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I am building a MK4, 3.55 IRS, Coyote engine, all parts order from Forte's. I had my mine set on a (TCET5008) TKO 600 2.87 first gear and .64 fifth gear. Now debating about using TCET4615 TKO 500 which has a 3.27 first and a .68 fifth gear. The car is just going to be used for fun, no racing planned. Forte said both would be a good pick but the Coyote with its high rev engine the gears in the TKO 500 might be better. Would anyone like to chime in please! Monday is the order date..
 

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Danwmn,

Second Strike Gearing Calculator

The SecondStrike gearing calculator might help to evaluate some options. If you have a basic idea of the torque curve it may start to make sense as to where you'll shift and where the power will be.

I run 3.27 gears and the TKO-600 w/ the .64 OD. Works for my 427 Windsor but the torque and hp curve is different than the Coyote. This combination does provide a first gear that works and doesn't need to be shifted right away.

Good luck on your evaluation and project. I hope someone with direct experience can offer suggestions.

Jim
 

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Forte's right. I think the engine will handle either just fine. The 600 has closer 1-4 but a big drop to 5th. The 500 is more evenly spaced but the lower 1st will have you grabbing 2nd before you get across the intersection and with that 3.55 you may want the taller .64 for cruising at freeway speeds.

Long, open roads near Mankato?
 

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If I had it to do all over again, I'd also go with IRS, but this option also allows you to use the new T56 Magnum 6-speed.
 

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I'd like to hear more opinions on this topic as well, but can make a couple of comments.
The coyote has a very wide operating range, so it will still be happy with a transmission that has a wide gear spacing. That would allow for the 3.27 / .64 OD combination, and it'd be perfectly happy. There are a lot of engines out there that don't have such a wide operating range and would prefer the TKO 600 with a closer gear spacing to keep it in the power band. You don't need the tight ratios, so enjoy all the range you can get. (at least that's my theory) :)

I'll be going with a TR3650 (similar gearing to the TKO 500), but I am struggling with which rear gears to throw in. I've done all kinds of analysis on speeds, rwtq, ect, and I am leaning towards 3.73s. I am still looking to hear actual experience instead of seeing numbers on a paper. But this is an engine that revs to 7k rpm, so I would think it'd be good to gear it to let it sing. When I searched what gears people were happy with on the DOHC 4.6 engines, pretty much everyone agreed at least a 3.73 helps a lot, and this is a 7K rpm engine too. Then again, it doesn't make the same low and mid range torque as the coyote, so a bit different....
 

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I have an older TKO with a 3.29 1st gear. I really like that low first gear. Easy to get going on a hill, easy to drive in parking lots, just generally easy to get moving.

You always hear that a lower first gear means you'll be shifting into 2nd so soon that 1st gear is "useless". That is a myth, and definatly not true. If you do the math, you'll see how little difference it makes in your shift point.
 

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If you do the math, you'll see how little difference it makes in your shift point.
About 13%:
2.87 first gear = 22 MPH @ 3,000 RPM; 36 MPH @ 5,000; 51 MPH @ 7,000

3.27 first gear = 19 MPH @ 3,000 RPM; 32 MPH @ 5,000; 45 MPH @ 7,000

Jeff
 

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If you do the math, you'll see how little difference it makes in your shift point.
I'm waiting for my Levy Super Alloy T5 and will be going from the 3.35 1st to the 2.95. I was a little worried about how it might affect take-off but, like the numbers say, there's not much difference. My 5th in the roadster is a .64 with 3.27 final and I like it. It is longer than most other vehicles between 4-5, but suits me because I like a calm rev cruising on the FWY.

THE biggest influence here is personal preference. The 2nd is the rear gears, but that is also a personal choice. For most people the numbers don't mean much unless you're trying to achieve a known goal.

Jeff's numbers don't lie, There isn't much difference between the two. You need to think about your driving style and what you want as far as revs from the engine.

I know the topic is gearbox ratios but I'll talk rears a bit because that is where my real world experiences are an I think there is a nexus. I've played with manual geared BMWs for years and changed the rear gears up and down the spectrum from 2.81 to 4.10. I like the 3.46 but it still winds up on the FWY above 70 with a .81 5th. This is also an engine that is happy to rev but I prefer to cruise at a lower RPM. In the BMW world, many owners rave about the 3.73 rears but that makes it worse at speed. 3K to go 60 MPH. The guys that run turbos on theirs usually run a 3.25 rear. Anything lower truly makes 1st useless.

Brian, by your avatars it looks like drag racing is your thing. 3.73s may be right for you. But the mentions of engines being happy at 7K is very subjective. The engine may be happy there, but how long do you want to be there? Living at 5-7k is a drag race or big track road race thing and I doubt most people would be comfortable with the frequency and the volume for very long while cruising the streets.

You can still let your engine sing with 3.55 or even 3.27 on acceleration and have more comfort and less shifting especially if you have a street car. These cars have plenty of power and are light enough to easily handle 3.27 rears.
 

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Yes, it certainly does depend on personal preference. This engine has such a wide torque band and is so flexible, it could be happy with nearly any reasonable gearing configuration. If it helps anyone, I made a chart showing the speed for 7000rpm with various gear ratios. It also shows the rpm at a 70mph cruise in 5th for each of the ratios. If you can cruise comfortablly in 5th at highway speeds, then you can keep the revs low enough to be comfortable in normal driving. The transmission gearing is based on the TR-3650, but the T45 and TKO500 have VERY similar gearing:



A 3.73 gear puts you at 2400rpm at 70mph, which can be perfectly comfortable. If you make long trips and drive 80mph, that'll put you at 2750 rpm, which could really wear on you. In that case, get something like a 3.27so you run 2400rpm at 80mph.

For drag racing, a 3.27 could work if you plan to run out 3rd at around 120mph. A 3.55 would be a PITA as you will shift just before the traps (110mph shift out of 3rd, on a car that should trap 115-120mph). A 3.73 could work as you'll shift to 4th just after the 1/8th. A 3.90 or 4.10 would be more ideal as you could run out 4th through the traps at 126mph or 133mph respectively.

For auto-X, you'll probably choose a gear and stay there the whole run (2nd gear). I am guessing the fastest you'll ever get to is 65-70mph on an auto-x course. Based on that, the 3.73 or 3.55 would work well. A 3.27 will run out to 79mph... so you may be wishing for more torque out of corners and a few more revs to make the most of your run.

The last analysis I did was to see what kind of acceration you'd see and what a summer tire could hook up. Full throttle in 1st will always result in tire spin, so we really care about 2nd. I tried to run a few calcs with the coyote and various gear ratios, and it seems to me like a 3.27 gear would hook a typical summer tire in 2nd. With a 3.73 gear, it seems like a typical summer tire may not stay hooked up. If you plan to run a drag radial or something else with some good bite, you could get away with a steeper gear.

So a 3.27 gear could work very well on a street tire coyote roadster: you'll be able to hook a street tire in 2nd, cruise 80mph at 2400rpm, and run out the 1/4 in 3rd at 120mph. But you'll have to be careful running out gears on the street... 2nd will take you to 79mph, and 3rd high enough to be thrown in jail.

I am still looking at a 3.73 gear since I am planning to run something sticky, like the nitto 555R or NT05R. The gear seems to work better for what I want to do, 1/4 mile, autoX, and letting the engine sing on the street without breaking the speed limits too badly (69mph in 2nd, and 105mph in 3rd). I don't think highway will be bad at all, at [email protected]
 
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