The reoccuring gearing question...

plev72

Registered User
Alright, so a '94 5-speed has 2.89 gears or some such... I know that a lot of people have been going up to 3.27 or 3.31. I understand the trade off is better low end at the sacrifice of some fuel efficiency and some top end.

Tentatively I am not planning on changing from stock gearing due to the following reasons:

1) I will probably be making reasonably frequent weekend commutes of 320 miles round trip. Posted speed limit is 75 mph but traffic (not me of course... 'cause I wouldn't think of disregarding a speed limit) generally travels around 84 mph without getting a ticket and sometimes a bit faster (I've seen convoys doing around 100mph).

2) I figure the engine after the rebuild is going to have HUGE amounts of low end torque (like 330ft/lbs wasn't enough)... I'm thinking that I am better of with the thing taking a bit longer to spool as it is difficult enough to keep the tires on a 5-speed on the ground in the first place.

3) Umm... was there a 3? Oh yeah... if I ever get back to Europe with this thing, I'd love to see the top speed ... top speed is higher with lower gearing correct??

4) This is more of a question... if I change gearing to 3.27 (or is it just the taller gearing???) I might get stuck making an extra shift when I run quarters??

Thanks in advance for the pro/con argument.

Oh.. and just to complicate things more, would the aluminum pumpkin out of a Mark VIII make the change more worthwhile due to the weight savings of going aluminum???

Thanks,
Paul
 
Stock is 2.73's. I had 3.27's in a '99 Cobra aluminum carrier for about three years, and my only complaint was having to shift into 4th at about 1000' at the track. I changed to 3.08's and now I can run through the traps in third @ 5600 RPM. It feels a little undergeared now after the 3.27's, but I still get 1.9 sec 60's on DR's.
 
I think technically, it is called "shorter gearing" with lower numbers, i.e. less torque multiplication. If you have shorter gears, you'll have a higher top speed. I believe with 3.27s, I am limited to about 150 or so (staying below 5200 rpms).
 
JJanney said:
I think technically, it is called "shorter gearing" with lower numbers, i.e. less torque multiplication. If you have shorter gears, you'll have a higher top speed. I believe with 3.27s, I am limited to about 150 or so (staying below 5200 rpms).

Actually, that's backwards.

3.27's are "shorter gears" when compared to 2.73's or 3.08's.

2.73's are "taller" than 3.27's.
 
I find my mildly modded 95 5-speed to have a bit faster top end with 3.27 gears ... this is because it will now pull right to the HP peak in 5th gear. Before, the car would only pull about 3900 rpm in 5th with the original 2.73 gears ... now, it goes to 4700. So that's about 151 mph vs. about 144 mph stock.

As far as drag racing goes, as Doug F. mentioned, if you are going to have a motor that will pull to 5600 rpm, then go with 3.08s to save you the shift to 4th.



cheers
Ed Nicholson
SCCoO
 
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Gary,

109 mph.....very interesting. Another peice of the MM&FF puzzel falls into place.

I should get all the nitrous stuff I ordered later this week. With any luck I'll get it installed over the weekend. I'm very curious as to how much quicker it will be with a 125 hp shot.

David
 
I am going back a step from 3.27 to 3.07. I got an alumimnum pumpking with 3.07 that I am rebuilding now. I had to shift into fourth at the end of the 1/4 which I think hurt my times.
Plus the car has more traction problems with the 3.27.
BUt mine puts about 280~ to the wheels.
I think if you are stock or nearly stock then go with 3.27 that way you get the grunt and not traction problems.
but if you plan to modify heavily go with 3.08s. The car winds up faster when you have more HP so YOu have to shift more often then a less modified car.
my .02
 
kuhnga said:
109 MPH wide open in 4th gear at 5500rpm

Assuming you've got an early M5R2 in the car.

5500 with a 26" tire, in 4th gear (1:1), with 2.73's works out to 151 MPH!

5500 with a 26" tire, in 3rd gear (1.43:1), with 2.73's works out to 106 MPH.

5500 with a 26" tire, in 4th gear (1:1), with 3.73's works out to 111 MPH.

So what transmission and/or gears are you really using? ;)
 
fast Ed N said:
IAs far as drag racing goes, as Doug F. mentioned, if you are going to have a motor that will pull to 5600 rpm, then go with 3.08s to save you the shift to 4th.

BTW, the 3.08's trick will only work with the 94-95 M5R2 with the 1.34 3rd gear. With the earlier transmission's 1.43 3rd, 5600 RPM is only 95 MPH.
 
hmm. got me thinkin here.

Sitting in my bedroom is a brand new Ford Motorsport 3.73 gear kit. Was going to put these in my 95 sc along with an earlier m5r2 tranny. I don't care much for top speed anymore, mainly because I get carried away and end up in 120+ mph battles with beamers. I just want a beautiful cruiser that can kill a T/A or Z28 / SS on a good day. I've heard of going too big, So any ideas?
 
I might be wrong on the exact RPM going across the line but I know I pull 4th gear a long time and the shift light is flashing. Does the light come on at 4500?
They are 2.73 gears and 2 different people drove it the same day and had the same result pulling 4th a long time. what do I know.

Since my rear end was broke I am putting in a different unit with 3.08 this week.

Dave,
I should have my wet kit done this week also, I guess we can play who can break their engine first. Good Luck

Gary
 
mark VIII rears have 3.07 but are open so they do not have track lock. The LSC versions have 3.27 but are still open diff (non-locking). they are made of aluminum.

the sc's ones are not alum
auto's have 3.27 or 3.31 some 3.08s but only pre 94 were lockers. Most LX birds have the 3.08 ring and pinion but are not lockers only a few are, but usually they have 3.27 in them.
Pre 03 Cobra mustangs I belive have 3.27 in them and are lockers but they have 28 tooth spline. Someone else can explain the spline deal
;)

Gary, at what speed are you shifting into third and fourth. maybe past the 320rwhp. the car is speeding so fast that you do have to use fourth at the end of the track
 
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