Need a 5th Gear

[Dr_Snooz]

Condition of the splines on the shaft looks fine. Even the blurry syncros look good. Again, I'm tempted to stuff it in without a rebuild.







Condition of the splines inside the gears also looks good.





So it's obviously not new, but all in all, it's very rebuildable.

[ShiRen]

So which trans had the splines not meshing right in the pic?

[Dr_Snooz]

That's the new one. They're meshing about as well as they ever did from the factory, I imagine.

[Dr_Snooz]

Here are some better pics of the syncros. They look nearly new to me.

[conozo]

I agree, looks new/unused.

[Oldblueaccord]

Snooze as far as failures all I remember seeing is the gear clusters teeth sheared off smooth...and I do remembering mentioning about drilling a hole in a shaft out to get more oil to the 5th set up.

[conozo]

Snooze as far as failures all I remember seeing is the gear clusters teeth sheared off smooth...and I do remembering mentioning about drilling a hole in a shaft out to get more oil to the 5th set up.

I agree, I've seen lots of pics of destroyed 5th gears and they are always like what is described here.

[Dr_Snooz]

Snooze as far as failures all I remember seeing is the gear clusters teeth sheared off smooth...and I do remembering mentioning about drilling a hole in a shaft out to get more oil to the 5th set up.

Do you think the spline failures are an oiling problem? I'm honestly not sure at this point. I'm halfway to having the busted trans out, so I'll take some pics when that's done.

I want to see if it can be rebuilt.

[Dr_Snooz]

Warning: graphic footage ahead. Viewer discretion is advised.


I pulled the broken trans this week and had a look inside. I was not prepared for what I found.




The gear teeth are gone.




You can see what looks like metal paste all mashed around the gear teeth, but it's not paste. It's actually melted metal. It must have gotten awfully hot.







Go back to the first photo and notice the piece of wire pointing from the shift fork to the union of the two gears. Do you see it? That is what remains of the detente wire on the 5th gear syncro.

Here's the syncro.




Notice the dark hot spots on it?

My hypothesis is that the wire failed somehow (thus producing the "crunch" every time I shifted into 5th) and was drawn into the gears with predictable consequences.

Notice how the syncro is cracked.

[Dr_Snooz]

The splines are fine.




But the mainshaft got hot.




The bearing turned black, though I'm not sure if that was from heat or the black, nasty oil that was in it.




Compare to the new trans.




So yeah, it's a mess. I can't say what happens to all these 5th gears, but it looks like this one had a syncro detente wire fail first, get caught in the 5th gear set and cause a lot of damage.

Hope that helps someone else.

[Oldblueaccord]

Nice work with the pictures!

I think that last picture that hole people drill out to get more oil out to everything.

I think your correct the syncro/wire caused a knot up and there went the teeth.

[Jinnai]

Thanks for the pics, very interesting! Much worse than my 5th gear, though mine still wasn't functional.

[InAccordance]

Someone's been grinding some gears in that box, some good ol chipping going on (the new one)
Can't find em, grind em.

but holy shit those gears in the old one are brutal

[ShiRen]

I think I see your problem Snooz, but you might need to check that gear mesh with your .75" feeler gauge to be sure.

Someone's been grinding some gears in that box, some good ol chipping going on (the new one)
Can't find em, grind em.

but holy shit those gears in the old one are brutal

YOURE ALIVE!

[conozo]

Thats interesting. When i swapped in a 5 speed on mine, i cracked it open and found the 5th gear synchro was pretty worn and that detente ring was broken loose but my gears were fine. I dont remember what exactly this detente ring does but i am wondering if its the reason these 5ths are failing. I've seen that detente ring broken on all bad 5th gears I've seen. I wonder if its partially engaging 5th gear when you are not in 5th gear causing excessive heat then it melts.

[ShiRen]

I bet the crunch on mine is a broken detent ring... Did we have a source for those or nah?

[Dr_Snooz]

Détente rings? Or 5th gear? There are these gears that someone posted earlier:

https://www.3geez.com/forum/3geez-ac...ml#post1223066

If you want a detente ring, you'll probably need to buy a kit. If you can find one.

[Dr_Snooz]

Thats interesting. When i swapped in a 5 speed on mine, i cracked it open and found the 5th gear synchro was pretty worn and that detente ring was broken loose but my gears were fine. I dont remember what exactly this detente ring does but i am wondering if its the reason these 5ths are failing. I've seen that detente ring broken on all bad 5th gears I've seen. I wonder if its partially engaging 5th gear when you are not in 5th gear causing excessive heat then it melts.

You sir, win the prize.

ALL - CLUTCH DRAG KILLS SYNCHROS! - Jacks Transmissions

What the link says is that a dragging clutch will cause your synchros to fail. My synchro definitely failed prior to 5th gear blowing apart. That was the crunch each time I shifted into 5th. That crappy clutch I showed earlier was definitely causing drag. I had to slam the trans into first sometimes. I didn't know it was the clutch though, because it came and went. I thought maybe the clutch fork was failing or something. When the synchro failed, it popped that ring, which got swept into the gears.

Had I known, I'd have pulled the clutch sooner. Now I just have a giant mess to clean up. The only thing I don't understand is why 5th blew apart and not 1st where I was actually hammering on the synchro.

[ShiRen]

When I changed my clutch the first time I magically had the issue of my clutch throw being too short and had to remove everything from behind the clutch and make the cable completely slop free. Never figured out how that happens, not like the clutch release shaft can really be bent out of adjustment, and its not bent or twisted, nor have I every stomped the clutch like a gorilla. I think all that happened the first time I was unable to engage the clutch was the clutch cable adjustment slipped, friggin weird still, I kept using that cable.

Just saying though, you've got tons of extra clutch travel if you need it. Also I don't agree entirely with that article. Either I'm really stupid and I am roasting the fuck out of my clutch and its taking it like a champ, or there is a harmonic issue keeping me from shifting over 6k rpm in 2nd. Its the only gear that vibrates the shifter and makes a stupid noise. I've just come the conclusion that this is not a racecar gearbox... oh, and its old, it works just about as well as you geezers. I still suppress that fact in my mind though.

No detente rings
Still no detente rings
Can that thing just be removed?

Snooz, can you measure the diameter of the synchro where the spring sits?

[Dr_Snooz]

Sorry. I sealed it all back up tonight.