Destroyed Synchro Ring (aka why I couldn't use high range)

ScubyRoo · Post by **ScubyRoo** » Mon Jun 27, 2011 4:18 pm

I am stumped as to how this happened:

Has anyone seen/done this before? Any best guesses as to what could have caused the failure? It is the synchro on the hi-range side of the hub. The synchro on the low-range side is slightly worn at the teeth, no other noticeable wear.

Other things that were noticed was the wear on the low range selector fork's 'feet' as I call them. on the Left is a new one, one the Right is the worn one. There was initially a whining sound that I liken to the sound of milling metal when I was trying very hard to get the bastard to engage hi range - I'm guessing that milling sound was actually the selector ring grinding out the feet. There was no freeplay in the feet originally - they were milled precisely to the depth of the selector's race.

Here's the selector ring - you can see the scratching on the surface on the hi-range side:

The tabs and retaining ring were still appropriately situated in the hub, everything else was in order and all other components of the gearbox are in perfect nic.

Any thoughts as to how this might have happened? Obviously I don't want this to happen again

Cheers,
Owen.

PS. check out the page out of the local paper I had down - didn't realise till I looked back at the photos just now! Gold.

Point · Post by **Point** » Mon Jun 27, 2011 11:10 pm

A mate is doing the L low range mod, and he said that the selector fork distorted when he welded it. Could yours have done the same?

YouTube · Post by **El_Freddo** » Mon Jun 27, 2011 11:22 pm

Mate its good to see that you're straight into the gearbox autopsy!

That syncro ring is cactus! I thought one of those little tabs that's held in by the circlip (schpelling??) may have come loose and done the damage, but if they were all there and accounted for there shouldn't be an issue - unless the clip was missing, but I don't know how it would have got out in the first place.

So what is it that you need for the fix - another L series gearbox? Glad it didn't completely let go on our last outing!!

All the best with the re-build. I hope the subi gods (gearbox department) are good to you! You should start a business with all the experience you've got through this...

Cheers

Bennie

Venom · Post by **Venom** » Tue Jun 28, 2011 8:37 am

Owen i've still got that L series box that came up on Ebay. You can take it for what i paid for it.

YouTube · Post by **El_Freddo** » Wed Jun 29, 2011 2:42 am

I've been looking at this pic of mine to work out what went wrong but can't pick it:

Unless there was some sort of interference from something when you engaged low range the first time or a couple of times after, or there was something floating around which I find hard to believe.

What Point said could maybe had an effect - not allowing the dog gear to slide parallel to the input shaft thus the synchro was engaged at one point rather than whole face on... maybe.

Any other thoughts on it?

And how's the rebuild/parts find going?

Cheers

Bennie

ScubyRoo · Post by **ScubyRoo** » Wed Jun 29, 2011 8:46 am

Yeah looking at your pic there bennie I'm stumped as well.

As I used a gen 2 lib gearset in this version, perhaps I didn't grind the synchro hub down far enough and there was play inbetween the hub, synchro ring and gearset? It was a tight fit when I put it back together but that is my only theory.

A good Point there (ahahahaa) I will check the selector and see if it is still straight as it did get hot when being modified.

In terms of parts I'm fine for liberty parts as libby's gearbox was toast when I bought it (binding issues in reverse - maybe you remember from the otways? I took the rear diff out last week thinking that was the problem but it is sweet, runs free in both directions with no wind up). Venom has offered his ebay special, but it's in ballarat... I really don't want to spend $150 at the wreckers for another L-series box.

Maybe I should just buy a synchro straight from subaru?

Cheers for the input fellas!

O.

YouTube · Post by **El_Freddo** » Fri Jul 01, 2011 2:31 am

ScubyRoo wrote: Maybe I should just buy a synchro straight from subaru?

Was the the ONLY damaged part in there? And was that synchro the correct one in the first place?

I think you need to work out what it was that went wrong so that you can make sure it doesn't happen again!

Is the selector fork bent at all?

Cheers

Bennie

RSR 555 · Post by **RSR 555** » Thu Jul 07, 2011 4:08 pm

From my experiances with gearboxes (mainly rally cars) is that when syncros get over heated (like what yours looks like but to extreme) then this is from the syncro being 'run' constantly and without any clearance and when they get hot they get very dry which in turns makes them hotter. I think you'll need to give some more pics of the parts in between so we can get a better idea.

YouTube · Post by **El_Freddo** » Fri Jul 08, 2011 6:06 am

RSR 555 wrote:when syncros get over heated (like what yours looks like but to extreme) then this is from the syncro being 'run' constantly and without any clearance and when they get hot they get very dry which in turns makes them hotter. I think you'll need to give some more pics of the parts in between so we can get a better idea.

I think this may have been caused when trying to get it back into high range

rather than when using the low range or just cruising around. But I am wondering about the clearances in that area, if something was tighter than it should have been the issue may have made itself apparent after using low range for a period of time, especially if high revs were used!

My thought on it anyway...

Cheers

Bennie

Phizinza · Post by **Phizinza** » Thu Jul 21, 2011 8:17 pm

Wow... I always wondered what you would use those personal sections in newspapers for!

Oh, and the damaged synchro, scary..
I'm assuming this is not the original low range? Not sure if your gearbox needed this but the inner synchro ring on mine had to have some spline machined out of it to fit properly on the shaft. I'm thinking if this was done on the wrong side or wrongly either there would be pressure against the synchro all the time form the inner synchro part or too much slop in there...?