Transmission Inquiry

[pdub]

Red is a 2006 Mustang GT. He's got the provided Tremec 5-speed transmission. 5th gear is overdrive.

I want a closer ratio 5th gear than the one that is in the box. I don't know where to even start looking. I don't know if that's even possible. I'm too sorry and too lazy to try to figure this out. And there's no way I can do this myself, a transmission job. It's beyond me. I just need to know, is this even possible? Same box, different gear. I want 160 mph. It's hiding behind that gear inside that box, and I can't fix it..Not by myself.

[RockJustRock]

http://www.moderndriveline.com/Technical_Bits/tremec_t5.htm

To know what you have. Are you more concerned with ratio or RPM drop on the shift? RPM drop on the shift would mean you are just going Bwaaaaa and not accelerating much at all. Ratio you are over-thinking and should just go to a shorter tire.

[DanStokes]

RJR makes a good point. What you're REALLY after is a bit higher (numerically) final drive ratio and a shorter tire gets that. Look at the Kumho ESCTAs - they're speed rated and really short ! Just by eyeballing them, I'll wager the tires you're running are 30 inches tall or so which is pretty tall. I'd think you would want to be at about 27" or so. Whether or not you buy from them Tire Rack has a really good catalog with tires listed by (among other things) diameter so you can look up the possibilities. If you look on Landracing.com there is a set of calculators that allow (among other things) the ability to calculate top speed based on HP, tire size, final drive ratio (in your case, the differential ratio, fifth gear ratio, and tire diameter) as well as other variables. It would be useful to see the effect of different tire diameters in those calculations.

Now if you REALLY want to make the difference in gearing you'll want to call Rockland Standard Gear or one of those folks. Their on-line tech guys will be able to tell you what's available and if you ship them your trans they can do the mods leaving you a simple R&R which is MUCH simpler than, say, installing a blower. You KNOW you can do this!

Dan

[cstmwgn]

I guess I would want to know the various ratios (1st - 5th) if (as with some ODs) 5th is a big jump then regearing will allow it to pull through the gear change better.

[Dan Barlow]

I keep wanting to say that you need more motor .......then I remember it has a blower . Most o.d.s are 21 to 25% overdrive so if you can find something in the 15% range that ought to get it .

[RockJustRock]

Let the guy answer.... I find it hard to accept that a blown motor is "Laying Down" in high gear due to the ratio being too wide, but maybe?

Then again a 4:11 rear end in a hopped up Mustang can't really be a bad thing, can it? Would make the first 4 gears much more umm.... shall we say, USEFUL? He still hasn't made that quarter mile pass he teased us about. Is a Drag Week Trip in Red's future?

Could Pee Wee give up Granny Shifting now the clutch is fixed?

[RockJustRock]

And I guess I'd have to go to an ECTA event and spy on people to see what tire pressures people run and if anyone is playing with Nitrogen fills.... I DID ask politely.

[pdub]

Wow, you guys are GREAT as always! The 5th gear is too tall. It's huge. It's even too tall on the highway. I can use it 60 mph+ on the highway but it's just about too tall to cruise at 55.

On the track I'm committed to 5th gear at or slightly before the 3/4 mile mark, going 144. That's it for 4th gear. Redline rev limiter.

Lemme dig out some numbers to chew on, stand by.

[RockJustRock]

As the fog clears my brain, top speed is HP vs. Wind Resistance factored by vehicle weight and acceleration distance. Even in the quarter mile, trap speed is power, weight, wind. Gearing decides what PART of the quarter the acceleration occurs. It's why 60 foot times are SO critical. 10 MPH is kinda too much to ask from gears alone. But there ARE longer tracks made out of SALT! And longer stretches of open road......

[pdub]

If Red would just continue to pull in 5th like he pulls in 4th, I could get there or SOMEWHERE better. The 4-5 shift drops him slam out of the power band. I'm blind hog guessing if 5th was something like .800 it would be at least more in the ball park.

1st: 3.38
2nd: 2.00
3rd: 1.32
4th: 1.00
5th: 0.675
Rev: 3.38
Rear: 3.55

[RockJustRock]

Red will NEVER pull in 5th like he does in 4th. Just like he will never pull in 4th like he does in 3rd. Do AERO first, cheaper, UGLIER, but cheaper. Wing, skirts, grill block off, trim mods, you can see where THIS is going.... RED was cussin' you out with that windshield bit.

Road trip somewhere with 2-3 mile straights, do a 50-60 roll instead of a dig and you will know a lot more.

Plus go get your graphs from Dyno Man.

[silver_bullet]

You could always have a 3.73 final drive ring and pinion installed....

[pdub]

Plus go get your graphs from Dyno Man.

You're late to the party Rock. You've gotta be quicker.

[pdub]

Thanks so much already guys, this discussion is exactly what I knew I needed !

Hmmmmmm.....Rock's 4.11 rear gear.......that.....I wouldn't even be able to shift 1-2-3 fast enough. It's a Hurst but the Tremec pattern is not speed-shiftable.

I'm liking Patrick's 3.73 as a compromise perhaps.......I'd be done with 4th gear somewhere soon at or about the 1/2 mile mark, and there it would be, that 70-foot tall 5th gear and what will it do? I dunno. That's an intriguing concept without trying to find a different 5th gear to put inside the box.

[pdub]

I'll bet y'all can do the math, I can't. With a 3.73 rear end, what would the final drive ratio be in 5th gear, as opposed to what it is now?