picked up this gearbox a few months ago with the intention of putting it in my 85 wagon eventually, and finally took it apart. It was extremely corroded on the outside, but seemed to work. Also had a MB sticker and appears to have been a relatively recently rebuild, however horrible looking.

   

I pulled the drain plug and found this- always a good sign

   

What happened is the 3rd gear brass clutch spring mechanism some how got out from the clutch/synchro, flew out into the rest of the transmission, and ultimately destroyed both front bearings. Related, but perhaps before this failure, the 3-4 shift collar teeth are all worn down for both gears, and part of the detent mechanism is damaged.
All the other bearings are good, and all the brass clutches are in perfect new looking shape except for 3rd gear, which is scuffed a little.

some pics of the damaged components-

   
   
   
   

What I am trying to determine is HOW this failure occurred, so when I replace or repair all the damaged components, it does not happen again. I keep coming back to this really confusing bit of the transmission that has me stumped.
Inside the input shaft, there is a spring, several unusual bearings, washers and spacers. They appeared to be sort of thrown in there when I took this apart and I feel like they have to be related somehow to the failure, but I can't figure out what the purpose of this spring is. I have not seen this before, and there is no load on it, or any thing about the output shaft that could be spring loaded.
some pics-

   
   

Anyone have any theories?

I've never seen that before

I've seen a spring and a large ball bearing in there? in some Toyota trans

waiting on classic center exploded views, but some of the hard gear parts may be NLA from what I have been hearing, which would be annoying.

In that case, I might have to put a bead of weld on EACH of the worn out nubs, file it down to the right shape, then figure out how to harden it, if such a scheme is even possible.

No wiser on what the purpose of this spring is either, took it by a buddy of mine that does a lot of transmission work, his response was "WTF is as this?"

it's probably something someone rigged in there to get it going... something got lost and/or broken and that's what the "solution" ended up being...

(07-20-2010 10:29 PM)SurfRodder Wrote:  it's probably something someone rigged in there to get it going... something got lost and/or broken and that's what the "solution" ended up being...

The spring is apparently factory from some EPC diagrams, but still have no idea what its for. It looks like there is some of that kind of hackage going on though, because it has some spacers that absolutely do not fit in there properly, and are not on the EPC.

I sourced another 5-speed to try and upgrade that connection. Turns out there was a little problem in that trans at the same location, which was a 717.411 that had the impeller I was looking for. Unfortunately, the impeller, if it was in there, has been ground to tiny little shards, as well as most of 4th and 3rd synchronization, and the input/output shaft tapered roller bearing.

Here are some horrible pictures-
this is a bad sign, when pieces of a synchro clutch have found their way through two small fluid holes in the case to the back of the gearbox. I figure this means that some inattentive driver drove around long enough for these large pieces of brass to be thrown perfectly through either the linkage hole above or the fluid hole below after the initial failure. They were jammed around and being sanded by 5th gear.
   

Two complete synchro clutches have failed and broken apart. 4th gear, and looks like later 2nd gear.
   

This bearing may not be re usable.
   

You can see here where the bearing heated up, seized around the output shaft end, and sheared it off
   

This is my favorite picture, this debris field around the shaft I think used to be the impeller. The synchronizer is actually seized together and the teeth are jammed together and melted on both sides. Notice the heat damage to the aluminum shift fork as well. This sucker got real hot, hard to imagine someone continuing to drive with the kind of noise the gearbox was probably making. Especially to do so much damage.
   

Unfortunately, this is a total write off to repair the other one, at least in the location that matters. Anyone with bearing noise from their tranny, for gods sake, don't just continue to drive it or this is the result!

Yikes those are some nasty views. Hopefully there is enough usable parts to salvage off of that trans.




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(08-11-2010 07:17 PM)DeliveryValve Wrote:  Yikes those are some nasty views. Hopefully there is enough usable parts to salvage off of that trans.

Im going to look into seeing if I can salvage the input shaft. If its usable, I might be able to press off the synchro teeth and whats left of the bearing race, and use the output shaft from the .412 and cobble something together so I still get something usable out of the two.

Also, amazingly, the countershaft and most of the gears are ok. Ive still got to clean it all off and see if anything has been heat blued, but there do not appear to be any chips in the teeth.

The case is actually in quite good condition, maybe this one will be the one that becomes a lamp.