Torque limiting clutch on a 3 cylinder

Ultradog MN

Well-known Member
Location
Twin Cities
Lisa's post about that 4000 SOS below got me to thinking about the TLC and input shaft on the 65 and newer tractors.
I know the clutch and input shaft failure on the 58-64 SOS tractors is well known and well documented.
But how common was it on the 3 cyl models?
When any SOS that doesn't move comes up the input is kind of a go-to guess as to why.
But I'm thinking Ford had that fixed with the new models and it wasn't a problem any more.
Yes? No?
Are there lots of experiences with bad input shafts and clutches on them?
Some?
Any?
Just wondering about it.
 
Cannot answer your question other than to say that I've never seen a stripped input shaft on a post 65 S-O-S or even a 6000.

Ford could probably have prevented this problem by using a torque limiting clutch with spring cushioning as is universal practice for operating clutches but, of course, that would have cost a bit more.

I suspect that the classical stripped input shaft failure is related to usage patterns, e.g., little used and/or lightly loaded allowing the disc to sieze to the flywheel resulting in the classical rotary cutter slip clutch no "torque limiting" issue.

Relatedly, the designers, and especially, the product planners certainly did not anticipate that these machines would still be in use 50+ years after they were designed.

Dean
 
Unfortunately for me I had to replace the stripped input shaft on my 1966 Commander 6000 2 months after I bought it. It showed 900 hours when I bought it so that was obviously incorrect and I have no information on how the previous owners used it. I had my shaft welded up by a man in Illinois and I also purchased another welded up shaft just in case the new one ever goes bad.
 
Best pics I have on splitting the 6000 to replace the input shaft.
a190691.jpg

a190692.jpg
 
I've seen plenty of stripped SOS input shafts on '65-up tractors, both 3 and 4-cylinder models. If you look closely at the parts book, Ford made a change to the spline count at some point during the production. I still don't think that solved the problem, because there was no kind of cushioning device in the clutch disc.
 
So,........all in all, it still sounds like the best plan is to run away from an SOS as fast as feet will carry one.
 

Like Bern said, stripped splines on the '65 and newer models seem to be just as common as on the older ones. The bigger (fewer) splines should have helped but didn't seem to.

stripped10sp.jpg


stripped10spdisk.jpg


.
 
Now that is a pretty funny response. All it takes to spoil is ONE WEAK link in the chain & the whole chain is worthless!
 
So Bern,
The topic comes up with enough frequency here but I don't recall you weighing in one way or another.
What is Your opinion of the 65+ SOS transmissions? Or the SOS in general.
Should a guy buy one and take a chance on it?
Should he buy one and try to fix it?
Or is it best to just run away from the darned things?
I know they have their supporters - and a lot more detractors. Though I might grant most of the detractors are relying on hear say and not personal experience.
Any advice on them?
Any quotes for posterity?
John Smith,
Those are very, very good photos that speak a thousand words.
Thank you for them.
 
So, UD, you are looking for an unbiased opinion from someone who makes his living fixing broken stuff? Can't make any money on things that don't fail!
 
Early SOS units obviously had their issues - the failures of those units are well documented. However, by 1965, a full 6 years after the SOS trans was first introduced, I'm of the opinion that Ford got most of the bugs worked out of them. I've worked on my fair share of them over the years, and the biggest problems I've seen are related to the stripped input shaft splines, along with input shaft front bearing failures. Other than those items, I think they're pretty rock solid.

I think the naysayers are more intimidated by them than anything else. Those trannies certainly don't scare me. The convenience of a powershift over that of a crashbox far outweighs any risks as far as I'm concerned.
 
Wouldn't more splines have been stronger than fewer ones? I know for axle shafts a 28 spline 9inch is pretty light duty, they upped it to 31 for 4x4 trucks and in the rock crawler/racing world you up it to a 35 spline axle to avoid stripping like in John's pics.

As it is, I appreciate reading this - I almost bought a SOS and I'm glad I got the 8spd instead.
 
Thanks for all the replys.
So I was looking on CNH at the parts for a 3 cyl 4000 SOS and it looks like the input shaft did go through a couple of changes but it seems that none of them are available any more.
Is this correct?
That would sure make a difference to a guy who was thinking about buying one.
If there is a known defect in the transmission but parts are NLA that would kinda put the Kibosh on any plans for fixing one short of buying used.
 
(quoted from post at 10:44:38 05/06/15) Thanks for all the replys.
So I was looking on CNH at the parts for a 3 cyl 4000 SOS and it looks like the input shaft did go through a couple of changes but it seems that none of them are available any more.
Is this correct?
That would sure make a difference to a guy who was thinking about buying one.
If there is a known defect in the transmission but parts are NLA that would kinda put the Kibosh on any plans for fixing one short of buying used.
ohn Smith has his own solution:
http://www.oldfordtractors.com/sosinput.htm
 
Henry Ford believed a car should last as long as a fine watch, which I take to be about 200 years.

Then there is the legend of the perfectly designed buggy, it worked fine for 100 years and a day, then fell apart, everything at once, nothing left but a cloud of dust.

One philosophy of design is to have the cheapest part fail first to protect the more expensive parts. However this should include the whole cost of fixing. Such as shear pins, keys, slip clutches.

Ford actually had as much wear as most, but his abundant supply of cheap parts made his cars seem to last for a long time. When I was a kid, a 25 year old car was pretty old. Now, my 93 pickup doesn't seem very old at all.
 
The later ones may well have been more reliable... but I'm not so sure the dislike of them was so much about being scared of P/S. The limited experience I had with them was simply that they sucked to work with. Everything was a jerk or a hop when it was shifted, they wouldn't free wheel very effectively and were just a general pain in the arse. A good 8 speed gave a lot better control to someone who knew how to shift the 8 speed. The SOS main claim to fame was that any dolt could drive one if they could sit in the seat. Even to this day I still rather prefer to drive the crashbox for any amount of roading I have to do. The only real failing of that transmission was it's lack of reverse ratios...

Rod
 
Yeah,
I've seen that too.
But as much as I respect John and see it as a clever idea I can't say I see it as a permanent fix. Those splined shafts were case hardened originally and still wore out.
Cut into the soft center of the shaft - halve the hardness of it - and I don't see it as lasting.
I have no scientific evidence for this. It's mostly just a hunch or guess.
 
(quoted from post at 01:30:39 05/07/15) Yeah,
I've seen that too.
But as much as I respect John and see it as a clever idea I can't say I see it as a permanent fix. Those splined shafts were case hardened originally and still wore out.
Cut into the soft center of the shaft - halve the hardness of it - and I don't see it as lasting.
I have no scientific evidence for this. It's mostly just a hunch or guess.

What's permanent? The shafts can be cut to a 13/16" hex without getting into the soft center. They're still hard. If you don't think so, try cutting a hex on one. You'll burn up about $40 worth of carbide inserts getting the job done. Will it last as many years as the originals? I seriously doubt it. But it's a way to get new life from worn out parts at a small cost. New factory replacements are no longer available for most models. Good used ones don't exist. So what are you gonna do with stripped splines? Welding and recutting doesn't work long at all. The welding destroys the heat treat and they either wear out very fast or snap off just behind the welds. Seen a bunch of welded ones snap off. If recutting to a hex drive will get you another 10 years of use from a tractor that would have gone to scrap otherwise, I say that's a good deal. Some of the first ones I did was a decade ago and I've had no reported failures yet. Permanent no, but way better than nothing.
 
The point is that technology was changing so rapidly at the time that no one anticipated that people would still be USING cars, trucks, tractors, etc, 50+ years after they were designed.

Dean
 
Maybe.
Only way to know for sure is split it.
I for one would like to see.
Meanwhile, if he gets more service out of it than the cost of repair who's to complain?
 

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