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Kirkham Motorsports

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  #1 (permalink)  
Old 12-04-2017, 06:51 PM
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Default 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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Old 12-04-2017, 07:07 PM
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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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Old 12-04-2017, 07:08 PM
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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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Old 12-04-2017, 07:37 PM
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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.

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Old 12-04-2017, 07:38 PM
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You said your old tranny was rated at 400 tq. What is it?

I'm looking for a 3550.

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Old 12-05-2017, 04:48 AM
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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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Old 12-05-2017, 04:59 AM
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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.

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Old 12-05-2017, 06:25 AM
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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.
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Old 12-05-2017, 11:58 AM
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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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Old 12-05-2017, 12:13 PM
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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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Old 12-05-2017, 02:40 PM
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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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Old 12-05-2017, 03:49 PM
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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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Old 12-05-2017, 06:29 PM
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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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Old 12-06-2017, 09:45 AM
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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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Old 12-06-2017, 08:34 PM
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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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Old 12-07-2017, 06:14 AM
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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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Old 12-07-2017, 08:15 AM
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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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Old 12-07-2017, 11:11 AM
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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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Old 12-07-2017, 11:11 AM
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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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Old 12-07-2017, 12:50 PM
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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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