3.55 or 3.73 Gears?

[RED98]

Hey it's been a while since I've been on here.. got a question. My car developed a whining noise in the rear, shop thinks it might be a bearing. And I said well as long as you're back there, now's my chance to install traction-lock and maybe bump the gears! So should I go to 3.55 or 3.73? Bear in mind about 75% of my driving is on the highway and if I suddenly find myself going 65 mph at 3000 rpm's and getting 20 mpg, well I'm gonna be mad. Has anyone actually changed their gears, and how's the highway fuel economy now?
At least the traction lock will mean no more one wheel squeals.

 

[moparsquid]

I personally myself would recomend the 3;55 I have these gears in a truck and like them I also had them in a car I owned with an auto ant it gave it a little grunt but was sano on the highway.

 

[MustangLX-5.0]

Just curious what the RPM's are at with the Auto trans OD at 65 MPH? With my 5 spd, going around 65 MPH is about 1600 RPM in 5th gear. That is a guesstimate. I forgot what it is actually. I know it's around 1600 - 1700 RPM. I forget what gear is in there currently. I think 3:18's . So the RPM's shouldn't jump all that much going to a 3.73 gear (most likely around 2300 - 2400 RPM) . Are you getting an 8.8 diff?

 

[RED98]

At 65 mph I'm about 1700-1800 rpm's. I did some research and it looks like a stock auto 98 comes with 2.73 gears. The shop has not finished their diagnosis yet, they are not 100% sure what the problem is. I may just go ahead and say **** it, put in an 8.8 rear end with traction lock and steeper gears. Take care of it all at once. But like I said before, I want to retain decent fuel economy, otherwise what's the point of having a V6?

 

[MustangLX-5.0]

If the shop don't know, just do the spin test. Remember, put a mark on the end of the driveshaft near the diff. Then spin the wheel one complete revolution. However many times the driveshaft makes a complete revolution (down to the decimal) per single tire rev is what your gear ratio is. I just haven't had my car off the ground lately to measure. May be different for an Auto.

 

[RED98]

Update: I wussed out. I was talking with the guy at the shop, decided since I drive 50 miles per day on the highway, to go with 3.27 gears. Since I had 2.73's in there stock, this will be a mild (very mild) increase. I'm keeping the 7.5 rear end, because switching to 8.8 would have cost too much. I am getting the traction lock, so I'll have power to both rear wheels. And I'll have new bearings.
So this increase certainly won't stand my car up on its rear wheels.. I may not feel any difference at all. But I don't care. Basically I need this car to last me 2 or 3 more years until I'm done with college, then I'll get one of the 2011+ 5.0 Mustangs with 400hp, and that'll be my beast. Heck, even the V6 Mustang for 2011 will have over 300hp, isn't that cool??

 

[shine1stang]

ford should have been bumping the v6 platform up years ago!!! Look at how long the 3.8 was in the v6!!!! started in the 80s? And 99+ were only putting out 190 at the crank. BOOOOO.
anyway good luck with the gear swap, 327s are a good gear. Youll really love the tlok