Can anyone confirm the thread size used on the bolts /studs used into the diff housing(6) from the driveshaft pinion. I need to drill and tap one of the holes in the diff housing after repair.
That's one of those weird Ford Threads. ws
The holes in the stock housing are 13/32". I don't know if the Ruckstell is the same, but I would expect it to be.
Steve is correct. This is an odd threaded hole. You could drill an tap for the next size hole, which if I did the math right, would be 7/16th or install a plug then drill and tap for 3/8 16 bolt. This would give you one odd bolt in the group. You might want to read the info in the first link before you proceed.
One of the posters in the past had some made up. The taps are not inexpensive for doing one hole but maybe someone has one that you could barrow.
Remember if you put an oversize hole in there you will likely have to ream out the holes in the drive shaft spool and the head of bolts have very little clearance at the spool so an oversize bolt hex head will be a problem there most likely.
You could always mill the head of the bolts down to 9/16.
Of the various possible solutions, I would vote for borrowing the 13/32" tap and doing the job right.
13/32" - 16tpi to be precise
When I fitted a Moore transmission to a diff with 3:1 gears, I needed to find bolts to fit the spool to the diff. From memory, we used 10mm x 1.5 socket head set screws. This size was a very close fit, only binding slightly as the last thread exited the housing inside the hole. It is still good after thousands of miles and many long interstate trips. No modifications necessary.
Hope this helps.
Allan from down under.