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Old 05-03-2016, 02:18 PM   #1
hope
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Default coupler pin (40) Ford

Saw the subject being brought up about the driveshaft coupling pin, and that reminded me about a question i have.


I had the rear end apart and reassembled a LONG time ago, and i don't seem to remember if i put the Pin in.

Question is : what would the symptoms of that disaster.
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Old 05-03-2016, 02:21 PM   #2
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Default Re: coupler pin (40) Ford

Addition to previous post::: (car is not on the road)
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Old 05-03-2016, 02:31 PM   #3
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Default Re: coupler pin (40) Ford

It will eventually destroy the splines in the coupler. Not sure how long it would take.
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Old 05-03-2016, 02:45 PM   #4
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Default Re: coupler pin (40) Ford

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Originally Posted by JSeery View Post
It will eventually destroy the splines in the coupler. Not sure how long it would take.
With due respect and the willingness to possibly be convinced otherwise, I don't agree with you. A splined shaft and coupler should fit together well enough to not require a pin to keep the radial movement in check.
Nope, I believe the pins were utilized to stop the fore and aft movement of the drive shaft.
If the spine fit was loose a pin would soon enough be sheared.
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Old 05-03-2016, 05:13 PM   #5
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Default Re: coupler pin (40) Ford

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Originally Posted by Kube View Post
With due respect and the willingness to possibly be convinced otherwise, I don't agree with you. A splined shaft and coupler should fit together well enough to not require a pin to keep the radial movement in check.
Nope, I believe the pins were utilized to stop the fore and aft movement of the drive shaft.
If the spine fit was loose a pin would soon enough be sheared.
Kube you could well be correct, I was just going on the number of folks that have reported shearing the splines (or ending up with massive ware on them) when the pin was not present. I have even read reports of welds not holding and ending up with the same issue. I have never run one without a pin, so guess I can't really say from personal experience!!
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Old 05-03-2016, 05:51 PM   #6
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Default Re: coupler pin (40) Ford

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Quote:
Originally Posted by JSeery View Post
Kube you could well be correct, I was just going on the number of folks that have reported shearing the splines (or ending up with massive ware on them) when the pin was not present. I have even read reports of welds not holding and ending up with the same issue. I have never run one without a pin, so guess I can't really say from personal experience!!
I am only going on my experience as tool & die maker. Splines were required to be tight. Most within .0015" clearance.
I am not saying I am correct on this and sincerely would like to hear from others that may have information that would support another reasoning for the pins.

Like you, I have seen splines on these shafts that were destroyed -pins sheared. I always wondered how that destruction came about.

Kind of on the same subject... does anyone know why Mercury shafts were welded vs. the Ford shaft coupled?
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Old 05-03-2016, 05:58 PM   #7
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Default Re: coupler pin (40) Ford

LOL, I also started life as a tool & die man and ended it as an engineer. Greetings brother!

Hear where your coming from, but depends on a lot of things in a car environment. I don't really have any personal insight on this one one way or the other.
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Old 05-03-2016, 06:42 PM   #8
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Default Re: coupler pin (40) Ford

The value the pin could add to a spline fit is it would limit lateral movement back and forth during braking and acceleration which might wear the .0015 fit somewhat. That is jut and opinion from a one time machinist, that has no personal experience to back up the seat of the pants theory. I believe I put the pin in the spline in '40 rear end in the roadster, but not sure or concerned about it.
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Old 05-03-2016, 07:11 PM   #9
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Default Re: coupler pin (40) Ford

I think that the pin keeps the drive shaft located forward and aft. With a broken pin, I think that the ujoint could be stressed a bit by a drive shaft being too far out of it's geometricly correct position. Not so much when the transmission shaft and the drive shaft would be perfectly in a straight line, lots more when there's an angle between the two. On the other hand, this stress would tend to force the drive shaft into it's correct position.

I've taken a few of these apart. found pins broken when splines were in bad shape.
There's some I've found that have a spring like strap that goes half way around the shaft, pin ends rivet through holes at each end. This keeps the broken pin parts from going through the pinion gears. I like that.

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Old 05-03-2016, 07:44 PM   #10
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Default Re: coupler pin (40) Ford

Im not an engineer. The pins are quite 'soft' personally it might stop some fore and aft but I think they are just to help hold the sleeve in its position not much more.
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Old 05-03-2016, 11:44 PM   #11
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Default Re: coupler pin (40) Ford

I've used a simple spring pin instead of the peened over factory pin. It was all I had at the time. I thought it might not work ok, but it seems to be just fine.
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Old 05-04-2016, 09:34 AM   #12
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Default Re: coupler pin (40) Ford

My 1935 was missing the pin when I bought the car. Drove it many miles that way. When I rebuilt the rear end the only damage was the universal joint which may or may not have been the result of not having a pin. I use a Grade 8 1/4" bolt in place of the pin with the nut tack welded on.
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