Gears question in my 03 Mach 1
 

First time post. Just bought an 03 Mach 1. It has had some modifications (short throw shifter, flowmasters, K&N, etc.) but dealer assured me everything else was stock. I felt though that it did not have the stock 3.55 gears in it. All I have to compare it to though is my 95 GT which still has the stock 3.27 in it. Checked the speedo on the highway and it was 8-10 seconds slow. Any idea how I can check this out to be sure? Also have 26,000 left on warranty. If gears were swapped will it void out warranty?

Re: Gears question in my 03 Mach 1
 

A gear swap will not void the car's overall warranty. If the swap was not done by a Ford dealership, then it will affect the warranty coverage of the rear end, but it will not affect the rest of the car's warranty.

One way you can determine the gear ratio is to jack up the rear end and rotate the wheel through a full rotation while counting how many times the pinion rotates.

Re: Gears question in my 03 Mach 1
 

That is by far the easiest way to check gear ratio. its only a rough estimate but it will give you good idea where to start.

Re: Gears question in my 03 Mach 1
 

Thanks for the info. As soon as it gets warmer around here I'll put the rearend up and check it out. I'm guessing it has a 4.10 in it. It's a DD so that is geared a little lower than I would like. Any ideas how much difference the 3.55's would make?

Re: Gears question in my 03 Mach 1
 

If you do have 4.10s I'd leave 'em. All 3.55s will do is make you feel like it bogs and takes forever to get into the powerband and your mileage won't change by more than 1-2 mpg if that.

Re: Gears question in my 03 Mach 1
 

we have just bought a 2003 mach 1, but it's all stock. we don't like the 355's that come stock, in 5th gear at 70 mph we're at 1900 rpm's. when i'm getting on the gears hard at about 6500 rpm's at shift, i go into 4th gear at 100 mph!! that's crazy. i still have one more gear to go. how big of a ticket do i want?!!! wouldn't 410's be a better choice? i want quick, not fast.

Re: Gears question in my 03 Mach 1
 

I would definitely recommend 4.10s or even 4.30s for an N/A 4-valve. Hell, I run 4.10s with over 400 rwhp.

Re: Gears question in my 03 Mach 1
 

I would definitely recommend 4.10s or even 4.30s for an N/A 4-valve. Heck, I run 4.10s with over 400 rwhp.

Re: Gears question in my 03 Mach 1
 

Cowboy, I answered your later post on the 4:10's. Lifted mine up and checked it out. Sure enough running a 4:10. It kind of lugs around town and your almost always in the powerband so it burns more gas. I wrap 2K at 60 and 2300 at 70. But when your ready to rock you can't beat that gear. Drove a stock 03 Mach 1 last night and it was like getting back into my 5.0 GT again. It's that much difference.

Re: Gears question in my 03 Mach 1
 

The difference in gas should only be 1-2mpg if that. It's only a 15% steeper gear than stock. Plus the TR3650 has a pretty tall 5th...

Re: Gears question in my 03 Mach 1
 

use the analyzer at this site i think its pretty close