Hi,
Justpicked upa '68 that was on its way to a pro touring set up. It has a Year One 400hp crate motor with a T56 manual trans. Problem is, it has a 3.1 rear gear, so it can hardly get out of its own way and you have to hammer it to get away from a light. It has the stock GM 10 bolt 8.2 rear. I would love a 3.9 in it but looks like my choices are a 4.11 or 3.74. Anyone have an opinion on which way to go? Final gear on the T56 is either a 0.62 or 0.5 (I havn't figured out which yet). Thanks, Jay

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If you do alot of freeway driving the 3.74 might be better for fuel milage. If you dont drive on the freeway the 4.11 would be better for performance. But there is alot of factors to consider when choosing a gear ratio. You should call Randys ring and pinion for more detailed advise, or maybe someone on here will be better.

 

yeah, 3.73 is best on street driven cars, but I would ditch the 8.2 an either install an 8.5 or a 12 bolt

 

I agree with ditching the 8.2 and have a Jegs complete 12 bolt on the wish list.For now I just need somthing to make it driveable.

I'm going with the 4.11. Foundan old Hot Rod that had a black pro touring Camaro called Fear in it. It had a T56 and a 4.11 and was highway driven frequently. The 0.50 trans to 4.11 rear with my tires should be about 85mph @ 2500rpm.The 0.62 version of the T56 brings itdown to about 70 mph. Thanks,

 

You want to tailor your cars final drive ratio to your engines power band. You need to think in terms of tourque, that's what actually moves the car down range not HP, ie: mine pulls hardest from 1800 to 3200, peak torque on an old SB was about 2400. I have a BW super T10 wit a 1.1 4th gear. I put 3.08's out back with 235/60R15's and at 2500 top gear I'm doin about 63mph. I'm cruising right where the engines torque is, the motors not bogged down trying to pull too high a gear and it's not screaning trying to keep up with too low of one. And the power is right there, I just roll into it and it gose. Find out what your motor has to offer and where the power is and gear it accordingly. You also need to take into consideration first and final trans ratios and overall tire diameter. I deffinately recomend ditching the 8.2, but, I can teel you that the 12 bolt is somewhat overrated. It dose have larger internals and 30spline shafts, but, the hosings have an engineered weak point I've had to repair a few of. The bearing cap bosses in the housing are not strong enough to hold alot of power, the threads pull out of the bores.I would recomend the 8.5 you can get 31spline carriers and axles for it and it has a slightly stronger housing.