LilJohn

I think that's a good decision.

Dustin11

Slip will do down a good but from putting the 4.56's in by taking a lot of load off the converter. With that tire size it should work well. I'd be more worried the stock 1.76's in the glide. When they come apart you can expect plenty of oil under your tires.

quik67

I'm a little worried with that. I think the 4.56 will ease the strain a little on the gear set. I plan to just leave on 10 to 12 psi and ramp up the boost just before the 1-2 shift.
Damn, I should just put the Th400 back in , but that's a whole new discussion.

Slowhawk

iTrader: (12)

I'd run 3.70.

Just swapped a 3.00 gear for a 3.55 gear on a 28" tire. Gained nothing in the 1/8th. Turbo's like load as said above.

When you turn your car up into the power it will run low 5's in the high 130's easy enough. 12psi isn't even efficient yet.

93camaro_zzz

iTrader: (13)

LastLS1 is right. You are not going to set up a turbo car like an N/A car, where you are trying to maximize your rear gear to the 1/8th mile trap speed to get the most out of it. You are saying that you want to put more gear in it to hit the tires harder, but if you want to do that, then you need to go up higher on the transbrake, and launch with more boost. And if you cannot go up that high on the converter because you think it goes up too high, then you need a different/tighter converter. Basically by launching with more boost with the 3.50 gear, you are matching the amount of rwtq of the 4.56 gear setup launching on less boost. Except here is the difference..... after the launch, the 3.50 gear is going to have a lot more load on the motor and spool much faster. Then your 330' time will be MUCH better, as well as your 1/8th mile ET.

Hope that made sense. Stick with a 3.50ish gear ratio. Especially with that much tire.

LilJohn

Then explain to me why switching from a 3.90 to a 3.73 slowed an Ultra street car down 2 tenths and 2 mph....

The days of "loading the motor with gearing" are over with the current converter technology.

quik67

I think the loading the engine theory may be bogus in some applications as well, not all, but some.
For instance 71chevy another board member, had a 5.3 with a 76mm T6 turbo in a super light, gutted, 71 Nova, 2500 lb. (with driver) , 31x12 tires, powerglide with 4.88 gears.
He had zero problems spooling and ran a personal best of 5.71 @121

Tuning probably has a lot to do with creating acceptable spool time

yenkomike

iTrader: (2)

I have seen the gear difference first hand . but I also know every car/engine combination is different. all I can say is make a few good runs with the car turned up and give it an honest chance. with the 3.70 gear then go ahead and try your 4.56 gear. if you give them both the same effort I bet you will end up going back to the 3.70.

on my car if I left at low boost like 5# with a 4.00 gear I dld not get to full boost until I made a shift to 2nd. but with the 3.00 gear the rpm was more steady and I whould get full boost in 20 feet. and the car was faster with full boost and a 3.00 gear than half boost and a 4.00. the fastest pass I made was at 3700 lbs with a 3.00 gear and 29.5 tall slicks including the fastest 60'. jmho.
'

007FJ

iTrader: (28)

I agree with that. I mentioned it to make a point that there are not big gains in throwing 5.13's in a car for a the 660 then run 4.10's in the same car in the 1320. The gains I have witnessed are nil using that logic. Plus it screws with the chassis set up when going track to track (depending on the combo and tracks of course). No perfect answer to any of these discussions for all set ups and goals.

High gear only cars wouldn't apply to our type of cars regardless. With my 225 Spitzer RED I never seriously considered high gear only even with the belief at the time, by many, that they would be dead consistent. What a run on sentence!

007FJ

iTrader: (28)

That aligns very much along what I have seen over the years with many combinations. A 280ish cid" class style engine in a 3000# car would be along the lines of needing max gearing to get it on the power band not modern muscle so much.