Choosing gear ratio

[Odmark]

Hi guys! I would like some help with choosing another gear ratio for my cougar, it currently has 2.75 wich is good if i go highway cruising but i very rarely do.

I mostly drive around town, little bit of street racing and a little bit of track use.

I would like some help on what to choose, my neighbour has a 66 fairlane with almost the same setup cleveland as me (his is a little more agressive) and he runs 3.70:1 and is very pleased.

Completely new to swapping out ratios so if there is any additional info you need to help me, let me know and i will provide. Thanks.

 

[mustang7173]

Odmark,

It maybe good to install a 3.25 to no more than a 3.50. What is your transmission? FMX or C6?

mustang7173

 

[Odmark]

I have an FMX transmission, i actually found an used 3.56:1 ratio just now for cheaps. Could that be a good one or is it to low?

 

[Mister 4x4]

That'll jump you off the line real good. ::thumb::

 

[mustang7173]

Odmark,

I would be good if you have an AOD installed. Alot of the mustangs with AOD's had the 3.55 gears installed. You will tach up wards of 2800 to 3000 or higher rpms with that gear cruising around 60 MPH. . Now, your off the line acceleration will be greatly improved. I would probably go with the 3.25 to round out both scenario.

Ok - Lets hear it from other forum members.

mustang7173

 

[Mister 4x4]

Odmark,

I would be good if you have an AOD installed. Alot of the mustangs with AOD's had the 3.55 gears installed. You will tach up wards of 2800 to 3000 or higher rpms with that gear cruising around 60 MPH. . Now, your off the line acceleration will be greatly improved. I would probably go with the 3.25 to round out both scenario.

Ok - Lets hear it from other forum members.

mustang7173

Actually, the majority of 5.0 Fox bodies with AODs came with 2.73, 3.08, or 3.27 (special order). That's why I'm not so worried about swapping my 3.00s out since I went with an AOD.

http://www.allfordmustangs.com/forums/5-0l-tech/219774-what-stock-gears-1989-mustang-5-0-a.html

 

[Odmark]

Highway speed rpm really dont matter that much since i almost never drive like that. But as you say it could be nice to have the ability to do so as well.

Still 2800-3000, could be worse found a brand new 3.50:1 for 100 bucks now. Lots of people in Sweden seem to have 9" gears laying around haha

 

[Mikes73]

I have 3.50 ratio gears in my car and love it, the car has great low end and mid range response. My car rarely sees the highway so these work very well. I changed them out from 2.75's and noticed a big difference in performance. My vote is 3.50.

 

[73pony]

I am going with a 3.70 but I also have a T-5. Had an FMX in it before I would not go over a 3.50 with the FMX.

 

[jbojo]

I would not go over 3.50 unless you have an OD tranny.

 

[will e]

I ran 2.72 and 3.25 and now a 3.50. When I had the 2.72 and 3.25 the car was a daily driver. The 3.50 is fine around town and it will work on the highway but your engine will be revving. This wasn't so bad on my 21 mile commute to work. Your cougar may even be more comforatable since it probably doesn't have glasspacks and such.

I did findally put an OD unit in the car and still have th 3.5. I do love being able to go into OD on the highways. My gas milage improved 20% or so too.

For you I would say 3.25 will be fun and better on the highway. The 3.5 will be funner. You mention track use. Are we talking road course or straight line.

3.50 for the straight stuff but it might be better 3.25 for a road course. You are going to find breaking the tires loose is easier with a 3.50. This means you won't be able to get in it as early on a road course which means less fun.

Careful with that street racing... there are a lot of innocent people around.

 

[Jim and Jutta]

I've got a C6 in my 71 (no AOD), went from 3.00 to 3.50, very happy with the choice. Gets off the line much quicker and can still cruise at 70MPH with no excessive RPM's. I believe it's only a couple hundred RPMs higher at 70. Would have stuck with the 3.00 if I used it as a daily driver, but the fun factor is worth the swap since I don't.

 

[Ajh1973]

I am currently redoing my rear ended and am going with a 3.25 with my C4.

 

[Don C]

3.70 in mine, lot of fun on the street, too low for extended highway use.

You can play around with gear ratios, tire sizes, and RPM with the spreadsheet here, to see what you can expect:

http://www.7173mustangs.com/thread-tire-sizes--11566

 

[Mister 4x4]

The AOD also has the same gear ratios as the FMX, but adding the final drive of .67:1. Based on the combination of the AOD final drive gear and the rear axle 3.00s, I'm anticipating something around 1750-1800 RPM on the highway (@ 65 mph).

The '89 5.0 my AOD came from (along with everything, including the stock Torque Converter) had 2.75s (it was an LX 5.0 'vert). That's why I keep saying I shouldn't have any problems using the stock TC with my combination, when everybody seems to think higher stall speed TCs are needed. It really is almost a direct swap.

Plus, if the 351C-2V was ever capable of doing a burnout with an FMX and 3.00 rear gears with only 245 hp, I'm pretty sure there shouldn't be any issues in that department with the 400-ish I believe I have now. :whistling:

That being said, I think the general consensus of going with 3.25s or 3.50s will definitely build-in a lot of fun, but anything numerically higher will definitely kill the top-end.

I remember when I went from 2.73s to 4.10s in my Jeep - I can't even make it across the intersection now without grabbing second... I can climb the side of a building with it, but the engine's definitely screaming at-speed on the freeway.

 

[LCB1]

I went with 3.70 and very pleased with it. I will be swapping the C4 for an AOD to make it more highway friendly.

 

[turtle5353]

I am running 3.73's with my c4 and love them. On the highway I am turning 2800-3000 at 65-70 mph. Drove mine 5 hours to Carlisle all ford nationals a couple years ago with no troubles.

If you have found 3.50 gear for $100 locally, I would say jump all over that especially since you wont have to wait on and pay for shipping internationally.

 

[Mister 4x4]

I am running 3.73's with my c4 and love them. On the highway I am turning 2800-3000 at 65-70 mph. Drove mine 5 hours to Carlisle all ford nationals a couple years ago with no troubles.

If you have found 3.50 gear for $100 locally, I would say jump all over that especially since you won't have to wait on and pay for shipping internationally.

I can't believe you're running a C4 behind that monster of yours.

I think he jumped on the 3.50s and is going that direction. ::thumb::

 

[turtle5353]

I am running 3.73's with my c4 and love them. On the highway I am turning 2800-3000 at 65-70 mph. Drove mine 5 hours to Carlisle all ford nationals a couple years ago with no troubles.

If you have found 3.50 gear for $100 locally, I would say jump all over that especially since you won't have to wait on and pay for shipping internationally.

I can't believe you're running a C4 behind that monster of yours.

I think he jumped on the 3.50s and is going that direction. ::thumb::

Built right, a C4 will take a hell of a pounding!! And weighs considerably less than a C6. Down the road i'm going to be looking for an OD tranny, probably a beefed up 4r70w. But my car had a c4 in it when I bought it so that's what I ran with. My buddy built it for me and it shifts HARD. Its pretty impressive. Broader did all the valve body work to it and its a great little tranny. Might be a different story if I could ever get it to hook up. But for now , it works!!