3.15 to 3.55 worth it
06-21-2012, 04:35 PM
#11
1st Gear Member
Join Date: Oct 2009
Location: TN
Posts: 131
I've heard it said or implied time and again that since the auto Mustangs have such a high 4.17 1st gear ratio, changing the rear end gears would not be needed or give beneifit. I disagree. You have to look at the other ratios as well. After 1st gear, they get taller really quick.
I think the Mustang would be just fine with 3.55 or 3.73, you're just going to be at a little higher RPM when cruising at hwy speed. But then you also have the traction issue, and getting the car to hook up on launch WILL be an issue with the stock tires. You can always just gine it less throttle on take-off. Or get wider rims with stickier tires on then.
06-22-2012, 09:07 AM
#12
2nd Gear Member
Join Date: Jun 2011
Location: NJ
Posts: 181
Sorry, it was not my intent to compare a Mustang to a KIA Sorento. I was just trying to make a point about gearing. The Mustang is worlds more powerful and sporty than a KIA, you cannot compare the performance of the two.
I've heard it said or implied time and again that since the auto Mustangs have such a high 4.17 1st gear ratio, changing the rear end gears would not be needed or give beneifit. I disagree. You have to look at the other ratios as well. After 1st gear, they get taller really quick.
I think the Mustang would be just fine with 3.55 or 3.73, you're just going to be at a little higher RPM when cruising at hwy speed. But then you also have the traction issue, and getting the car to hook up on launch WILL be an issue with the stock tires. You can always just gine it less throttle on take-off. Or get wider rims with stickier tires on then.
I've heard it said or implied time and again that since the auto Mustangs have such a high 4.17 1st gear ratio, changing the rear end gears would not be needed or give beneifit. I disagree. You have to look at the other ratios as well. After 1st gear, they get taller really quick.
I think the Mustang would be just fine with 3.55 or 3.73, you're just going to be at a little higher RPM when cruising at hwy speed. But then you also have the traction issue, and getting the car to hook up on launch WILL be an issue with the stock tires. You can always just gine it less throttle on take-off. Or get wider rims with stickier tires on then.
06-22-2012, 02:00 PM
#14
5th Gear Member
Join Date: Mar 2006
Location: ATL
Posts: 2,955
IMO Ford put 3.15 in these cars to try and get a better MPG out of these cars, not because of the tranny gearing. Reason I say this, my wife's KIA Sorento seems to accelerate easier at light throttle, especially off a dead start than my GT Mustang ! I wondered why, so I looked up the specs, and the KIA uses higher ratios in the auto tranny than the Mustang. Check this out:
KIA Sorento 3.5L V6:
1st 4.651
2nd 2.831
3rd 1.842
4th 1.386
5th 1.000
6th 0.772
Final drive 3.195:1
Mustang:
1st 4.17
2nd 2.34
3rd 1.52
4th 1.14
5th 0.87
6th 0.69
Final drive 3.15:1
As you can see, the gear ratios for my wife's KIA are much more favorable for acceleration than my Mustang GT 5.0. But KIA can run those because they Sorento uses a smaller 3.5L v6 to our 5.0L v8 and so they can get good acceleration out of a heavy vehicle and still have good MPG.
Sorry for the long post, but it goes back to my opinion that Ford used a 3.15:1 rear end ratio for better MPG. And yes, hell yes I think 3.55 gear would make a nice difference in acceleration and make the Mustang feel lighter and take off faster off the line IF you can get it to hook up!
3.73 might be a bit much. Would not go 4.10 with the auto for sure.
KIA Sorento 3.5L V6:
1st 4.651
2nd 2.831
3rd 1.842
4th 1.386
5th 1.000
6th 0.772
Final drive 3.195:1
Mustang:
1st 4.17
2nd 2.34
3rd 1.52
4th 1.14
5th 0.87
6th 0.69
Final drive 3.15:1
As you can see, the gear ratios for my wife's KIA are much more favorable for acceleration than my Mustang GT 5.0. But KIA can run those because they Sorento uses a smaller 3.5L v6 to our 5.0L v8 and so they can get good acceleration out of a heavy vehicle and still have good MPG.
Sorry for the long post, but it goes back to my opinion that Ford used a 3.15:1 rear end ratio for better MPG. And yes, hell yes I think 3.55 gear would make a nice difference in acceleration and make the Mustang feel lighter and take off faster off the line IF you can get it to hook up!
3.73 might be a bit much. Would not go 4.10 with the auto for sure.
First gear of the 6R80 with a 3.15 rear gear equals first gear of the 5R55S with a 4.10 rear gear (3.31 was stock)
5R55S
1st gear 3.22
2nd gear 2.29
3rd gear 1.55
4th gear 1.00
5th gear .71
Also, shame on you for using this as a logical comparison, lol.
Last edited by Bmr4life; 06-22-2012 at 02:09 PM.
06-22-2012, 10:47 PM
#15
1st Gear Member
Join Date: Oct 2009
Location: TN
Posts: 131
Sorry, but you're wrong bud.
First gear of the 6R80 with a 3.15 rear gear equals first gear of the 5R55S with a 4.10 rear gear (3.31 was stock)
5R55S
1st gear 3.22
2nd gear 2.29
3rd gear 1.55
4th gear 1.00
5th gear .71
Also, shame on you for using this as a logical comparison, lol.
First gear of the 6R80 with a 3.15 rear gear equals first gear of the 5R55S with a 4.10 rear gear (3.31 was stock)
5R55S
1st gear 3.22
2nd gear 2.29
3rd gear 1.55
4th gear 1.00
5th gear .71
Also, shame on you for using this as a logical comparison, lol.
And so that tranny with 3.31 rear gears has a gearing advantage over the 6r80 in 2nd 3rd and maybe even 4th. So to me you could at least run 3.31 with the 6r80. But would it be worth the money to change gears to bump one ratio? Probably not. Would 3.55 be too much? Maybe so. Maybe I am wrong and I am the dumb.
I will tell you this, and I know this for a fact: a good tune makes a world of difference on these 6R80 auto trans. By good tune I mean one where the tuner knows how to set it up well for the auto. First two tunes I got had the trans way to eager to upshift, just like the stock shift schedule. Except at WOT, then it would wind high. This tune I have now, it lets the revs climb higher before it shifts, which keeps the 5.0 in it's power band and really enhances performance. Yep, best bang for the buck if you have an auto is a good tune - you don't know how much you're missing til you try it. My latest tune is from VMP and it rocks. I hear Steeda has a good tune for the autos as well, but have not sampled on of theirs yet.
06-23-2012, 12:31 AM
#16
5th Gear Member
Join Date: Mar 2006
Location: ATL
Posts: 2,955
I completely agree that the auto needs a proper tune. I just switched from Bama to Steeda and the new time does exactly what you mentioned. Holds gears longer than Bama did. At first I was confused but then realized it not a bad thing. I've had this Steeda tune for all of one day but I like it so far.
As for the gearing, the 5R55S does have a tiny advantage over the 6R80 in a couple of the later gears. But the stock power advantage of the 5.0 over the 4.6 more than makes up for it.
.......6R80 versus 5R55S (both with stock rear ends, higher means quicker acceleration)
1st. 13.1355 - 10.6582
2nd. 7.371 - 7.5799 (2.6% higher = pretty much even)
3rd. 4.788 - 5.1305 (7.2% higher = slight advantage)
4th. 3.591 - 3.15
5th. 2.7405 - 2.3501
6th. 2.1735 - NA
That said, if I could I would definitely change some of the gears IN the 6R80. 2nd, 3rd, and 6th specifically.
As for the gearing, the 5R55S does have a tiny advantage over the 6R80 in a couple of the later gears. But the stock power advantage of the 5.0 over the 4.6 more than makes up for it.
.......6R80 versus 5R55S (both with stock rear ends, higher means quicker acceleration)
1st. 13.1355 - 10.6582
2nd. 7.371 - 7.5799 (2.6% higher = pretty much even)
3rd. 4.788 - 5.1305 (7.2% higher = slight advantage)
4th. 3.591 - 3.15
5th. 2.7405 - 2.3501
6th. 2.1735 - NA
That said, if I could I would definitely change some of the gears IN the 6R80. 2nd, 3rd, and 6th specifically.
Last edited by Bmr4life; 06-23-2012 at 08:41 AM.
06-25-2012, 03:21 PM
#17
Mish-ogynist
Join Date: Nov 2007
Location: Helena, MT
Posts: 3,780
Sorry, forgot to check this thread again.
To answer OPs question about combined MPGs I think im at around 17, that is because when I drive it I typically floor it a couple of times because I only drive it once-twice a week
highway is around 21-22mpg, city depends on how mean i am on it 9-16mpg. (14 avg)
basically a full tank of gas only gets me 270-280 miles, as opposed to 305 it did stock.
You can look at numbers and ratios all you want, but I think 4.10s are fun.
I also agree, the 3.15s are in there only for the fuel economy.
To answer OPs question about combined MPGs I think im at around 17, that is because when I drive it I typically floor it a couple of times because I only drive it once-twice a week
highway is around 21-22mpg, city depends on how mean i am on it
9-16mpg. (14 avg)basically a full tank of gas only gets me 270-280 miles, as opposed to 305 it did stock.
You can look at numbers and ratios all you want, but I think 4.10s are fun.
I also agree, the 3.15s are in there only for the fuel economy.
06-26-2012, 07:41 AM
#20
4th Gear Member
Join Date: Jan 2007
Location: Palm Beach to South Carolina
Posts: 1,567
Yes, it would be noticeable as 3.55s are 12.7% lower than 3.15s.
I think 3.55s on the newer autos would be a good compromise. 4.10s IMO would be too low and first gear would be useless.
I think 3.55s on the newer autos would be a good compromise. 4.10s IMO would be too low and first gear would be useless.