Close Ratio / Wide Ratio Opinions 427 Cobra

[brandosaac]

Going to be putting a big shaft toploader into a 427 Cobra , I have the option of using a close ratio or a wide ratio , I believe the rear end gear is 3.31

I realize from a dead stop  the close ratio would be a little less aggressive off the line , but with the amount to torque from the 427 and the somewhat light weight of the car wouldnt those factors make up for itself? The starting line ratio of wide ratio toploader would be  9.20 (2.78 x 3.31), and the close ratio  7.67 (2.32 x 3.31)  , I realize tire height , vehicle weight , available torque and even flywheel material play important factors but
looking for your personal opinions .
maybe some of you out there have used both close and wide and have some real seat of your pants feedback ?

thanks

[shelbydoug]

That first gear/rear end "product" ratio would be for best 1/4 mile times. Are you going racing?

Unfortunately, all the serious Cobra racers that I knew of are no longer around to answer that question specifically BUT when you are serious about it, there are also other factors that enter into the equation such as disconnecting the front anti-sway bar and using uplock front shocks.

How you do that in a 427 Cobra and not get killed with sudden snap steer is way beyond me. I know that just putting slicks on stock Cobras in the day opened a can of worms and I was just a kid that was the fly on the wall that everyone was attempting to swat with the fly swatter!

I was just "the Joe College kid" with white leather "Joe Namith" Puma sneakers, looked like an under cover Cop that no one would talk to, just mutter under their breath about. That's how the east coast racers were back then. No one talked less they get 'busted' for something? 


I can add a tangential observation on a car that had similar f/r weight distribution but not the same amount of off the line torque that perhaps one of the ultimate Pantera builder guys here can check in on?

Back in the day, Gary Hall took one of his Panteras, put 5.22 gears in the ZF and told Mike Cook to go out and try to blow it up. The car immediately dropped down into the 9's. I don't remember the trap speeds off hand and Hall didn't talk about other chassis changes they had to make but I did talk to Mike about it several times.

I believe it was a non-stock block and I know it had A3 heads on it. Other then that, and the 5.22's, I have no other details. The sound of the engine was definitely a 8,000 rpm rev sound but there was no tell-tale tach mounted to spill the beans.


I at one time ran that question of first gear/rear gear product ratio past Randy and I got no response to it. I let it go since I presumed that since he IS, not was a C4 guy, he might look at it differently but as he departed here, he was working on a different engine/drive line combination looking to drop his '66 GT350 into the nines. I haven't heard anymore on the progress since.


MY experience with a top loader, a wide v. close ratio is that on a street car, you want the close ratio. The reason being that the rpm drop between first and second is too drastic to make the car "enjoyable".

I think that back in the day, "Liberty" was combining the 2.78 into a close ratio box 4 speed intended to match up with 4.88's.


IF you are intending to apply all of this to a CSX3000 something original car then the close ratio would be something to use. However, IF by chance you were playing with alchemy my suggestion would be to consider a more practical transmission selection to go with the 3.31 rear of a 5 speed Richmond/Nash. That is typically a 3.26 first gear with a T10 close ratio spread.

I long ago went that route in my GT350 with 3.50 rears and after 30 some years is still running. Everything including the speedometer drive just bolts up.


The only thing you would need to mess with on it would be a shifter mount which is one of the simpler things to do, and maybe the rear transmission mount which varies somewhat from the Ford top loader.
The tail shaft configuration on it more closely RESEMBLES that of the Ford tail shaft so there is SOME flexibility there in mounting the shifter v other 5 and 6 speed transmissions.

I would suspect that with a BB Ford engine, a six speed with it's overdrive top gear could be a breakage issue but can't speak to that combination scientifically?


That transmission, the Richmond 5 speed, uses a Chevy fine spline 22 input, a big Ford 31 spline output and yoke, is a Ford bolt pattern and is the 24" Ford length so it adapts itself well.

The only thing I had issues with were the friction welded shifter inputs that I promptly snaped off first round. That was a simple fix with billet shifter cams which should have been in the box initially to begin with but were part of the "fun" of the learning curve.


So that's what I know and perhaps there is something in it that you can find useful for your application?

[rkm]

For road racing I used the close ratio with a 3:54 rear end. Good for most tracks except the long straight at Road America and any super speedway. Tops out at about 140-150 mph at 6000-6300 rpm. Not the best for highway cruising but pretty good all round.

[Bob Gaines]

For road racing I used the close ratio with a 3:54 rear end. Good for most tracks except the long straight at Road America and any super speedway. Tops out at about 140-150 mph at 6000-6300 rpm. Not the best for highway cruising but pretty good all round.

Is not the final gear regardless of close or wide ratio 1 to 1 ?

[shelbydoug]

All stock Ford transmissions of the era are 1:1 in top gear.

They started putting in an overdrive 5th sometime in the '80s. The question with those transmissions is the gear spacing. It is not spaced for performance applications and is more like a wide ratio top loader would be.

What you would do with something like a close ratio Richmond five speed is move the rear end ratio down. A 3.00:1 rear and the 3.26 first gear give you the effect of the original 2.32 and 3.89 rear with an overdrive in 5th.

A six speed would probably be more ideal but six is almost always an overdrive gear of .70:1 instead of 1:1, and a BB Ford may in fact be over the torque limit rating in most applications.

Guys are changing out the 4.22's in the Panteras for 3.25's so they can go 200mph. Yea...right!

[brandosaac]

Thanks for the replies,
no racing ,  just enjoyable spirited driving

[Bob Gaines]

All stock Ford transmissions of the era are 1:1 in top gear.

They started putting in an overdrive 5th sometime in the '80s. The question with those transmissions is the gear spacing. It is not spaced for performance applications and is more like a wide ratio top loader would be.

What you would do with something like a close ratio Richmond five speed is move the rear end ratio down. A 3.00:1 rear and the 3.26 first gear give you the effect of the original 2.32 and 3.89 rear with an overdrive in 5th.

A six speed would probably be more ideal but six is almost always an overdrive gear of .70:1 instead of 1:1, and a BB Ford may in fact be over the torque limit rating in most applications.

Guys are changing out the 4.22's in the Panteras for 3.25's so they can go 200mph. Yea...right!

I knew that . With both the same ratio in 4th there would not be a advantage one over the other in 4th gear which conflicts with a previous post which stated  "except the long straight at Road America and any super speedway." . 

[shelbydoug]

Yes, that is the way the post was written but I think he misstated it and meant something else? 

As far as just looking for free spirited driving, that term can be interpreted in different ways?

[FL SAAC]

Just had my bearing go out on my 69s top loader. We have a lovely RUG AE2 that is a close ratio. It drove fine,  but we have decided to change the gears in it and make it a wide ratio.

Why ? Although it drove fine on the street we wanted more get up and go.

We drove two of our friends Shelbys, both 428, both top loader equipped.  One with a close ratio box, 232 first, the other with a close ratio box BUT retro fitted with wide ratio gearing that now has a 278 first gear.

Both cars weight the same, same body style,  same HP rating on both 428s.

The car with the 232 first dives fine just like ours did.

The car with the 278 first  gear takes off CONSIDERABLY much faster. 

Although the same vehicles,  blind folded you would say they arethey are two different cars

Thus our deciding factor as to why we are going with new gears on our rebuild.

Oh by the way, no one can see the gear change inside the box.

It will be our little secret, please don't make this public knowledge.

For your eyes only.

Gracias

[rkm]

I learn something new every day.

[crossboss]

Wide ratio hands down.

[Cobrask8]

If any other input helps, I open track a FFR Replica, with a 472 HP 331. I have 3.55 gears out back. For years, ran a wide ratio T-5. Yes, first is fun, but also just about worthless unless the car had slicks to hook up. The drop off to 5th (OD), made that gear worthless, unless on the highway at high speed.

I am converting it to a new Tremec TKX Close Ratio, so I have closer spacing between gears, and OD is .82:1, so now I can use 5th on the track, instead of banging off the rev limiter, and having to lift halfway down any decent straight.

The new Tremec TKX is rated 600 HP, and available in both close and wide ratio.

Since any Top Loader is a 1:1 4th, I say go close, so you keep the motor in it's power band. Then again, as you correctly identify, all that power with no much weight, will it really matter?

Dan

[crossboss]

Thanks for the replies,
no racing ,  just enjoyable spirited driving

I believe some of the posts missed what the OP asked: no racing, just enjoyable spirited driving.
The wide box is the choice for the street.
As for racing, I have used both. The wide was better getting off the line to accelerate out of the pit lane. The close box was as mentioned better for less drop off of RPMs. That said, when I raced my T/A Boss 302, there was very little difference of lap times between both transmissions, going around the big track @ Willow Springs. Later, what made a big difference were: 457s with a modern T-5.

[rkm]

Hey Dan, will you be done in time for Philly?

[Cobrask8]

Kim - Pitt?

Yes, I will be there with the Cobra.

Just got it running this eve, lots of work still to do