What's up! I'm trying to figure out what rear gear to run in my 12 bolt. I'm running a 383 and a 700r4 that has a 0.7 over drive. I want to be able to do smoky burn outs as well as take It on road trips down the high way....any help would be great! I was thinking Something along the lines of 308 maybe?? Posted using the Full Custom H.A.M.B. App!
I would think more of a 3.73 to 4.11 with the 700R4 since 4th gear is O.D. The 3.08 wouldn't pull a sick whore out of bed off the line.
Maybe something around 3.5 : 1 if you're interested in highway mileage (as indicated by the 700R4), otherwise, the 3.7 - 4.1's are probably going to be a bit quicker
Oh I'm running 20 inch rims and low pro tire, I didn't want to bring that up because people tend to get all judgey judgey on me. With the taller wheels, if I run he 373s I should be good down the highway right? Posted using the Full Custom H.A.M.B. App!
There are all sorts of gear calculators available online that take tire diameter into consideration, definitely a valuable tool that should help you out. My OT Nissan with O.D. has a 4.10 "rear" and is just about perfect around town and out on the road.
Your 'taller wheels' probably aren't really that much, if any, taller than what you'd otherwise run. The extra wheel diameter is usually offset by the much lower profile of the tire sidewall. You can either find the tire diameter and/or revolutions per mile in the tire specs from the manufacturer or simply measure the tire height as installed on your vehicle. Then take the diameter and factor it into the gear calculator mentioned above by 'bobss396' and play with alternate rear end ratios to find engine rpm at speed.
The 700 has a 3.06 1st gear, so the 1-2 shift will be quick with a low gear in the rear. This calculator allows the transmission ratio input as well as the rear axle. So you can figure the engine RPM in any gear. I pluged in 28 inch diameter tire, 3.73 rear and 3.06 1st gear. 30 mph is over 4000 rpm. http://www.crawlpedia.com/rpm_gear_calculator.htm
You should be good down the highway with 3.73-4.11:1. A stock GM gear for an OD depending on the application runs in the 3.73 to 4.10 range. By the way tire wheel combo is not important to us when you are asking about gears. Outside diameter is what is important. You need to know the outside diameter of the tire in order to figure final drive ratio. Ideally you want your engine to be within its operating range when you are cruising for best efficiency.
To reference todays production cars................GM typically uses a 3.42 rear ratio in most of the standard car combinations utilizing an OD trans which puts the highway RPM at 70 miles an hour in the neighborhood of 2000 RPM. They have maximized fuel economy for this set of data in order to keep their CAFE milage in a range that satisfies Government mandates. Frank
Great info, thanks everyone, by using that calculator it looks like I can go to a 4.80-1 an still curse down the highway at 2300 or so....that's great Posted using the Full Custom H.A.M.B. App!
I want to say my tire diameter Is 38 inches but I'm not sure, will have to check Posted using the Full Custom H.A.M.B. App!
Wow my mistake 26 inch tires so 373's it is... Thanks for the help!! Posted using the Full Custom H.A.M.B. App!
what do you have on this thing semi tires ??? a 20 with rubberbands is ussually about 32" and a 4:10 will be apx 2000 @60 you posted while I was writing . nevermind
I would say 373 would be the minimum. My pickup runs 456 gears but with overdrive (.67 on mine) it acts like a very low 3 series (3.05 is what it equates to). My Chevy has 3.08s with a standard 1:1 trans and I can't imagine wanting something taller than that. Gears can make a world of difference. Posted using my chicken and 2 cigs
It's a 700 r4 with an overdrive of .70, you think I should go higher then the 373's? Posted using the Full Custom H.A.M.B. App!
my truck has 30" tires on it and 4:10s with a .75 Od ratio ( 3:08 final) moves pretty good with a low Hp 454 in it . at 60 ( around 2000 rpm ) its not obnoxius cruising with dual 3" pipes if I kick it in the butt it will get going quick without downshifting , my buds 350 truck with 3.73 ( 2.79 final ) at cruise sounds and sounds and feels like its struggling @ 60 but his other truck with a 350 and 4:10s ( 3:08 ) sounds and pulls nice if you know your cam torque range try to set it so cruise at 60 is at the bottom portion of it .
Ok great, I will have to decide between the 373's and 410's. Kinda what everyone has been saying! Thanks guys! Posted using the Full Custom H.A.M.B. App!
4.10 x 0.70 = 2.87 3.73 x 0.70 = 2.61 When the torque converter locks up in 4th, you are going to be in engine lugging territory, unless you are really hauling ass. Posted using the Full Custom H.A.M.B. App!
Ok that's great info! Thanks so much, i will be workin the lock up with a switch. Thanks a ton! Posted using the Full Custom H.A.M.B. App!
And you think the 700r4 with the 410's will be good on the street as well? Even with the 3.06 first gear? Posted using the Full Custom H.A.M.B. App!
I was quite surprised to see that the stock gear for a 2014 Corvette is a 2.73:1. 3.42:1 is an option. Kinda explains the 30+ mpg highway mileage people say they get. I actually replaced the 2:73:1 gear in the wife's 50 Chevy with a 3.73:1 when I replaced the TH350 with a 200 R4.
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