Quote:
Originally Posted by Merv and Sharon
Exactly how do you calculate a diff/final drive ratio (without counting gear teeth)? I put a mark on the drive shaft near the diff housing and some tape on a rear wheel relative to the edge of the body/sill. So the final drive is the number of rotations of the drive shaft produced by one wheel rotation? I multiplied this by 10 to get some better accuracy and 10 wheel rotations produced 22 drive shaft rotations (in neutral). FD = 2.2 therefore???!!!@@## It has been a long day and the brain is obviously missing something very simple ....
Merv
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Theory sounds right to me Merv but not the result.
i.e. I calculated my Wheel/Tyres 17" 315/35/17 are spinning at 812 RPM at 100 KPH. At this speed with a diff ratio of 3.45 my Tailshaft is going around 2800 RPM. In 6th Gear (ratio on T56 is 0.50 in 6th) this equates to around 1400 RPM which is about what I am seeing.
All this talk about diff ratios got me thinking about my own Cobra - I actually made a handy little Excel Spreadsheet that allows you to input your Gear Ratios, Wheel/Tyre sizes and Max Engine RPM and gives you what KPH per gear at what RPM - even a little graph.
The websites I checked only had Mile per hour not KPH.
PM me if you want a copy.
Rgds
Gregg (I need a beer now my head is done in)