max2000jp

Anyone considered changing the gear out on the 05? I was thinking about going with a 3.90 or 4.11, since that would make a pretty recognizable change from the stock 3.55's. Does anyone know what rpm a 4.11 would be at doing 60 and 80 mph? Also, would you have to shift into 4th going in the 1/4 with the above gears?

BillP

With the stock gears and stock redline, you shift into 4th just around the end of the quarter mile, hopefully just after the 1/4. This is for the manual transmission.

Any change in gearing to 4.10's will make you do a 3-4 shift unless redline (and gas cutoff) is moved up to 7000rpm or so (6000rpm*4.10/3.55)

V10

Stock 3.55 gears - MTX, 5th gear (OD)

60 MPH: 1633 RPM
80 MPH: 2178 RPM


4.10 gears - MTX, 5th gear (OD)

60 MPH: 1886 RPM
80 MPH: 2515 RPM


Those RPM #'s will be close, but are not exact as I used tire diameters calculated off the tire size. The actual rolling diamter will be a little different. Sorry, but I'm too tired and lazy tonight to research what the actual rolling diameter is.

V10

I agree, if you make a change you might as well go all the way to 4.10s.
3.73s will be a complete waste of money and 3.90s just barely worth it.

However before you make any gear change, you have to decide what your objective is.

Are you trying to get better 1/4 mile times?
Are you just looking for more zip on the street?
Or is there a different objective?

If your objective is a faster 1/4, 3.73s and 3.90s will most likely slow yo down. This is because a MTX GT will just be able to finish the 1/4 in 3rd gear. So if you go to 3.73s you will make an extra shift just before the line which will most likely lead to a slower time. So if you're going to make an extra shift you might as well go to 4.10s and get some time and pull in 4th gear.

max2000jp

Stock 3.55 gears - MTX, 5th gear (OD)

60 MPH: 1633 RPM
80 MPH: 2178 RPM


4.10 gears - MTX, 5th gear (OD)

60 MPH: 1886 RPM
80 MPH: 2515 RPM


Those RPM #'s will be close, but are not exact as I used tire diameters calculated off the tire size. The actual rolling diamter will be a little different. Sorry, but I'm too tired and lazy tonight to research what the actual rolling diameter is. [/b][/quote]
Thanks for the help and the numbers. Seems like 4.10s are the way to go IMO. The extra 400 rpms at 80mph are small.

The Boss Hog

I have a slightly different point of view on changing rearend gears. I think the real problem with the manual is the huge split between 1st (3.38) and 2nd (2.00) gear. Shifting at 6,000 rpms means the engine drops to about 3550 rpm! Far below its torque peak. The auto has a much better split (3.22 - 2.29) meaning it drops to about 4250 rpm which right in the fat part of the curve! To me, the ideal drag-racing solution would be to change out the 1st gear in the 3650 to something like a 3.00 and then go with the 4.10.
I checked the Tremec website but they don't list any alternate gearing for the 3650. Anyone know of a source?

The Boss Hog

BillP

Ford used to list (on fordracing.com) a narrow ratio version of the heavy duty 3650, but my last visit there didn't show it.

It would be nice to get a narrow ratio version, and then choose the rear end to match your desired engine speed at the end of the quarter. Same thing you are saying, said differently.

max2000jp

Or a close ratio 6 speed would have been nice.

V10

The 4.6 has plenty of torque @ 3,500 RPM.

With my 01 GT the ratios seem spaced very well. I rarely rev it over 5,500 RPM as it doesn't have as much pull above 5,500. When I shift to 2nd the RPM is right at 3,000 and it still pulls strong. If I bang 2nd gear I have to be careful no to spin the tires.

The 05 - 3V with its VVT and more sophisticated intake manifold will pull even stronger at 3,000 RPM. If you watch the drag race videos your biggest problem with a good 1-2 shift wil be to keep from spinning the tires.

You don't want to shift from peak RPM down only to the torque peak as you won't have as much pull. You want to be in the sweet zone, but enough below peak torque RPM to take advantage of the whole torque band.

The Boss Hog

V10,
I sincerly hope you are right. Since I don't own (yet) a 4.6 and you do, you have more first hand experiance with it. I also recognize there is a lot of people successfully using the 3650 for racing. Also the VVT should help extend the torque curve. That being said, I still think the auto has better splits (1-2-3) and will be the equal of the manual from 0 to 60 mph. MT states the performance of the auto really falls off when it shifts to 4th. If you check the splits you will see that the 3rd to 4th split in the auto is larger than the 1-2-3 splits and the engine drops down to 3900 rpm. By contrast the 3rd to 4th split in the manual is actually smaller than the 1st to 2nd or the 2nd to 3rd.
You brought up the drag racing video. If you really look at the one of the '05 against the GTO, the Mustang clearly out pulls the GTO through first gear but then the GTO quickly reals it back in. Again, IMO its because of the large split from 1st to 2nd gear. Time will tell.

The Boss Hog

MrMorden

3.55 to 3.73 is not a huge jump, and not worth the cost. Either stick with 3.55 or go to 4.10s (maybe even 4.30 in the auto). I'll personally probably go to 4.10s. They are fine at the track and much more fun on the street!

Best thing to do is drive it with the stock gears for a while and see how it feels.

97svtgoin05gt

I think that changing the gears for primarily road going GTs isn't worth it. Car pulls well with 3.55s and with 4.10s the mileage is going right out the window. On the other hand, if you're going to drag it all the time and going to best ets, the 4.10s are probably the way to go. 3.73s while very useful in DOHC cars I don't think will prove very useful here.

Mach1Nut

For those that think you will get worse gas mileage with a lower gear ratio, you are wrong. If you were to switch to 4.10 gears and drive normally, you would actually get better gas mileage due to less load on the engine on acceleration. The increase in RPM's in negligible at freeway speeds going from 3.55's to 4.10's. Unfortunately though, when you change to a lower gear ratio (numerically higher) it is so much more fun to drive that you end up revvin through the gears more often!

Nathan_H

my uncle uses a set of 3.73 's in his fox, so that he his max speed is still high, yet has better accleration at the track. Youve got to take into consideration what you want and when you want it. But as far as the 05 goes, 3.73 arent worth the cost. Although i dont see why 3.90's would be so bad, unless of course you have to put that extra shift in, its late and i dont want to pull out the calculator...

Dan

It think the point being missed here that Bill keeps trying to show is that switching gear, while it may improve your acceleration, will not show up in your quarter mile time because switching out the stock gears will result in a 3rd to 4th gear shift in the quarter.

BillP

I think that if you are going to have a 3-4 shift, you'd probably want to do it really early. That's the way old 4-speed muscle cars did it... 3 quick gears in the first 8 secs or so, and 4th the rest of the way.

The other way to say this is that if you are going to take the hit for another gear change, then pull really deep in the gearing (as deep as tires will allow), and carry 4th through the power band.

Remember, if you drop the gearing too low, 1st will spin the tires and never bite. So you add fatter tires, increase the bite, and now you have to worry about bogging them down, so then you go more HP, and the cycle of spending and upgrading and breaking parts continues

BillP

Oh, by the way, after driving my car around for 2 days, I'm not even thinking about changing a thing. I'm not into 1/4 mile drags (although I plan to try them out after I get 1000 on the odometer), but I do love the great flexibility and broad spectrum of power and performance this current package gives. It sure beats rowing a high RPM, low torque 4banger. Not that it isn't fun to row your way to high RPM, it's just not something I want to do all the time. I prefer the flexibility in gearing that comes with higher torque.

Dan

That's great to hear Bill. Gearing and power felt great when I drove it as well.

Enfynet

I got bored at school and did a little playing with my calculator. At 6000 RPM in 3rd, the 3.55s peak around 103mph; the 4.10s peak around 90mph...

As far as gear spacing,
3.55: The 1-2 shift at 40mph will take you from 5950rpm down to 3520rpm. The 2-3 shift at 65mph will take you from 5720rpm to 3780rpm, and 3rd will peak at 103mph.

4.10: The 1-2 shift at 35mph will take you from 6020rpm to 3560rpm. The 2-3 shift at 60mph will take you from 6100rpm to 4030rpm. The 3-4 shift at 90mph will take you from 6040rpm to 4580rpm, and 4th peaks at 118mph

70mph in 5th
3.55 = 2090rpm
3.73 = 2200rpm
3.90 = 2300rpm
4.10 = 2420rpm

*shrug* I'm sticking with the stock setup only because I don't plan on racing and know little about modifying a cars performance.

MrMorden

4.10s are great for these cars. They accelerate wonderfully, and launch well once you get used to them. ~2500rpm @ 80mph is no problem. I gained 3/10ths in the quarter with just 4.10s in my 2001 GT.