I"m a new mustang owner and just picked up a near mint 95 GT 5.0. I've noticed it has pretty tall gears in it as it only revs around 1700-1800 RPM. On further investigation, the tag on the differential says it is a 2.73 ratio in it.

I'd like to upgrade the gears in the car without killing my fuel mileage. I was considering 3.55's or 3.73's but am unsure of which is the best gear to go with?

Any help is greatly appreciated....

 

Depends on what you want to do with the car. If you do a ton of highway driving 3.73's might be the better choice. If you don't do alot of highway driving I would go to 4.10s. We have a gear sticky in the general tech section that has alot of good posts check it out. Either way though I wouldnt bother with 3.55 rear gears. And I know the feeling of 2.73 my friends Procharged v6 had those and man it sucks so slow in any gear other then 1st. Added 3.73's and it pulled nicely in 1-4 gears.

 

So how does the gear changed effect mileage. According to a gearing calculator I looked at, the RPM's would increase about 400-500 RPM @ the same speed.

 

Im surprized its only that small amount of rpms for such a large gear swap that doesnt even sound right.
In the city they will help get you better mileage actully on the highway you will lose 1-3mpg.

 

My dilemma is this:

The car is a daily driver -- not a race car. Yet I do enjoy the odd blast between lights and the occassional highway cruise @ 75 mph. Fuel mileage is a concern nowadays as well. With the stock gear, the car is barely in it's power band. I run 17" rim with 245/45/17 rubber and according to the gear calculators at 60-80 MPH the rpms are as follows:

2.73

60 - 1457 RPM
70 - 1700 RPM
75 - 1822 RPM

3.55

60 - 1895 RPM
70 - 2211 RPM
75 - 2369 RPM
80 - 2522 RPM

3.73

60 - 1991 RPM
70 - 2323 RPM
75 - 2489 RPM
80 - 2655 RPM

With this being said, there really shows negligible difference between 3.55's and 3.73's...until you get into the upper rpm range. I frequently drive 75 MPH and 3.73 would put me at 2500 rpm.

I've been doing ALOT of reading on this topic over the last few days and I keep hearing that the 3.73s are a great city gear and OK on highway but 1st gear becomes somewhat unusable due to the need of a quick shift.

My question is this: Would anyone actually be able to tell the difference between a 3.55 and a 3.73 gear set in the same car? Will a 3.73 car accelerate any quicker or just go up in smoke?? Will the car be more gas friendly with the 3.55's in comparison to the 3.73's??

I know these cars aren't fuel misers, but this isn't a full blown race car. Sure, I want to squeeze ever bit of peformance I can out of the car, and 3.73s might do that, but I don't want it squeezing every cent out of my wallet either?

I guess I just looking for some reassurances.....

Any help is appreciated....

 

Do the 3.73's not the 3.55's you will be dissapointed at best with 3.55 gears. For the small rpm difference between the two go 3.73 and be happy. Your first gear will go by quicker but it will be far from unuseable with those 3.73's.

 

3.55's and downward are best left to pretty strong engines. I'd go with the 3.73's on your 5 litre.

EDIT: I have 3.55's. They're a great highway gear but you really will like 3.73's better. If I didn't have the 5.4 swap I'd be using 3.73's.

 

How much fuel mileage will I realistically be loosing by going from 2.73 -->3.73?

Will the fuel mileage be better with the 3.55's in comparison?? If so, how much better?? ....or is the difference negligible??

 

mileage difference will be negligible between 3.55 and 3.73. The performance difference is enough to justify it. You're going to have a whole new car going from 2.72 to 3.73.

 

How much worse will it be compare to stock 2.73 on the highway?

 

depends on your right foot and the specific car. you'll lose a few mpg in all probability but you'll have an assload more fun doing it.

 

In the city it will be alot better, on the highway because of how bad those stock gears are you might not be that much worse at all with the better gearing.

 

well....i just recently got back from europe, and i ended up at an old friends shop...

what theyre doin now is really mixin up the gear ratios. for example: say you get 4 10 gears for your 5L
and end up switching it all out...take your 5th gear from ur 2.73 ratio and switch it with the new packaged 4.10 gearing for highway use only.......my friend ended up payin quite a bit for his on a VR6, but its kinda sweet. i couldnt tell ya what the before and after ratio was, we just kinda skimmed over the topic.

this is what i heard, saw, and felt. i took the golf for a spin and when i hit 5th gear, you could definitly tell it was slower then all the rest.

ive never heard of this being done untill like 2 weeks ago. ask about it, and sorry if i hijacked the thread.

 

I've got 3.73 in an essentially stock '95 GT and it pulls very nicely and the mileage diff on the highway is 1-3 MPG depending on how I drive. I can get the tires to squeek a little if I jump on it in 1st but they by no means "go up in smoke"..... If I launch it above 3000...then yes, traction is an issue but it's that way with 2.73 too. It really woke the car up but didn't make it ridiculous (not like my little '67 with 4 speed and 4.10 I had years ago)

 

I have read through every post on this subject and right when I think I have it figured out, someone else makes a point that totally changes perspective. It really sounds like guys running 3.73 are the guys going to the race track and racing between lights than highway cruisin?

I would like to squeeze every ounce of performance I can out of it, but still NEED to get decent fuel mileage. I can't have it suffer 3-5 MPG. According to my tach with the current gears I have it run the following RPM in 5th gear:

60 MPH - 1600
70 MPH – 1850 ish
75 MPH – 1900 ish
80 MPH – 2100 ish
85 MPH – 2200 ish

If I was to put in 3.55's:

60 MPH - 2000ish
70 MPH - 2350ish
75 MPH - 2500 ish
80 MPH - 2650 ish
85 MPH - 2800 ish

3.73's:

60 - 2100 ish
70 - 2450 ish
75 - 2600 ish
80 - 2800 ish
85 - 2950 ish

Most of the time on the highway, I"m cruising 70-75 MPH. My main concern comes from the posts that states with 3.73 gears, 1st gear is very short with the 3.35 ratio in my tranny. I’d hate to be in the city and starting out in 2nd gear most of the time? I don’t go to the race track or race between lights very often, so I could maybe sacrifice some performance of the 3.73’s if I’m not going to use it?.....but at the same time, I”d hate to spend money/time on a 3.55 gear set and be disappointed.

I DON’T KNOW WHAT TO DO!

 

Your first gear will still be plenty useful. The rpm difference between 3.55 and 3.73 is not much and well worth the little extra rpms to get the 3.73's. I couldn't even consider 3.73's as a drag racing gear at all those are highway gears.

 

3.73s are a good all around gear. they cruise really nice on the hwy, and they will significantly wake your car up. 4.10s are a little impracticle for a 5.0 unless its a track car, however they are ok for a 2v. i wouldnt waste money on 3.55s. and not to be an ***, but if you are on the fence b/c of a 1-3mpg loss, dont bother putting gears on it.

 

dittos to the man.

 

NO offence taken. As much as I'd hate losing 1-3 MPG, I'd hate spending the time and money putting in a gear set and then being unhappy with the end result.

Any comments on the subject are helpful in making the final decision.

 

Like we said go 3.73 you will be happy and the difference in rpms is little between 3.55 vs 3.73. But 3.73's will pull harder then 3.55 trust us when we say go with the 3.73's you will be happy you did.