I picked up about 2 mpg with the addition of an alum DS. next gas booster is the UDP's... just replacing what I lost with the 3.73's

 

I had the 3.73s put in earlier this year and by far my best mod. With the five speed third gear is my favorite. You can drop right into the power band at 65mph and the car pulls like a freight train. Figure the effect is similar with the auto, just hammer the go pedal at cruise speed and hang on.

 

No downside with 3.73s if they are installed correctly. One of the best mods for the money.

 

Just got back from a 70 mile MPG run over varied terrain. Its looking like 3.73s lost 2 to 3 MPG from the 3.31s. Speeds averaging 73 MPH netted 24.5 MPG down from 26.5 to 27 MPG on previous similar runs. In town MPG was not affected or if it was I picked up 1/2 to 1 MPG.

 

I wished I had gone to the 3.73, but I got the 4.10 both FRPP. The problem is with even my 365hp, the 1st gear is way tooo short. If you got a mostly stock motor, then go 4.10 for a quicker launch. If not, really look for the 3.73 choice.

 

I had 3.73's in my 06 (automatic) I loved them. I had numerous people talk me out of 4.10's. They said 4.10's would not work well in the auto, although some have done 4.10's in auto's and love them. Do the 3.73's. You won't be disappointed.

 

Some say that 1st gear is pretty much useless w/ the 3.73, especially with higher hp & tq cars, i.e., GT500, Roush, Saleen, or other blown set-ups reaching 500 hp/tq. I'm referring to street application, not drag or track... Opinions?

 

I'm still running my '05 with GT500 clips fore and aft - inspired by your previous car. I think mine still looks great. Just doing a little touch up here and there lately. Still feels like a new car.

And, I may do the 3.73's soon. Just need a little more cash

Joe

 

I put 4.10's in when I got my CAI. What a difference between 3.55 and 4.10 gears. Then I almost got talked out of the 4.10's when I put on the Saleen S/C. Glad I left them in. A perfect match for around town, daily driving and having a little fun. I have got over 70,000 miles on this setup and never had any problems. One thing I did not do and regret is when I had the gears put in I should have had them put in a TruTrack.

 

I wouldn't call 1st useless. You hit red line about 5mph slower than with 3.31s. I noticed it takes less clutch to get it rolling. Acceleration is snappier and so you don't stay in 1st as long. Which was the point I thought.

Some with high horsepower cars may have some traction issues with the 3.73s and claim their 3.55s or even the stock 3.31 have all the go they need. Lighting up your tires does not make go only makes smoke.

 

Joining the 3:73 gear club. I ordered a set tonight. I had the 4:10's in the past but I think I will really be happy with the overall performance of this gear ratio. This for all the feedback on this thread from you folks that already have them. I can't wait and I already updated my signature.

 

I am also interested in making the switch to 3.73s in 2010...we'll see...

 

I like em.

 

I'm having mine installed on Thursday. After I get them broken in I give everyone my impression.

BTW, how is everyone breaking their gears in?

 

The shop I had do mine told me 2 things:

1. High quality gears should not need a real break in period.

However:

2. If you feel you need to do a break in (which I did), they recommended 3 sessions of 15 minutes of normal driving (no WOT) with an extended cool down period in between.

 

Thanks Jeff I guess the best thing is for me to ask the installer.

 

My installer recommended 300 miles of "normal" driving. No rabbit takeoffs and no burn outs. That was it. Expect a 12 percent loss of MPG on the highway. Thats about what I am seeing. Guess that goes along with the 12 percent increase on RPM. Car is more "well behaved" with the 3.73s. Mustangs should have some with that from the factory and most likely would have if not for COLA.

 

It's also not a bad idea to change the diff fluid about 500 miles after the install, to remove any metal or other particulate that may occur during break-in.