Reading some of the posts on this topic, I had to chime in.
I recently had my stock 2.73s swapped for 3.73s and had the posi rebuilt. What a difference like night and day. In my opinion, 3.55s would be ok but not as torquey as I imagine, never actually rode/drove a car with those gears though.
Here are my specs:
90' LX hatch
Stock 5.0 HO
Moroso CAI
Underdrives
Flexlite Electric fan kit
Ford Motorsport Ceramic Shorties
Pype's Catted X-Pipe w/ Chambered catback
stock 8.8 28 spline rear w/3.73s, all rebuilt
W/C T-5
Out of the hole, this car is absolutely awesome, even for a stock engine. It will chirp the tires all the way till 3rd gear, maybe fourth if I was a better driver. It pulls all the way to 5000 rpm or so. Top end is awesome as well. Drop it into 3rd at around 50-55mph, it still pulls hard. And gas mileage...believe it or not, about 16-17mpg city and I pulled off about 26mpg highway at 55mph, no b/s.
Overall in my opinion if you do go with 3.73s, you won't be disappointed.
Ok, read this whole thread and finally came to this conclusion:
3.55's........... Here's why, this winter I will be putting a 375 hp motor into my 90 gt backed by a Tremec 5sp backed by an FMS Driveline backed by an Auburn. My car is being built for Road Racing. I will have the hp and tq to push/force my car into motion very quickly. I DO NOT WANT to chirp the tires and I feel that with the 3.73's I would be doing this, not good on a road course. If it was going to stay stock with some bolt on's then it would be the 3.73's. Good news is I will be getting the 3.55's by end of July and be able to get back to this and give everybody some feedback on what 3.55's do on a stock motor with bolt-ons, Tremec 5spd, FMS driveline and Auburn. I will also post in the 5.0 tech forum too.
imo a 375hp motor and 355s are barley cutting it with a tremec tko.I have 410s and had an auto,big difference from a 5spd my tko loves 410s and I couldnt imagine it being any lower.Im right at 400hp
I think your gonna be a little low for your liking.,
ESPECIALLY WITH A STOCK MOTOR!!!Do the 410s and the stock car will be real fun And The 375hp motor is gonna be right on the money.
ANd.....if your gonna be on a road course,theres no way in heck ur gonna like the 355comparedto410 forget 373 355 I would do if I had 450 and over hp or really love to fly over 135-150mph tire size plays a big role and tire chirping is more about how you shift in a 5spd.
If its auto......yea your gonna get chirps with a stockmotor and 410 1-2 shift all day at wot.
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aode to tko swap done
x3z cobra eec pih harness, victor efi intake,edelbrock rpms 202,11.5compresion,eagle i beams,xe282hr cam,main girdle,fms crank306,msd6al,dualcenterforce
VERY INTERESTING GUY..... Now my situation.... I have! 3.55s and was actually thinking of 373,s,,,,,,,,,,,,,,now after reading and reading...im confused.....i have a stock low end...with some gt40 heads and all other suggested bot ons.....inlcuding upper and lower edelbrock intakes.......................now should i stay 355 or move towards 373 ..........thanks nick
I put 3.55s in my car and DOUBLED my in-town mileage... (I was getting 6-8 in town, now I'm getting 14... and I did replace the speedometer gear when I did the swap.) My engine doesn't lug and bog in town anymore, I don't have to floor it and force the AOD to downshift on the interstate to pass people anymore (my highway mileage stayed about the same, in the 23-27mpg range depending on how hard I hit the onramps and how many people I want to pass. ) I'm seriously wishing I'd done the swap from the stock 2.73s ages ago! The only downside I've noticed is that I no longer have a useful 2nd gear, before, with the 2.73s, if I floored the gas from a dead stop or near-stop, I'd get a 1-2 shift, a 2-3 shift, and when I'd finsihed accelerating I'd bump the shifter from D to OD to get into overdrive... since the 3.55 install I have a 1-2/3 shift then I shift into overdrive... it's a little annoying.
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1976 Ford Mustang II Ghia: 302 with a 600cfm Edelbrock carb, Edelbrock Performer 289 intake, Dynomax Blackjack headers, 2.5" exhaust with Flowmaster Super 44s. RJS 11-gallon fuel cell, C4 tranny, chrome 16" pony wheels, fuzzy dice, brown vinyl half-top, and painted in the tackiest color ever (harvest gold, that's why I call it "The Goldenrod").
Also have a 2003 Dodge Ram (lightly modded daily driver/tow rig/office/dining room/home away from home/workshop... I call it "The Big Blue Dawg".)
Go with the 373 and if some one told you theres a big diff in gas mileage between a 355 and 373 they need the head looked at your talk maybe 100 to 200 rpm diff and i got better gas mileage a round town when i put the 373 in the only bad thing is to get the same mileage on the e way i had to drop 5 to 8 mph like thats so bad the only reason ppl say they lose gas mileage is because when you first put it in you want to race every one to see if it made a diff and if you have your foot in it all the time you will lose mileage but thats true about any car no matter what gear it is i say do it right the first time go with a 373 its a stick you have overdrive
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1989 Mustang LX 5.0 Edelbrock Performer 5.0 EFI Intake Msd 6AL MSD blaster coil March Performance under drive pullys a/c ELIMINATOR smog ELIMINATOR cam bbk cold air bbk70mm THROTTLE BODY 73mm mass air ford raceing headers and H pipe 40 flowmasters T 5 TREMEC 373 9' ford rear end
go with 3'73's or 4.10's when using lower gears you multiply the torqe factor and it helps to keep the motor at its peek hp from shift to shift. also at 375 to 400 hp i don't think gas mileage is an issue.
i have an 89 coupe 5 spd basic bolt ons and 3.55's. i really like them and i can take my buddys hatch with basically all the same stuff and 3.73's but i dont think much of his driving to be fair. i get a little rubber into 3rd with new 245/45/zr17's i wouldnt change them out for 3.73's.
i bought 3.73 gears and i will be installing them on thursday, and i just wanted to know if i am going to lower 0 to 60 and 1/4 mile. With all my mods listed above plus the 3.73 gears will i be able to beat a mustang gt 2000 in a 1/4 ???
I am a little confused with all of the options and things to consider. I do have one main question that will settle it all for me. With a World Class t5 and 3.73 gears what will my crusing rpm be @75mph
i have 3.73 my top speed it well over 130 miles per hour..
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DSS 331 stroker, AFR 185 heads, Performer rpm 2 intake, Accufab 75 mm race TB, 30lb injectors, 80 mm Pro-M mass air, Extreme energy cam 266.
Anderson ford power pipe the big one, Ford motor sport shorty headers, Bassani x pipe custom cat back with flows, World class T5, center force duel friction clutch.
I had 3.73's in my 95 GT and found myself shifting way to often! So now that i have a 91 GT i'll give 3.55's a try i have a feeling i'll like the better!
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1995 Mustang GT
373's
Flowmasters
H-Pipe W/High Flow cats
190 lph Fuel Pump
K&N Air Filter
Kirban Ajustable Fuel Pressure Regulator
MM Subframe's
Air Silencer removed
I am a little confused with all of the options and things to consider. I do have one main question that will settle it all for me. With a World Class t5 and 3.73 gears what will my crusing rpm be @75mph
scroll down-use calculator to get exact wheel diameter-scroll down again,use the tire diameter and gear choice to find out speed at RPMs on chart-chart shows RPM in 4th gear(1:1 ratio,so more can use it)
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"Life is not a journey to the grave with intentions of arriving safely in a pretty well preserved body,but rather to skid in broadside,thoroughly used up,totally worn out and loudly proclaiming.....WOW!.....What a ride!
"As you grow older,don't slow down,speed up-there's less time left"--over 45 and just now realizing how much I don't know
Re: 3.55's or 3.73's Tech Discussion. 
into my 90 gt backed by a Tremec 5sp backed by an FMS Driveline backed by an Auburn. My car is being built for Road Racing. I will have the hp and tq to push/force my car into motion very quickly. I DO NOT WANT to chirp the tires and I feel that with the 3.73's I would be doing this, not good on a road course. If it was going to stay stock with some bolt on's then it would be the 3.73's. Good news is I will be getting the 3.55's by end of July and be able to get back to this and give everybody some feedback on what 3.55's do on a stock motor with bolt-ons, Tremec 5spd, FMS driveline and Auburn. I will also post in the 5.0 tech forum too.
) I'm seriously wishing I'd done the swap from the stock 2.73s ages ago! The only downside I've noticed is that I no longer have a useful 2nd gear, before, with the 2.73s, if I floored the gas from a dead stop or near-stop, I'd get a 1-2 shift, a 2-3 shift, and when I'd finsihed accelerating I'd bump the shifter from D to OD to get into overdrive... since the 3.55 install I have a 1-2/3 shift then I shift into overdrive... it's a little annoying.
