JCStang

Just wondering how big a difference in the "seat of the pants" as well as 0-60 times would there be changing from the 3.31 to 3.73 rear end? Took car into local Ford dealerships oil change facility today for an oil change and was talking to the guy behind the counter...turns out he races an older mustang at tracks around the country. Got to talking about some of the changes I had done and mentioned about maybe swapping out the rear end to a 3.73 and he said with parts it would only be a little over $400 with the gear. For those that have gone to that gear, does it make a big enough difference to go through with it? If Ford does the install, is it covered by warranty or at least does it not void any part of the current warranty?

Mr. V

I don't want to speak to warranty because it always gets ugly. As far as the feel, I test drove a 3.31 and thought it was amazing. I really enjoyed driving it. It felt quick and I couldn't understand why people said you had to get the 3.73. I drive one and that it was better. Maybe not a world better but better. It could be the "it costs more so it has to be better" demon talking. I'm glad I got it.

kylerohde

It's going to feel faster at the speeds you'll be driving on normal roads, certainly. For me, it's a question of whether slightly better acceleration is worth the lower gas mileage. No, I didn't buy my car to be a Prius but when you drive it 20K per year, like I do, 2-3 MPG is a chunk of change at the end of the year that could be spent a lot of places. Which is why I bought my GT with 3.31's.

dmichaels

Also depends what you are doing with the car - 3.73's should be better for road course driving since 5th gear becomes usable as opposed to too tall, and 3rd gear is better for many mid-speed turns (55mph corner with 3.73's results in 4300rpm vs 3800rpm wtih 3.31's). 5th gear with 3.73's is 152mph at 7k rpm, vs 171mph (theoretical) at 7k rpm...

But for daily driving, 3.31's are probably best. I'm not so sure a difference of 2-3mpg would be realized, as at 75mph we're talking 2000rpm vs ~2250rpm... I highly doubt 250rpm higher rev results in 2-3 mpg difference

JCStang

I guess I was thinking since I only have the 6 banger that that gear may compensate for the lower torque that the 6 has compared to the v8, thus giving it a little more off the line boost...I don't drive it a ton, just for cruising on nice days ( have only put on 3700 miles since Oct 2011) so mpg isn't really an issue...

fivepointgo

Not saying you are completely wrong or that I will keep this up but I've been getting a consistent 15.5-15.8 mpg on daily street driving so far with my 5.0 with 3.73's...mind you that means only being able to stomp on it only 2-3 times a day but hey thats what weekends are for when there is less traffic

Ajcruz1

I have 3.55s in my Stang and I love them. I originally had 2.73s and when I changed them out I felt better acceleration and I had an overall better driving experience. I also didn't see much of a drop off in MPG. 3.55 seems to be perfect imo for V6 if you want to achieve better performance and still get good mpg. Since you already have 3.31s though the cost to gain benefit would not be worth going to 3.55 so you should go with the 3.73s. Especially since you don't drive it that much. Also I talked with the service department at my dealer and they told me as long as they installed the gears it wouldn't void my warranty. I didn't have them do the work though b/c I didn't care about voiding the warranty.

wiz_of_wuz

If you are not going to blow it...........Why not go 4:10's. the seat dyno is awesome but if you have a blower we are talking 1 second in first............

denlem

I haven't reset my trip B since new, and my 12K mile average is 17.0. Weekly average comes out to 16-18 mpg depending on the driving mix.

Midlife Crisis GT

I owned a 2010 RS (v6) Camaro manual. I switched the gears to 3.73 best thing I ever did to that car. Just made it a lot more fun to drive. As far as MPG I was getting between 29 and 33 MPG.

kylerohde

And I've averaged 21.5 mpg through 33,000 mixed use miles, so I'm pretty darn happy with that, especially since I don't baby it constantly. I shift at 3,000 typically and enjoy the heck out of the car.

Bucko

I've heard that going from 2:73's to 3:31's with Ford can easily be changed for the speedometer difference, but if you go any higher, then a tuner is required to make the change....If Ford installs the taller gears (anything over 3:31), is this true that Ford will not correct the speedometer readings via the PCM?

David Young

I went from 3.31 gears to 3.73 on my 11 V6. Worth every cent. Great performance gains, if you can get traction. I had mine installed by my dealer and they offered to redo the computer so the speedometer would be right, i told them i had a SCT tuner and could change things like that myself . A couple years ago the dealers couldn't change the speedometer calibration when changing gear ratios but they can now for $50 (at my dealer anyway). I really don't see any warranty issues if your dealer changes the gears for you.

David Young

A couple years ago they couldn't, but now they can.

dmichaels

Should be no impact to speedometer readout - that's based on wheel speed, not engine speed. Think of it this way - does speed vary in different gears i.e. different engine speeds at same vehicle speed? Nope...

Mr. V

I am no expert but I believe you need to reprogram the ecu for a gear change. I researched this before I purchased my gt to see if it was better to buy it now or add it later. I decided to buy a car with the 3.73 because of the added cost of install and reprogramming.

Five Oh Brian

You're spot on. Gears are - by definition - a torque multiplier. Therefor, the lower torque from your V6 can be bolstered by the torque multiplication of going to lower (numerically higher) gears (i.e. 3.73's, 4.10's, 4.30's, 4.56's, etc.).

I've swapped gears in just about every car I've ever owned. It's one of the most satisfying mods available and a great bang-for-the-buck!

Tron84

That's exactly how I understood it.... BUT after I went from 3.55 to 3.73 gears and changed nothing else my speedo was off 3-4 mph
Now after getting a new tune for the 3.73 gears my speedo is right on again

Five Oh Brian

IIRC, the speedo is driven by a speed sensor at the trans tailshaft and it's measuring driveshaft rotations. Therefor, any changes byond the driveshaft (i.e. ring & pinion ratio and tire diameter) will require adjusting for the speedo.

Going from 3.73's to 4.56's in my car threw my speedo way off, but I changed the settings in my SCT tuner and easily fixed it.

JCStang

You would think Ford dealerships would be somewhat consistent in their pricing quotes...the local Ford guy where I got my oil changed said they do gear changes all the time, runs a little over $400 with the gears included ( don't know if that includes adjusting the speedometer)...thought I would give the dealership where I bought it a chance...today some guy calls from the shop and when I tell him what I am thinking of doing, right off the bat he says..."well the labor alone is gonna run you 1200 to 1300"....I said yikes, the gear is only $160 through American Muscle and people on the forum were being told $250 to $400 for labor...he starts saying first that that $160 is probably only the ring gear not the pinion and I said no that it was both...plus I said I had heard with only 3700 miles they could probably reuse the bearings but even then the install kit is under $100 as well...he starts rambling about having to press the gear or something like that and all the labor involved ( he wasn't making sense to me) needless to say, I won't be going there...