8" gear ratio recommendation

I have a 8" rear in my '65 Ranchero. I have no idea what gear ratio is in it, but they are very short. Most likely, less than 3.00. I want to install new gears and some kind of posi/traclok system so I can realize the power the motor is starting to make. The motor is a slightly built 289 w/ Edel 600, RPM Air Gap intake, tri-y headers, 2 1/4 dual exhaust, a mild cam, stock heads and C4 auto with a mild shift kit. I plan on installing aluminum heads, a little larger cam, and a 2000-2300 stall converter in the next year or so. I use the car as a weekend show & cruizing car. It never sees the track, but an occasional stoplight sprint or race isn't out of the question. What would be a good gear ratio the would give me a good cruizing rpm on the highway (about 60-65mph), but still give me some good acceleration? Would 3.55's be what I'm looking for, or even taller?

How about finding a complete 8" third member in the junk yard? I know that little, if any, vehicles were offered with traclok in an 8". However, if they did, what models and years should I be looking for? What type vehicles should I look for that may have an 8" with the gear ratio being recommended?

Thanks

I would go with the 3.5:1. I have a 3.25 with a 5speed and am looking for a 3.5. A 3.25 would do you well also with what you want to do. There were a lot of those installed in the automatics.

You're running a 5spd, though. If I'm correct, your final gear is much lower than mine, giving you a much lower rpm at hwy speeds. I'm afraid I may be turning too many rpms on the hwy. This is my concern. I don't want to give up drivability for acceleration, but a good compromise of both. Right now, she cruises at 65mph very leisurely (can actually accelerate pretty hard from 65 and above), but can't get out of it's own way from a stop.

I found an 8" limited slip pumkin in a Mustang II with a factory v6. Works good behind a warmed over 302.

I would NOT buy a high stall torque converter for your C4. Buy an AOD from a pre-computer car and it is pretty much a bolt on deal.

Have that in my cougar with 3.25:1 and the overdrive giving a 2000 rpm on the freeway.

My Mustang II with the 3.55:1 is 3500 at 75. It gets there very fast and still has enough momentum to coast to the next gas station!

Find a calculator program on the web and feed in your tire size, gear ratio, trans gears (1:1 or OD) and determine the rpms at cruise speeds.

jb


Oh, your gears are not "short" --> they are "tall". Pushing tall gears is what you do to maximize top speed at low rpms ex. 2.75:1 is a tall gear. Running short gears is what you do for max acceleration 4.56:1 is a short gear.

At least that's how we all used to BS about it back in the day...

3.25's are good street gears for a non-overdrive vehicle that can't use tall tires. They were my favorite STREET gear when I had to drive back and forth to college in the mustang... back in the day. 3.55's buzzed the engine more than I liked on the interstate, but were great off the starting line.

And yes, back when you could find them in the junkyard, many V6 mustangs came with 3.55 gears, but few had t-locs. Factory 8" t-locs are HARD to find. However, they do currently offer a real Detroit Locker for them!

Good Luck!

Originally Posted by john_bud

Oh, your gears are not "short" --> they are "tall". Pushing tall gears is what you do to maximize top speed at low rpms ex. 2.75:1 is a tall gear. Running short gears is what you do for max acceleration 4.56:1 is a short gear.

At least that's how we all used to BS about it back in the day...

Oops.

*Thanks for the recommendations. Now I'm really torn on what direction to go. Should I consider an AOD with SHORTER gears or stick with the C4 that's in it, run a taller gears, and sacrifice some potential accelleration? Would the transmision swap and gear change be much more involved than changing the torque convertor on the C4 and the gear change? Would there be a big swing in cost between the two options? Too many decisions.... I don't want to say cost isn't an obsticle, either. It is, to a point. If I dip into my wife's shopping funds, all heck will break loose. Gotta keep her happy. Those designer shoes and purses, to them, are like Fords and engines to us:-)

What should I look for when searching for a third member with 3.25 gears, and possibly trac-loc? What cars, trucks, years where they used in?

I have a Tremec TKO with a 5 speed(.83 5th gear ratio). I cruise 50mph @ 2000rpms.........60mph @ 2300rpms....and 70mph @ 2600rpms with 3.55 gears and 25.89" tall tires. Get a 5 speed, they are lots of fun. The normal .68 5th gear ratio, you could probably go with 3:73's or 4:11's. The .83 ratio vs the .68 ratio is about 500rev rpms faster.

I love the idea of a 5spd, but, agian, I'm trying to keep the asthetics of the car as stock as possible. Plus, I have factory air and I think the a/c unit would be in the way of a floor shifter.