Hood Flex at Speed and Axle Ratio

Yesterday I flew home from a business trip I was on all week and when I got off the plane, the only thing I wanted to do was get in my GT and head to the house. Fortunately for me that involves two main interstates and 40 miles. So, with very little traffic I decided to crank it up for the first time. The car only has about 500 miles on it and I was purposely waiting till it was broke in before dropping the hammer while at speed. So, I was doing about 60 and hit the gas. Mine is an automatic and it just jumped up and before I knew it I was doing about 110 and climbing fast, however I noticed the hood seemed like it was about to pop up on me, so I backed off it. It was the two sides that seemed like they were loose. I have had a hood come open at 90 mph once and it was not a pretty thing. Anyway, when I got home I checked the hood and it was totally secured. I was wondering if anyone else had this experience with their hoods ? If it does that at 110 I can only imagine what it would be like at 140 or 150.

One other thing, while this car does get up and move from a dead stop, it seems much slower than my previous 12 GT that was a 6 speed and had a 3:73 rear. This new GT has a 3:15 rear. I didn't know they even made an axle with that ratio for the GT. I don't want to necessarily go back to a 3:73 as the car is used on the highway a lot. So what gear ratio would be the best of both worlds for that application ? Thanks guys :cheers:

Another person with a 3.15 GT? I test drove a 3.15 and could hit the fun pedal just fine.

Old car is an 02 GTi with less than half the power and torque.

3.15 is standard on the GT Auto

The hood's slight movement is not confidence inspiring, but higher speeds than that will not yield a missing hood.

The difference between 3.15:1 and 3.73:1 is pretty significant. At peak prop shaft torque, the extra torque multiplication of the 3.73 puts roughly another 1350 lb-ft of torque to the tires than the 3.15 would. That makes a big difference in initial acceleration. But a nice middle ground would be either the manual's standard 3.31 gear or the optional 3.55:1 set. Not as much torque multiplication as the 3.73, but lower RPM at highway speed and still a big improvement over what you have now...

If you're worried about hood flutter, you can just raise the rubber bump stops on the sides of the front engine bay.

JimmyTwoTimes said:

If you're worried about hood flutter, you can just raise the rubber bump stops on the sides of the front engine bay.

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So the bumper stops are adjustable? If so that's good to know mine is pretty whacky at 75mph.

Had mine up to 150, hood was shaking like it was having a seizure...freaked me out a little but didn't go anywhere.

Kahboom said:

So the bumper stops are adjustable? If so that's good to know mine is pretty whacky at 75mph.

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Yeah; early builds had them too high from the factory, which made the hood look warped since the center latch was lower than the outside bumps, causing a curved panel gap there. They screw up and down, takes a bit of pressure to turn them.

140+ this morning... no flex that I could tell. Lot's of chassis float though at that speed, needs lowering badly.

I've had my GT up around 110 and didn't notice any hood shake or movement. Sounds like having the rubber bumpers and latch adjusted just right should prevent any shaking at high speed.

3.55 is the right rear for the auto IMO

Ive gone to 146mph and the hood didn't flutter any more than it did at 85.

See the 1/4-mile sticky threads. AT/3.15s are running 12.8 or so. PPs are a tick or two behind, AT/3.55s are a tick or two ahead. Pretty hard to say the AT/3.15 cars are "slow." They do rev about 12% more slowly than the 3.55 cars, that's just math. But they twist the speed needle at just about the same rate.

My hood has the shakes above 60.