anyway to tell if i have 3.73's

[low9sGT hahajk]

Hey everyone,

I bought a 1997 Mustang GT about a week and a half ago. I was told from the small-time dealer that the car was fitted with 3.73's, catback, and some cobra tranny. I know it has a catback, but I haven't had the opportunity to check on the cobra trans. But what I am wondering is whether there is anyway to tell if the car actually has the 3.73's. Also, I know this is a little off topic but I'm curious O0 .. if the car has 3.73's what times should i run with a pi cam and intake swap? (BTW if there is a thread with a car with that setup with 1/4 numbers I haven't found it, and trust me I have looked!)

Thanks.

 

[Matt94GT]

you can tell by the mph/rpm ratio. try a search there is some sort of calculator. im sure someone will chime in here.

 

[low9sGT hahajk]

yeah I tried to find something but all the calcs come out with these crazy answers..like at 60 with 3.73 i should be at 4500rpms or some crazy stuff...hopefully these don't have to be overly precise. if they do I'll have to head up to the highway and redo these..anyway I had my girlfriend take note of the rpm:speed and it came out to be:
rpm's in 5th gear : mph

1650 : 55
1900 : 60

Thought it might help?

 

[Jrgunn5150]

Well just FYI, a Cobra trans is the same as a GT trans, just a different mount, so they either B.S.'d you on that or it was all the previous owner could get his hands on to swap in.

As for gear's, unless it was corrected your speedo would be off, and possibly pop a CEL for it. You can chock the wheels, put the trans in neautral, jack the rear of the car up, and then spin the tire one complete time and watch how many times the driveshaft goes around. For 3.73's, it should go three and three quarters of a turn.

 

[Jrgunn5150]

http://www.car-videos.com/tools/spe...o7=&Redline=6250&Increment=500&B1=Recalculate

Your stock tire size is probably 235/55/16, so I entered that, and the 5th gear in a T45 is .68 so I entered that. But you can play with it.

 

[low9sGT hahajk]

First of all, thanks for all the quick responses and help! Jrgunn, even at the time of purchase I didn't really put too much faith in his word, I made sure I was ok with buying it if the trans and 3.73's weren't in it like he said..and i was haha..Also, I might jack it up later to find out..but if the speedo is correct then 3.73's at 60 should put me right near 2000rpms.
At 2000rpms with 3.27 gears it would put me at 67mph...so i dont know..

 

[Jrgunn5150]

Sweet, some states have the whole "buyer's remorse" thing, so I figured I would let you know. Of course the guy who traded it in could have just lied himself also, most dealer's are completely clueless. Anyway, enjoy it! And welcome to the slow but cool looking car club!

 

[Mr. OAM]

Do as Jrgunn5150 said. It is the most simple way to accurately determine your ring gear. It only takes about 5-10 minutes. Real simple.


Steve

 

[Black97GT]

First of all, thanks for all the quick responses and help! Jrgunn, even at the time of purchase I didn't really put too much faith in his word, I made sure I was ok with buying it if the trans and 3.73's weren't in it like he said..and i was haha..Also, I might jack it up later to find out..but if the speedo is correct then 3.73's at 60 should put me right near 2000rpms.
At 2000rpms with 3.27 gears it would put me at 67mph...so i dont know..

you are talking about 5th gear right? I have 3.27's and in 5th gear at 80mph I am at approx. 2100rpm.

 

[Marc@UPR]

3.73's at 80mph you will be at 2500rpm
4.10's at 80mph you will be at 2750-2800rpms

 

[justinschmidt1]

well..with those mods you should run low 14s....

what rpm are you at going 70 mph?...

if your at like 2k..its stock...anything higher..like 2300 is 3.73s

 

[danroadking]

Take you car, jack it up, make a reference mark in your driveshaft, put your car in neutral and rotate any wheel, if you have 3 ¾ revolutions in your driveshaft per tire revolution you have 3.73 gears.

 

[voidfinger]

hey guys , i'm thinking of gears and i thought i would chime in since the op question is answered... what would i be running with 4.30's at around 65 75 80 or 85? I'm swapping in a t45 and a cobra motor and everyone is telling me to do 4.30's for the 4v. Thanks

 

[Willis_98GT]

http://www.car-videos.com/tools/spe...o7=&Redline=6250&Increment=500&B1=Recalculate

Your stock tire size is probably 235/55/16, so I entered that, and the 5th gear in a T45 is .68 so I entered that. But you can play with it.

thanks dude. i was actually wandering if mine had 3.73s too. but i now know that it has the 3.27s.. thanks..

 

[Jrgunn5150]

hey guys , i'm thinking of gears and i thought i would chime in since the op question is answered... what would i be running with 4.30's at around 65 75 80 or 85? I'm swapping in a t45 and a cobra motor and everyone is telling me to do 4.30's for the 4v. Thanks

If you aren't after all out strip performance, and you don't have a T-56, go with 4.10's. I have 4.30's and they are a bit much, even with T-56. You'll be shifting alot.

 

[voidfinger]

got ya, my buddy has a t56 in his cobra and he has 4.56's and he recommended the 4.30's ... he even said that the 4.56 wasn't enough... o well.

 

[Jrgunn5150]

Well like I said, it depends on what is important to you.

 

[voidfinger]

i don't know.... i would like to know what i will be turning at 65 mph with the 4.10s and the 4.30's. Shit i guess i won't go over that on normal driving so. Plus i guess it won't hurt the mpg to much on the cobra as long as the IMRC are closed so as long as its under 3250. But i'm hopen around 2800...

 

[Jrgunn5150]

4.10's will put you at about 2800 at 70. I used to have 4.10's with my T-45. If you don't do the long haul everyday on the freeway 4.30's will be fine. It made me kinda nervous to hear that thing screaming for that long on longer trips though. I like to be around 2200 for my peace of mind.

 

[voidfinger]

so i should just stick to 4.10's then...