View Full Version : Gear Question

07-10-2006, 09:25 AM
I am having a hard time deciding what gear to put in my '94 Cobra and I am looking for some info. I am going to go with either a 3.55 or 3.73 gear. Can any of you other '94-'95 owners with 5-speed trannys tell me the following:

1) What RPM are you running at 70 MPH with a 3.55 gear?
2) What RPM are you running at 70 MPH with a 3.73 gear?
3) What change did your gear, 3.55 or 3.73, make to your gas mileage. Of course, performance, not mileage, is the main concern here, but I do not want to hurt mileage too much, especially not at nearly $3 a gallon.

I used to run the 3.55 gear in my '85 GT and I was very happy with it. It did not hurt my gas mileage at all. However, I am leaning towards the 3.73's for a little more punch in my '94, but I would like to hear some other's experience/advice first. Thanks for any help you can give.

07-10-2006, 09:54 AM
Go for the 3.73's....
I have them in my 94 & they are perfect, to me anyways. At 70 the RPM's are around 2400 rpms or so, if I remember correctly.
Gas mileage only went down 1 or 2 mpg on the highway.

07-10-2006, 02:50 PM
I have 4:10s and at approx. 70mph I run around 2500rpms :cool:

07-10-2006, 03:27 PM
I never like the 3.55 in my previous 94 cobra. I love the 3.73 in my current 94 cobra with a t5. I plan on going to a six speed soon, though. Over 480lb of torque to the wheels is hard to hook up in first gear. If you were planning on big power and a five speed, 3.55 might be better.

Probably most important: get a rebuild kit (ratech) and have someone qualified do the swap! I did this and have not been disappointed, actually used the local ford dealership (thier guy was pretty slick).

07-10-2006, 09:48 PM
Thanks for all of the advice. Cobrapace94 told me all I needed to know. I wanted to keep the revs @ 70 MPH at or below 2500 and did not want to lose more than 3-4 MPG. So, I am going to go with the 3.73 gears.

I doubt I will need the rebuild kit. My car only has 39,000 miles on it and has never been raced.

I have one more question for cobrpace94, if you don't mind. You said that you only lost about 1-2 MPG when you switched to the 3.73 gears. What was your mileage before? I am getting 26-27 MPG on the highway with the stock 3.08 gears! I have checked it 3 times and I am still surprised.

Thanks for all of the replies.

07-10-2006, 09:53 PM
Your stock mileage is correct for highway miles. My bone stock 94 gets 23.5 in city/highway miles and 27-28 on all highway. What's funny about all of this is that these cars get as good of gas mileage as some of these imports.

My modified 94 you saw at the show still gets almost 24 on the highway and 22/23 going back and forth to work. I do have 355 gears though....and I'm doing 2200 rpms at 70 mph. :thumbsup:

07-10-2006, 11:35 PM
I was getting around 24-26 mpg on the highway & 17-19 city when it was mostly stock.
I'm getting over 22 mpg now with the supercharger, if I keep my foot out of it & is all high way miles. City is still not bad, 17 mpg or so if I don't do any racing.

07-11-2006, 09:10 AM
Thanks again for the additional responses and comments. They serve to reinforce my decision to go with the 3.73's.

Tony - I agree, it is funny how we are getting about the same MPG as some of those imports. In some cases they may have some HP, but the torque certainly is not there and to me the torque is what truly makes a car fun to drive.

I like all kinds of different cars and trucks, Ford, Chevy, Mopars - you name it. However, there is just something about that import/tuner crowd that tends to annoy the crap out of me. An 80 HP car with a $5,000 paint job, $5,000 stereo, $3,000 wheels and an 6" sewer pipe stuck on the end of the tailpipe (my wife says it looks like a big d--k on a little bug!). And then there's the worst part - the sound!!!!!!!!!!!! Sounds like someone pissed off a swarm of hornets. A whole generation may be growing up without any clue as to how a performance car should sound. Well, I better stop now before I really get going. Thanks again for the responses.

07-11-2006, 09:50 PM
If you are doing just cruising around GA or maybe an occasional drag strip then I'd go with 373's. If you plan to modify and go open tracking, then I recommend 355's. Either way...get those 3:08's out of there. Also, I took mine to the Ford place to change out the gears and remember you have to change the speedo or tranny gear to get the speedo correct again or otherwise you may be racking up invisible miles. :D

07-12-2006, 11:48 AM
And tickets with the speedo off. Been there done it with over size tires on the truck. But officer my speedometer said 55. clocked at 69 pay the fine

07-12-2006, 01:50 PM
I learned about the speedo gear years ago when I changed the 2.73's in my 85 GT to 3.55's. I got in the car and drove up the street in front of my house and watched the speedo rise at a ridiculous pace. Had me wishing it was true.

I can't wait to get the 3.73's in my '94. I know when I changed the gears in the '85 it felt like an entirely different car. The car pulled hard (compared to stock) and kept the engine more in the power band up through the gears.

RF Cobra
07-12-2006, 04:07 PM
And tickets with the speedo off. Been there done it with over size tires on the truck. But officer my speedometer said 55. clocked at 69 pay the fine
Fortunately those are easy to get out of here. You can go to a shop with calibration equipment and have them certify the speedo was off and they throw out the ticket. I've even seen someone swap out tires, get it certifed with the oversized tires as being off, and put the original tires back on to get a ticket thrown out.

07-13-2006, 09:52 AM
I paid the fine and went back to the original size tires. Didn't know about getting certified out of calibration. Live and learn.