Bolisk
Well-known member
So here is what I have.
1970 Coupe
origional 4speed Muncie
3.55 diff
non-stock sized B.F.Goodrich 235 65R15 with a overall diamater of 26.1 inches.
So, according to all the driven gear calculators on the internet, they all say I should be using a 22 tooth silver driven gear. Ok. . .fine by me. . .
Now, those same calculators also say that with stock F70 R15 tires with a diamater of 26.9 - 27.1 overall diamater. . .should have been using 21 tooth red gear. Also fine by me.
Now, before I swaped the driven gear for the 22 tooth, the car was reading about 3 mph faster than actual speed. After the 22 tooth swap the car is now reading 5 mph slower than actual speed. . . .
So what's the deal you might ask? Well, when I jacked the car up and removed the driven gear. . .my car. . .supprizingly had an 18 tooth gear installed!!!!! How in the hell is that stock? To add to that, the speedo cable was not connected directly to the transmission. . .rather is was connected to a 90 degree adapter device. I'm assuming that it's an adapter with a gear ratio change in it.
So. . .the question is. . .is that 90 degree device with the 18 tooth driven gear stock in 1970? Anyone know? I can't find any info in any docuementation (shop manual, chassis / overhaul manuals, or the assembly manual).
The reason I ask is, I would like to keep stock parts. I figured that if it was stock then I would continue to use the 90 degree device and just but a 19 or 20 tooth driven gear installed.
1970 Coupe
origional 4speed Muncie
3.55 diff
non-stock sized B.F.Goodrich 235 65R15 with a overall diamater of 26.1 inches.
So, according to all the driven gear calculators on the internet, they all say I should be using a 22 tooth silver driven gear. Ok. . .fine by me. . .
Now, those same calculators also say that with stock F70 R15 tires with a diamater of 26.9 - 27.1 overall diamater. . .should have been using 21 tooth red gear. Also fine by me.
Now, before I swaped the driven gear for the 22 tooth, the car was reading about 3 mph faster than actual speed. After the 22 tooth swap the car is now reading 5 mph slower than actual speed. . . .
So what's the deal you might ask? Well, when I jacked the car up and removed the driven gear. . .my car. . .supprizingly had an 18 tooth gear installed!!!!! How in the hell is that stock? To add to that, the speedo cable was not connected directly to the transmission. . .rather is was connected to a 90 degree adapter device. I'm assuming that it's an adapter with a gear ratio change in it.
So. . .the question is. . .is that 90 degree device with the 18 tooth driven gear stock in 1970? Anyone know? I can't find any info in any docuementation (shop manual, chassis / overhaul manuals, or the assembly manual).
The reason I ask is, I would like to keep stock parts. I figured that if it was stock then I would continue to use the 90 degree device and just but a 19 or 20 tooth driven gear installed.
