Transmission opinions?
 

I've got a Superformance on order. Engine will be a 351w from Performance Engineering with approx. 460 hp. Right now the car is slated to get a TKO 500 tansmission. Any thoughts on the merits of upgrading to the TKO 600 road race? The rear end ratio is 3.46. I'm most concerned with first gear, and fifth gear. With the 500, the first to second shift point will be at 44 mph. With the 600, it would be at 50 mph. For cruising at 70 mph, the 500 will be at 1980 rpm and the 600 would be at 2380 rpm.

Which way should I go? Feedback from the dealer suggests that folks are very happy with the TKO 500 now the the rear diff ratio is higher than it used to be.

For the price difference (I think its less than $100) go with the TKO 600. I am currently installing mine and went with the .82 overdrive. Using the gearing calculator the following numbers are calc'd for 5th gear..first number is the .82, second is the .64

2000 56 72
3000 84 107
4000 112 143
5000 140 179
6000 167 215

If you were going to do a ton of highway driving you may want to consider the .64 5th.

The .82 VS .64 debate will be better answered by where your engine is happy.
If you do a lot of highway driving and your engine is happy at 1900-2200 RPM the .64 will be fine. If it doesn't smooth out until 2600 then get the .82

The RPM drop from fourth to fifth with a .64 OD makes it all but unusable for anything. Most Cobra engines have bad manners when asked to operate below 2000 RPM. They tend to buck, chug and fart because they work better in the midrange. The RPM drop from fourth to fifth with the .82 OD makes it feel like a real fifth gear and gets away from the bucking and farting.

There is a bigger issue yet you may want to ponder. The TKO transmission is a direct decendant of the 3550. Some internal gear design changes improved steels and presto 500 and 600 lbs-ft torque capacity. The transmission's weakspot is a mainshaft/countershaft misalingment on third gear that is 0.140" (or more on some). The misalignment leads to a premature third gear failure if you are hooked up and hit third with the kind of suds a 500 HP engine can produce.

You may hear a lot of that won't happen to you kind of talk but the more significant statement might be why put yourself in harm's way when you don't have to? So what's the alternative?

The T-56 is, not withstanding the published specs, a superior unit from both a design and shifting standpoint. The shifts are much smoother and cleaner because of the basic design but also because of the triple cone synchronizers used in the unit that are not available in the TKO. Additionally there are significant aftermarket gearsets available that had their genesis in factory backed race efforts. These previously unobtanium based pieces can raise the transmission's power transmission limits to a reportedly 1200HP and 1000 lbs-ft of torque level!

Are the numbers real? Don't know. Lets say the real numbers are 25% lower; you're still at 900 HP and 750 lbs-ft of torque! Additionally you have very nice fifth and sixth gears with .89 and .75/.76 ODs in fifth and sixth. The fifth and sixth gear changes actually feel good and the engine doesn't take a big gulp as it drops to near idle rpm on the gear change like a 1:1 going to a .64OD.

The transmission is bigger than a TKO and about 20# heavier than a TKO but it will fit in the car with a little bit of the same elbow grease we used to put everything else in the car. Here is the link for the Transzilla option ==>http://www.rsgear.com/transzilla.asp These are basically the previously unobtainable gear sets GM and Chrylser used in their Corvette and Viper factory race cars. They's potent!

Attached is a pic of a broken TKO600 third gear. It ain't pretty.

I'm having difficulty uploading the image. You can read the whole story (and see the pictures) on CC here ==> http://www.clubcobra.com/forums/transmission-talk/73975-tko600-warning.html

If you haven't purchased yet give serious consideratioin to the Transzilla offering. It'l fit and it is impressive!

Ed

edited because I can't spell worth a damn

TKO 600

Gear 1st 2nd 3rd 4th 5th 6th
Trans Ratio 2.87 1.89 1.28 1.00 0.64


The TKO 500 has a 3.27 1st gear
note the 600 has a 2.87 1st gear, this made a big different to me. I have a 3:55 rear end with 25 1/4" tires. My TKO with a 3.27 1st was useless. I love my TKO 600 with a .64 OD and a useable 1st gear for me. My small block will cruise smoothly at 1400-1500 rpms because of the low end torque I have.

Tire size, rear end ratio, engine torque range and the way you will drive your car will determine what trannie you need.


Dwight

This is not aimed at anyone inparticular as i've seen it repetively on this and other boards.Why do a vast majority of people think the idea is to get cruising rpms as low as possible?
The trans should be "plugged" in to the equation from the beginning.Where your motor makes it power/trans/rear gear.1st gear ratio is another consideration.
Cruising at 1950 rpms?Hell,that's high idle for some engines here.In and out of the idle circuit,advance not fully in makes for crappy fuel economy and your motor will hate you.

TKO 600 with 0.82 5th. perfect

CobraBill

there was a time when I could not cruise under 2100 rpms without "trailer hitch jerk".

Last winter I build a stroker small block with lot of low end torque and fuel injection. Now I can cruise at 1500 rpms. And my buddy Coach Mike, with his stroked 428 can not cruise under 1900 rpms with out the trailer hitch jerks. Different motors, different everything and they cruise smoothly at different rpms. After 5 years of changing things to get a Cobra that cruise smoothly and is quick, well I happy. And 21 mpg, it's just right for ME.:)

Dwight

TKO 600 for sure.
Your cam will determine whether or not your motor will be happy at 1600-1900 rpms or happier at 2300 for cruising. I have a mild cam and can cruise at 2000 happily. I enjoy my .64 OD but the rpms do certainly drop. It's just for the highway-if you're racing and for some reason need to use 5th, you will lose and .64 is not right for your usage.
I never need 5th on the track, so I'm fine. And you should be too.
With the stock 3.73 rear end, my 1st gear is useless. Your 3.54 will be much better.
But I get 20.02 mpg's on the highway with that .64, which is better than the wife's Explorer! :LOL:

Dwight-like i said-it's a combination thing................

Madmiles-at 2000 your advance isn't even fully in.

[quote=ztarum]I've got a Superformance on order. Engine will be a 351w from Performance Engineering with approx. 460 hp. Right now the car is slated to get a TKO 500 tansmission. Any thoughts on the merits of upgrading to the TKO 600 road race? The rear end ratio is 3.46. I'm most concerned with first gear, and fifth gear. With the 500, the first to second shift point will be at 44 mph. With the 600, it would be at 50 mph. For cruising at 70 mph, the 500 will be at 1980 rpm and the 600 would be at 2380 rpm.[quote]

ZTARUM;

Your engine will not like any performance demands below 2-grand on the tach. Having said that, forget about "cruise rpm" for highway driving -- the .82 fifth is the ticket in these cars.

With regard to the TKO 500/600 issue, the 600 is just a beefier transmission, designed to handle more torque without turning into a 5-speed hand grenade. Spend the extra few dollars to buy some piece of mind -- go with the 600.

By the way, you'll like the engine Eric and his crew builds for you. Our powerplant came from PE, too. Man does it ever roast some rubber!


Bryon

Of course, there is always the option of the Gforce T5 or Gordon Levy's Super Duty T5. Both will easily handle the horsepower and torque you'll be putting down and are quite a bit lighter.
Just another option to look at.

TKO 600 with the .82 all day long.... best trans I have had yet.... I have the T-56 in my Viper, not near as easy to shift and easy to miss a gear (2nd to 5th, 4th to 1st!!). Never missed a shift once with the TKO.

For those worried about mpg and cruising at 2000rpm, maybe an auto would be the ticket!!! :) lol

Thanks all for the comments. I guess I need to speak to the engine builder and see what he thinks about the various overdrive ratios and how the engine will behave.

I have the TKO 600 with .64 5th and 3.73 rear gear. My rear tires are 28" tall with the drag radials on the 15" wheels. I like it, but would rather have the .82 5th gear if I did it again. I can fart along in 5th at 1500 rpm with the .64, but would rather fart along at a little higher rpm with a change to a .82 5th.

The 351 Eric built for me - 469 HP with a 'mild' cam, well suited for the street - came into its own at 2,800 RPM and it was most comfortable at 3,400-3,600. The higher RPM's gave ample engine braking entering a corner along with predictable and immediate response accelerating through and out of a corner. Above 4,000 the acceleration was too quick for my reflexes in any but a long, continuous corner.

Highway driving at 2,200 only invited what the folks who stopped to visit termed 'excessive speed.' The 351 tolerated low rpms without loading-up but the engine was clearly better suited to agressive, involved driving, the sort you get into on two lane county roads through the foothills. The 0.82 final will work fine; you are only a downshift away from the engine behavior that suits these cars.