Quote:
Originally Posted by 66 C10 383
I went to that site and it wouldn't let me open it due to not being a member.
We spoke of this previously in the past but I couldn't understand what everything meant ... numbers aren't really my forte' ... LoL
Can you help me understand it?
I plan on running a 28" tire (275/60/15) with an aftermarket T56, my tranny gear ratios are
(1st) 2.97
(2nd) 2.07
(3rd) 1.43
(4th) 1.00
(5th) 0.80
(6th) 0.62
I can't decide on using a 3.73, 4.11, or 4.56 rear gear. The cam I have (hyd roller) is a 230*/236* duration @ .050" lift. & has a usable range of 2000-6000 rpm. I was advised to have my highway rpm about 2100-2300 rpm. I will be running multi port fuel injection (TPI based setup). "Estimated" power will be in the 450-500 range on both horsepower and torque.
Most of my driving (to work ... ) is at 55-60 mph right now but if I move (very likely) my drive will be interstate driving at 70-75 mph.
Here's what I've come up with on my own but I'm not sure what to run rpm wise for the best mpg's.
3.73 x .62 = 2.31 final gear ratio
55 = 1525
60 = 1663
65 = 1802
70 = 1940
4.11 x .62 = 2.55 final gear ratio
55 = 1683
60 = 1836
65 = 1989
70 = 2142
4.56 x .62 = 2.83 final gear ratio
55 = 1868
60 = 2038
65 = 2207
70 = 2377
3.73's seem too low based on my rpm recommendations, 4.11's may even be a bit too low, the 4.56's seem about right ... based on mph's and rpm's ... ???
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I considered using a 1988 WC Camaro T5 with my 250 L6 but decided against it. Fifth gear is 0.63 and calculations suggested my engine would lug unless I was doing 70MPH. RPMs would be 1906 at 70 MPH and 29" tire + 3.73 rear. So basically I'd have to downshift to 4th gear below 65 MPH. I decided to use a T5 with a 0.73 5th gear.
What kills me is that GM put that same T5 with a 0.63 OD in a 1988 Camaro with a 26" tire and 3.08 rear. Yes! A 3.08 rear!!!!
That Camaro had a 305ci V8 and RPMs would be 1755 at 70 MPH with a 26" tire and 3.08 rear. The V8 had enough torque to make it work but 1755 RPMs is kinda low. It seems to me that the Camaro would have had the same problem and couldn't use that 0.63 gear below 65 MPH. That's a guess of course since I have never driven a 3rd generation Camaro with a T5 and 0.63 OD.
If my truck had a V8 then I would have used the T5 with the 0.63 OD.