Hi All, This is our second post and need help. We have bought a 1936 Chev Pick-up that has XJS rear end and have found that the diff pinion shaft is facing downwards by 5.5 degrees using a magnetic protractor. But when taking measurements from floor to centre of diff and gearbox shafts and working with graph paper and doing the maths, the angle from diff to gearbox works out to +3.6 degrees. Can anyone tell me if Jag diffs do face downwards? If I put the protractor on the rear casing of the diff where the cover fits (no cover is currently fitted), it is -5.5° (ie.tilts downwards). Any thoughts would be greatly appreciated.
www.hotrodders.com/forum/jag-rear-ends-12205.html Lists the install topic, and a site named "OzRodders" has at least one listing for jag rears. I think I would determine my trans output shaft angle, then parallel (ie match) the rear pinion angle with it, THEN locate the relative heights (and or offsets to the side) between them to achieve a 3 degree total angle at each joint. The driveshaft joints will thank you!
Just make the two U-joint angles equal off the trans and off the rearend. Like any other driveshaft. It may mean you need to shim the back mounting to tilt up the pinion a couple degrees. What is your angle off the trans? If it is 5.5 degrees, then you are equal. A bit more than desired, but not that bad. 3 degrees is about ideal. You do not want straight 0 degrees, the needle rollers inside the U-joint need to have a few degrees so they rotate and lube properly.
It should NOT point downward. The imaginary line through the pinion gear should tilt up, as it goes from rear to front. the imaginary line through the output shaft of the transmission should go down, as it goes from front to rear. Those two lines should be parallel, theoretically, when viewed from the side. If the imaginary line through the pinion gear points toward the earth, when going rear to front, then the differential is mounted incorrectly. This is, sadly, not uncommon. It will need to either be shimmed, or mounts re-done.
As these were a very popular mod here in the UK I would suggest posting in the technical section of the NSRA. http://www.nsra.org.uk/newforum/forumdisplay.php?f=9 There is a lot of knowledge there to help you out. P.