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Gear ratio decision, 4.1 4.3 or 4.56?

1338 Views 24 Replies 12 Participants Last post by  PHWOARchild
Currently a blast to drive but I want to try dial in the whole system even more, wondering of the 373 are just too mellow for what this combo needs? sometimes at part throttle acceleration it seems a little sluggish.. id like more instant snap if that makes sense..

Currently have 373, and its nice, but i wan to push the street factor the the limit - the 383 doesnt always have the brute low end of the big bocks, so some mods are necessary.

Cam is around 2000-6000 236° / 242°, 288° / 294°, 11:1 (installed straight up), 200/64cc alu heads, 5.7 rods. 850 dbl pumper brawler, Vic JR, 1-3/4 LT headers into 3 inch collector and 2.5 true duals. 373 posi, 2004R, 3k stall..

18-20 initial, vac adv disconnected .. Hei stock.
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I'll probably grab a set of 4.10s as well and compare down the road-

With 4.56:
65mph rpm is 2400rpm.
125mph est trap speed 1/4 mile its 4585rpm

4.10
65mph = 2150rpm
125 mph= 4250rpm

373:
65mph = 1950rpm
125 mph= 3750rpm
The numbers look correct,....
But you should never be in overdrive in a drag race, the Od gearset is not capable of living with that for long. It is strictly a low power, cruising speeds gear, not a performance gear.
Trans valvebody shouldn't even make/allow the WOT upshift to OD.
You also shouldn't be in lock-up on the converter at WOT, most converter clutches aren't capable of withstanding WOT for long either.
Takes an expensive converter to get one built to handle full power in the converter clutch.

Figuring 1:1 in Third gear, 4.56, 28" tire, 7% converter slip for a nice tight 3200 stall converter would put you at 7300 rpm @ 125 mph for a WOT drag pass.
 
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