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
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?
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.
Quote from: rkm on February 16, 2023, 09:11:39 AM
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 ?
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! ::)
Thanks for the replies,
no racing , just enjoyable spirited driving
Quote from: shelbydoug on February 16, 2023, 01:01:04 PM
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." .
Yes, that is the way the post was written but I think he misstated it and meant something else? 8)
As far as just looking for free spirited driving, that term can be interpreted in different ways? ;)
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
I learn something new every day.
Wide ratio hands down.
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
Quote from: brandosaac on February 16, 2023, 01:39:32 PM
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.
Hey Dan, will you be done in time for Philly?
Kim - Pitt?
Yes, I will be there with the Cobra.
Just got it running this eve, lots of work still to do
I've owned a replica Cobra big block for 29 years. There have been 2 Toploader transmissions in my car, both wide ratio. Rear end ratio is 3.70, but I also ran a 3.50 rear for a number of years. The current transmission is a David Kee-built aluminum body unit with a big input shaft and small output shaft.
The 1st gear ratio in my car is just right for pulling away from a stop, engine speed slightly above idle and normal clutch engagement. I state that because I know a Cobra owner with a big block, 3.54 rear end ratio, and a close ratio Toploader. Each time he pulls out from a stop it's obvious he has to raise his rpm's and slip his clutch more than I do. I once asked him about what I was hearing and he became defensive and said "It's fine like it is."
Quote from: dmb496 on February 20, 2023, 09:13:14 AM
I've owned a replica Cobra big block for 29 years. There have been 2 Toploader transmissions in my car, both wide ratio. Rear end ratio is 3.70, but I also ran a 3.50 rear for a number of years. The current transmission is a David Kee-built aluminum body unit with a big input shaft and small output shaft.
The 1st gear ratio in my car is just right for pulling away from a stop, engine speed slightly above idle and normal clutch engagement. I state that because I know a Cobra owner with a big block, 3.54 rear end ratio, and a close ratio Toploader. Each time he pulls out from a stop it's obvious he has to raise his rpm's and slip his clutch more than I do. I once asked him about what I was hearing and he became defensive and said "It's fine like it is."
+ 1
Thanks for the replies.
But a 3.70 rear gear, with a wide ratio, in a somewhat lightweight car with a big block with tons of torque?
On paper that sounds like 1st gear would be extremely aggressive ? and almost un usable ?
A 3.70 isn't the quantum leap above a 3.50 as you may think. I stated I previously had a 3.50 rear end in my Cobra so you could buy into my overall evaluation of a wide ratio Toploader.
Unusable? It doesn't matter if you have a wide or close ratio, a 3.50 or a 3.70 rear in a Cobra that has substantial horsepower. That's why prudent use of the right foot is so important when driving a Cobra. I never stab the throttle, I 'tip in' to reduce the surprise factor.
The last gentleman I took for a power ride, remarked after we ran through 1st, 2nd and 3rd gears that he thought the car's rear tires were almost breaking traction. I grinned and said the tires were actually roasting rubber for the majority of the sprint.
In my opinion ................,
3.70 rear with 2.78 wide ratio 1st , seems extremely aggressive with a big block cobra,
you could loose it pretty fast under partial throttle
Well, you asked for opinions and you definitely are getting that here. There are a variety of experiences and none are wrong.
The 427 Cobra transmission that I had was a big input, small output, 24", close ratio.
I do not think that there was ever a wide ratio box ever made by Ford for that application?
If you look down the list that David Key has posted, any original displacement larger then the 390 that he knows of is a big input, close ratio box.
The 390 applications are small inputs, like the 289's.
There are wide ratio 390 transmissions but are small inputs.
With Ford, it seems there is always a rare combination they made that was never made in mass quantities but did exist somewhere, somehow mostly unknown to even experienced Ford appliers?
I do believe though that in the original CSX 3000 cars, the most common, if not all applications was a 3.31 rear with a close ratio (2.32 first gear), 24" long, 1-3/8" big input and small (28 spline) output. So in my OPINION, that would be an original 427COBRA application.
One of the considerations on close v. wide ratio that is not mentioned here, is the smoothness the close ratio gives as you accelerate through the gears v. the wide ratio. You need to consider the wear and tear on the drive line because of the torque loading of the larger displacements.
The 427 Cobra is very sensitive to throttle input but more specifically, to torque inputs. You want to be as smooth as you can when driving it spiritedly.
You shouldn't compare another vehicle such as a big block "Mustang" to the Cobra application. They are not the same. They are beyond apples and oranges.
Many Cobra "kit" cars are not using IRS Cobra rear suspensions but solid axle "Mustang" variants. That changes the equation somewhat as well.
Initially, the 427 Cobra was subject to what was described as "snap steer". What was happening was that the balance of front to rear steering was not right initially.
I'm not sure of the EXACT formula that came to be for stabilizing the car but there was work involved which included a smooth transition of power to the car, which does include the transmission and rear gearing.
When you build your own Cobra, you are varying from the Shelby factories solution. You need to be aware that this is at your own risk and you are applying your own solutions which may need some testing to verify the car is stable even under normal driving not to mention track characteristics.
All vehicles with weight bias front to rear with the majority of that weight is on the rear, 40% front, 60% rear, are extremely susceptible to the rear suddenly steering the car. That IS involved in the "snap steer" issue.
One thing that you must insure is that the rear tires have noticeable toe in. Somewhere in the 3/16" to 1/4" vicinity. With an IRS rear that is adjustable. With a solid rear, it is not.
Someone asked here before, what are the factory suspension settings for a "Comp/SC Cobra". All they could find were stock 427 street settings. The reason for that is that each car needs to be set up individually according to it's track reactions. So therefore there is no specific setting, you just start with a street setting and work from there.
Why do I mention that here? Gearing of the car is involved in that. When you step off of the throttle, you don't want excessive rear end steer because of the braking effect of taller gears.
Honestly though, the only way that YOU are going to be able to determine the best setting is for YOU to experiment with these combinations.
Picking the gearing profile you like is probably close to trying to pick a camshaft profile that YOU will like rather then what was recommended to you by others. Simply put, each is going to have their own interpretation of what is streetable, what idles well and what pulls the best, not what others tell you.
Gearing is very similar. That's why people like Miles were at the "tracks" so often testing combinations. I'd go with his picks they put originally in the Cobras.
Again, this is my opinion. Others certainly have taken different avenues and likely may disagree.
What he said :
There is never enough horsepower......just not enough traction.
Carroll Shelby
I'll add my 2 cents here. I've driven the same car with both a close ratio 2.32 to 1 first gear toploader as well as a wide ratio 2.78 to 1st gear. I much preferred the the 2.78 gearbox on the street.
If you wish to convert a close ration box to a wide ration these are the parts you'll be swapping: 2nd gear, 3rd gear, the cluster gear, and the input shaft. There are no factory 2.78 big spline 1st gear inputs, you'll have to have it made which requires two inputs, the original big spline input and a donor wide ratio input. Liberty Gear in Michigan used to do that kind of work but I don't know if they still offer that service. I was very happy with the work they did for me and it would still be in the car except I switched to a TKO600 (happy with that transmission too).
Quote from: S7MS427 on March 14, 2023, 07:05:03 AM
I'll add my 2 cents here. I've driven the same car with both a close ratio 2.32 to 1 first gear toploader as well as a wide ratio 2.78 to 1st gear. I much preferred the the 2.78 gearbox on the street.
If you wish to convert a close ration box to a wide ration these are the parts you'll be swapping: 2nd gear, 3rd gear, the cluster gear, and the input shaft. There are no factory 2.78 big spline 1st gear inputs, you'll have to have it made which requires two inputs, the original big spline input and a donor wide ratio input. Liberty Gear in Michigan used to do that kind of work but I don't know if they still offer that service. I was very happy with the work they did for me and it would still be in the car except I switched to a TKO600 (happy with that transmission too).
+ 1 actually your 2 cents in real life is worth 1 dollar, that's how I felt when I experienced the difference
Same cars, same motors, same 3.5 rear, just different 1st gears on toploader......wooooosh!
Quote from: S7MS427 on March 14, 2023, 07:05:03 AM
I'll add my 2 cents here. I've driven the same car with both a close ratio 2.32 to 1 first gear toploader as well as a wide ratio 2.78 to 1st gear. I much preferred the the 2.78 gearbox on the street.
If you wish to convert a close ration box to a wide ration these are the parts you'll be swapping: 2nd gear, 3rd gear, the cluster gear, and the input shaft. There are no factory 2.78 big spline 1st gear inputs, you'll have to have it made which requires two inputs, the original big spline input and a donor wide ratio input. Liberty Gear in Michigan used to do that kind of work but I don't know if they still offer that service. I was very happy with the work they did for me and it would still be in the car except I switched to a TKO600 (happy with that transmission too).
New, one piece, 2.78 large input shafts are available through David Kee and other drivetrain parts places. They even make the longer version, big input for a small block.
Dan Williams Toploaders