transmission
Thread Starter
Pro
Joined: Aug 2007
Posts: 515
Likes: 9
From: St. Paul MN
transmission
I tried the formula for checking between close and wide ratio. 4th gear at 1000rpm-23mph 1st at 23 mph tack reads 3050 rpm. 411 rear gears. did I do it wrong or what tranny do I have? Bill58.
Race Director
Joined: Jan 2003
Posts: 17,696
Likes: 3,683
From: Central Arkansas
I doubt the old factory tachs are accurate enough to make this work well. Plus there are probably some other pitfalls I can't even think of. I guess in theory a wide ratio should take 2-1/2 times as much rpm in first gear to maintain the same speed in fourth gear. But your example shows it doesn't work exactly like this in the real world.
But, I would guess wide ratio. 50/50 chance at being right.
But, I would guess wide ratio. 50/50 chance at being right.
Burning Brakes
Joined: Sep 2004
Posts: 1,224
Likes: 49
From: Ventura Calif
Okay as an **** engineer here goes!
Running the numbers this is what I got:
(3050/4.11)(rev/min)(26"*pie/rev)(ft/12")=(23)(mi/hr)(hr/60min)(5280ft/mi)(1st Gear)
So:
1st Gear=(3050/4.11)(26*3.14/12)(60/23)(1/5280)
1st Gear =2.45 ~2.54
I think the math is correct but the equation might have a typo?
Running the numbers this is what I got:
(3050/4.11)(rev/min)(26"*pie/rev)(ft/12")=(23)(mi/hr)(hr/60min)(5280ft/mi)(1st Gear)
So:
1st Gear=(3050/4.11)(26*3.14/12)(60/23)(1/5280)
1st Gear =2.45 ~2.54
I think the math is correct but the equation might have a typo?
Last edited by JohnFromVentura; Aug 15, 2009 at 04:27 PM.
Melting Slicks
Joined: Jul 2004
Posts: 2,867
Likes: 195
From: Maryland
1000 RPM in 1st gear w. 4.11 & 26.5" diameter tire =
Wide box w. 2.54= 7.55 mph
Close Box w. 2.20= 8.719 mph
http://www.angelfire.com/fl/procrastination/rear.html
Wide box w. 2.54= 7.55 mph
Close Box w. 2.20= 8.719 mph
http://www.angelfire.com/fl/procrastination/rear.html
Last edited by Donald #31176; Aug 15, 2009 at 04:59 PM.
