Thread: Rearend Leak
View Single Post
Old 07-09-2020, 07:46 AM   #10
BRENT in 10-uh-C
Senior Member
BRENT in 10-uh-C's Avatar
Join Date: May 2010
Location: Eastern Tennessee
Posts: 9,578
Default Re: Rearend Leak

Originally Posted by john charlton View Post
The bolts are a machine fit and are very carefully made they are not a common UNF bolt . I am not sure if the reproductions are made to the same tolerances so could be you have repro bolts installed by someone because they look pretty . No lock washers should be fitted .

John in Suffolk County England .

John, you have hit on something that many are not aware of. The former Roy Nacewicz bolts were manufactured correctly however I cannot speak for other vendors, however it is typically not the bolts that are the problem. The Differential Housing's hole thread pitch that Ford used was a Class 4 which is a size that is typically not used commercially any longer since the advent of thread locking compounds. I think most pitches go from Class 1 - 5 with a Class 5 being almost a locking fit. The standard bolts will seal when the holes are threaded with a Class 4 cutter. Below is a PDF I made off of my A-4025 print that shows the specs for the holes.

Attached Files
File Type: pdf Threads.pdf (1.58 MB, 60 views)

BRENT in 10-uh-C
...(...Finally Updated!! )

BRENT in 10-uh-C is offline   Reply With Quote