Question on gears

What speeds will u hit on the tracks you race? What size diameter tire will you run?

If you know what transmission you currently are using, you can research the gear ratio for each gear. Using the rear end ratio and OD of the tire it is very easy to figure out your MPH at any RPM in any gear. Given tire expansion will be minimal for the tires you will be using, calculated speed will be within (1) MPH.
This can be adjusted slightly by changing the OD of the tire – example -
4.1 rear end gear, 1 to 1 trans gear ratio @ 6000RPM -
26” tire = 113.2 MPH
25” tire = 108.84 MPH

stkjock said:

What speeds will u hit on the tracks you race? What size diameter tire will you run?

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This. What tracks are you on? 3.73 might be great on a shorter track like Summit Point but might suck at Road America.

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3.73 is BRILLIANT at Road America. 5th gear, on the other hand.... There are very few tracks in my neck of the woods where the straights are long enough to hit 140+ MPH and require a shift up to 5th gear. Road America is one of them, and it sucks serious ass rowing up, but I wouldn't trade the grunt off the corner everywhere for more top speed. Really, the fault isn't with the 3.73 screw (or even a 3.90), it's with the 0.63 5th gear ratio on the early S197s. 3.73 is just a great all-around gear, with good grunt off the corners (a little weaker than the 3.90 or 4.10), but still lets you carry good speeds on the longer straights in 4th.

SoundGuyDave said:

Really, the fault isn't with the 3.73 screw (or even a 3.90), it's with the 0.63 5th gear ratio on the early S197s.

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Ford stuck it to us with that one. Thankfully, changing a transmission gear is cheap and easy. Right on par with a CAI swap. 5th gear should have been about .80-.85 IMO.

sheizasosay said:

Thankfully, changing a transmission gear is cheap and easy. Right on par with a CAI swap. 5th gear should have been about .80-.85 IMO.

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Do tell... Last time I researched it, it would take a custom main shaft, and of course, custom 5th gear to make that happen, all for a price slightly north of an Emco sequential box... The TR3650 is NOT a T5!

SoundGuyDave said:

Do tell... Last time I researched it, it would take a custom main shaft, and of course, custom 5th gear to make that happen, all for a price slightly north of an Emco sequential box... The TR3650 is NOT a T5!

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I think Liberty Transmission would offer some hardened and polished parts (forks, gears..etc) that would supposedly make the T3650 shift better and they offer a closer ratio and other ratio gears aswell. It's unfortunate that it does cost so much, but it cheaper than a magnum(barely). I think you will find more folks that even bother thinking of messing with the transmission just go ahead and go with the T56 kits like D&D offers. There are some pretty amazing transmissions out there. I've always thought the Jericho tranny's were cool. I just googled the Emco. That's what I'm talking about! Only $25k..... Just think of all the students that could just skip your "heel toe" trials.

I hated the stock 2.9x gears in my v6, until I got 275/35/18s which are some 1.5 inches smaller in diameter. Now its good. You'll want to run a degree or two more caster in front if you switch to this tire though because your mechanical trail will decrease.

sheizasosay said:

I think Liberty Transmission would offer some hardened and polished parts (forks, gears..etc) that would supposedly make the T3650 shift better and they offer a closer ratio and other ratio gears aswell. It's unfortunate that it does cost so much, but it cheaper than a magnum(barely). I think you will find more folks that even bother thinking of messing with the transmission just go ahead and go with the T56 kits like D&D offers. There are some pretty amazing transmissions out there. I've always thought the Jericho tranny's were cool. I just googled the Emco. That's what I'm talking about! Only $25k..... Just think of all the students that could just skip your "heel toe" trials.

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If anything ever happens to my transmission, I'm dropping a Magnum in it.

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Sky Render said:

If anything ever happens to my transmission, I'm dropping a Magnum in it.

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Tremtec 6 – Speed Magnum is a great transmission for the $$$ but it also weighs a ton - Dry 135+ LBS

TKO 5 Speed - Very Good transmission – Prox 100LBs Dry. I had a friend who had problems shifting at RPMs above 7200. He had to open the trans and make some changes.

T-5 acceptable transmission and can handle what I will ever throw at it. I do not drag race. 3rd gear is the week link with these transmissions. With an upgraded main shaft & gears weighs - 81.2 LBS WET – Not including bell housing or remote shifter assembly – Verified -

Raw weights are only half the story, though...

T56 Magnum XL is indeed a great trans for the money, BUT the ratios are not exactly optimized for track duty. Close, but not quite there for a SERIOUS track toy.

TKO is an older box, has a tendency to shift like a truck, and I have seen more than one lock solid due to internal shifter issues.

T5 is nice and light, and with the "Road Race 5th" from Astro, the ratios are about right. The only problem is that (as you mentioned) 3rd gear is made of glass. With my old CMC car, we went through FOUR of them in two seasons... They simply aren't up to handling the torque of a stock-ish pushrod 302 (260HP, 300lb-ft), much less a modern Mustang motor.

If you're going to do a trans swap, AND you are a SERIOUS track rat, then the best bang for the buck that I've seen is the T56 out of the Boss 302R. Yeah, they're six grand, not including clutch, crossmember and driveshaft, but what you gain is a close-ratio box designed for road racing, and including an internal cooler pump... The ability to keep the engine within the powerband at all points on track is well worth the small weight hit you take with this trans. Hell, with this box, 2nd gear is actually useful!

SoundGuyDave said:

Raw weights are only half the story, though...
T5 is nice and light, and with the "Road Race 5th" from Astro, the ratios are about right. The only problem is that (as you mentioned) 3rd gear is made of glass. With my old CMC car, we went through FOUR of them in two seasons... They simply aren't up to handling the torque of a stock-ish pushrod 302 (260HP, 300lb-ft), much less a modern Mustang motor.

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260 HP – 300 Torque - BOOM?
Dave - What were the internals – Shaft & gear cluster?
What kind of disk material & pressure plate clamp pressure?
Was it always 3rd that let go?
Thanks as always for the input DAVE. I always enjoy your threads.

SoundGuyDave said:

3.73 is BRILLIANT at Road America. 5th gear, on the other hand.... There are very few tracks in my neck of the woods where the straights are long enough to hit 140+ MPH and require a shift up to 5th gear.

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DAMN you're geared high. 120-130 is the end of third for me... At autocross the other day I almost got into fourth. Almost.

Personally, I like having WAY too much power and longer gears. Less shifting is always nice, and I can still pretty much smoke the tires whenever I want. At autocross I pretty much stay in second and third. I use first for some of the really tight, technical stuff, but that's about it.

2008 V6 said:

260 HP – 300 Torque - BOOM?
Dave - What were the internals – Shaft & gear cluster?
What kind of disk material & pressure plate clamp pressure?
Was it always 3rd that let go?
Thanks as always for the input DAVE. I always enjoy your threads.

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Per the CMC rules, the internals must be stock, so.... Stock. Clutch was the FRPP King Cobra kit, so not aggressive, nor high-clamp-load. And yes, it was 3rd gear that went pop. The teeth quite literally sheared off the gear, which then chewed up EVERYTHING in the box. My buddy Joe popped two, and I popped one, and all three times it went, it was under accel right about peak power. Yes, you could upgrade the trans to handle more torque (The 2014 CMC rules allow this, and the parts are already in to rebuild the trans...again...), but the jury is still out whether the Astro guts will be able to handle the 260/300 under race duty with a 2950lb car, let alone 400+ in a 3600lb+ car...

I'm not saying that the T5 couldn't be made to live in an S197 chassis, but I think that you'd spend so much money bullet-proofing the thing that you may be better served selecting a different box to start with. The T5 stock was marginal with stock Cobra power levels behind the 5.0 HO motor. If you, or anybody, is sniffing around a trans swap and they race/TT/HPDE-aggressively, take a peek at the 302R trans. Pricy, but from what I've seen bulletproof and the ratios are absolutely dream-like. Usable 2nd gear, close 2/3/4/5 ratios, and even a reasonable 6th gear. It'll suck donkey balls at a drag strip though!!

Dubstep Shep said:

DAMN you're geared high. 120-130 is the end of third for me... At autocross the other day I almost got into fourth. Almost.

Personally, I like having WAY too much power and longer gears. Less shifting is always nice, and I can still pretty much smoke the tires whenever I want. At autocross I pretty much stay in second and third. I use first for some of the really tight, technical stuff, but that's about it.

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3.73 gears, 25.5" tires, stock 3650 trans; 3250lbs, 313RWHP, 345-ish RWTQ. 2nd is almost unusable (except for getting off a tight corner when you went in two-wide), 3rd is good to around 100, 4th to around 140/145. For MOST tracks, this seems to be a pretty good setup, but it falls on it's face when you hook 5th on really long straights.

SoundGuyDave said:

3.73 gears, 25.5" tires, stock 3650 trans; 3250lbs, 313RWHP, 345-ish RWTQ. 2nd is almost unusable (except for getting off a tight corner when you went in two-wide), 3rd is good to around 100, 4th to around 140/145. For MOST tracks, this seems to be a pretty good setup, but it falls on it's face when you hook 5th on really long straights.

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Ahhhh... I'm 3.55 gears with a stock 6060 transmission. I would guess I'm around 500hp at the wheels, but really I have no clue. First is useless except at really, really low speeds, second is much better, but I can still blow the tires off pretty much whenever I want. Third is great for the longer, more open stuff. Even fourth still pulls pretty hard, but I've never gotten that high at autocross.

Here is a gearing calculator. Download the gearing.txt file change the extension to .xls and open with excel. It will calculate everything you need.

http://s197forum.com/forum/showpost.php?p=1657770&postcount=54

SoundGuyDave said:

I'm not saying that the T5 couldn't be made to live in an S197 chassis, but I think that you'd spend so much money bullet-proofing the thing that you may be better served selecting a different box to start with. The T5 stock was marginal with stock Cobra power levels behind the 5.0 HO motor. If you, or anybody, is sniffing around a trans swap and they race/TT/HPDE-aggressively, take a peek at the 302R trans. Pricy, but from what I've seen bulletproof and the ratios are absolutely dream-like. Usable 2nd gear, close 2/3/4/5 ratios, and even a reasonable 6th gear. It'll suck donkey balls at a drag strip though!!

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T-5 costly – Yup on par with a stock rebuilt T56. I was building our car to be a competitive class specific NASA TT - C or B runner (Early 2012) Points added into the equation for upgrades – HP specific for class.
Not gona happen now.
The T-5 I had re-worked to help meet the minimum weight (Not even close with out losing a lot of comforts for a DD / Training tool)

My driver – Wife needs air-conditioning on the street in S-Kalifornia for a daily driver (Frigin Women) – same reason I didn’t have the T-5 made into a dog box. I like dog boxes but for the street the wife wouldn’t have been happy.

The ratio I went with is –
2.95 / 1.95 / 1.36 / 1.0 / .80

This would have worked well with the engine combo 4.0 - V6 and mods that were planned.

295 / 30 / 18 A compound Hoosier on an 11” rim – Now seems the typical but not in early 2012.

1st – 10 MPH @ 1600 RPM Pits
2nd – 60 MPH @ 6500RPM
3rd – 87 MPH @ 6500RPM
4th – 119 MPH @ 6500RPM
5th – 149 MPH @ 6500RPM