Hot Rods leaking "banjo" rear axle

Does anyone know a GOOD method to plug the bolts on a 1940 "banjo" rear axle to keep them from leaking?

I know of at least ONE bolt that goes all the way through and I believe this is the one that is giving me problems. I coated each bolt prior to installation.

Any suggestions are greatly appreciated................

Thank you in advance.

Mike

 

I switched from bolts to studs with lock washers and chrome acorn nuts. Studs make it easier to install the gasket. Also let permatex on both mating surfaces sit overnight. Yes, I know that the "quick change" is phony, but a lot of people don't know the difference.

 

I can't ever recall seeing any thru bolts on a stock banjo... Although my QC has thru bolts. These ford bolts actually have a specially shaped (standard pitch, though) thread and if they've been replaced with standard fine thread bolts at some time, you can count on them leaking.

 

Thunderbirdesq is right.

It is a common problem on banjos that have had the thread chased on the housing. The stock threads are tapered, much like a pipe plug. Chasing the threads ruins the taper and they will always leak thereafter. NEVER CHASE BANJO HOUSING THREADS! I see it done all the time even by pro shops. The only solution I know of other than replacing the housing is to use a ton of prmatex on a spotlessly clean housing and hope for the best. Otherwise it will be just another Ford marking it's territory.

 

Yes on the threads being special. I learned this one in a topic here when someone said they were chasing their threads. Pretty sure Bruce Lancaster was the one that quoted the exact thread pitch. Arent they some sort of interferance fit?

 

According to my Dad, who was a Ford factory trained mechanic back in the early fifties, the threads in the housing are tapered, not the bolts. He made a big deal out of that when I was a kid just learning in his shop. I always just took his word for it and never checked. Banjo's are an easy to work on rear but they do have their tricks. My understanding is there is a Ford service bulletin on this dating to the early thirties. Maybe somebody on here has a copy? I've seen it mentioned in various service publications and retoration manuals over the years.

 

Also, from the factory, those housings were coated with grease and then the gaskets were installed and then when torqued down, the paper gaskets soaked up the grease and expanded creating a seal. This is how Ford intended those to work and that's how flathead restorers still do them.

 

Kevin Lee, Can you buy class three bolts from a domestic source? I've gotten bolts from Macs and some other places and they semed to be the same as regular hardware. Is the thread also different or are they just tighter?

 

Hi, I purchased all the bolts new from Macs and coated each bolt with permatex..........I recall at least one bolt that goes all the way through. I have a real minor leak but a leak non-the less and I'm thinking that it is this one bolt that is causing all the trouble. I will have to do some further investigating and find the source.
I'm thinking maybe a copper washer on the leaking bolt with a lot of compound.

Thanks for response,

Mike

 

Bolts are actually standard, pretty sure on that, straight from hardware section of Ford catalog. Threads in banjo are extra deep, heavier flanks, something like a class three but most likely predate that system and have different nomenclature or standards. I'd like to see the specs on the drawing if I ever get to Ford archives.
Once tapped with a standard macinest's tap they are permanently fubar for sealing, as they now have same threads as nearly all automotive fasteners and cannot really seal.
On alternative sealing. probably biggest issue will be getting things clean enough to hold thread goo after being bathed in gear oil.
Strength I would think is likely adequate, so I'd experiment with perhaps a thin O-ring mashed under washer. I have heard of people winding cotton string around last threads on bolt...easy to try too. There are plenty of sealing compounds, but as I said getting clean metal for them will be challenging.

 

When I rebuild a diff, be it an 8", 9" or banjo etc I always put a copper washer under the bolt head just as an extra precaution, sure as hell seals your brake pipes where they screw into the wheel cylinder. Probably solve your problem.

 

Most pumpkins on a 9" Ford have a copper washer under the nuts. Why wouldn't it work on the banjo's bolts too?

 

A POSSIBLE problem area, and I have no idea if it would be an actual problem, is that the bell-to-banjo bolts are holding together the weight-bearing axle, wheras on 9" types the load bearing piece is continuous from side to side. How about good steel washers mashing a thin-section o-ring around the bolts to backup the sealing of the damaged threads?

 

i asked Roy Naciwicz, the Ford standard parts guru about the bolts and housing threads being special. he said it was an "old wives tale".

 

The bolts are standard, as posted. Now remove a few from an original banjo and try a tap on the female threads...

 

I had good luck with studs and "hardening" Permatex. Allow the permatex to set up and harden overnight, if possible. Ford was known for using "special" hardware types. 4TTRUK

 

Copper washers did the trick for me.

 

I stick an 'o' ring under the head of the bolt - that works. Theres gizmos called stat-o-seal or dowty seals, these are washers with captive 'o' rings on the inside and they'll seal it right up too.

 

Got a vent installed to relieve the pressure when hot?

 

Thanks a bunch for the GREAT suggestions. Sometimes the most simplest things are the ones that give the biggest headaches.

The BOLT situation is an easy fix.

BUT...................

¿Is it mandatory to coat the paper seals??

I was very careful in getting the gapping, with the paper seals, correct that I figured I would by pass putting anything on them.

¿Could this also be a leaking problem?

I guess I will soon find out when I fix the bolt situation.

Thanks again,
Mike

 

I doubt that you could coat the side gaskets without altering carrier load. Surfaces obviously need to be good...if there is a ding or pit deep enough to cause a leak I would fill it wtith something...hardening Permatex, maybe epoxy, and shave it flush with surface with a razor blade. They do not ordinarily leak there.