driveshaft pin

[Brian]

Over the years I've gone through a few driveshaft pins; they shear and you get that familiar [in my case] dink, dink, dink sound. I've machined them up out of various materials; high tensile steel , med tensile, mild steel. Ultimately they all fail. Yes...excellent fit, machine the pin to exactly .250", drive in, pein ends over. Then the splines wear, so that next time you replace the pin, it is taking all the drive, consequently, soon fails.
I've recently built yet another new diff, all new parts, and have just experienced yet another pin failure! I made this pin out of mild steel. OK, my question is; what grade steel should these pins be made of?

[Tinker]

my understanding is the pin is to just locate and keep it in place. most stockpins are sheared in the rear ends i've seen. is this due to play in the coupler? intersting post


softer the metal less likeliness to shear

[Lawrie]

Brian, maybe a pin with free play,that is ,smaller than the hole,I thought the pins job was to locate the length of the shaft,and not take any of the drive,that’s why they break,
I have found that if you only use an original ford coupler they last a long time,the replacement ones the suppliers sell are way too soft.any shafts I modify I only use the original couplers,these are the 33/34 shafts to fit the 6 spline pinions,
Maybe with a bit of creative machining you could eliminate the pin,
Lawrie

[Brian]

I see on eBay, driveshaft safety pins. I can see how they work. Included with them is a spring which is to be fitted over opposite end of driveshaft between the speedo drive gear and universal joint. This keeps a preload on the shaft, precluding any tendency to move forward once the pin up back shears [again]. I'm going to add a spring this time [looks like one out of a fuel pump kit ought to do the job], also going to fit a 'bandit' strap around the ends of the pin. No more dink dink dink for me I hope!

[Mart]

Last one I did I fitted a hose clip over the pin so if it does shear, at least the ends will be retained. I added two more hose clips spaced at 120 degrees to rebalance it. An earlier one where I used an allen bolt as a pin failed.

I found it was really important to make sure the shaft runs true and the torque tube is also dead on. It's no good if the shaft is perfect and when you bolt up the torque tube it pits a bind on it. I haven't really thought it through fully but my gut feeling is that a out of square torque tube end will wear out a coupler faster than an out of true shaft, just my gut feeling.

Mart.

[JM 35 Sedan]

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My experiences with sheared pins on Ford banjo rears from 32 to 48, has been too much wear on the male and female splines.

Edit: worn splines = increased radial movement between pinion splines and drive shaft/coupler splines, which causes a shearing action on pin. Shearing of pin(s) becomes more prevalent when harder pin materials are used. Softer pin materials will wear and deform quite a bit before shearing or breaking.

[Bursonaw]

Brian,

I had the same problem until I had an old gentleman tell me the secret not to break pins.

I’m assuming you have a solid driveshaft. Not the hollow shaft on some of the earlier cars.

1. Attach your coupling to your drive shaft with our pin.

2. Pack your coupling completely full with grease.

3. Push your coupling onto the pinion shaft. (The grease will squeeze out from the splines and be difficult to line the pin hole up. You should see grease oozing out from the splines on both side of the coupling.

4. Install your pin. I use a quick disconnect type.

I’ve run my 41 Ford for 40 years without breaking stock NOS pins.

Hope this helps.


Sent from my iPad using Tapatalk

[Andy]

The holes in the coupler are .250. I think the holes in the pinion/driveshaft are bigger. I would enlarge the pinion/driveshft holes to allow the pin to float if I thought the splines were questionable.

[deuce_roadster]

After installing a new pin of any kind of steel to set the length, tack weld each end so if it does break, it cant come out. Easy to grind off tack if needed to remove.

[19Fordy]

I have found that the 1/4 in. pins are too small and that they have to be cold swedged in place so that they expand to actually fill the hole completely. Stock pin is shown below after removal with pin punch. Other wise there is play. This is very difficult to do. I applied solder to the shank of a 1/4 in. bolt and them hammered in through the coupler and drive shaft, shearing off the extra solder while at the same time filling the hole so that there is zero play. Then applied Locktite, a nut and "staked" it in place with center punch. Red thing is a torque tube banjo drive shaft seal needed if you car is "raked". So far, so good after a year. Car is 40 Ford.

[JSeery]

There really should not be any load on the pin. I've never heard of pin breakage being an issue with vehicles coming off the assembly line. I would be incline to think there is slop in the splines that is allowing them to move around.

[RalphM]

I used a standard spring pin(roll pin) and it has worked great. I am running a hollow driveshaft though.

[19Fordy]

JSeery: I think you are correct. As I recall, the tolerance between the coupler splines and the banjo/driveshaft splines is very, very close. No play.

[Brian]

In my application I am running brand new crownwheel and pinion [6 spline] and tubular driveshaft that I modified to suit used genuine Ford coupler, so no slop! Also runs dead true! I used a mild steel pin I machined up to exactly .250" drove it in and peined the end over. And still it broke after a short period! [less than 10,000 miles].

[19Fordy]

Brian, Is it possible that your modified drive shaft is too short allowing the forward and backward movement of the drive shaft to exert pressure on the pin causing it to fail over time.

Can you post a photo of your set up?

[Brian]

Sorry, it's all back together....However, modifying the driveshaft involved boring the 10 splined end out, and machining the 6 spline coupler for a .001 interference fit. Press the 'insert' in until the pin holes in both portions are exactly in line, and weld up assembly. Chuck up a pinion in lathe, install driveshaft, check for runout. [within.002"] I call that good. So, driveshaft length must be right, unless Henry got it wrong!! lol
When installed, prior to fitting pin, I notice that it won't go back any more anyway as where it sits is where the splines begin to 'sweep out'. This time I've fitted a fuel pump diaphram spring betwix universal and speedo drive gear. This should preclude any tendency for driveshaft to want to migrate forward.
My original question was what material to make said pin out of. As John Mason said, softer steels will deform more before breaking. Last pin was mild steel, this time I've gone to a medium tensile, and it is 'retained' via a stainless steel 'bandit' strap. Time will tell how these modifications hold out.
I am of the opinion that Henry's method of securing driveshaft to pinion shaft is not one of his better ideas.

[19Fordy]

Brian, Sounds like you covered all the bases and thought it through. I know it's a bad idea but, I wonder what would happen if the coupler was welded to the drive shaft at the end facing the transmission?

[Newc]

Hi all; In a previous post... a mention was made of a Loctite product that is designed to fill spline to spline clearances. I have found this material in spline joints of modern trucks driveshafts with lots of miles on them and intend to try it on a 'loose' '37 coupling soon. Newc

[Brian]

Fordy, With the tubular shafts the coupler is indeed welded to the driveshaft [tube] at the end facing the transmission.