Speedometer gear question

[RUFF]

What number speedometer gear do I need to run in my 727 trans with 355 rear gear?

 

[70CUDA4SPEED]

http://www.mymopar.com/index.php?pid=112

 

[moparleo]

:3gears:Here is an RPM to MPH calculator if you want to know how fast you are going at any RPM. Enjoy.

http://wahiduddin.net/calc/calc_speed_rpm.htm

 

[RUFF]

Thanks!! Red gear it is....

 

[72ls5fla]

hey

you will need a 35 or 36 tooth gear.
it will really depend on the tire and the rim, how inflated etc..

you may find that one gear will get you more accurate readings at lower speeds, and the other will get better at HWY speeds.
and how well your speedo is calibrated makes a HUGE difference too.

Bill

 

[RUFF]

Will be running a 295-50-15 on a 10 inch wheel at 30lbs of air...Tire is 26.65 in diameter.

 

[moparleo]

Obviously nobody with a 40 year old mechanical speedo or tach for that matter can expect perfect calibration. The chart in post three will get you to the factory option gear. Or go to a speedometer shop and get it done perfect? When is the last time any of us have honestly had our speedometers cablibrated with all of the rim and tire size changes over the years.

 

[Avalanche]

Great way to find out if your speedo is correct.
Most GPS systems have the speed on them. Great to see if your speedo matches it.

 

[dongei]

I installed an aftermarket speedo in my Challenger ,looks good but is 7 mph slower than the reading on the face. Speed showing 70mph on speedo but gps speed is 63 mph. Would the teeth on the trans gear need to increase or decrease? Kind of lost on this one. Could use some advice.

 

[BeauBonyx]

I could be wrong but you would want to go up. to spin the pinion faster. Right?

 

[moparleo]

Here's the color code and pinion tooth chart
http://img.docstoccdn.com/thumb/orig/152393575.png

 

[BeauBonyx]

ok i have question. I am not trying to high jack this.
I have a 904. the gear that was in there is 25 tooth and blueish gray. the whole thing is plastic. I need a new one. any ideas where i can get one. i have looked at a bunch of places on line but nothing is stock.

 

[moparleo]

Pretty much a used part only. No repros that I am aware of. Check with a few transmission shops. They may have some laying around.

 

[BeauBonyx]

yea that is what i was thinking. I may get get a gps sending unit and gauges

 

[Bill]

I installed a free speedometer app on my smart phone to compare.