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#1 |
Registered User
Join Date: Aug 2006
Location: LaSalle Mi
Posts: 504
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Rear gear ratio question
I am considering a different gear ratio for my truck. Currently has 3.73:1. Playing with an online calculator, I could go down to 4.56:1 and still be able to get to 135 mph in 3rd. My fastest trap was about 118 mph, and I can only add so much more power with my current setup, that I do not see me hitting 135 mph in the quarter.
So is there a reason not to go with the lower gear ratio? It should make the truck faster, correct? The only down side I can think of is traction,but their are ways to overcome that. |
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#2 |
Senior Member
![]() Join Date: Dec 2009
Location: TN.
Posts: 8,075
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Re: Rear gear ratio question
You could go with a 5:14.
The math is there. ![]()
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________________________________________________________________________________________ ____________________________________________ 84 Chevy K-20 63 Impala (my high school car) http://67-72chevytrucks.com/vboard/s...Crew Cab Build |
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#3 |
Senior Member
![]() Join Date: Mar 2008
Location: tyler texas
Posts: 1,537
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Re: Rear gear ratio question
A lot of things come into play on choosing the right gear. Tire size, transmission gear ratios, tq converter slip, max rpm etc.
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NHRA Super Street 469C It only runs 10.90 at 156 mph |
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#4 | |
Registered User
Join Date: Aug 2006
Location: LaSalle Mi
Posts: 504
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Re: Rear gear ratio question
I am aiming to up my mph some. That would put me at "redline" at the stripe with the convertor locked
Quote:
Trans ratio would be 1:1 I have a lockup convertor, so slip could be zero Max RPM is 7000 With those numbers it comes out to about 135 mph at 7000 rpm. |
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#5 |
Yeah baby!
Join Date: Feb 2001
Location: United Kingdom
Posts: 436
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Re: Rear gear ratio question
I calculated that changing from 3.7 to 4.1 would give me a tenth or two. It made no difference at all, although it became more consistent. These trucks hit aero problems at the top end.
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11.37 @116 |
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#6 |
Senior Member
![]() Join Date: Mar 2008
Location: tyler texas
Posts: 1,537
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Re: Rear gear ratio question
I think 4.56 will work. Especially with the lockup converter.
__________________
NHRA Super Street 469C It only runs 10.90 at 156 mph |
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#7 |
Registered User
Join Date: Dec 2012
Location: Temple City
Posts: 3,587
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Re: Rear gear ratio question
I run 4.88's daily with a Detroit locker in a 32" tire. Or a 285/65R17.
To me the biggest hold back of the combo is the TH700R4. If I had the money's to do over. A 4L80e would of been a more optimal choice. Even though my engine is just a highly tuned gen2 LT1 it is a absolute blast to drive. I do miss the way bigger cam I had before. If I replace the cam it will be with a smog legal performance cam to get a little more out of her, but keep my drivibility. My gear ratio, and Detroit effectively stop me from burning out. So that would be good for the 1/8 mile. The same gear ratio hurts my top end charges a bit because my engine is more torquey vs 4500 rpm plus performance. So with out mentioning engine specs or build list, and tire size. Even 4.11's or 4.33's maybe a better split the difference overall combo. |
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#8 |
Registered User
Join Date: Aug 2006
Location: LaSalle Mi
Posts: 504
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Re: Rear gear ratio question
I ordered the 4.56s and a detroit locker last week. Can't wait till the Spring to try them out.
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#9 |
Registered User
Join Date: Aug 2006
Location: LaSalle Mi
Posts: 504
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Re: Rear gear ratio question
![]() That is the theme song of the truck now. ![]() |
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