Why lock washers AND safety wire???

M

Marshall V. Daut

Well-known member
I am going through a Model A transmission for an acquaintance that was a terrible leaker, mostly from the rear. While replacing the usual suspects during the rebuild - something I have done dozens and dozens of times over the years - I mechanically from habit put new lock washers under the heads of the four bolts that secure the main shaft bearing retainer to the back of the transmission case. As I was tightening the bolts, I was mentally going through the remaining assembly steps, which include safety wiring these bolts. Then I wondered - why are lock washers used here with safety wire? Isn't that like guys, who wear a belt AND suspenders? Jeez! How safe does a guy need to feel? Because the holes for these bolts are threaded into the transmission case and therefore "open", placing lock washers beneath the bolt heads is just creating a pathway for oil to leak. Lock washers are generally not used in such applications because of the tendency for leakage. I'm wondering if the presence of lock washers here wasn't a factor in why the transmission leaked so much in the back, even though the correct heavy 600w lubricant had religiously been used. The special washer was also in place inside the universal joint and was glued in place to reduce leakage. But the fluid was definitely leaking into the U-joint housing, as all the spilled fluid attested when the u-joint halves were separated.
I checked the standard transmission "blow-up" drawing that appears in most catalogs and in some specialty booklets and I see no lock washers. Yet in the bolt set sold by the vendors, there they are - lock washers!
I never thought about this before until tonight and never really paid attention in the past to original transmissions I have disassembled in the past 50 years whether there were lock washers or not. It's still not too late for me to go either way on this, but I'm leaning more towards leaving the lock washers out as being as useless in this application as t*ts on a chicken. The safety wire run through the four bolt heads will more than secure them from backing out. Or is this a high vibration area that the Ford engineers decided needed both lock washers AND safety wire??? I can't think of any other place on the Model A where both are used in tandem, can you?
Marshall
 
"I am going through a Model A transmission for an acquaintance who was a terrible leaker, mostly from the rear" Is the acquaintance or the transmission a leaker from the rear? Sorry, just had to ask....
 
Nothing. I can see the tips of the top two bolts by looking into the case. Remember - the bolt holes are drilled entirely through and threaded into the case so that the pathway is open to the inside. The bolts are not bottoming out against anything, as they do up front into the external "swells" that encase the bellhousing-to-transmission case bolts. The bolts in the rear could be even longer, I suppose. Because they do not protrude past the holes and into the case, that's why I'm leaning towards leaving the lock washers out and just using the safety wire. Even when lock washers are compressed by tightening the bolt, the gap between the washer ends - even squeezed together - still forms a minute pathway for lubricant to ooze out, especially in a turbulent environment like inside the transmission. I put sealant on the threads of the bolts to slow the leakage down, but I believe without the lock washers beneath these bolt heads, the chances of leakage are greatly reduced. This transmission, as well as others I have worked on, had lock washers here when I disassembled it. There were signs that someone had worked on this transmission since it left the factory, so all bets are off on originality. Since the bolts have holes in their heads for safety wire, I just can't understand why lock washers would have originally been used here. Mechanics and restorers in the past 85 years must have added them when working on the transmissions. As I wrote in my original posting, I'm at the point where I can either go with or without lock washers. I just want to do it the way Ford did, the reason for starting this thread.
Marshall
 
I have taken a lot of Model A transmissions apart and found that all but a very few had lock washers and were safety wired. That must be the way Henry ordered it.

I also wonder about the need for both. It is not an easy place to safety wire and there is only one hole through the bolt head. I torque the bolts to 45 ft. lbs. and end up with the holes at awkward angles. I see no need to add safety wire, but I do, and it usually looks terrible, but the customer might complain if left off. Henry wouldn't like it either.

Tom Endy
 
A high vibration area with lubricant exposure, oil, would call for max engineering for security. 1) Torque spec applied secures the item. On low surface area nuts and bolts, the oil will penetrate the threads over time, as penetrating oil does. The oil can help the vibration break the torque applied and loosening. 2) Lock washers will help with applying additional friction and pressure to assist with the applied torque from moving at all. 3) Safety wire is only to help prevent the initial movement. Safety wire was used extensively in the 30's on aircraft for the same reasons. It is still used today as regular practice with in high vibration areas and/or areas that may be exposed to lubricants. Heavy large fasteners (nuts and bolts) have sufficient contact of material to avoid the need for these additional securing methods.
Use the safety wire application properly with tight side applied to not allow any initial loosening movement. Safety wire is not used as a cotter key.
 
What about the rear bearing? Isn't most of the original bearings not sealed? I have installed new bearings with the oil sealed bearings and have no leaks. I think that is the area that these leak are prone to happen.
 
Indeed, opening up a can of worms here.... I do not believe lock washers are generally any use anyway... to join in the controversy google "lock washers are they any use"!
 
The automobile manufactors, of today, do not use lock washers, at all.
You won't find them on the car that you are driving.
MIKE :) (mikeburch)
 
Just safeties mine during the genie build...FYI, .041 wire is a pain in the butt to use .032 is much easier and will hold the bolts just fine...I used .041 anyway but it's a pain...
 

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Haha yes, I do use wire pliers. Doing it by hand doesn't give as consistent of results. I also spent the last 5 and a half years as a jet engine mechanic so I'm used to safety wire. For those of you have never wired before I highly recommend the .032 wire, it's just much much easier to work with.
 
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