills where I drive is kinda lugs around. I find myself having to push more on the throttle to get out of over drive or I just down shift out of overdrive. I noticed after switching from billet wheels to the truck steel rallies this was more prominent. I do miss my billet wheels just base on the rolling mass difference.

[Custom 68]

Originally Posted by 1970 CST Short Wide

I'm running a 5.7 with a T56 six speed, Ford 9' with 350 gears. At 80 mph I'm only tacking 1740 rpm. I'm thinking at least 3;73 range if not 4;11 in the near future.
1st - 4th pull very strong 5 & 6 Freeway only. A LOT of FUN to drive

I was running 3.73 in my 12 bolt when I originally was running my 4l60 and it was a great setup. I went to the T56 and felt the need for the 4.11 because of the double overdrive. It was a blast to drive with that gearing so I would recommend it.
Now I am at a 4l80 and not liking the 4.11 so much lol and may eventually swap back to the 3.73. I would like your 3.50 but in my 12 bolt it is not much option...