Rear End Gearing

[Bill D]

Can the buyer select what gears he wants in the rear? And what gears are available?

Thanks

[TurnpikeBoy]

Can the buyer select what gears he wants in the rear? And what gears are available?

Thanks

Yes. Pretty wide range - a lot would depend on your engine and driving choices.

Seems most with big blocks like the 3.31 to 3.54 sets. Some go lower (3.08) when they see lots of highway running in their future. Some go much higher (4.09) when they see stoplight grands prix as an agreeable pasttime.

You really do have plenty to choose from.

[Bill D]

I'll have a Keith Craft 515 HP 408W

[davebetts]

We have a Southern Automotive 427 side oiler, stroker 484 cu.in. with a Jaguar gear set of 3.31. The transmittion is a Tremec 5 speed driving 15" diameter wheels/ 295 BF Goodrich's on rear.
I have road raced, cruised, even did some autocross and never been dissatisfied.
As you can see there are a number of variables to consider.
My advise; decide what driving you want to do most and call Maurice or Alan ( Unique Motorcars) and discuss. Bill Parham ( Southern Automotive) can certainly get you through this, as well.Years of experience and solid "real" answers.
Do it once, do it right.

[TurnpikeBoy]

500+ ft-lbs torque; 3.73's with truly sticky tires would be stunning and fear-inspiring, 3.54's would make cruising roll-ons feel like an afterburner.

3.23's would be excellent all-around - still give easy cruising with a top loader or loafing with an .82 5th gear Tremec and good steam down low.

You'll have around 2400 lbs of car. Really don't need lots of gear with strong torque numbers but there are always trade-offs. Steeper gears (i.e, 3.73 and up) will limit your hiway capabilities some and will most certainly affect economy all around. Lower gears (3.54 and down) will be easier to live with on the hiway but trade off that shot-from-the-barrel, squirmy-rearend acceleration.

Traction problems are almost always guaranteed with these cars, much more so with steeper gearing. 408's are awesome power makers, with tons of torque for their size - going toploader, I would use the 3.54's. Using the Tremec with the overdrive 5th, I would be inclined to the 3.73's.

I like steep gears - hence, went with 4.09's and the .68 5th Tremec. Also small block powered (331") and this gearing helps the smaller torque numbers (be silent, Tony!). 80 mph cruise is right around 2700 rpm. Can easily outrun (3-4 lengths) buddy's 427FE Superformance (has 3.23's) up to about top end of my 3rd gear...after that he's closing quick.

Really could only suggest staying away from the 3.08's or the 4.56's. Everything in between has their application and strengths. Whatever you choose, you will really be grinning because these thngs are like nuthin you've had before.



-Roger

[Bill D]

Thanks for all the great information

Bill

[YerDugliness]

Whatever you choose, you will really be grinning because these thngs are like nuthin you've had before.

Oh, Bill's been here before !

Dugly

[Bill D]

Duglys right. I had a 645 HP BBF FFR Roadster that was MORE than a handfull

[RJacobsen]

I found a very helpful calculator to compare tire size, trans ratios and final drive ratios. http://www.gtsparkplugs.com/GearCalc.html you can put in tire size, rear axle ratio, transmission ratios for all gears, engine max RPM and max horse power RPM and it will calculate more info than you need to know.