Stock gear ratio

md02geist · 12-02-2012, 12:53 PM

Wasn't the stock ratio for the 66 V8 a 2.79?

Am I correct in assuming this is a pretty slow gear off the line, like almost to the point where you feel like you have to ride the clutch from a stop or it will feel almost like it wants to stall?

Maxum96 · 12-02-2012, 01:01 PM

V8 cars usually had gears somewhere between 2.79 to 3.25 from the factory. Special performance cars (i.e. Boss 302, Boss 429, Shelby's, Cobrajet 428 powered cars) often had lower gear ratios like 3.50, 3.91, 4.11, etc. 2.79 gears are what are commonly known as "highway gears". This is because they were used to keep the engine rpm's low during highway speeds. This gears are not optimal for off the line performance and hence the reason you have to "ride the clutch" from a stop. With a modern overdrive transmission (AOD, T-5, TKO, etc) in your vintage Mustang, you can run lower gears (3.50, 3.91, 4.11, etc) out on the highway and still turn fairly low engine rpm's. I have 4.11 gears in my car with a TKO 5 speed transmission and my engine rpm is around 2,100 at 60mph.

md02geist · 12-02-2012, 01:02 PM

Thanks that was a great answer. That explains it then. My mustang has what I'm pretty sure is still 2.79 in it and you really do feel like you have to ride the clutch, it's mighty slow on the takeoff. 2nd and 3rd do okay though.

sdmustangrider · 12-02-2012, 01:07 PM

Definitely they start off slow as hell but when you're moving already, it'll accelerate. I swapped mine out to 3.40 and I get it great for take off and while I'm driving.

horsehead · 12-02-2012, 02:30 PM

3.40's in mine with a four speed----Not to change the subject but did you fix your engine problem or figure out what it was blowing out your exhaust??

md02geist · 12-02-2012, 02:44 PM

Quote:

Originally Posted by horsehead

3.40's in mine with a four speed----Not to change the subject but did you fix your engine problem or figure out what it was blowing out your exhaust??

My buddy comes by to look at it tomorrow.

I started it up yesterday when it was about 60 degrees and there was almost no smoke...the TINIEST little bit that you could only see if you got your viewing angle JUST right, but not nearly what it was before.

I'm honest to goodness wondering if it wasn't just a s-ton of condensation built up. I've just never seen condensation that heavy.

1-18-68 · 12-02-2012, 05:40 PM

'68 J code fastback (now w/ 351W) 4 spd toploader and 8" 3.5 open rear. As built from factory.
No clutch slipping required.

MrFreeze · 12-02-2012, 08:17 PM

Quote:

Originally Posted by md02geist

Wasn't the stock ratio for the 66 V8 a 2.79?

Am I correct in assuming this is a pretty slow gear off the line, like almost to the point where you feel like you have to ride the clutch from a stop or it will feel almost like it wants to stall?

I've owned several '66 V8 Mustangs, and looked at a lot more.

Every C code I ever saw came with 2.80 gears.
Every A code I ever saw came with 3.00.
K codes varied from 3.50 on up.

I'll also throw this in: every T code Mustang I've seen had a 2.83 rear axle if it was an automatic car, and a 3.20 if it was a stick.

FYI, the 2.79 ratio didn't appear until '67 or '68 (I forget which).

You would probably enjoy your car a lot more with 3.25 or 3.50 gears.

Regards,
MrFreeze

Huskinhano · 12-02-2012, 10:26 PM

I'm running 2.79's with a wide ratio Toploader 4 speed. Mine starts of ok. One important think you have to remember is the over all final drive ratio. Close ratio 4 speeds have a taller 1st gear then a wide ratio 4 speed. As such, it'll need lower rear gears to take off from a stop easier. A wide ratio 4 speed with 3.25 rear gear is going to have a lower over all final drive in 1st then a close ratio 4 speed with 3.89 gears. You'd really ride the clutch with a close ratio 4 speed with 3.25 gears! Big block cars with lots of torque can do this though. It's really important to match your rear axle ratio to your transmission ratios to have an effective combo.