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#1
10-09-2008, 08:06 PM
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Need rear gear input?
As my ex-super stock Trans Am nears completion, I need some input on the rear gear. It has a Dana 60 with 4.88 gear, Turbo 400 (trans brake)with a 2.75 first gear and an aluminum rod 474 with Butler ported (315 cfm)E heads, Victor, 1050, 660 lift roller. Vendors only list 4.88,4.56,4.10 gears for a Dana. I think 4.88 is too much and ideally feel a 4.30 would be perfect with 33x16x15 Eagle slicks. Does anyone know what the 4.88 gear would equal out to with 33 inch tires? I will be running it 1/4 mile...
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1969 GTO hardtop(warwick blue) 1969 GTO Judge Ram Air III 1970 GTO Ram Air III 1972 GTO 455(Feb.2006 HPP shootout) 1971 Trans Am (Super Stock) 2006 GTO ( Cyclone Grey) 1973 Firebird Formula 1979 Trans Am 4 speed 1967 Olds 442- Pinks All Out -Zmax 2010 |
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#2
10-09-2008, 09:53 PM
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That thing is Soooo bad lookin
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69 Grand Prix 428 H.O. loaded "J" 11.51 @ 116 |
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#3
10-09-2008, 11:59 PM
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We run a 486 in my sons 96 bird. We used a 14x32 tire on it for the pinks all out in St Louis this summer. He shifted it @ 5800 and trapped around the same. We run a 29x1100 on it for our local 1/8 mile track, shift it @ 5200 and trap around 5800.
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#4
10-10-2008, 01:29 AM
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Real Nic, My favorite 2nd gen !!! I'd say 4.33-4.56 gears, 4.88 if you are willing to wind it up!
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D.S.R.E. Your NW Pontiac Street/Strip Engine Builder, Specializing in Cylinder Head,Intake Manifold,and Exhaust Manifold Porting services and Building the Most Efficient stock rebuilds to Hi HP Pump Gas and Race Combinations for Pontiac,Buicks,Olds,FE Fords,385 Series and HP Gen 3 and 4 LS engines! 2006 silvy Z71 4X4,383 LS 600+hp NA Shared Toy-66 Lemans 470cid by me 537hp 580tq-manifolds, 570hp 590tq-2"headers,custom cam,rpm intake, mild e-heads, Looks stock ;-} |
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#5
10-10-2008, 06:36 AM
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#6
10-10-2008, 01:25 PM
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John, I would try it as it is and go from there, that's a big tire.
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LIFT HEAVY, LIFE IS TOO SHORT TO BE SMALL! |
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#7
10-10-2008, 02:32 PM
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that big of a tire really drags down the engine..i agree, leave it at 4.88 and go...its probably about correct..
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#8
10-10-2008, 06:14 PM
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My Dad's car runs 33" tall tires. He runs a Dana 60 and it had 4.88 gears. The only difference is he runs a glide and steel rods and a smaller solid cam. He shifts at 6000 rpm's. It was turning 7300 in the 1/4 at 138 mph. A set of 4.30's would be perfect for his car. They make them but not in a pro gear. He has 4.10's in there right now. It is a little slower now but the rpm's are down to 6400, more where he wants them.
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#9
10-11-2008, 09:23 AM
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My combo is almost the same but I run a Toilet on alcohol. Car has a 3.90 gear and ran 9.59 at about 140 with a low 1.40's 60ft and 8.96@152 with a 1.32 60' on NOS. My tires are 32" and I think a 4.30 gear would get me some more ET. If I was you I would try the 4.88, log some data, and go from there. ... Eric.
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Runner Up Q16 Norwalk 2013! |
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#10
10-11-2008, 07:30 PM
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4.88 will work in the eigth.I would drop it some numerically for 1/4 mile racing.Nice shop dude!!Brian
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Be carefull of the feet you step on today.They may be attached to the a$$ you kiss tomorrow. |
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#11
10-11-2008, 09:56 PM
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MPH = (tire diameter x rpm) divided by (gear ratio x 355)
example (33x6500) / (4.88x355) = (214500) / (1732.4) = 123.8166 4.56 = 132.5 4.3 = 140.517 4.1 = 147.37 355 factor is used to account for convertor slip. If you come up with an intermediate number like 4.67 gear to get close to target mph, chose the next lowest numerical gear like a 4.56. Dont gear or tire for a mph that you dont have the horsepower to attain. Check with Strange for a 4.3 gear for your dana. If they dont have it pm me and I'll contact a friend who got a 4.3 gear set for his Dana about 8 or 9 years ago. he was field testing them for one of the gear companies then and the same set is currently in his 557 B1 headed Mopar Cuda. |
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