Drivetrain Calculations

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Today, I dropped off the rear axle to get it rebuilt, powder coated, and reinforced. It is the original 9″ rearend, with 2.75 gear ratio. I will post the details of that build when I get it. But I will say I am changing the ratio to 4.10:1.

In order to figure out the whole drivetrain, I did a quick search online for a drivetrain calculator and came across this here. I am giving all credit to the author. I just took it and modified it to fit the resto-mod I am doing, add a few formatting and graphs so I can quickly do a visual check as I change values. The excel is very simple to use. Just enter some of the values you control like which transmission you have, wheel size and tire types, etc… and it will spit out the RPM and MPH. My goal is to go for acceleration in this case, and not top speed.

If you want my version of the calculator, send the request in the comments and I will post it.

Let’s start with the engine: Top RPM = 7200 per engine spec.

PRODUCT SPECIFICATIONS:
Displacement: 4.957L (302 ci)
Bore / Stroke 3.629” bore / 3.649”stroke
Horsepower: 700
Torque: 606
Compression: 9.5:1
Block: New Ford Aluminum
Cylinder Heads: Factory Aluminum 54.5 – 57.5cc
Supercharger: Edelbrock E-Force
Pistons: Mahle Forged Aluminum
Crankshaft: Forged 4340
Camshaft Duration: Intake: 260°; Exhaust: /263°
Camshaft Lift: Intake: 12mm; Exhaust 11mm
Rocker Arms: 2:1 ratio
Spark Plugs: Ford M-12405-M50 (.032 Gap)
Fuel Type: Requires 91 Octane At All Times
Firing Order: 1-5-4-8-6-3-7-2
Maximum Rated RPM: 7200 RPM
Warranty: 2 Year/Unlimited Mileage

With that input, I am looking at the following dyno results. I will of course be running my car on the dyno when it is ready. but until then, I am going to trust this run.

Edelbrock Coyote Graph

Edelbrock Coyote Dyno Run

With this much power coming out of the Coyote, the whole drivetrain needed to be updated. After much reading and talking to people on different forums or by phone, I settled on the transmission; a TREMEC T56 Magnum. It fits the range of the HP and Torque the Coyote will put out.

Tremec T56 Magnum Transmission (copyright Tremec) taken from their website

Tremec T56 Magnum Transmission (copyright Tremec) taken from their website

  • The aftermarket’s premier 6-speed performance manual transmission
  • 700 lb-ft. of torque capacity
  • Reasonably light at 135 lbs. dry
  • Multiple shifter locations & dual speedo pickups for unmatched versatility
  • Choice of two different gear ratio sets (2.66 or 2.97), with unique double overdrive ratios
  • Incredibly short, extremely low-effort shift throws, with crisp, precise engagement
  • Modern OE supercar technology for the ultimate pro-tourers, road-racers, and more.

With the major components picked out, I went ahead and finalized the Drivetrain Calculator. I will add more details specifically to the transmission and engine as I get those in and installed. they are special enough to get their own reviews.

Drivetrain Calculator Inputs:

Input values for the calculator

Input values for the calculator

The one note I am going to add is that the tires are a placeholder. Given that until I get the rearend in place, and the fenders on the front, I will not be able to measure the clearance I have to get the biggest tires in there. The goal here is to get the biggest wheels I can get in, and the widest wheel for the back. Width does not matter for the calculation here. I opted for 19″ for the front and back, and I have seen pictures and talked to people who were able to fit a 19″ or 20″ in the back without any modifications. I will measure it once i am done with the setup. It is an expensive purchase (wheels and tires) to get it wrong and not be able to use them once you have them. The threshold for the complete diameter (wheel + tire) is to keep it as close to 26″ total. In my case, it is 26.30″. If I can more with the rear suspension I put in, I will push it to 20″, otherwise, 19″ it is.

With that, the following is the data table:

Drivetrain calculator output table

Drivetrain calculator output table

The cells with the reddish tint are based on the 7200 RPM limit I am using for the engine.

So what do I know from here: The car will go fast…but will also accelerate faster. Acceleration will be calculated when I get it on the road.

The above tables in a graph format:

 

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