Rim with 354 gear set

[dan juhasz]

I took out my 67 gtx that I acquired over the winter. Pretty sure the po told me he was running a 3.54 rear gear. At 60mph the tach was around 4 grand. Does that sound about right? Running the stock 14 inch wheels 215 70 14. If the tach is accurate I think I could use less gear. I like to drive my cars and winding a 440 at 4 grand plus on a longer drive makes me uncomfortable, or am I worried about nothing.
What a good all around gear, I think my RT uses a 3.23

 

[69b3rt]

Sounds to me you probably have 4.10 gears. Time to jack up rear end and look for ratio tag and count how many times driveshaft spins to one revolution of wheel.

 

[moes]

with the information you gave 4000 rpm, 60 mph, 215 70 14 (25.9 inch tall tire) gearing would be 5.14 using a rear gear calculator. Sounds like a gear that would have been used in a race car or a truck.

 

[dan juhasz]

with the information you gave 4000 rpm, 60 mph, 215 70 14 (25.9 inch tall tire) gearing would be 5.14 using a rear gear calculator. Sounds like a gear that would have been used in a race car or a truck.

If that's the math I need to check the accuracy of the tach, maybe it's just reading high.

 

[moes]

If that's the math I need to check the accuracy of the tach, maybe it's just reading high.

yes, I would check the accuracy of the tach out

 

[66Satellite47]

Sounds to me you probably have 4.10 gears. Time to jack up rear end and look for ratio tag and count how many times driveshaft spins to one revolution of wheel.

I agree just jack the back up & count the turns on the drive shaft, then you know what the gears are. Limited slip, both wheels turn the same direction, open diff they turn opposite directions. 4000 rpm at 60 mph does seem too high for 3.54 (3.55 if 8 3/4).

 

[dan juhasz]

I'm using a base pertronix for ignition, do these work well with the original console mounted tach?

 

[RJRENTON]

Dan,
FYI....My numbers mstvjing '70 GTX, RS23VOA *****, with a 4.10:1 Dana 60, A34 super track pack option, with P275R6015 tires (all 4 corners) yields at 3000 RPM (factory TicToc Tach and Prestolite dual point distributor) 56/58 MPH using the correct speedometer takeoff gear (white 40 tooth gear). I've been paced by a State Police friend, with his certified accurate speedometer resulting in almost identical results (+ / -).
Beside checking your tach's accuracy, did you check your speedometer's takeoff gear application against published tables in Mopar's parts manual? A few mph off is no big deal.....
Bob Renton

 

[dieseldazzle]

Use a gps program on your cell phone. Free download to verify

 

[dan juhasz]

Use a gps program on your cell phone. Free download to verify

Good idea