Banjo Bolts

[BRENT in 10-uh-C]

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.

You are correct. They are Class IV.

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[Bruce Lancaster]

Hmmm...now, what other extra-tight threads are there on early Fords? An earlier discussion that I can't seem to find on here showed specs for the head stud threads, with drawings from early and late production provided by uber-researchers Marco and Vince...those threads started as class threes, and were changed to fours later in production...unmolested threads with original studs gives leak-free installation with no goo and studs that stand up at 90 degrees so head can go right on.
I know for sure that I wallowed out a bunch of those holes with a standard machinist's taps years ago, before I learned the threads were not normal modern class 2's...
Are there others around the car?

 

[BRENT in 10-uh-C]

Hmmm...now, what other extra-tight threads are there on early Fords? An earlier discussion that I can't seem to find on here showed specs for the head stud threads, with drawings from early and late production provided by uber-researchers Marco and Vince...those threads started as class threes, and were changed to fours later in production...unmolested threads with original studs gives leak-free installation with no goo and studs that stand up at 90 degrees so head can go right on.
I know for sure that I wallowed out a bunch of those holes with a standard machinist's taps years ago, before I learned the threads were not normal modern class 2's...
Are there others around the car?

I dunno Bruce. I have never really thought to look at other prints. Those pictures above are mine that I got at Bensen. I also have the A-6015 Cylinder Case drawings and I did not see anything about class of threads on the prints.

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[Tom Wesenberg]

There's a lot of better threads on the Model A. The best way to clean the threads is to use a Dremel with a thin cutoff wheel and make 4 slits in a bolt, then use this bolt to clean threads.

 

[Bruce Lancaster]

Brent, I found the earlier discussion.
Marco's drawing calls out the tap size as "7/16-14 N.C. 4" and Vince's later dated drawing (now removed from the thread--?) says/said N.C. 5. I assumed those were the fit class designations, and the discussion by Marco and Vince seemed to indicate that they accepted the numbers as such. What remains of the discussion is here:
http://www.fordbarn.com/forum/showthread.php?t=39285&highlight=threads&showall=1

I think yours shows a 5...or maybe a 3? Can't quite resolve it here.
On all of this I am groping a bit...the info I have on 1930's thread designations is sketchy, and I have no experience in interpreting the Ford designations in the drawings.

Your Banjo drawing is much more definite!

 

[BRENT in 10-uh-C]

Bruce, it does say 5 on my drawing. I need to look as I may have some alternate drawings too. I have tried to obtain as many mechanical and body-wood drawings as possible so that we know what standard we are restoring to.

Marco's copy is the same as mine with the exception mine is a 2/10/31 drawing and his the 3/29 drawing.

 

[Bruce Lancaster]

I found a copy of Vince's drawing showing the 5 designation, too...I had cut and pasted the discussion when all was still there.

 

[George Miller]

If I remember correctly from my machining days. Class 5 is a interference fit.

 

[Bruce Lancaster]

I don't have enough information OR engineering education to sort it all out, but I suspect that we are looking at different classes in 1930's material and modern. WWII stirred up all sorts of change in fastener and thread standards, some of it involving unification of US and british threads. Also, then as now, I think a lot of standards encompassed mostly standard hardware, and critical fasteners in cars and especially in flying/space stuff were all either specced by manufacturer for their jobs or moved into a whole different world of standardss, like AN and NASA...
Ford fasteners would divide here between those with Ford part numbers like head studs and some brake bolts and those from the hardware bin, listed as standard hardware by Ford.

 

[Cracker39]

Thanks to all - but check back to post #15 and let me know if I should simply use silicon, or the Permatex suggested in post #16? If it still leaks after I replace the bolts I'll buy another bag of kitty litter and continue happily on my way.

 

[BRENT in 10-uh-C]

Thanks to all - but check back to post #15 and let me know if I should simply use silicon, or the Permatex suggested in post #16? If it still leaks after I replace the bolts I'll buy another bag of kitty litter and continue happily on my way.

Depends, ...check back to Post #21 to see what the likely issue is and how to properly correct it. I guess my point is, are you trying to correctly repair it, or just repair it good enough to use?

 

[Mitch//pa]

Thanks to all - but check back to post #15 and let me know if I should simply use silicon, or the Permatex suggested in post #16? If it still leaks after I replace the bolts I'll buy another bag of kitty litter and continue happily on my way.

your post #15 was answered in post #17

 

[Cracker39]

To clarify - the leaking differential is a problem I could live with indefinitely but, if simply replacing the bolts with a bit of sealer would alleviate the problem or solve it, all the better. Right now, it doesn't lose more than an ounce or so in 500 miles - well within my lubrication schedule.

 

[1955cj5]

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?

I am having a similar issue with the differential. I've removed all the bolts, one at a time, cleaned, sealed with Permatex #2, re-assembled and it still leaks enough to be annoying..

Did you get the bolts from Snyders and install them?

Did it help?

Thanks

Randy

 

[Synchro909]

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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It's good to see repairs being done properly. Brent, when you do this, do you ever end up in the situation where the carrier bearings are too close together so there is no adjustment for the pinion on what you call the ring gear? Maybe you have to machine carrier too to compensate?

 

[BRENT in 10-uh-C]

It's good to see repairs being done properly. Brent, when you do this, do you ever end up in the situation where the carrier bearings are too close together so there is no adjustment for the pinion on what you call the ring gear? Maybe you have to machine carrier too to compensate?

Actually, at least one supplier is selling bearing races that are not of the same dimension as original, --thus the reason why vendors sell brass shims to compensate.

As for machining, you could do that but often times the housings only need .010"± of material removed to make it true. The bigger issue is the housings are generally tweaked (likely from towing/jerking/hitting something.) which creates not only leaks but causes the rear wheels to be out of alignment. Think about what happens when the rear wheel alignment is out with regard to the axles & differential parts.