Controlling Drive-line R-P-M.

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predator
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Controlling Drive-line R-P-M.

Post by predator » Thu Jul 02, 2015 7:08 pm

Hello"


Does anyone have any experience with any of the 6-speed Transmissions that are being sold for our Cars? Such as the Richmond Gear 5 and 6 speed. Or the Tremec 5 or six speed.

I am just now looking into a 6-speed for my 71 road-runner. Right now I have a Torque-flight coupled up to a Gear-Vendors over-Drive. That is in turn hooked up to an 8 3/4 rear end, with 4.88's. I'm thinking that I might run a taller gear in the
rear-end. That way I could have the needed gear in the Transmission.

In the recent past I had thought about adding a second O-D. But that would have my Drive-shaft spinning at near Hyper-Sonic speeds at 200 M-P-H. The mere thought of having a drive-line failure at 200 M-P-H simply freaked me out!

I'm sure you Guys understand what I am trying to do with my Car. I want my car to have good Gearing for under 100 M-P-H. I want the Car to have good Gearing at 200 M-P-H Plus!

So back to my opening question: Does anyone have any experience with the 5 speeds, or 6 speed transmissions out there on the Market?

Guys, thanks for any thoughts you guys might have: The Big Guy CCMCK@GOLDSTATE.NET
925-497-1059

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Re: Controlling Drive-line R-P-M.

Post by Supershafts » Thu Jul 02, 2015 8:52 pm

How much power are you making?" i have the same same 27 and GV and 489, i can reach 200 mph. are you're looking to cruise there or just reach it.

The 6 speed isn't going to slow the driveshaft down, unless you want to kill the final ratio and use the trans ratios. you might want a new 8 spd trans
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Re: Controlling Drive-line R-P-M.

Post by predator » Fri Jul 03, 2015 12:29 am

I have been thinking as of late that it might be a good idea to run a Drive-line in my Car that will bring my Drive-shaft down to a sane R-P-M. You mentioned an 8 speed. QUESTION: Who MFG's an 8 speed that I might want to take a look at?

My intention for my Car is to have a Car that could enter say an event like the Silver-State road-race up in Nevada. While also be able to make a respectable pass down the Quarter Mile. While my Car is not a runner right now. I do have my Engine, with the Torque-flight attached to the engine, with a Gear-vendors over-drive bolted up to the Transmission.

Maybe, just maybe an 8 speed just might be the answer to my drive-line woes. Right now my car has a set of 4.88 rear-end gears. I had for a short spell, I had thought about adding a second O-D to the first I already have. But, I thought about it some more: While running two O-D's would take care of allowing my car to run up into the 200 MPH range. But, spinning the Drive-shaft at hyper-sonic rotational speeds might not be such a good idea.

The mere Thought of experiencing having my Drive- shaft becoming a super fast spinning projectile, quite frankly freaks me
. . out!

See Ya The BIG Guy.

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Re: Controlling Drive-line R-P-M.

Post by Brian P » Sat Jul 04, 2015 12:42 am

The driveshaft RPM is going to be governed by the rolling diameter of the drive wheels (which presumably you can't change by much) and the final drive ratio ... nothing else. It doesn't matter how many speeds or what ratio is happening upstream.

You do need to be concerned about the critical speed of the driveshaft if you are going to be doing very high road speeds.

Here is a calculator that you can use to figure out what this critical speed is: http://www.wallaceracing.com/driveshaftspeed.htm

If you know what your maximum road speed is going to be, and what the rolling diameter of your tires is, you can figure out what RPM your drive wheels will be turning at that speed, and then if you know what that critical speed is, you can figure out what the maximum final drive ratio can be. Remember that you need to stay below that critical driveshaft speed by some decent percentage just to make sure.

If you can do something to make the driveshaft shorter (e.g. by making your transmission longer!) it makes a HUGE difference in what that critical speed is. Play with the numbers in the online calculator - you'll see. This is why front-engine long-wheelbase trucks and buses use a two-piece driveshaft with a center hanger bearing.

Again, the driveshaft doesn't care how it's getting to that speed, whether by a single gearbox with a big overdrive or by add-on overdrive units or by a really high revving engine ... it doesn't matter how that speed was arrived at.

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Re: Controlling Drive-line R-P-M.

Post by Splitter » Tue Jul 07, 2015 2:34 am

Look at the Richmond/Doug Nash 5 speed. Low gear 3.47, high gear 1.00. Advantages of running a direct drive top gear instead of overdrive: lower driveshaft speed, less transmission wear/heat buildup/horsepower loss, direct drive is far stronger than any other gear. Disadvantages: you may require a higher rear axle gear than what is available (<2.50:1).

You've probably read about Dan Gottlieb's 'Big Red Camaro', according to the link below the car runs 220mph+ with a Jerico 4 speed and a 2.49 rear axle ratio:

http://www.hotrod.com/cars/featured/113 ... et-camaro/

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Tranny's I need links

Post by predator » Sun Jul 12, 2015 3:59 pm

As of right now. with my Car not even running "YET". I have the car sitting in my Garage. It has 4.88's in the Rear-End. I have a Torque-Flight, that has a Gear-Vendors over-Drive. I think that this will be a pretty good set-Up for running the Quarter-Mile. But I need to face physical facts/Reality. To have my Car be able to run upto 200 Miles an hour or More. I will need more gears. Who knows? maybe I will end up running a Six-speed.

HOW ABOUT GIVING ME SOME LINKS TO THE mfg's of these 6-speed or 8 speed transmissions?

Thanks Guys:

Good By: PREDATOR

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Re: Controlling Drive-line R-P-M.

Post by Dan Timberlake » Sun Jul 12, 2015 8:23 pm

Have you provided info yet about the driveshaft material, tube diameter, and length from u-joint center to center ?

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Re: Controlling Drive-line R-P-M.

Post by Supershafts » Sun Jul 19, 2015 8:43 pm

Why are you worried about shaft speed ??? That's something that whichever shop you choose will handle.

I have a B body with a 727 and GV, the shaft isn't a issue at all and i have a final of 4.89 I sold my 72 RR which was also B body and it had a 727 w/gv... the shaft isn't long. and if you are gonna do SSC runs and hang around 200mph you are gonna modify the floor to keep the angle down. Both my b bodies the motors are down and back. if you want to run in the 200 mph area id start worrying about the motor location and angle and forget the shaft speed.
Shaft speed in that configuration is nothing to worry about, even without moving the motor.
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Re: Controlling Drive-line R-P-M.

Post by Supershafts » Sun Jul 19, 2015 8:57 pm

Dan Timberlake wrote:Have you provided info yet about the driveshaft material, tube diameter, and length from u-joint center to center ?
Without setting the motor better to deal with those speeds that shaft is so short in it's current configuration it will easily be able to run the speeds. If i remember right my RR was like 31", at that length in regular stl 3" diam he'll never get to the rpm where it will fail which would be somewhere around 16,000 rpm and he would need to have a motor in the 7500 rpm area to reach 200 with the GV and 4.9 with a 28" tire and his shaft would be around 8900...


Of which predator if your shaft breaks upstairs they'll cut right thru the cage and car, unless you build a scatter tube like we use in off shore boats, and then you have the issue we don't have in offshore boats of suspension travel.
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Re: Controlling Drive-line R-P-M.

Post by Brian P » Mon Jul 20, 2015 9:59 pm

If I plug in 31" center-to-center between U-joints, and 3" driveshaft OD into that calculator linked to above, it predicts critical speed near 20,000 rpm.

At 200 mph, with 28" drive wheels, the drive wheels will be going 2400 rpm. Even with the 4.88 final drive, that is 11,700 driveshaft rpm. Well below critical speed.

On the other hand, if the driveshaft is 40" long center-to-center between U-joints then things are going to head south with that road speed and final drive combination. The critical speed is very sensitive to the length.

I do not know if the input shaft seal and bearing on a typical rear axle is rated for that sort of speed ...

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Re: Controlling Drive-line R-P-M.

Post by Supershafts » Tue Jul 21, 2015 9:31 pm

Like i said this issue of shaft speed isn't the problem...

I have the same set up in 2 cars and have maintained 170/180 for 1.5 hour playing with 200 here and there.

He should be concerned with cooling, and if he has the power to get there and maintain it without the motor being held to it's limits.

If the idea is to touch 200 then things can be done differently.

If i was predator id be more concerned with laying out the driveline, suspension and using Anze suspension shocks all around , then get cooling in order.
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Re: Controlling Drive-line R-P-M.

Post by Brian P » Tue Jul 21, 2015 11:06 pm

From what I can tell, the Gear Vendors overdrive that the original poster has, is a 0.78:1 overdrive.

If the original poster wants to go 200 mph and presumably has an engine making peak power at (let's say) 6000 rpm then if he wants 6000 rpm in overdrive with the main transmission in direct drive, the driveshaft speed will be 6000/0.78 = 7692 rpm, and with the wheels rotating at 2400 rpm at that speed, the final drive ratio will have to be (ideally) 3.205:1 (or in reality, the closest axle ratio you can get to that). If the engine's peak power RPM is something different then re-crunch the numbers but it ain't gonna be 4.88 if you want that sort of top speed.

Aerodynamics (not just drag, but also lift, and stability), tires, suspension geometry, etc are a lot more critical than the speed of the drive shaft ...

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Re: Controlling Drive-line R-P-M.

Post by Mohr HP » Mon Aug 17, 2015 9:51 pm

Please see my reply in your other post, "Speed transmission."

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