Random Transmission Failures

Well, its been a busy few months. Normally the off season but despite the COVID situation I have been blessed with more work than I normally see over the winter months. But with this week in a deep freeze I thought I would take the opportunity to catch up a few things.

One note: I shot video of a core tear down a month ago that I had intended to edit and post. However, the computer that had the video has packed it in and I need to pull the drive to get the video off it. Hopefully, I can get that done soon.

In the mean time I have photos that might be fun to post here.

First up was a little different. One of the things that causes me all kinds of grief is removing the clutch actuator arm. These have to come out to clean the case properly and to recondition the pivots so it can move properly. Many release bearing failures result from the clutch arm being so bound up in its pivots that it never fully releases and runs the release bearing continuously, causing the failure. I have also seen the arms so tight they won't fully release the clutch so the clutch slips and burns up. The biggest challenge is getting the clutch arm out is the fork rusts in place on the shaft. If its really bad the retaining bolt rusts in place and simply shears when I try to turn it, as this one did.

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Getting the broken bolt out is problematic. One solution is to grind down its dowel pin end. I have done this before and, while not a simple task, it isn't the worst outcome. The worst outcome is the fork being severely rusted in place, and a broken bolt. Which is what we have here.

Even if the bolt come out it usually takes a torch to heat up the fork enough that it can be worked loose with a big mallet and carefully driven off the rod. Care must be taken because its easy to break the case. The job is time consuming, often taking an hour or more to extract the actuator shaft. This time I punted and just cut the arm with an angle grinder.

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It still is an effort to get the arm out but this is way easier.

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Note the top pivot bushing was broken. This is because the pivot was rusted inside the plastic bushing causing the bushing to pivot in the case. It won't last long like that.

Different unit:

I frequently get asked about differential bearings. Its rare that I don't replace them. I can usually tell when somebody has replaced the bearings and I am always surprised to see how many units I get that someone has "rebuilt" but not replaced the differential bearings that were clearly needing it. In this instance the bearings were in fact replaced but the rebuilder obviously didn't know to re-shim the differential preload. The result, I assume, was excessive preload on the diff bearings with were worn worse than most any I had ever seen.

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There was a ridge at the edges I could easily feel with my fingers. This unit must have whined miserably.


Finally, a core teardown that was unusual. Now this thread is full of "I have never seen this before...." comments. That's usually related to damage caused by abuse, neglect or failure, or errors by a previous builder. This "unusual" doesn't appear to have been any of those but what I found in the bottom of the case.

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I have no idea what that is or where it came from.

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This was stuck on the drain plug. The stuff in the bottom almost cover the drain hole.

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Anyway, it seems that no matter how many of these transmissions I tear down, I still get surprised.
 
Urban legend says that people used to stuff a banana peel into old transmissions to quiet them down.
Does the stuff smell kinda sweet? :)
 
Apparently they didn’t peal the banana when they stuffed it in there :)
Urban legend says that people used to stuff a banana peel into old transmissions to quiet them down.
Does the stuff smell kinda sweet? :)
 
I've heard of the use of sawdust but not a banana. o_O The other I've seen is an incredibly thick lube, resembling that "STP" type of oil additive, apparently intended to help overcome excessive wear.

That gunk in Steve's pics almost resembles (visually) the stuff I find in old Fiat fuel tanks. But the stuff in fuel tanks has a "tar" quality to it, which I believe to be the result of some sort of inner coating that was applied to the later tanks at the factory - after it dissolved over the years. In the trans I'm guessing it is perhaps a combination of water, metal shavings (from wear of internal components), and old lube. The shavings and water could cause that "rusty" look to some of it. And the old lube and water can make that "yellowish" stuff. But just a guess.
 
Regarding the clutch fork. On the units I've taken apart there is always some rust/corrosion there. Fortunately mine have never been so bad that the shaft needed to be cut to remove - thankfully. But the bolt has broken off on most, and the plastic bushing was trashed an all of them. I don't know if this is something most would try as I'm sure it is not "correct". But I've modified mine to utilize a regular hardened bolt instead of the odd stepped stock type. That allows use of a larger size to repair any resultant damage, and a better quality fastener to prevent future issues (I suppose a stainless fastener could even be used). The other thing I do is ream out the bores for the shaft and resurface the shaft itself to allow installing bronze lube-impregged bushings in place of the plastic one. Notice I said bushingS, as I add a second one to the lower end of the shaft. My hope is they will won't destingrate and will allow smooth turning of the shaft long into the future. I guess we'll see in another 20 years. :)
 
The stuff in the bottom of the case had the consistency of mostly dried mud. Or maybe the accumulation in the drip pan of my grill, from a whole season. It was so odd. It literally looked like nothing I had ever seen before. That there was gear oil in the case but it hadn't appeared to have soaked into this had me very puzzled.

Many of the cores I get have been sitting for years and that's often the reason the fork is rusted to the shaft and the bushings are locked up.

The factory's plastic bushing works fine as long as its kept in good order. I have never had one give any trouble on any of my cars. The ones that are bad are typically cars that were neglected or sat for long periods of time outside.

I remember the old 'sawdust in the transmission' story from when I was a kid. Supposedly to quiet a noisy unit. How? No idea.

When I owned an AAMCO transmission center several years ago (another career ago) I saw all kinds of crazy things people did to try and make transmissions work long enough to sell/trade a car or truck. Sad that so many people think that's OK.
 
I've had two of the stock plastic bushings actually rust (corrode) onto the shaft. The shaft still turned (with great difficulty) because the bushing was turning in the case bores, rather than on the shaft. As a result the bushings were completely destroyed in both instances.

The same thing with the plastic bushing for the brake/clutch pedals in the pedal box; bushing rusted onto the shaft so the whole bushing twisted in the box housing - also destroying the bushing. Although plastic doesn't "rust", that's exactly what it was. I guess the shaft rusted and the deposits somehow bonded into the plastic, making them one solid piece. Even after getting the shafts and bushings out, it was impossible to separate them without cutting the bushing off in pieces. I don't know if there is something about the type of plastic that was used for these bushings - possibly it is more porous? But I've never seen any other plastic parts rust onto metal ones on other vehicles like this.
 
Mixing and matching parts between different transmissions is full of pitfalls. You have to be very thorough and very careful that you have figured out all of the various differences and how the affect the final assembly for form, fit and function.
 
Its been a while since I posted here as I have been busy with the launch of our new venture back in April.

I did get a core from somebody here (as usual I'll let them identify themselves if they choose to do so) recently. I was able to do the teardown and inspection over the weekend. If you notice a trend here you're not alone; the majority of the units I get that have serious issues result from the efforts of a previous rebuilder. And as I have stated previously, I don't know why these units seem to give otherwise experienced rebuilders so much trouble but they obviously do.

After discussions with the previous owner I know this unit had just under 30K miles since overhaul. The rebuilder missed the worn out synchro hubs on 1st and 2nd, which would have resulted a grind on selecting 1st and 2nd to reoccur after only a short time. A new reverse idler was fitted and it likely also got new forks along with new 3rd and 4th synchros. But the biggest issue was the differential bearing failure.

The differential bearing failure was the direct result of the differential being improperly shimmed, likely resulting from the use of the thick, aftermarket, paper gasket. The differential bearings were obviously way to tight and that caused the left side bearing race to spin in the case. Because bearing races must be driven in place to properly locate and retain them the case is now ruined. I also found something had damaged the passenger (right) side seal bore. And it appeared that a piece of the linkage's centering spring had previously broken and was left in the case!

So the rebuilder replaced the 1st and 2nd synchros but never knew to check the synchro hubs for wear. Replaced the reverse idler, the shift forks and 3rd & 4th Synchros. All good. But then completely messed up the differential bearing preload and that started the cascade of failures that ruined the case and the 3rd and 4th synchros.

Instead of photos I shot a simple video this time.

 
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Its been a while since I posted here as I have been busy with the launch of our new venture back in April.

I did get a core from somebody here (as usual I'll let them identify themselves if they chose to do so) recently. I was able to do the teardown and inspection over the weekend. If you notice a trend here you're not alone; the majority of the units I get that have serious issues result from the efforts of a previous rebuilder. And as I have stated previously, I don't know why these units seem to give otherwise experienced rebuilders so much trouble but they obviously do.

After discussions with the previous owner I know this unit had just under 30K miles since overhaul. The rebuilder missed the worn out synchro hubs on 1st and 2nd, which would have resulted a grind on selecting 1st and 2nd to reoccur after only a short time. A new reverse idler was fitted and it likely also got new forks along with new 3rd and 4th synchros. But the biggest issue was the differential bearing failure.

The differential bearing failure was the direct result of the differential being improperly shimmed, likely resulting from the use of the thick, aftermarket, paper gasket. The differential bearings were obviously way to tight and that caused the left side bearing race to spin in the case. Because bearing races must be driven in place to properly locate and retain them the case is now ruined. I also found something had damaged the passenger (right) side seal bore. And it appeared that a piece of the linkage's centering spring had previously broken and was left in the case!

So the rebuilder replaced the 1st and 2nd synchros but never new to check the synchro hubs for wear. Replaced the reverse idler, the shift forks and 3rd & 4th Synchros. All good. But then completely messed up the differential bearing preload and that started the cascade of failures that ruined the case and the 3rd and 4th synchros.

Instead of photos I shot a simple video this time.

I always enjoy these reports. ;)

I'm curious, do I recall correctly that the diff carrier bearings typically aren't problematic, usually lasting quite long? That is aside from being mis shimmed.

I wasn't clear on this, possibly I misread. But wouldn't a thicker gasket between the case halves cause more clearance (loose) at the bearings, not less (tighter)?
 
I always enjoy these reports. ;)

I'm curious, do I recall correctly that the diff carrier bearings typically aren't problematic, usually lasting quite long? That is aside from being mis shimmed.

I wasn't clear on this, possibly I misread. But wouldn't a thicker gasket between the case halves cause more clearance (loose) at the bearings, not less (tighter)?
The differential bearings are fairly robust. If shimmed correctly, and the transmission serviced regularly, the bearings throughout the unit will last a long time.

You are correct in that a thicker gasket will open up the clearance. This will also cause a failure because the bearing will run off-center in the races. It will also ruin the pinion gear. But that's not what happened here. Note there were two shims installed. One was a standard thickness. Most factory installed shims will fall into the range of .080 to .100. In this case the shims were .091 and .034 totaling .125. Using the thicker gasket would require a thicker shim, or an additional shim to go with the original, but that gasket isn't .034 thicker than the OE unit. My guess is the preload was greater than .030. That's a LOT. I doubt you could turn the transmission by hand at all once it was assembled.
 
... The differential bearings were obviously way to tight and that caused the left side bearing race to spin in the case. Because bearing races must be driven in place to properly locate and retain them the case is now ruined. ...

A friend of mine who is a retired Millwright once told me about Loctite 660, a product that is made specifically for repairing bearing pockets that have this kind of problem. It was commonly used on production machinery in a major manufacturing facility, where he worked. I'm not trying to second guess your procedure. Just thought I'd mention it on the outside chance that you're not already familiar with this product, and it could save the case.

Best regards,
Brian
 
A friend of mine who is a retired Millwright once told me about Loctite 660, a product that is made specifically for repairing bearing pockets that have this kind of problem. It was commonly used on production machinery in a major manufacturing facility, where he worked. I'm not trying to second guess your procedure. Just thought I'd mention it on the outside chance that you're not already familiar with this product, and it could save the case.

Best regards,
Brian
Hmmm, interesting product. And it may work just fine. I appreciate the suggestion.

Here is my problem with using it: I would have to test it by using it on a customer unit. One that is likely to be shipped cross country for installation. If there was a problem I would have to ship a replacement and the customer would have to pull and re-install the replacement. If you were a customer would you want to risk that?

I have enough of a challenge now finding quality replacement 3rd/4th gear synchros and sliders, I really am not ready to put another variable in the mix. :(

I might keep the case and use it on a unit I would use closer to home or as a last resort when good cases aren't available. Until then, I'll keep the info for reference.
 
Henkel (Loctite) makes a few versions of that product. For various gap thickness, heat ranges, stress loads, chemical exposures, etc. I view it as a last resort to try and save something that either cannot be replaced or a situation where it isn't overly critical and cost is a consideration. But my understanding is they work pretty well. Effectively some sort of modern adhesive I guess. Somewhere I have their product info sheets about that line, got it from a contact I have there. But I'm sure you can find it online.
 
Hello Steve,
For all of the community it will be great if you can make video on how to do the preload shim properly.
I found some write up but a video complement will be great.
...If one day you have time.

Thanks
 
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Its been a while since I posted here as I have been busy with the launch of our new venture back in April.

I did get a core from somebody here (as usual I'll let them identify themselves if they choose to do so) recently. I was able to do the teardown and inspection over the weekend. If you notice a trend here you're not alone; the majority of the units I get that have serious issues result from the efforts of a previous rebuilder. And as I have stated previously, I don't know why these units seem to give otherwise experienced rebuilders so much trouble but they obviously do.

After discussions with the previous owner I know this unit had just under 30K miles since overhaul. The rebuilder missed the worn out synchro hubs on 1st and 2nd, which would have resulted a grind on selecting 1st and 2nd to reoccur after only a short time. A new reverse idler was fitted and it likely also got new forks along with new 3rd and 4th synchros. But the biggest issue was the differential bearing failure.

The differential bearing failure was the direct result of the differential being improperly shimmed, likely resulting from the use of the thick, aftermarket, paper gasket. The differential bearings were obviously way to tight and that caused the left side bearing race to spin in the case. Because bearing races must be driven in place to properly locate and retain them the case is now ruined. I also found something had damaged the passenger (right) side seal bore. And it appeared that a piece of the linkage's centering spring had previously broken and was left in the case!

So the rebuilder replaced the 1st and 2nd synchros but never knew to check the synchro hubs for wear. Replaced the reverse idler, the shift forks and 3rd & 4th Synchros. All good. But then completely messed up the differential bearing preload and that started the cascade of failures that ruined the case and the 3rd and 4th synchros.

Instead of photos I shot a simple video this time.

I found your video to be extremely interesting and informative. I have not had to open my case since the 80s but it is great to have the information you have provided on this site for future reference. Thanks for the effort.
 
The gearbox in the video came from my 82. The car has 179,950 miles on it, but as Steve mentioned, the gearbox has been rebuilt before.
I had no idea of its condition other than it liking to grind in third and fourth (and first, but that wasn't as obvious) and its biggest issue the bearing whining at speed, especially highway in fifth.

The car was owned by Ben (cbax19 here on xweb) and offered for sale here in 2015 when I bought it with 174k on it. https://xwebforums.com/forum/index.php?threads/1982-x1-9-renton-wa-1200-obo.28038/#post-236115

Ben bought it in 2003 with what looked like 150,000 miles on it. From then until 2015 when I bought it, nothing in the records shows a gearbox rebuild other than a clutch and master/slave cylinders being replaced.

Ben bought it from one of the early members of SeattleX1/9, John Hurlock. He was active on xweb back in 2000/2001 or later, and authored a dash repair article that people have referenced. (he had a 300,000 mile 1980 X1/9 from what I can see?) Not sure how long he owned my 82, or if he was the one who had the gearbox rebuilt or not, or even when it was.

But Steve's estimation was made that we are pretty sure it didn't happen after 150k miles when Ben bought it in 2003 until 2020 with 179k miles on it when I pulled the drivetrain. Must have happened prior to 2003/150k but not sure when.

Thanks for taking the time on the teardown and video Steve. Fascinating stuff, love your work.
 
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