373 vs 410s
 

Our next project is to upgrade the rear in the 88GT 5-speed. We're stuck on the age ole question - 373 vs 410 gears? We've got a power adder in the future - most likely a supercharger.
The car will not be taking any long highway trips etc and may end up a weekend warrior.

What do you guys think about gears on a 5-speed?

Great place to invest the next phase of time, effort, and money. I haven't seen you here in a while. (mabey just me) While you are in there, make it possi. Rebuilding the stocker works well. $100.00 and a call to Pyle Bros Perf Differentials in Houston, TX. will do the job. Mine worked flawless for about 7 years of total abuse of street and track duty. The gears, big choice, I had both, I prefer the 4.30s that I have now. With more gear you can run a taller tire, which gives a better 60ft, and this yeilds lower ET's. I currently use a 26" tire with the 4.30s It crosses in fourth at 6000. Perfect untill I choose to make the next step, and when I do, I will adjust by going with a 28" tire. I do a lot of daily driving, pull the boat and bike trailers, I think I get 20 or better MPG. Its crazy, But just remember your will be more of a track car, so you can deal with a little more than 3.55s or 3.73s. Good luck either way.

88workcar - thanx for the info! No it's not you I've been kind of silent on this forum for a while. Started a new job - my wife started a new career. Painting the house, doing some carptendary work, new floors etc....

Man, I'm looking forward to getting back to some fun stuff like getting our project car running stronger.

BTW - we're upgrading the axles and putting in an Eaton posi in addition to gears. My son just said he would still like to keep the stang on the road instead of simply a weekend warrior. I'm trying to get him to define his goals for the car and work towards them.. With this said, do you guys recommend 373s over 410s if the car will still be on the road? Shouldn't get a lot of highway miles - but around town. How will gas mileage be affected with 410s?

3.73 gears
 

Being that you're running a 5-speed, I'd definitely recommend the 3.73s. They are a great all around gear. I have some friends that went with 4.10s and regretted it, because these Mustangs were still driven on the street weekly. Plus, with 4.10s your 1st gear is almost useless except with slicks...or some seriously sticky tires for the street. 3.73s have my vote!

I also agonized over which gear ratio to go with..I finally decided on the 4:10's, and love them!
I average around 15mpg with mixed city and highway driving..

I have 3.73's and I kind of wish I went with the 4.10's... But my car is an AOD :D

On a 5-speed that will not be taking long hwy trips and maybe be a weekend warrior, I'd probably suggest 4.10s over 3.73. But I too have had at least 2 friends that have gone from 3.73s to 4.10s and regretted it-- both with 5-speed manuals-- but mainly b/c they couldn't get any traction on the launch-- these launches were on drag radials also. Yeah, 1rst gear is SHORT-LIVED. But with slicks, i think you'll love the 4.10s. Launching with those will be a little more difficult than with the 3.73s, but with someone who knows how to drive and with good tires, you'll get use to them...

Of course, the best thing to do would be to get the car dynoed. Observe your power band and trap speed and rpm at the 1/4 mile and then match the car's gears to that.

I just last week upgraded from 3.73's to 4.10;s the launch was a little better but then I have a C4 and 26" tires Mine is drag only and not street driven,for a 5 speed I wouldnt think you could actually tell the difference between 373 and 410 with that low 1st gear,if I was still running a tremec I would have gone to 4.30's I think and banged 2nd before the 60,as for having to run slicks?,you can launch just as well with MT ET's and hook up.I run ET class NHRA here in Jax and love my 4.10's but still wish I had gone 4.30's sort of,wasnt that much of a difference with my C4.Just my thoughts on the matter.

for the street with normal (near stock height) tires my 3.73's are too low for me. I wish I had 3.55's. First gear is useless on the street, it just blows them away. I quess it depends on where you want the most benefit to be, on the street or track.
:p