Help Selecting the RIGHT 5spd Transmission
 

I have had my Backdraft sitting under a cover in my garage since I picked it up from Florida last May, and I am finally unburying myself to where I can actually see about getting a transmission and installing my engine.

The only Cobra I've driven was a friend's "sister" Backdraft with a 3.46 rear end (like mine) and a relatively mild 375hp 351W (like mine). I have a mild cam favoring the mid-range with decent low-end torque.

He has a T-5 in his, but I didn't care for the gearing at all.

I have owned a several HiPo cars (Corvettes and TVR Tuscans), and have been very easy on them all. I will never track the car, and doubt my car will ever see full throttle or 6000rpm, so I don't need a race-strong transmission.

1st on the T-5 was too high for around town, or hilly country, where starts required a lot of slipping of the clutch. I didn't mind the gear spacing from there through 4th, but I HATED 5th OD with its super OD .62 gearing. WAY too wide a hole between 4th and 5th.

Since I drove my friend's machine, he's installed a 3.91 rear end (I haven't driven it since I am half a country away), which he says has made
1st gear better, but it left 4th too low now, leaving the same big hole to 5th, which is now a reasonable highway gear.

Most of my local driving will be between 45 and 50mph under very light throttle, which I would like to be able to loaf-around at maybe 1500rpm in 5th gear (30 or 32mph per 1000rpm). That would seem to give absolute top speed at around 5000rpm in 5th, which sounds right to me.

What 5spd transmission would give me a good set of stock ratios (no internal gearing changed needed) with decent spacing between 4th and 5th OD? Preferably w/o having to change rear gearing, please.

Ideally I'd like 5th to be .74 or thereabouts, but the only 5thODs I see are .62 or .82, with nothing in between.

Physically, my driveshaft is sized for standard length transmissions like the T-5, so I'd favor one not requiring shortening of the shaft if possible.

Thanks,
Bob

Gforce makes a T5 with the .72 fifth and .80 is also available in the T5 from Astro and a couple others I can't recall right now.
You might check what first gear you have in your particular T5. The T5Z and some of the aftermarket T5's come with a 2.95 first gear. However, the earlier T5's came with a 3:35 first gear which would work better for your purposes.

Having a T5 built with the right combination of gear ratios would probably be your best bet, all things being considered. Check with Gordon Levy or Modern Driveline and you should be able to find what you need.

Bob

I don't have a T-5 (or any transmission yet), but I will see about going with the taller 1st and maybe a .82 5th.

Hopefully that is a lower cost alternative to some of the pricey alternatives.

Thanks-

Hi Bob,
If you have the 3.46 rear gear you'll be going about 67 MPH @ 3000 RPM. If you have a TKO-600 with a .82 5th it will reduce your RPM to 2460 RPM. In 4th gear your 2000-3000 RPM is about 44-67 MPH. In 5th your 2000-3000 RPM will be 54-81 MPH. These speeds are all figured with a nominal 26 inch rear tire.
Before you purchase a transmission you need to think how and where you plan to drive your car. Back roads, highway cruiser, fast lane blasts and at what speed will determine which model and gear ratio will fill your needs best.
Call me with any questions.
Mike Forte

Have you considered the Richmond "Road Race" 5 spd? 5th gear is 1:1 but the gap from 4th to 5th is about half way between the two tremec options. You just need to get the correct diff for your application.

If you're going to be easy on the car, I would suggest a World Class T5. They're rated for about 400hp. First gear on those are 2.95:1, roughly the same as a TKO 600 or wide ratio Toploader.

If you're dead set on a lower 1st gear, you can opt with a TKO 500, with a 3.27:1 1st gear.

However, I don't think you need anything that low...and any engine with any torque at all should be able to move a 2500 lb car (on a hill or otherwise) with a super low 1st gear. If 5th gear is too high for you in a 55-60mph zone, then just use 4th gear.

If I were in your spot, just wanting a cruiser, I'd go with a new T5.

I sell all of the above and can help you fine tune a decision.

Shoot me an email, brent@b2motorsportsllc.com or give me a call: 502.759.1431

Go with a new T5 you can get it with a .73 gear installed... Mac

I agree, I have the T-5 with the .82 fifth gear and a 3.73 rear end. Big jump to 5th from fourth, but an excellent cruising gear. I'm turning around 2400 rpm at 80 MPH.

With your rear end, the .82 might be a little too high to effectively cruise. Drop to a .73 and be happy.

When I first assembled my car I used an early t-5, 2.95 1st and a .73 5th. I loved the ratios. I replaced it with a t-5z because I thought I needed a stonger tranny. Don't know why, the t-5 never gave me any trouble; I still have it. Never thought about selling it...T-5z feels like a 6 speed without 5th gear. Maybe why I still have the t-5

I'm a Toploader guy. A built 4 speed Toploader with the gear ratios of your pick is the way to go.
Regards,

There is another option which is the Richmond "super street" 5 speed which is overdrive in 5th gear @.77 ratio. They have 3 different 1st gear ratio options and it is rated for 600 ft-lbs of torque. They cost a little more than a Tremec TKO 600 but the Richmond has correct input shaft lengths for all Ford engines so that you don't have to spend another $150-$300 to get a spacer or shortened input shaft for some engine applications. It includes a "Long" brand shifter unit.
If this would be right for you, shop around because I bought mine for about $400 less than Summit or Jeg's want. I bought mine from Gilbert Chev in Oregon or Wash. even though I was buying a Ford unit. They are a large Richmond dealer.

The Ford M-7003-Z T5 is a winner and cheap for what you get. -- if it is a street car, i would consider the rear gear set being knocked down to a 3.23 would get you where you want to be and have a very nice driving car.

Brand: Ford Racing
Product Line: Ford Racing Super-Duty T-5 Transmissions
Part Type: Manual Transmissions
Part Number: FMS-M-7003-Z
Number of Gears: Five
Input Shaft Diameter (in): 1.062 in.
Input Spline Quantity: 10
Output Shaft Spline Quantity: 28
Output Shaft Spline Diameter (in): 1.500 in.
Tailshaft Length (in): 7.180 in.
Bellhousing Included: No
Yoke Style: Bolt-on
Yoke Included: No
Shifter Included: Yes
Shifter Style Required: Stock
First Gear Ratio: 2.95:1
Second Gear Ratio: 1.94:1
Third Gear Ratio: 1.34:1
Fourth Gear Ratio: 1.00:1
Fifth Gear Ratio: 0.63:1