As a newbie Mustang owner, my old 87 GT has the ID tags missing that many mention about determining gear ratios, etc and the different factory options when the car was new. I was wondering what gears my car has, the seller said 3.73's but I don't think so. What should I be reading at specific speeds, at the tach? It's a five speed, so what I mean at 55mph in high gear what would it be? If I remember correctly , at 100KMph in 5th I was at around 15-1600 RPM on the tach. Thanks in advance.

 

2.73; 3.08; 3.27

 

100K Mph....damn, you was flyin.' [sm=icon_stickpoke.gif]

At 100 Kph (62 Mph) you should be a 1600-1700 rpm. At 55 Mph, you should be around 1500 rpm with a 3.27:1 gear. The other gears will give you a little less rpm (about 250 rpm less @ 55 for the 2.73).

Here's a helpful equation:

RPM = ((gear ratio)*(MPH)*(336)) / (tire diameter)

or

MPH = ((tire diameter)*(RPM)) / ((gear ratio)*(336))

Plus I have a little spreadsheet that does all that for ya, too...

 

Thanks for the replies guys, kilometers per/hr is what us what us Canadians use. I didn't think it would be 2.73, I'll do the equation to find out. Thanks again

 

Jack up the car, spin the rear tire 1 revolution and count how many times the driveshaft turns. You will need to put a mark on the driveshaft. If it turns 3 3/4 turns, then you have 3.73`s

 

2.73's are GM gears. i believe. its probably 3.08's or 3.27's

 

No. 2.73`s did come in mustangs.

 

i just bought an 8.8 rear that was supposed to have 4.10's, but by the wheel/pinion rotation test, it went a smidge over 3 1/2 so im guessing it has 3.55's. i offered him 10 bucks less and bought it anyway. thats off topic i know, so here's a gear calculator i found in the process http://www.merkurtech.com/merkurtech...ors/rpmmph.php