I will swap to a . 64 one day if I keep the TKO-600. I cruise 70mph+ a pretty good bit and it just makes since if you start throwing gears in the car.
It has been said that it is expensive and heavy but the T-56 offers awesome gearing selection. I think you will be pleased.

Sounds like you have a .80 5th and .64 6th.

Yours would be all closer ratios with 1st to 3rd all taller than the box we get here.

A much better ratio combo than the useless .74:1 5th and .5:1 6th.

I have a 26.3" diameter tire and a TKO 600 with the .64 5th gear. When I got the car it had a 3.5 rear end.

In 4th gear I tacked 2550 rpm at 57 MPH -- this is getting loud (typically drove 50 if no traffic so I could talk to the wife)
In 5th gear I tacked 1625 rpm at 57 MPH -- Quiet - careful on the throttle! Don't get it bucking) dang it shift back to 4th.
In 5th gear I tacked 1850 rpm at 65 MPH -- not happy until you get a speeding ticket

My engine will not run well below 1800 and it would prefer 2000.

I changed to a 3.92 rear end ratio
In 4th gear I tacked 2850 rpm at 57 MPH -- wow is this loud. Amazing the difference 300 rpm makes
In 5th gear I tacked 1825 rpm at 57 MPH -- quite and manageable
In 5th gear I tacked 2000 rpm at 62 MPH -- engine loves the highway

Basically I went from a useless 5th gear to a useless 4th gear, by choice. I felt that was the best compromise, as I can drive 55 MPH in 5th gear.

I hate the .64 5th ratio. They should call it 6th gear cause there is no 5th gear. I hate the huge rpm change from 4th to 5th. I had to rebuild the rear end, as I had a bad bearing, and it was cost effective and simple to change the ratio. It's a lot better than it was, but I would still prefer the .82 5th gear. If I do change to the .82, I will change back to the 3.5 rear end.

I am replacing a 2.32/1.69/1.29/1 toploader with a T56 from Rockland Standard - 2.29/1.60/1.21/1.00/0.84/0.67. My Unique FIA has a 3.54 rear, with 245/15 Avon CR6ZZs.

Previously, I had another cobra with 3.31 rear gears and the 2.32 toploader. I really like the 4 speed CR gearing, and the T56 is very close.

The T56 is a heavy thing....I'm still not over the hard part of the install. But I went from an iron block & head windsor to an aluminum Dart/Kaase headed engine. It will be lighter than before! Brent Lykins gathered all my clutch parts - knowledgable and quick!

I'm booked for the next few weeks so getting this thing running is a ways off. There's always a few more details than I can see.

9-10-2016 Update
All the things below are on the table to be part of the overhaul. After driving the car for a year I know more about what I want it to be so these are the modifications below that we have come up with. I strongly considering going to a stroked 385 engine but I have convinced myself to upgrade other parts of the car in hopes of it providing sufficient power to hold me over for longer.

The motor was pulled about a month ago. Work has been very busy so I haven't had much time to start on the cleaning of parts but I plan on getting a few hours in tomorrow. Below is a tentative list of some of the upgrades we are kicking around
http://i1291.photobucket.com/albums/...psbd4jlavo.jpg
http://i1291.photobucket.com/albums/...psx2bzhowq.jpg
http://i1291.photobucket.com/albums/...psjipis7tv.jpg
http://i1291.photobucket.com/albums/...pskmqdhqdp.png
This picture is all Perry. I've been in the office trying to make the money to pay for all this!
1. We are swapping the cam to what Brent with Lykins Motorsports has specified. The cam that is being replaced is 252/262 at .576 /.576 lift with112LSA at 112 ICL. The cam that is going is 244/248 at .580/.590 lift with a 108 LSA installed at 104 ICL. New cam is expected to peak around 6000rpm and will allow for 6200-6500 shifting if needed.

2. While the engine is out I have a new waterpump that is going on it. I am also swapping the current victor jr to a polished victor jr.

3. It is time for tires.....the 17" wheels seem to pick up most road imperfections are quite harsh on most backroads....... I want to try a set of 15" wheels and I want to run the NittoNT555 drag radials on all 4 corners. This is only a fair weather street car so getting in wet weather isn't a concern. I've spoken with Boby Lacy at Vintage wheels and he can shave the inner hub of the rear wheels to allow me to run the 325-50-15 on the rear as Greg Schroeder did in this older thread I came across http://www.clubcobra.com/forums/supe...rformance.html

4. Currently the car has a 3:31 and I would like to put more gear in it but the TKO-600 doesn't allow for what I would call cruiser friendly RPM with more gear. We are currently looking at the possibility of going to a T56 as it would allow for more gear and more variety in speed ranges. Brent says minimum cruise for my new cam is 2000rpm. With the T56 and 4:10 rear the 4th gear looks great for 40mph+, 5th 50mph+ and 6th a nice 62mph+. Some may not be irritated with going down the highway but I've done the 3000rpm maintained RPM and I hate it. A Quicktime bellhousing will be used regardless whether the TKO-600 is kept or a T56 is used. I have highlighted some off the speeds below that look like they appeal to me.

TKO 600-.82 5th and 3:31 rear
Gear 1st 2nd 3rd 4th 5th 6th
Trans Ratio 2.87 1.89 1.28 1.00 0.82
315/35/17 rear tire size
1500 12 18 26 33 40
2000 15 23 35 44 54
2500 19 29 43 55 67
3000 23 35 52 66 81
3500 27 41 60 77 94
4000 31 47 69 88 108
4500 35 53 78 100 121
5000 39 59 86 111 135
5500 42 64 95 122 148
6000 46 70 104 133 162
6500 50 76 112 144 175
7000 54 82 121 155 189

T56 with 2.66 1st gear and 4:10 Rear gear
Gear 1st 2nd 3rd 4th 5th 6th
Trans Ratio 2.66 1.78 1.30 1.00 0.80 0.63
325-50-15 rear tire
1500 11 16 22 29 36 46
2000 15 22 30 39 49 62
2500 18 27 37 49 61 77
3000 22 33 45 58 73 93
3500 26 38 52 68 85 108
4000 29 44 60 78 97 123
4500 33 49 67 87 109 139
5000 37 55 75 97 121 154
5500 40 60 82 107 134 170
6000 44 65 90 117 146 185
6500 47 71 97 126 158 200
7000 51 76 105 136 170 216

5. With the use of 4.10 gearing and sticky tires we thought that it woud be wise to look into a 31 spline axle upgrade. This would require me to send the differential out.....new bearings, new seals, 4:10 motive gears, Eaton Tru-Trac, Drive shaft shop chromoly 31 spline axles. The T56 will also require a new driveshaft.

6. The flywheel in the car is aluminum......with the 4:10 gears and it being a street car I'm not sure whether we will use the aluminum or go to a billet steel flywheel. I believe the aluminum one is currently around 13lb. Looking at going to a RST twin disk .

7. The 2" headers were covering up a portion of the exhaust port because the bolt holes in the flanges were too far down. Working with GP headers to have the headers modified for the proper flanges. Also considering having my 2.5ID exhaust opened up to 3". Perry had performance engineering modify his SPF pipes and they are about 3 times deeper than mine.....it is what a cobra should sound like in my opinion.

8. The Brodix TRX 1 heads are going to be sent back out to Craft racing to be freshened with new seals ect.

9. I'm going to take the seats to a local shop to get them restuffed......much flatter than other SPF I have been in. Just a wear and tear item.

SPF 522 has a new KC 427 with ported Air Gap dual plane, 236/242 @ 050 cam, aluminum flywheel. excellent street manners, cruises at 1600 rpm, instant throttle response, and a very broad torque curve... ample power everywhere.

4.10 is a lot, especially with an aluminum flywheel. my motor unwinds quick, shifts need to be very fast or rpm drops too much. Currently have 3.90s and plan on dropping to 3.27


On the diff, solid bushing mounts will take care of wheelhop, a major contributor to broken halfshafts. Purchased them from Craigs Cobras.

Congrats on your new motor it sounds like a great power plant. I can see why you desire a gear change as you probably have a great range of power whey my car did not. With the broad range of power that you have the 3.27 will probably work great for you.

Maybe I am thinking about this incorrectly but when you go from 3.90's to 3.27 isn't your motor going to unwind quicker? My car with the 3.31 would drop rpms very quickly and i was really noticable in the 1-2-3 shift aroud town. I have been advised to keep the aluminum flywheel if I go with 4:10's

I spoke to Craig about his solid mounts and he said he did not advise using them on a street car used for cruising IF the sound of the differential clunking around would be noticed as it could be irritating to some. Have you experienced this with your upgrade?

Update 9.12.2016

Spent a few hours prepping the block and timing cover to be repainted. The cylinder heads are boxed up and are going out to Craft racing this afternoon.
This is the Ram aluminum flwheel that Oltoff put in the car about 6000 miles ago. I am told new friction inserts can be put in this flywheel if needed. I was not aware of the aluminum flywheel until we pulled it out of the car as I didn't pick up on it in the build sheet. Does anyone see any abnormal wear? .
http://i1291.photobucket.com/albums/...ps3vvznqsi.jpg
http://i1291.photobucket.com/albums/...psqlek1zok.jpg
This is the McLeod Clutch that was in the car also put in about 6000 miles ago. I cannot tell what model clutch this is and the Oltoff reciepts just reference it being a McLeod
http://i1291.photobucket.com/albums/...psoc1ecd84.jpg
http://i1291.photobucket.com/albums/...psu6qn69rk.jpg
http://i1291.photobucket.com/albums/...ps3zkhhglb.jpg
Check out the headers and how the bolt holes were not exactly where they should have been to create a good seal on the header which was causing the header to sit too far down. The flanges were overlapping a small portion of the ports but more than anything were not sealed correctly. You should be able to get a good indication by the cylinder head image.
http://i1291.photobucket.com/albums/...psumcxcjdz.jpg
http://i1291.photobucket.com/albums/...psdsyu1kwv.jpg

[quote=Ace23;1403250]Congrats on your new motor it sounds like a great power plant. I can see why you desire a gear change as you probably have a great range of power whey my car did not. With the broad range of power that you have the 3.27 will probably work great for you.

Maybe I am thinking about this incorrectly but when you go from 3.90's to 3.27 isn't your motor going to unwind quicker? My car with the 3.31 would drop rpms very quickly and i was really noticable in the 1-2-3 shift aroud town. I have been advised to keep the aluminum flywheel if I go with 4:10's

I spoke to Craig about his solid mounts and he said he did not advise using them on a street car used for cruising IF the sound of the differential clunking around would be noticed as it could be irritating to some. Have you experienced this with your upgrade?[/QUOTE








Yes, there is some additional noise due to the solid mounts. Only noticeable when coasting in neutral, 3 inch mufflers mask it well. I love the aluminum flywheel, but shifting is VERY busy when combined with 3.90s.

Those are SPF headers?

Yes, back in 2004 when the motor was built there is an email printed out in my receipt booklet that explains that there was an early set of 2" headers built for the SPF and this was the 2nd set they built. They fit the car well but obviously the bolt holes in the flanges were higher than they needed to be.

Looks like a 10.5" diaphragm plate with a 500 series disc. Rated for 525-550 hp.

Probably a McLeod super street pro Diaphragm with a dual friction disk. I have the same setup with an Aluminum Flywheel behind a 351w 495HP TKO 600 and 3.27 eaton trutrac with moser 31 spline axles. Absolutely no issues with the McLeod Aluminum 15lb. flywheel and I had the McLeod billet steel in there last year. The response from low rpms is Quicker than the steel FW. I got away from the thought of drag racing to autocross that's why I switched.

What do you guys think about the McLeod Street Extreme? Looks like it is rated for 700hp.

I have also been looking at the gearing calculator and I've spent some time looking at the MPH in all gears instead of focusing on just the 6th...... When you consider the change in tire size going from a 315/35/17 to a 325/50/15 plus the changes in gear ratios the gearing isn't as drastic as I thought it would be. Looks like you need to run a minimum of a 4.10 to make it worth wild.

Be careful with the Street Extreme, the only difference between the 550HP and the 700HP is the disk. The 700HP doesn't have an organic side and will probably chatter more off idle. I really don't think you need it. The Cobra is a light weight car.
As far as transmissions and gearing, you can drive yourself nuts with the formula. What do you plan on doing with the car. Are you a long hauler (Highway), do you just cruise the streets? Your car is cammed like mine. I have no issues with the TKO 600. I've had both the .64 and the .82. with a 27" tire. My motor is cammed like yours also. If I had one complaint it would be the large rpm drop of the .64, but 2200 rpms on the highway was quiet. .73 would have been ideal. I'm more concerned about my gearing for the autocross ( I run tight courses in my area, and will try 3.55 rear gears. So, you see what I mean, it really depends on what your going to do with your car.

I do a million of these combos....if you're wanting something to hold big horsepower and not chatter or have on/off engagement, you need a twin disc. Otherwise you're stuck with a very aggressive single disc that won't be fun on the street.

As for the rearend, a 3.73 to 4.10 is usually the sweet spot for these cars. Going from a 3.27-3.31 to either one of those ratios will be a dramatic difference.

I want my cake and I want the ice cream to go with it! My car is purely a street car and all I want is insane roll on power and a cruising gear.....thus I have been looking at the T56 tranny option. I know it cost more but if I can get more aggressive gearing than what I have now and still have a 6th gear for interstate / faster back road cruising then I think I would be really pleased with the car. I have looked at all the .82 TKO-600 combos and the 5th gear is too short when you get into 3.91+......I also don't like the idea of the .64 4th to 5th rpm drop. This new cam Brent specified and all the other freshening that is taking place should make a world of difference.

I have no issue with using a twin disk and I'm not willing to save a few hundred dollars to deal with chatter ect. I think you estimated my HP to be around 550HP with this new cam so while it isn't big horsepower it may future proof the car for future upgrades. I will take a look at the McLeod RST.....I believe this was in my previous 03 Cobra.

I see no benefit in running a T-56. It will be hard on your wallet, not only for the price of the trans, but for the driveshaft and everything else that you will have to buy for it. If you run a twin disc, the midplate will need to be modified for an adjustable ballstud plus you'll have to run a notched fork. Otherwise, it will be hydraulic throw out bearing.

I'm a T-56 hater, plain and simple. Too long, too big around, too heavy, not enough benefit from another gear to spend that much money.

You would not be able to tell any difference in performance between a 3.73 and a 4.10 gear. My $.02 would be to run the TKO 600 you have, put a 3.73 in the rear, and cruise at 70 in the lower 2000's.

If you stick a 3.73 in it and go the route of the 325-50-15 tire that pretty much is equivalent to running the current 315-35-17 with the 3.31 so I would expect no change in gearing performance. Would you still advise using an aluminum flywheel in this instance or would you be moving to billet steel style.

Forgot about the tire swap.

If anything I'd swap to a .64 OD TKO 600...or just leave it alone until you see how the new cam works.