Figuring out what 3rd member gears ?

[FUNFER2]

Many years ago, I heard of a shade tree mechanics way of finding out what gears you are using by marking the tire and the drive shaft, then rotating the wheel and count the revolutions the drive shaft makes to equal one rotation of the wheel. Is this correct ?

I have a Ford 9" with a Currie pumpkin. The man I bought it from said it's a locker with 331 gears. I red the Currie tag on the axle housing and it's 7136.
When I called the company, he said he does not have any listed of that number ? Plus, they don't even make a 331.

Here's what they have- 300-325-350-370.

They and Lone Star Classics said their sure, it's a posi with 370 gears.
The axle may be a 28 spline not the 31.

I talked to a elderly man that has raced many different drag cars since the
60's, has had Cobras before and now has a Superformance with a side oiler with 570 HP and makes some cobra parts and has a dyno for many years testing racing parts. He sounds like he knows what he's talking about.

Anyway, he thinks since our cobras are so light, that my 3550 tranny and the posi will be fine unless I plan on using slicks at the track and dumping the clutch. He knows several people that have big HP/TQ with these same parts and have never had a problem. I too believe that but, I could sell my tranny and have at least some money in my pocket versus blowing the thing up.

I found a TKO dealer that will sell me the 600 for far less than the $2,195 most of them sell at, including Summit.

on what to do.

[blykins]

Yes, just count the number of revolutions it takes on the driveshaft to turn the wheel over one revolution.

If I were you, I'd sell your existing stuff and get the 600. I've heard of those transmissions lasting forever, and I've heard of them breaking easily. I wouldn't take a chance. They're rated for 400-425 lb-ft and if you ever hook up once, you could break some parts.

[undy]

Kev, You've gotta been smoking those corn husks it you think a 375 lbft rated 3550 is going to hold up to that 600+ lbft FE you're getting ready to order. This is especially going to be true with the sticky tires I know you'll be running. If you don't use race rubber you'll never be able to plant that 482 either. Ask me how my Cobra swapped ends on the interstate at 65 mph when I semi-romped into it in 4th gear with standard 315/35/17 street rubber. That's why I run the M/T ET Street drag radials now. It was virtually unsafe with standar street rubber.

BTW... the standard Currie bill-o-fare for LSC when your car (and mine) was built was the 3.70s, mostly all with 28 spline axles too. If so, you better roll out the check book, again like I did. It ain't going to hold up to that 482.

You can pay 'em now or pay 'em later, I've got $30K invested in the engine/drive train upgrade..

Originally Posted by FUNFER2

Many years ago, I heard of a shade tree mechanics way of finding out what gears you are using by marking the tire and the drive shaft, then rotating the wheel and count the revolutions the drive shaft makes to equal one rotation of the wheel. Is this correct ?

I have a Ford 9" with a Currie pumpkin. The man I bought it from said it's a locker with 331 gears. I red the Currie tag on the axle housing and it's 7136.
When I called the company, he said he does not have any listed of that number ? Plus, they don't even make a 331.

Here's what they have- 300-325-350-370.

They and Lone Star Classics said their sure, it's a posi with 370 gears.
The axle may be a 28 spline not the 31.

I talked to a elderly man that has raced many different drag cars since the
60's, has had Cobras before and now has a Superformance with a side oiler with 570 HP and makes some cobra parts and has a dyno for many years testing racing parts. He sounds like he knows what he's talking about.

Anyway, he thinks since our cobras are so light, that my 3550 tranny and the posi will be fine unless I plan on using slicks at the track and dumping the clutch. He knows several people that have big HP/TQ with these same parts and have never had a problem. I too believe that but, I could sell my tranny and have at least some money in my pocket versus blowing the thing up.

I found a TKO dealer that will sell me the 600 for far less than the $2,195 most of them sell at, including Summit.

on what to do.

[FUNFER2]

I hear you bud. I thought I had saved your number but, don't see it.
You have a PM.

"Ask me how my Cobra swapped ends on the interstate at 65 mph when I semi-romped into it in 4th gear with standard 315/35/17 street rubber. That's why I run the M/T ET Street drag radials now".

4th gear ! wow,....that had to be hairy on the interstate !!!
Power does not bother me but, the strength of components does.
Can you imagine in your case, if at that speed +, if a axle broke !

[MaSnaka]

FunFer2,

There is another way to verify what rear end you have. I have a chart that has tire diameter, speed and rpm's. While tachs and speedos can be off a bit it is just more info that might back up what you think it is. For instance 28" tire dia. at 60mph with the 3.31 rear in 4th gear 1/1, your rpms should be 2383. With the 3.73 rear end the rpms would be 2686. If your tire dia. is bigger or smaller let me know and I can give you the calcs... 27" dia. would be 2471 and 2785 rpm. I hope this helps.

John

[FUNFER2]

Hello John,
I would have to measure my Good Year Eagle II's but, I'm in the process of changing to the Billboards and their supposed to be like, 26.5" all the way around. I now believe I have 370 gears not, 331's. Currie does not even have that selection. The previous owner told me the rear end had 331 gears.

With the Eagle II's and my Tremec 3550 trans, at 60 mph I'm right at 2,000 rpm's. That's really nice. With my KC alum. 482 and apx. 600-650 HP/TQ and hopefully the TKO 600, I would be curious as to the rpm and the Billboards with the 64. or the .82 overdrive ?

I would appreciate your time.

[FUNFER2]

Ok, with the Eagle II's. They are 82.75" diameter.

I also made a fast check on the Gears. I get 1.25 turns of the tire with the drive shaft.

What would that equal and maybe 1/3rd ?

I don't get this. I marked the drive shaft at 9:00 and the tire at 6:00. Each time I rotated the tire, (which I believe was 4 rotations) I got a different number so, what do I go with and which time is correct ?

[danc30]

If the driveshaft only makes 1.25 revolutions for 1 full tire rotaion, you've got 1.25 gears. Your not doing something right.

How many revolutions does the driveshaft make when the tire is rotated 1 complete revolution?

Easier with 2 people, have one mark and count the driveshaft and the other turn the tire slowly for one revolution.

3 and a quarter turns of the driveshaft equals 3.25 gear

[undy]

Originally Posted by FUNFER2

Ok, with the Eagle II's. They are 82.75" diameter.

Dem's some big frigging tires Ya going 4 wheel off-roadin' with the cobra Kev?? That must have been painfull carving out those wheel wells

[FUNFER2]

Yep, that's why I'm the only cobra owner that gets 1,000 miles per gallon

[MaSnaka]

FF2,
when your cruising at 60 make sure your in 4th gear and not your overdrive. 4th gear should be 1/1. At 60 mph in 4th gear with 28.75" dia tires you should be taching between 2686-2593 rpms. My chart only shows 3.73 rear at 28" and 29", so it's just a ballpark estimate but should be close enough. Like Danc30 said 1 tire rotation and 3 1/4 turn of the drive shaft would be 3.25. If you have 3.70 gears then you would see almost 3 3/4 revolutions of the drive shaft.

John

[FUNFER2]

Sounds like a plan.
Thank you much.

[MaSnaka]

With 28-29" tire dia, at 60 in 4th gear, a 2.90 would have 2088-2019 rpm. A 2.73 would have 1966-1898 rpm.

[FUNFER2]

I guess this calls for a way to get out in the cobra for a while.

[MaSnaka]

It's called research. Have fun.