Opened up my gearbox after hardcore road racing on 800ft/lb tq engine.

[J. Fast]

This is the third gearbox I’ve seen with expelled shift forkroll pins. I think when they get hot and vibrate the pins work themselves loose. I road course this gearbox and lean on it REALLY REALLY hard with no lift shifting and full on driving to the limit. I slowly started losing 3rd gear last week while making large left hand sweeping turns registering in the 1-lateral-G range. After about 120 consecutive laps third gear began to sneak some grinding. After about 140 laps I was consistently grinding and then suddenly I was blocked outof gear entirely and 3rd gear disappeared altogether. I opened up the gearbox and these were my observations.

http://i788.photobucket.com/albums/yy163/JFastMotorsports/20130704_172450_zps5bf6c6c4.jpg

http://i788.photobucket.com/albums/yy163/JFastMotorsports/20130704_172501_zps20bc8ee4.jpg



http://i788.photobucket.com/albums/yy163/JFastMotorsports/20130704_172403_zpsb9f7223b.jpg


Shift fork roll pin is expelled on one fork (it snapped inhalf when I tried to pull it): gahh: The roll pin worked itself out it allowed the shift fork to slide toward the end cover about 5mm. I observed the fork resting on 4th gear entirely. It was locked below the hub/slider keeper step and consequently didn’t have enough reach to grab third because of how far it slid down the shift fork rail. At first I thought I rounded all the teeth on third gear because I ground it at least 20 times at 7500 rpms and then I finally whizzed the gear and it hummed for a second or two and blocked me out. After further inspection the gear/hub slider teeth are in good shape and it appears I just need to replace the synchro. I also discovered I melted the oil splash pan at the mount. Also appears the adjacent shift fork roll pin is starting to work itself out also (it’s projecting about 3mm).

Surprisingly, I didn’t observe any metal flakes or chunks in the gearbox or in the fluid I drained. Just before I hit the road course I drained my Mitsubishi OEM Diamond Gear Lube and swapped in Royal Purple 75w-90 Full Synthetic Hypod Gear Oil. Can't say wether or not the full synthetic was a contributing factor. For the most part everything else in the gearbox is good to go. The synchromesh looks good on 3/4 but I’m going to swap in new synchros for my own sanity.

[CoopKill]

Weak, old roll pins, or metal is just being flexed enough with extreme use they move out of place?

[MR2]

You got lucky... Taz popped the box when his DID engage both gears at once

guess it's time for upgraded pins

[J. Fast]

If you look at the first picture, you can see the roll pin is starting to work itself out on the 1/2 shift fork. You can also see that the 2nd shift rail over is projecting a little bit higher than the others. Thats the fork binding on 4th gear.

[J. Fast]

These are the original shift forks. They have never been disassembled or modified. What I was most surprised about was how brittle the roll pins are. When I tried to pinch them with vice grips they snapped and when I tried to punch them out they chipped. I'm going to have to add opening my transmission and checking the roll pins to my nut and bolt list.

[RealMcCoy]

I would assume it is the usage that contributed... That is not a real common failure. I have seen it happen on the selector shaft a few times, and I do feel the pins are a little bit suspect in their construction. My fix for the selector shaft is some thick wall spring steel 1/4" roll pins. You have to ream the hole slightly to use them as the factory ones are 6mm, but I've yet to see one move... I guess maybe it's time to consider the same treatment for the forks.

The thick wall single wrap pins also allow you to drive a second smaller pin through the middle if you need make them even tougher...

I don't remember where we sourced them, we've had them on the shelf for years, be they appear to be very similar to these: 1/4" x 1" Plain Finish Steel Slotted Spring Pin | Fastenal (http://www.fastenal.com/web/products/details/1164247?searchMode=productSearch&rfqXref=&rfqKeyword=&rfqId=&rfqLineId=&zipcode=&filterByStore=)

[Erron Spalsbury]

Good info, Jer! Glad it's something fairly easy to fix.

[anyonebutme]

Seen it several times on cars that are drag raced. Bang the gears an that is a possibility, also broken select forks.

[J. Fast]

It would appear the spring pins have undergone some type of annealing process but when heated they relax? I'm thinking maybe solid pins would be siffice to aid in keeping them from walking out? What about swapping the spring pins out for a tapered dowel and inserting a cotter pin? I was actually having a conversation with my dad about the issue this evening over dinner. He metioned in old muscle cars they used to drill holes and use tie wires on pins, dowels, and any bolt they didn't want to back out. I think that's a good idea but we're talking about potentional interference due to close proximity to gears... I would like to use something that won't temper and become brittle and snap later on. Any ideas on a fix for this? I don't think new pins are the answer...but? Open to discussion. What works?

[anyonebutme]

safety wire and bolt if enough room, or maybe a clevis pin....I'll have to take a look and see if there is enough room there. 100 ways to skin a cat...

[J. Fast]

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?

[fullracegt]

the second option seems to the better of the two.

[anyonebutme]

pretty sure the couple split cases I've seen due to HP, the forks were intact.

[RealMcCoy]

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/k252/lnmccoy/ForumPics/Fork2_zps5e184239.jpg (http://s90.photobucket.com/user/lnmccoy/media/ForumPics/Fork2_zps5e184239.jpg.html)

Then enlarge the hole to 1/4":

http://i90.photobucket.com/albums/k252/lnmccoy/ForumPics/Fork1_zps5105901b.jpg (http://s90.photobucket.com/user/lnmccoy/media/ForumPics/Fork1_zps5105901b.jpg.html)

Then install the 1/4" single wrap spring steel roll pin:

http://i90.photobucket.com/albums/k252/lnmccoy/ForumPics/Fork3_zpsd32832ff.jpg (http://s90.photobucket.com/user/lnmccoy/media/ForumPics/Fork3_zpsd32832ff.jpg.html)

Then install a 5/32" pin inside that one:

http://i90.photobucket.com/albums/k252/lnmccoy/ForumPics/Fork4_zps1d39edd0.jpg (http://s90.photobucket.com/user/lnmccoy/media/ForumPics/Fork4_zps1d39edd0.jpg.html)

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...

[J. Fast]

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/yy163/JFastMotorsports/20130706_163950_zpsb109c95b.jpg
http://i788.photobucket.com/albums/yy163/JFastMotorsports/20130706_190932_zps17cf7f2a.jpg
http://i788.photobucket.com/albums/yy163/JFastMotorsports/20130706_182947_zps5c4d6475.jpg
Gearbox is fixed and ready to go!
http://i788.photobucket.com/albums/yy163/JFastMotorsports/20130706_190917_zpse94ac5be.jpg
Goes back in tomorrow...

[donniekak]

You could always use a longer pin, and mushroom the ends in a press.

[J. Fast]

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...

[J. Fast]

http://i788.photobucket.com/albums/yy163/JFastMotorsports/Mobile%20Uploads/20130707_222343_zpseb902f77.jpg

http://i788.photobucket.com/albums/yy163/JFastMotorsports/Mobile%20Uploads/20130707_222407_zps07422c5d.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.

[sergechronos]

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.

[J. Fast]

…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/yy163/JFastMotorsports/20130709_184055_zpsd615e08d.jpg

http://i788.photobucket.com/albums/yy163/JFastMotorsports/20130709_181958_zps6707cb1d.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/yy163/JFastMotorsports/20130709_182553_zps5b9fc65a.jpg

http://i788.photobucket.com/albums/yy163/JFastMotorsports/20130709_182546_zpsa188021f.jpg

That’s my final drivetrain and gearbox fix… Any interest in this item for retail? :mitsu::dodge1:

[MR2]

Looks too good/expensive for anyone on 3si to buy lol (truth hurts)

[J. Fast]

I can build for $150 each. Not that expensive. Good insurance and a nice functional bling item.

[KeithMac]

The transfer case mod is ths best idea I've seen for a long while!.

For the roll pins, can't you dot punch 4 times around the fork after install to stop them backing out?.

[Erron Spalsbury]

…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/yy163/JFastMotorsports/20130709_184055_zpsd615e08d.jpg

http://i788.photobucket.com/albums/yy163/JFastMotorsports/20130709_181958_zps6707cb1d.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/yy163/JFastMotorsports/20130709_182553_zps5b9fc65a.jpg

http://i788.photobucket.com/albums/yy163/JFastMotorsports/20130709_182546_zpsa188021f.jpg

That’s my final drivetrain and gearbox fix… Any interest in this item for retail? :mitsu::dodge1:


These look familiar! Pretty cool. You don't need one for the tranny though, just a good filter on the end will do it.

Catch cans are always a hard sell buddy. Those that can will build their own. Those that can't don't know why they need them. :P

[sergechronos]

I can build for $150 each. Not that expensive. Good insurance and a nice functional bling item.

Would be something added to my list long term to pick up whenever I get my transmission beefed up/rebuilt. Very good idea (and definitely nice bling)

[J. Fast]

These look familiar! Pretty cool. You don't need one for the tranny though, just a good filter on the end will do it.


Stock transmission has a plastic battle underneath the check valve. When the plastic gets hot the baffle falls out and the tranny breather system is left without a windage tray to capture the oil vapor. The vapor climbs up the check valve and clogs the little one millimeter hole and prevent the transmission from breathing and it blows the seals.

I'll post up some pictures of the windage tray/baffle and the condition of the vents. Any breather that's installed right there on the transmission will eventually become clogged when a filter gets saturated with oil. The clutch vents are in close proximity to the breather cap. I'm thinking and oil soaked filter and fine brake dust is a recipe for a clogged breather. You have to check it out bro, it's pretty slick!

[Erron Spalsbury]

Stock transmission has a plastic battle underneath the check valve. When the plastic gets hot the baffle falls out and the tranny breather system is left without a windage tray to capture the oil vapor. The vapor climbs up the check valve and clogs the little one millimeter hole and prevent the transmission from breathing and it blows the seals.

I'll post up some pictures of the windage tray/baffle and the condition of the vents. Any breather that's installed right there on the transmission will eventually become clogged when a filter gets saturated with oil. The clutch vents are in close proximity to the breather cap. I'm thinking and oil soaked filter and fine brake dust is a recipe for a clogged breather. You have to check it out bro, it's pretty slick!

Wow, really? Mine has basically a metal tube that had a black plastic cap on the top of a steel tube that looks to be press fit in the housing. I pull the cap off and ran a hose up to a basic fuel filter that I cut the top off of. I think you've seen it.
Looks like this little gem.
http://www.arkansas-ope.com/GPS_0F0106_FUEL_FILTER.jpg

I filled the tranny with it once, took forever too. haha

I'd really like to see yours, you have the 6 speed?

[J. Fast]

It probably took forever to fill because you still have a windage tray or partial windage tray in the transmission itself. The orfice is only like a millimeter. Its severely undersized for high-speed high heat application. It's definitely a breather restriction. How long did it take to fill your transmission up with gear oil through that little 1mm hole with the stock baffle installed, haha?

[Erron Spalsbury]

It probably took forever to fill because you still have a windage tray or partial windage tray in the transmission itself. The orfice is only like a millimeter. Its severely undersized for high-speed high heat application. It's definitely a breather restriction. How long did it take to fill your transmission up with gear oil through that little 1mm hole with the stock baffle installed, haha?

It wasn't that bad, 15 minutes I'd guess? Whatever it's doing it's got to be enough or we'd see seepage coming from the CV's and output shaft.

[Bloodlust182]

Id be interested in a can for the TC if it would be possible to refill the TC from not under the car lol.

[futurevr4man]

J, you gotta quit typing in black, I can't read it!!

[Rakuny]

J, you gotta quit typing in black, I can't read it!!

Highlight the text!

[striker2]

or go to the very bottom left of the page and select "light GTO" style from the drop down box.

[sergechronos]

J, you gotta quit typing in black, I can't read it!!

Reading is for rich people and totally overrated.

[J. Fast]

Functioning as intended.
http://i788.photobucket.com/albums/yy163/JFastMotorsports/Mobile%20Uploads/20130713_120805_zps0c95d90c.jpg

[Chris@Rvengeperformance]

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/k252/lnmccoy/ForumPics/Fork2_zps5e184239.jpg (http://s90.photobucket.com/user/lnmccoy/media/ForumPics/Fork2_zps5e184239.jpg.html)

Then enlarge the hole to 1/4":

http://i90.photobucket.com/albums/k252/lnmccoy/ForumPics/Fork1_zps5105901b.jpg (http://s90.photobucket.com/user/lnmccoy/media/ForumPics/Fork1_zps5105901b.jpg.html)

Then install the 1/4" single wrap spring steel roll pin:

http://i90.photobucket.com/albums/k252/lnmccoy/ForumPics/Fork3_zpsd32832ff.jpg (http://s90.photobucket.com/user/lnmccoy/media/ForumPics/Fork3_zpsd32832ff.jpg.html)

Then install a 5/32" pin inside that one:

http://i90.photobucket.com/albums/k252/lnmccoy/ForumPics/Fork4_zps1d39edd0.jpg (http://s90.photobucket.com/user/lnmccoy/media/ForumPics/Fork4_zps1d39edd0.jpg.html)

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...

I know this is an old thread, but I have a box here that the roll pins have backed out of. When I install them I use loctite, but I'm not sure if that is enough for ones that have tried to walk out already. I'm thinking of taking this approach and wondering what you thought:

https://www.jackstransmissions.com/pages/supra-v160-forks

[Chris@Rvengeperformance]

Did some research and the issue is finding the right size bolt. 1/4" leaves only .010" thread engagement, the hole is too big already. 5/6 or 8MM seems big enough to compromise the strength of the fork, so I'm not sure there is a solution. There exists such a thing as a 7mm bolt, but it is hard to come by, especially in high strength.

[2fnloud]

Did some research and the issue is finding the right size bolt. 1/4" leaves only .010" thread engagement, the hole is too big already. 5/6 or 8MM seems big enough to compromise the strength of the fork, so I'm not sure there is a solution. There exists such a thing as a 7mm bolt, but it is hard to come by, especially in high strength.

What thread pitch?

[Chris@Rvengeperformance]

What thread pitch?

1/4" neither fine or course has enough thread engagement

[2fnloud]

I thought you wanted M7 bolts?

[Chris@Rvengeperformance]

I thought you wanted M7 bolts?

ah yeah, I think fine pitch is stronger. I can't find above grade 8.8 was going to just do real mccoy's method.

[2fnloud]

Isn't stainless like grade 10?

[Chris@Rvengeperformance]

Isn't stainless like grade 10?

no normal stainless is like grade 2

[2fnloud]

no normal stainless is like grade 2

Here: https://shop.wheelflip.com/products/torx-wheel-bolt-m7x1

Class 10.9 = Grade 8

[anyonebutme]

I would just peen in a solid pin or use that fatter pin trick above. Finding a bolt with the proper grip length is damn near impossible, and I would never install an all threaded bolt in a shear application. Threads can not support shear loads and will smash, allowing the fork to move, and will eventually shear apart.

[Chris@Rvengeperformance]

Thanks for the input guys, I'm going to try the dual roll pin approach as it seems the most fool proof.