gt gears 3:31 and 3:55

The car I test drove had the 3:55's, but my car that I got has the 3:31's and I can't tell the difference, it's getting 4:10's anyways.

tommyroc said:

For the $100 that they charge to upgrade to 3.55's it's worth it. I would have done it however I got a great deal on mine off the the lot and the rest is history.

Click to expand...

Me too. I went from 05 auto to 07 manual with the 3.55's and I love it. Also got a good deal.

tommyroc said:

For the $100 that they charge to upgrade to 3.55's it's worth it. I would have done it however I got a great deal on mine off the the lot and the rest is history.

Click to expand...

I agree that's why I got them on mine last year, but aren't they a 300 dollar option for 2008?

93GrunT said:

I agree that's why I got them on mine last year, but aren't they a 300 dollar option for 2008?

Click to expand...

Labor alone is around $300+ if you do it later. Plus the price of the gears and an install kit.

fartingchicken said:

I have an automatic. I read somewhere where 4.10 gears were discouraged for autos, but don't know what to think. I think the complaint was the hardship on the transmission from the demands of a lower gear.
Where do you recommend buying the gear? How do you find somebody who won't botch the job?
Thanks.

Click to expand...

Actually it is going to be easier on your transmission on a basic car. The only time you are going to have major problems is 1) put a set of slicks on the back. It will cause a lot of stress on the driveline as a whole. 2) put a power adder on the motor. Too much torque out of the motor and you can damage stock auto parts but then again, thats why they make aftermarket autos also.

These cars are very heavy and the shorter the gear, the easier it is to get that mass moving hence the easier it is on the driveline (i.e. auto, driveshaft, axles, gears, etc).

Finally, 3) abuse with any gear combination will cause problems.


My question for those that have done the gears, what are your 1/4 mile trap RPM's with the automatics? Ideally you want to be at the top of 4th gear at the top end of your HP curve just as you cross the line. Any input?

LB

speed1972 said:

My question for those that have done the gears, what are your 1/4 mile trap RPM's with the automatics? Ideally you want to be at the top of 4th gear at the top end of your HP curve just as you cross the line. Any input?

LB

Click to expand...

I have an 07 GT Coupe automatic with 4.10's. I go through the 1/4 mile traps at 102 mph, which is 5300 rpm's. HP dies off after 6500 rpm's, but peak torque is at 4200 rpm's, so the 4.10's fall right in that spread in 4th gear at the finish line.

More important to my decision was being able to go about 120 mph in 4th gear just in case I do a power adder with this car so that I don't have to shift into overdrive at the dragstrip. I also wanted to stay under 3000 rpm's at 80 mph in overdrive on the highway (4.10's = 2800 rpm's at 80 mph, FYI).

I had 4.30's in my 03 Mach 1, but it was a manual trans with a much steeper overdrive (.62 vs the .71 in my 07 automatic), so I could get away with more gear. Plus, that 4V motor pulls strong to 7000 rpm's whereas the 3V motor drops off after 6500 rpm's.

For those with 05-08 GT automatics who really want awesome launches, get 4.10's and a high-rpm stall converter for your trans. The high-rpm stall converter allows my car to launch at 3800 rpm's - just like a stick shift car when you rev up and dump the clutch. I would recommend something in the 3000 to 3200 rpm range, though, as my 3800 rpm stall converter is a bit much for the faint of heart (but I love it!). The factory torque converter in the 05-08 GT automatic only flashes to about 2200 rpm's, so launches are lackluster when stock, although the 4.10 gears out back will help a lot.

As many have already advised, the 05-08 GT's are heavy cars and the automatics are 180 lbs more than the manuals, so gearing really helps make these cars get up and dance.

Casey4s said:

Labor alone is around $300+ if you do it later. Plus the price of the gears and an install kit.

Click to expand...

I realize that, but once the option starts becoming half the price of changing gears I would rather have 4.10's. I just meant ford is starting to charge alot of money for something that is no added cost to them and it isn't that much of a performance gain to go 3.31's to 3.55's. a hundred...okay, 300 personally I would just go ahead and wait now that it costs more.