Banjo Bolts

Cracker39

Cracker39

Senior Member
Does anyone have a photo - or can they describe the physical appearance - of the correct banjo bolts? I want to pull a couple of mine to check - on the possibility that my leakage is due to the incorrect bolts - but without a photo or description I don't know what I'm looking at?
 
The photo shows original banjo bolts. Note the head is slightly thicket than most bolts. There is an unthreaded area under the head. The stud is one of ten I use to line up the gaskets.

Tom Endy
 

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Ford used a tighter tolerence screw on the banjo housing to prevent leaking and so they did not require a lock nut.

If someone uses a tap and die on the bolts and housing they have effectively ruined them. Well you had best use the right lock tight product.

If the threads are clean, which must be done by hand, then you should have a lot of troubles getting the bolts to go in by hand. That is using your fingers. After a 1/4 the way in it should feel stiff and getting to 3/4 should be difficult. If you can put the bolt in all the way by finger then the threads are loose on one side or the other.

I went through around 150 bolts to get a set for my rear. I hand cleaned the bolts and used a pick to clean the banjo threads. At that I had several that I used on the top side of the banjo because they were a bit looser. As usual, the really nice looking bolt heads were the loosest and a few rusty ones got used as they fit better.

Please keep in mind many of the threaded mechanical fasteners are done with higher tolerence threads. I hand clean almost all my threads anymore after I saw the difference.
 
The pitch diameter on the threads of the special thick head hex bolts is a little larger to ensure the lube seal along with the special unthreaded area just under the head of the bolts.

The Banjo has the normal 3/8" NF threads and may be rechased. I cleaned up the bolt threads by using a very wine wire wheel.

Larry
 
Articles that are published about the special thread size on the hex bolts seem to suggest that the Banjo tapped holes are standard. Can't have both.

Would be interested in some credible proof of your thoughts..

Larry
 
See page 61 of Schlid's shop manual.

The section of a print shows the drive shaft tube bolts, which would have no need for sealing, are to be class III. Class III is the tightest fit.

Ford would have done this on the sides because it created a seal and acted as a lock as no lock washers were used on these bolts. Plus Henry's engineers were doing some amazing production high accuracy machining throughout the A's mechanical.

I personally remember chasing the holes in a center section and was amazed that I took a bit of clean metal from each hole. That was before I was aware of the thread classes. I also remember it written on one of the Model A magazines, after I did the tapping, that Ford used tighter tolerence threading at these points.

My experiences since have found Ford used the Class III threads in many other areas. Now I hand clean all the nuts in bolts just to be safe.
 
While draining Minervas' rear end, took one bolt out at a time, put just a smidge of #2 Permatex on the bolt threads & NO more leaks. Permatex #2 will stick to the threads, even when they're OILY! Same goes for the drain & filler plug. IF any red shows, just clean it off with a toothbrush & solvent. EASY!
Bill W.
 
I read the differential rebuild articles of Tom Endy to be correct on his procedure. The internal threads of the banjo he cleans with a round wire brush on the end of a drill. As for using a tap to clean the banjo threads, yep they will leak after chasing with a standard tap I know a guy who did it.
Bob
 
Pretty sure the bolts are normal (from the standard hardware list) and the tight threads are in the casting. Class 3 would be modern tight fit, classes were different back then, I think they may be 4's in the early classes...these are called out in the Ford trade school shop practice book somewhere, I don't have a copy here, and of course in the Ford trade school Mechanics (meaning Machinist's) vest pocket book which has class 3 as medium, 4 as "close fit." I think fit number would be on the parts drawing from the archives if anyone has that.
 
On timing gear cover where there are bottomless threaded holes, sometimes leaks oil out of the lockwasher slit. A dab of Permatex #2 on the bolt threads will stop the leak. Bill W.
 
I went ahead and ordered a new set of "original design" bolts from Snyders. Provided the banjo has never been re-tapped, I should apparently expect a resistance at a certain point, while hand tightening the bolts, that will then require a wrench to finish tightening the bolts to the required torque. If this is the case, would the use of silicon, or lock-tite still be a good idea - or would it be over-kill?
 
When I rebuild my diffs I use Indian head shellac on the banjo gaskets and bolt threads. So far so good...i feel this is better than silicone for this particular repair...
drain the diff and brake kleen out the holes then install the bolts...
you may hear that only ford originals are acceptable. i have never used snyders but i have used Roy Nacewicz bolts as they were frowned upon in the past but worked fine....
 
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Bruce Lancaster said:
Pretty sure the bolts are normal (from the standard hardware list) and the tight threads are in the casting. Class 3 would be modern tight fit, classes were different back then, I think they may be 4's in the early classes...these are called out in the Ford trade school shop practice book somewhere, I don't have a copy here, and of course in the Ford trade school Mechanics (meaning Machinist's) vest pocket book which has class 3 as medium, 4 as "close fit." I think fit number would be on the parts drawing from the archives if anyone has that.
Click to expand...

Kevins post above says that page 61 of Schlid's shop manual shows a section of a print that shows the drive shaft tube bolts, which would have no need for sealing, are to be class III.
 
If you want to clean the threads, and don't want to use a tap, find a spare housing bolt. Run a 4" grinder across the threads on one side, with the grinder layed over. This will cut a lop sided V groove. Run this bolt up and down the housing threads cleaning them without removing parent metal.
 
I'm still puzzled over my 28 rear end suddenly deciding to leak. For years it stayed dry, but over the past couple years it leaks a few ounces over the winter, even though all the bolts are original and tight, and the rear end has not been worked on or taken apart.
 
FWIW, it is amazing to me just how many rear housings that we find are bent. I'd venture a guess that maybe 7 out of 10 we find with at least .100" or more of run-out, and likely 30%-40% are over .250". They are not hard to straighten really just using heat and water.

The 2nd part of this (which is why I think some of y'all are finding the need for Shellac or Gasket Sealer) is that often times the gasket surface is not true. See below where we are machining the gasket surface of the housing. Don't forget to file the surface of the Differential (Banjo) Housing to ensure it is smooth and does not have "proud" threads. It makes a huge difference with regard to leaks.


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