Rears and Gears: What is too much?

[Zeke]

I've been offered a deal on an Olds rear end including nos 5.12 gears for the Gasser Stude wagon. My thought's are That the Stude will see as much street time as it can once it's ready. I'm gonna use it to haul stuff for catering events and such. Talk about a business card!!

The Question: Would 5.12 gears be to much for daily driving around town and on the hiway with a 5sp or a auto/od? Or would I be better off with two sets of gears and just swapping them out when I hit the track?

[Hot Rod To Hell]

A GM overdrive (700r4) has a .70 4th gear. If you Do the math (5.12 x .70), you can see that it would have a final drive ratio of 3.58, which seems TOTALLY streetable to me!

[Rainer]

jep should be arond 2600 rpm at 60mph - sounds good to me

[Zeke]

Cool! Gotta love this place!

Thanks guys

[Deyomatic]

The diameter of your rear tire makes a difference also.
Go to Richmond's site and play around...I love this calculator.
http://www.richmondgear.com/101032.html

[FLAT6]

Check this site, you plug in the speed, rear end gear, trans gear, and tire diameter and you get the rpms:
http://www.btc-bci.com/~billben/mphrpm.xls
Hope this helps
Mike

[Blownolds]

Did you say "gasser"? If you just want the look of a gasser and want to simply cruise the car, then an OD would be OK I guess-- but an OD really is about as far removed from gasser stuff as you can imagine.

[Zeke]

Yeah I agree about the OD being out of place. the key is that I'm not planning on putting on a trailer to get it to HAMB drags, Day of the Drags or where ever when it's done. I don't feel like doing 40mph on the highway to get there either so an OD makes sense. Honestly I don't give a damn anyway cause I'm building it to suit me. http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif That's all that matters anyway.

[AnimalAin]

My coupe has a 4.57 gear and a Ford AOD, which gives about a 3.04 in high gear. It is very satisfactory on the highway. It can also get out of its own way in the lower gears. Without OD, the 5.12 gearset will be a collossal pain in the butt, but if you don't plan on too much long-distance running, it will be fine with a modern OD trans.

[phat rat]

Depends on you. I ran 5.14 gear in a 53 Ford sedan with a flatmotor and 3 speed back in the early 60's. I would drive it 90 mi one way to the strip. Course 70 mph on the speedo was only about 45 mph actual. Sounded great with the straight pipes.

[Mutt]

[ QUOTE ]
Did you say "gasser"? If you just want the look of a gasser and want to simply cruise the car, then an OD would be OK I guess-- but an OD really is about as far removed from gasser stuff as you can imagine.

[/ QUOTE ]

I don't understand why an overdrive transmission is "about as far removed from gasser stuff as you can imagine". What difference does it make what transmission you use, as long as it will hold up to the horsepower. Overdrive will allow you to launch better due to lower first gear ratios, and still be able to use the car on the street. And that's what Gas class cars were in the beginning - modified street cars.

As far as the 5.12 gears go, use the formulas to decide on what gear/tire/engine combo will be best for your needs. You have to keep your engine in the 'sweet spot' in overdrive, and avoid lugging it. Personally, 4.56 is about tops I would go on a car that's going to be driven often. Unless you do most of your driving on the freeway, you have to take into consideration how much you'll actually be in overdrive...

Dan

[Zeke]

I'm getting 3.90s with that olds rear just to make life easier. Thanks for all the help guys.