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18Likes
12-04-2017, 06:51 PM
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CC Member
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Join Date: May 2012
Location: Wickenburg,
AZ
Cobra Make, Engine: Superformance, 427 FE
Posts: 197
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Not Ranked
TKO 600 failures?
I am replacing my engine, a 400 HP / 500 TQ 428 to a 580 HP / 665 TQ 427.
the old trans is only rated to 400 TQ and the new to 600. My question is, has anyone had problems when the engine is producing more than the trans is specked for?
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If enough people disagree with me, I know I am doing it right
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12-04-2017, 07:07 PM
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CC Member
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Join Date: Jan 2009
Location: Las Vegas,
NV
Cobra Make, Engine: Shelby CSX4005LA, Roush 427IR
Posts: 5,585
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Not Ranked
The cost of a new compatible transmission now will be less than repairing the damage and buying a new one later.
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Cheers,
Tony
CSX4005LA
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12-04-2017, 07:08 PM
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CC Member
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Join Date: May 2006
Location: St. Louisville,
Oh
Cobra Make, Engine: A&C 67 427 cobra SB
Posts: 2,445
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Not Ranked
Although you will have more than 600 torque, I think you will be OK. For one you will not be able to hook it all to the ground in most gears. Two the TKO has some safety factor built into the rating. Three you are going to loose a bunch of power when you install it in the car. That said, I wouldn't recommend beating on it in 5th gear.
Last edited by olddog; 12-04-2017 at 07:10 PM..
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12-04-2017, 07:37 PM
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Senior Club Cobra Member
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Join Date: May 2001
Location: Florence,
AL
Cobra Make, Engine: RCR GT 40 & 1966 Fairlane 390 5 speed
Posts: 4,511
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Not Ranked
If you are not doing burn outs with slicks you will be find.
My buddy has a 620 hp / 637 tq FE in his Unique with a 3550. More than ten years of burns outs with out a tranny problem.
Oh yea, he has 12" rims on the back.
Dwight
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''Life's tough.....it's even tougher if you're stupid.'' ~ John Wayne
"Happiness Is A Belt-Fed Weapon"
life's goal should be; "to be smarter than inanimate objects"
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12-04-2017, 07:38 PM
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Senior Club Cobra Member
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Join Date: May 2001
Location: Florence,
AL
Cobra Make, Engine: RCR GT 40 & 1966 Fairlane 390 5 speed
Posts: 4,511
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Not Ranked
You said your old tranny was rated at 400 tq. What is it?
I'm looking for a 3550.
Dwight
__________________
''Life's tough.....it's even tougher if you're stupid.'' ~ John Wayne
"Happiness Is A Belt-Fed Weapon"
life's goal should be; "to be smarter than inanimate objects"
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12-05-2017, 04:48 AM
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CC Member
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Join Date: Dec 2001
Location: Louisville,
KY
Cobra Make, Engine: I'm Cobra-less!
Posts: 9,417
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Not Ranked
I've got guys putting 700 lb-ft through a stock TKO 600.
The transmissions are rated for "continuous torque" and are underrated.
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12-05-2017, 04:59 AM
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Senior Club Cobra Member
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Join Date: Dec 2001
Location: Shasta Lake,
CA
Cobra Make, Engine:
Posts: 26,596
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Not Ranked
I have a stock TKO 600 and my engine now doesn't put out that much power but the one before did and I have had no problems with it. But I also don't use slicks or do burn outs as I like road racing over any other and never did drag race so I don't know how it would have taken that.
Ron
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12-05-2017, 06:25 AM
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CC Member
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Join Date: May 2012
Location: Wickenburg,
AZ
Cobra Make, Engine: Superformance, 427 FE
Posts: 197
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Not Ranked
Thanks for the info, makes me feel better. My old one I believe is a 3550. Dwight, I will get the numbers off it for you.
__________________
If enough people disagree with me, I know I am doing it right
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12-05-2017, 11:58 AM
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CC Member
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Join Date: Dec 2012
Cobra Make, Engine:
Posts: 973
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I think most of our Cobras have a built in "safety" feature in regards to keeping our cars together in that our tires all suck (relatively) and are the weak links in the chain. Not necessarily a bad thing unless you are tracking at 10/10ths with your car.
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12-05-2017, 12:13 PM
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Half-Ass Member
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Join Date: Jun 2005
Cobra Make, Engine: ERA #732, 428FE (447 CID), TKO600, Solid Flat Tappet Cam, Tons of Aluminum
Posts: 22,005
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Not Ranked
In an ERA, assuming you can hook the tires up enough to cause some damage, you're way more likely to eat the stub axles than you are the Tremec.
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12-05-2017, 02:40 PM
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CC Member
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Join Date: May 2012
Location: Wickenburg,
AZ
Cobra Make, Engine: Superformance, 427 FE
Posts: 197
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Not Ranked
All reassuring words. I would hate to put a new trans behind a new engine and then have it go boom. Before install is the time to get it right.
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If enough people disagree with me, I know I am doing it right
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12-05-2017, 03:49 PM
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CC Member
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Join Date: Jul 2005
Location: Virginia Beach, Va & Port Charlotte, Fl.,
Posts: 2,284
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Not Ranked
I run M/T drag radials and have lifted the front end off the ground on several occasion. (16lbs of air pressure with a good prior burnout). I've a TKO 600 and it's never been hurt.
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Too many toys?? never!
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12-05-2017, 06:29 PM
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CC Member
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Join Date: Apr 2016
Location: Phoenix,
AZ
Cobra Make, Engine: Ex owner of a polished Kirkham 427 S/C. Now Cobra-less and driving a mid-engine German hot rod.
Posts: 828
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Not Ranked
I have the Avons on my car (20-22 psi) with a TKO600 and if I hammer it in 2nd gear it will hook up and get very light in the front and I haven't broke the Tremec yet. I hit it hard in 5th pretty regularly too. I don't think you will hurt a TKO600 with your setup Scott
Make sure you know what overdrive ratio you want. I have a 3.54 rear and the 0.82 overdrive and it is perfect in my view (3000 rpm at about 80).
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12-06-2017, 09:45 AM
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CC Member
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Join Date: May 2012
Location: Wickenburg,
AZ
Cobra Make, Engine: Superformance, 427 FE
Posts: 197
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Not Ranked
I spent time on the rpm/trans calculators with regard to the 5th gear ratio. And read every post on here I could find on the subject as well as consulting with Charlie.
I am going with the .64. Here is why. My rear axle is a 3.73. If I drive around my town, speed limits are 35-45. When I leave town to go to Phoenix or Prescott the posted speed limit is 65. This means I drive around 70-75 just to cruise. This keeps the RPM's around 21 to 2200 witch is good for gas mileage....kidding..kidding
The trans coming out was a .68 and I was not disappointed.
I am still back and forth on the tires.
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If enough people disagree with me, I know I am doing it right
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12-06-2017, 08:34 PM
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CC Member
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Join Date: May 2006
Location: St. Louisville,
Oh
Cobra Make, Engine: A&C 67 427 cobra SB
Posts: 2,445
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Not Ranked
As one who has the .64 and hates it with a passion, I will make two points. The 4th to 5th shift is really like shifting from 4th to 6th. I had 3.50 rear gears and when I rebuilt the rear end I tossed in a set of 3.89 gears. 1-4 was perfect with the 3.50 gears, but 5th was too tall to go under 70 mph. Now with the 3.89 4th is too low to talk over. If you have very much cam you will learn to hate it. A BB with a mild cam will run OK.
Point two. If you really need the .64 then look at a 6 speed transmission. You will be happier.
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12-07-2017, 06:14 AM
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CC Member
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Join Date: Dec 2001
Location: Louisville,
KY
Cobra Make, Engine: I'm Cobra-less!
Posts: 9,417
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Not Ranked
I have never seen the use for a .64 OD in a Cobra......nor have I ever seen the use for a T-56 in a Cobra.
I believe if the engine/drivetrain/tires are designed to work together, a .82 OD is all that should be needed.
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12-07-2017, 08:15 AM
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CC Member
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Join Date: Dec 2012
Cobra Make, Engine:
Posts: 973
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I also have a the .64 and find it minimally useful. Unless I am touring on the Highway at speeds of 75 MPH all day long it's too steep of a gear and I am typically trying to find the happy point between 4th and 5th gear and it doesn't exist.
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12-07-2017, 11:11 AM
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CC Member
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Join Date: May 2012
Location: Wickenburg,
AZ
Cobra Make, Engine: Superformance, 427 FE
Posts: 197
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Not Ranked
If I had 3:50 rear gears, I see going .82. If I drove at 55-60 on the highway, same. But my highway drive is 75. The 428FE did fine for me with .68. So I am thinking with a 70% increase in power should be good. Torque is a beast from idle to 5500. Highest at 3600. According to the calculator, I will be over 2000 RPM. From the engine dyno that is around 650 TQ and 300 HP.
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If enough people disagree with me, I know I am doing it right
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12-07-2017, 11:11 AM
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CC Member
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Join Date: Sep 2002
Location: Grand Rapids,
MI
Cobra Make, Engine: FFR Challenge Car, RDI aluminum 427w
Posts: 355
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Not Ranked
3.27 rear and .64 OD by choice. I like it and wouldn't make a change to the .8 whatever it is. Started with 3.73 gears and switched, never looked back.
That said I'd like a 6-speed to have the option of the two ODs and better shifting. The .8 5th gear would fill the long jump between 4th and 5th.
80mph at 2,200rpm worked well for my cross country cruising. I used 4th if I wanted to go fast, easy 140 and 150+ was possible.
My new FFR build will be 3.31 gears with same engine/trans combo.
It might make a moments worth of sense to decide on a few parameters first:
What do you expect?
How to you drive or plan to drive?
Distances or type of driving?
Racing - HPDE, auto-X, road racing, drag racing?
Engine and power bandwidth?
Tires and sizes?
Do you want to shred the tires on every take-off?
Would you like a first gear that will actually work in town or is starting in second OK?
How fast do you want to cruise on back country roads?
At what speed are you comfortable on the expressways?
I think engine performance has a lot to do with the gearing selected.
The "best" is rather academic as everyone lives with different parameters, performance and expectations.
Jim
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12-07-2017, 12:50 PM
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Senior Club Cobra Member
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Join Date: Feb 2007
Cobra Make, Engine: KMP 539, a Ton of Aluminum
Posts: 9,591
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Not Ranked
I think I have the earlier 3.42 rear diff from Kirkham and the 0.82 5th gear and it's pretty close to being perfect. I'd actually wouldn't mind going to a numerically higher ratio, like Mike, who has 3.54, but it's not worth the pesos.
I just installed Avons and I think they're wee bit smaller than the Yoko's, so maybe that'll help get the rpms more.
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