Factory Five Racing Forum banner
1 - 13 of 13 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter · #1 ·
Greetings everybody,

I just have a quick question. I am looking at a 94 Mustang GT as a potential donor for a Factory Five sometime down the road (hopefully starting within a couple of years!!) The Mustang has 2.73 gearing out back, so I am definitely going to be in the market for an upgrade, but don't know what kind of gearing to look for? I am wondering what some other people have your gearing in their Factory Fives?

Any advice and wisdom would be greatly appreciated!

Thank you in advance
 

·
Premium Member
Joined
·
9,683 Posts
Lots of posts on this subject, but generally you will be happiest with a 3.27 or a 3.55 rear end ratio.
 

·
Junior Charter Member
Joined
·
2,688 Posts
The more power you make, the taller (lower numerically) you'll want the gearing. I run 2.73's and love them, but I make a lot of torque. At the opposite end of the spectrum, for a totally stock 302, I'd probably use 3.55's or 3.73's to help get the car moving. Cheers.
 

·
Registered
Joined
·
11,831 Posts
Thomas W nailed it, but keep in mind that he has an AOD (4-speed auto with overdrive)

http://www.ffcars.com/forums/17-fac...-rear-end-ratio-thoughts-recommendations.html

above is the best post i found.

to search the forum, don't use the forum search, use google.

TYPE: ffcars.com rear end gearing

you will find loads of posts, but i am very surprised i could not find a poll.



the basic answer is 2.73 is too short for most of us, but some guys with mild, high revving 302's swear by it.

you must also consider your final drive ratio and highway cruising RPM. not only is it a matter of noise, it's a matter of MPG.

3.55 is by far the most common. i had a 3.08 with my donor, i changed to 3.55 and it was much better. but now, i have a torquey 347, about 450hp, and i do wish i could be in the middle with a 3.27.
 

·
FFCobra Craftsman
Joined
·
6,086 Posts
Gearing is a substitute for TQ. It just add mechanical TQ multiplication. Look at tire height and trans ratios - figure out what your RPMs will be at various speeds you drive in various gears. Also remember that your car will weigh 2000-2500# while a Mustang is 3800+ pounds. We are pushing about 1500# less.
 

·
Master Student
Joined
·
1,499 Posts
The more power you make, the taller (lower numerically) you'll want the gearing. I run 2.73's and love them, but I make a lot of torque. At the opposite end of the spectrum, for a totally stock 302, I'd probably use 3.55's or 3.73's to help get the car moving. Cheers.
X2

That's not a quick question though. You can be hours going over this topic. Here are some more links.

http://www.ffcars.com/forums/17-fac...94942-last-decision-before-placing-order.html

http://www.ffcars.com/forums/21-ffr-type-65-coupe/285375-regrets.html
 

·
BigA4327
Joined
·
270 Posts
Just a thought, since these cars can get away from you quickly in the rear, it may be wise to not go too low a gear. This will give you a little grace. The stock gear could be just right for many entry level Cobra owners who aren't use to the amount of "pucker factor". Nothing personal, I could be way off base. Have fun.

Sent from my ADR6400L using AutoGuide App
 

·
Registered
Joined
·
804 Posts
The one issue I see with 2.73s and that I have to wait for the traffic to get moving in front of me before I take off. The gear a bit tall and I need to have room in front of me to get going. Idling in traffic is also a pain. I'd like a little lower gear so I don't have to be on the clutch as often.

On the track I'm in one gear lower than most cars but since I have some torque it is ok. I also have to wait a while when I punch it in 2nd and 3rd as my stock 302 takes a while to get up to speed.

On the freeway in 5th gear I'm turning 1200 to 1500 at 65 and 75mph. Get some great mileage but my 302 is fuel injected.

I have a mustang with 3.73s and it will lay a mean strip of rubber. My FFR does not lay a mean strip of rubber (on the race track of course)!
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #9 ·
Thank you everybody for all the words of wisdom and knowledge. That is why I love this site so much! The amount of helpful people on this site is staggering and I can't tell everybody how much I appreciate it.

Keep 'em coming!
 

·
New
Joined
·
1,143 Posts
My donor came with 3.73's which I though I wanted. First gear felt too short in that car and with the blower I could burn the tires off all the way through third, but overall not too terrible for what it was. Without the blower it needed them. In the roadster they feel too steep. I think I would prefer a 3.27. I'm going to get it on the road before I decide but just from go-carting I'm not thrilled with it. I like my forward motion to match or exceed my noise level.
 

·
Registered
Joined
·
434 Posts
With a stock T-5 (3.?? 1st) and 3.73 gears, I can hardly get the gas pedal down before needing 2nd. 3.55s would probably be much better. Big blocks or power adders could go 3.23 or taller. IMHO

Don H
 

·
FFCobra Craftsman
Joined
·
25,961 Posts
As you can see there is a lot of experience here. One thing to add is that the trans gears also have an effect. W/ 250-300 hp the stock T5 gears first will get real short real quick w/ more than 355 but the OD ratio will be good and useable down to maybe 45 mph. W/ more power the first gear problem just gets worse. So a World Class T5 will help w/ it's taller first gear. Or you could go w/ a taller diff like a 308. My 400 hp w/ a tko 500 w/ stock T5 gears works fine on the street w/ my 308 diff although the 5th is a little tall and can't be used below 50 mph. But, I am swapping in a 331 gear after christmas since I run a lot of autocrosses and it will give me more grunt in 2nd gear. The other thing to keep in mind is that near anything other than a 273 will be OK. Not absolutely perfect, but OK and a ton of fun.
 

·
Registered
Joined
·
32 Posts
I had a very streetable 505hp and 520lbs hi performance pump gas motor in with a broad torque band in Superformance with independent suspension. I had a Tremec3550 with a 3:73 in the rearend first. Like other here said already, wound out in 1st before you could get halfway accross an intersection. Then I installed 3:27 and it was perfect. I then changed the transmission to a TKO600, with a .82 (If I remember correctly) 5th gear, and it was perfect with the 3:27. lots of gear to use at all speeds and highway cruising around 1,600rpm. I now have a high hp race motor in my FFR, with a Jerico 4 speed with road race gears. A completely different setup with a 3:55 rear that works perfect.
 
1 - 13 of 13 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top