This winter I decided to swap the 3.54 differential gearing in my 1965 FHC to a more pleasant 3.07.
I have got the 3.07 ring and pinion gear from SNG Barret and they are getting them produced at the British company Tran-X (part of Quaife).
The new gear-set does not have a pinion depth marking (eg. +2) but instead it is marked MD=mounting distance which is the distance from top inner pinion bearing to center line of crown wheel. The MD on my pinion is marked MD 109,22. See photo. This figure is in millimeter.
I don’t have the tools to measure the MD (my depth gauge is only 100 mm) so my plan was to calculate the initial shims from the old shims and pinion depth marking (the plus/minus marking). Then I can convert this figures from the old pinion and shims to MD because the Jaguar Service Manual on page H.21 luckily has a figure for the standard MD. I can then compare this to the standard pinion depth (or Zero Cone Setting as it is called in the SM).
There are some calculations in between but I hope it is clear what my plan is.
I have two problems with this. First of all I can't read the plus/minus marking on the old pinion. I enclose photo. In my eyes the number is +15, but this can't be true. I have never seen a pinion with a number above plus or minus 4. I also don’t believe that the figure is 1.5. I have never seen a figure on a pinion split in half a thousand inches. Can any one give me a clue? Is it simply +1 with a letter or sign after??
My second problem is the MD in millimetres in the Jaguar SM on page H.21. It says 4.312” = 108,52 mm. But this is not true. If it is 4.312” my conversion to millimeter gives me 109,52 mm (4.312 X 25,4.) I assume that the figure 4.312” is the correct number and the 108,52 simply is a print error in the SM book. Any comments on this?
Jesper
