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It’s definitely fretting fatigue on the spring pins. I’m thinking the pins are subject because they’re moving and lack lubrication. Whatever goes in there has to be press fit and can’t move or it will be subject to the same fretting and may potentially shear. A bolt will rotate if used in the pin holes and failure might still occur because there’s no lubrication to keep the contact area lubricated. In many of the engineering designs I see, in order to mitigate fretting a consideration is made in preventing movement and provides adequate lubrication. In this case we can only have one because there no localized oiling so I’m thinking two possible solutions; 1. Welding castle nuts to the forks and using bolts with tappet holes and pins. 2. Pressing in stainless taper pins and locking them with stainless cotters pins/stainless tie wire.
In any effect, I was thinking this could also be a large contributor as to why high horsepower cars crack transmission cases. Roll pin works itself out and drops into the gears, gets munched, and pushes them apart. Drives the shafts right thru the bell housing or endcover when the helicals spread?
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the second option seems to the better of the two.
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pretty sure the couple split cases I've seen due to HP, the forks were intact.
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I really don't think heat or lubrication is much of a factor... They are supposed to be a press fit, and not move at all. I think because of the spiral wound design, with very thin material, they are flexing and getting work hardened under heavy use.
The repair I proposed above is very effective... I don't remember what brand or model trans I saw it done from the factory on, but it certainly made an impression when I attempted to disassemble it...
I grabbed an old 5 speed fork today and took some pics for a demonstration of what I'm talking about.
First the factory spiral wound pin. You'll want to drive it out:
http://i90.photobucket.com/albums/k2...ps5e184239.jpg
Then enlarge the hole to 1/4":
http://i90.photobucket.com/albums/k2...ps5105901b.jpg
Then install the 1/4" single wrap spring steel roll pin:
http://i90.photobucket.com/albums/k2...psd32832ff.jpg
Then install a 5/32" pin inside that one:
http://i90.photobucket.com/albums/k2...ps1d39edd0.jpg
You'll notice how the 5/32" pin is mushroomed after install.... That's because I had to beat the crap out of it to get it in. Obviously a press would be a better install tool, but I was simply trying to perform a demonstration.
This thing is not going anywhere... Ever... Just for giggles, I tried to take it back out. I broke my punch...
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I modified the forks very similar to what McCoy illustrated. I used ¼” taper pins with end locks and made some additional subtle improvements. For starters, I chamfered the oil guides and enlarged them at the end races to increase the oil supply at the bearings. I also beefed up the springs in the gearbox by increasing the wire diameter/spring rate for all the springs in the transmission (shift return and key springs}. Lastly, I built my own aeriation baffle inthe transmission and drilled/enlarged the stock transmission breather. I plan to install a remote transmission breather on the firewall with a vac and temp gauge to keep a closer eye on the gearbox.
http://i788.photobucket.com/albums/y...psb109c95b.jpg
http://i788.photobucket.com/albums/y...ps17cf7f2a.jpg
http://i788.photobucket.com/albums/y...ps5c4d6475.jpg
Gearbox is fixed and ready to go!
http://i788.photobucket.com/albums/y...pse94ac5be.jpg
Goes back in tomorrow...
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You could always use a longer pin, and mushroom the ends in a press.
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Hey guys... a member named Andr3w just posted this picture for some basic info on reassembly after intslling a Merkel Brace. Take a look at the far right shift fork. The roll pin is on its way out!
http://img.tapatalk.com/d/13/07/07/bavehu7y.jpg
Also, I went thru my spare gearbox and guess what?... Pic's on the way...
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http://i788.photobucket.com/albums/y...pseb902f77.jpg
http://i788.photobucket.com/albums/y...ps07422c5d.jpg
This pin was moving in the other direction.
Now I'm pretty much convinced it's worth it to have a looksee in the tranny every so often if you've got the power.
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I'll be interested to see how this works out next time you head out. Seems like a good preventive idea, however I'll confess I know little about transmission and wouldn't want to tear mine open and screw it up. Perhaps if I get it rebuilt I could have whoever rebuilds it do something like that for good measure.
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…and so I designed this remote expansion setup for our applications, however, it's universal for any differential, transmission, and t-case breather setup on any vehicle :D. I had some push-lock brake line fittings custom machined and tapered to bolt directly into the t-case and tranny without drilling either. What do you guys think?
http://i788.photobucket.com/albums/y...psd615e08d.jpg
http://i788.photobucket.com/albums/y...ps6707cb1d.jpg
Here’s what my surge tank design looks like. It's a 2" diameter cylinder with two baffled chambers in the shape of an inverted "U". One side has an overflow drain, the other side divided by an internal baffle is the expansion entrance. The one depicted has push-lock brake/oil/gas/gear oil rated hose. The lines were pressure tested to 100psi at a temperature of 300 degrees. At the pinnacle there’s a single gold anodized mesh and carbonized breather.
http://i788.photobucket.com/albums/y...ps5b9fc65a.jpg
http://i788.photobucket.com/albums/y...psa188021f.jpg
That’s my final drivetrain and gearbox fix… Any interest in this item for retail? :mitsu::dodge1:
