I encounter a (strange) problem related to my speedometer which i need to calibrate when i swap my rear end ratio. 191 camino
Recently i replaced my speedocable, and since then the speedo gives a reading.
1. Not very stable
2. It makes a soft noise from behind the dash(yes i lubed the new speedocable)
I did some runs with gps to check current actual speed with gps.
Dash speed 35, gps 31
Dash speed 50, gps 47
Dash speed 60, gps 57
Dash speed 65, gps 62
So lets say the reading is 3mph high
So far so good.
I am running 2.56 rearend (checked).
Running 255/60 15" tyres (27.05inch diameter in theory).
If i match the tyre size with my rpm gauge at certain speed and then I recalculate to tire size it returns 26.75" so it will be around this size in reality.
My th700r4 currently runs a 19tooth and 40tooth wheels for the speedo.
If i do all the math and compensate for the 3mph offset as mentionee above, it returns in a rev per mile of 871. Even without the 3mph offset it returns in 917rev per mile.
On every website, I found 1000 or 1001 rev per mile for a 1971 el camino.
Is it possible something is wrong in my speedometer? That is should be 1001 rev per mile but something messed up inside and now return in a weird number.
Btw, if i do the math for my tyre size and take 3.55 rear end with 1001 mile per rev. The gear selection is 15tooth with 40tooth and this is almost the higest gearing possible (t15/t45 is max).
I hope my question is clear. I am glad to give more info if needed.