Which Gear Ratio?

[Venom S]

I was planning on using 3.73's in my 650+ hp big block. But some automotive friends said that such a low gear will just exacerbate wheel spin, and suggested 3.08's. Just would like some input from other owners and their experiences.

Thanks

Venom_S

[Wade Chamberlain]

3.08 or 3.27 at most for that monster. Even then, you won't be able to put 650hp to the pavement.

[Venom S]

Thanks Wade, but aren't you experiencing traction problems with a blown 302? What gears are you using?

Thanks

Venom_S

[Todd Hedges]

I wanted lighting fast responce/acceleration when building my kit.
I went with a 450hp 428 with a Richmond 5 speed.
Turns out that the 3.01:1 ratio is a hair to low for my taste.
The BFG's spin through 3rd gear like a normal car on ice.
I wish I went with the 2.76:1 instead.

I really feel as though you would accelerate quicker with a taller
gear because of the excessive wheel spin as a result of poor traction. (295x50 - 15's)

On the highway, the sidepipes sing at 3,000rmps in 5th gear,
(75mph+-) and still has plenty of power to take-off without down shifting. (cam shaft power curve is 2500 to 6500)

my peak hp is at 5600rmps.

Unfortunately, I can not afford a second set of pin drive wheels for track tires. Once these burn up, I will look for a "stickyer" set.

I do know that the tremec has an overdrive 5th gear unlike the Richmod 1:1. That will help with the 3.++:1 ratio's on the highway. Watch out for 1st and 2nd especially with 600+ hp.

I hope this is of some help.

[Venom S]

Thanks

[Wade Chamberlain]

Traction? What's that??

I have 4.10's and a 3.35 first-geared T5. Yup, traction doesn't exist until 3rd gear at best. I can launch semi-hard in 2nd if I feather the clutch. I'm building another 302 right now that'll run around 450hp. When I swap engines, I'll swap the rear gears too. Probably 3.55 or 3.27's. Still working on that one. It depends on whether I swap transmissions too (something w/ a better first gear).

[klayfish]

Wade,
Isn't "traction" what you wind up in after being hospitalized from having WAY too much gear in your Cobra?

Seriously, I only have a regular breathing 302, and I'm putting 3.73s in that now to pick up the speed. (Speaking of, anyone out there have a good used posi 8.8 rear?) With my T5, I'd think even I'll be able to spin 1st and 2nd gears.

The mechanic who works on my car has a 514ci with over 600 hp. I think he said he has 3.50's in it, with the toploader 4 speed. He said he can smoke the car in a heartbeat, almost too easy. Other cars he has built like that, with a 5 speed, he recommends low 3's or real high 2's.

Steve

[Venom S]

Thanks everyone for the input. Looks like I will go with 3.08's to start, and order my Tremec with the .84 5th gear.

Venom_S

[Jack21]

Another place to look for improving traction is tires and wheels. BFG's on 15" wheels just don't work that well. If you want to get into the AA Traction rated tires, you have to go with 17"ers.

Wanted better wet road traction mostly (safety factor), and the dry road traction on these Falkens is awsome.

Wade (and other FFR guys) Purple Flirp has 4 bolt 17" w/ Bridgestone RE730's. These also have AA traction rating. Try swapping rear wheels for a test drive and see if it makes any difference. My wheels are 5 bolt Ford if anyone wants to experiment.

Don't think my 351 is anemic by any means, running 3.55 gears, and they don't break loose very easily, dry or wet.

[Cobra Dude]

Look at one of the gear-ratio calculators (search google) and start there. Then factor in things like traction, fuel economy (yeah right!), noise (I chose 3.08's over 3.55's or 3.27's so I could cruise at 1800rpm at 70mph).

I absolutely think 3.73's will be too tall for the street, and annoying to drive.

Have RE-730's on my Audi and absolutely hate them!!! I can skate these things with a 1.8 as if I were on ice. Could not do that with the RE-71's I had before.

Cheers,
-Neil.

[gsharapa]

I have a 8.8 center section set-up with 4:10s traction loc if anyone with a small block is looking for one. It was out of my last Superformance I had with a 351/385 HP crate engine. I changed the 3:73 to 4:10s and really like it with the 60 series tires.ThenI put a Paxton Supercharger on and the 4:10s were too much so I just bought a whole new center section with 3:73 again.

Anyone interested $ 250.00 for complete carrier center section all setup with the 4:10s just bolt it in and you pay the freight or pickup. Dallas, Texas gsharapa@ford.com

[CobraEd]

It all depends on where your torque is and what your redline is. If you have a hot high reving naturally aspirated small block, you want lower gears around 3.73 or so. If you have a high torque lower rpm engine (not too radical big block/forced induction small block) you want higher gears around 3.08.

This all boils down to matching and optimizing your whole drivetrain (engine transmission/rear end) as an integral unit. Getting this right is what makes the difference in a fast car, and an "ok" car!!!

Ed