Can't Shift Into First

[rcecale]

Originally posted by UTKarmann_Ghia
Randy, maybe I missed it, but why are you taking the diff apart?

Matt,

John suggested that I removed this cover so I can clean out any bits of metal that may have migrated here when 1st gear came apart.

Randy

[UTKarmann_Ghia]

Ahhhh, nice You'll have to post pics of that one since most of us have probably never seen inside of that beast!

[rcecale]

As if you even had to ask....

Randy

[rcecale]

Been playing around with a few of the broken pieces and noticed that all three teeth on the guide sleeve were broken in the exact same manner.

I can see what's wrong with everything,, no problem. I'm just trying to figure out what exactly happened...or, for that matter, which happened first, the broken sleeve, the busted dogteeth or the bent synchro band. How about, which caused which?

Here's a couple of pics of the guide sleeve showing the way the teeth were broken.





Randy

[Jim Sims]

Failure theory: First gear synchro became worn; this made it possible to more easily "beat" the synchro thereby jamming the 1st gear side sliding sleeve teeth and 1st dogteeth together while they were still moving relative to each other. This of course causes the teeth to wear and also impact loads them. Finally during a downshift the first gear dog teeth were worn enough to break off due to the impact loading. This allowed the synchro ring to spring open releasing the energizer block and a brake band. You found the energizer block on the shift fork guide plate and the brake band was bent coming out or when it got caught in something. The failure downshift may have happened successfully and the synchro system came apart during the next upshift to second. Then during the next downshift to 1st the 1st gear side teeth of operating sleeve were abruptly jammed against the 1st gear synchro ring that was sprung out. This abrupt stop overloaded and fractured the ends of the three arms of the hub or spider. It is also possible that the failure shift into first was not successful but instead the synchro ring released partway through the shift and everything broke then. Jim

[UTKarmann_Ghia]

Sound good to me Or bad...depending upon how you look at it

[rcecale]

Thanks, Jim!

That scenario seems to make sense. Sounds like it just basically beat itself up and knocked its own teeth out. I don't imagine the replacement parts will do this for quite some time!

Randy

[rcecale]

The circlip is off of 1st Gear. Checking the orientation of everything underneath it.


1st Gear Brake Band with Anchor Block. Notice the wear marks on the lower left-hand corner of the Anchor Block.


The old set of dog teeth...sorry for the blurry shot, was kinda dark in the garage...


And the new dog teeth...


When installing the new dogteeth, can I just work them on with a hammer, using a block of wood between the hammer and the teeth? Should I heat the teeth up in the oven first...200 degrees or so?

Randy

[john walker's workshop]

first dress the swage on the actual gear with a fine file. it makes the toothed ring start and go on easier, and most important, less chance of deforming the inner bearing race. you should use a press of course, but a vise would probably do it. don't get it cocked as you squeeze it on. hold the gear up to the light when you're done, to be sure it's flush all the way around. they might go on easier heated, but with the press, i just do it cold, and they go on fine.

[rcecale]

I pass a few auto-repair shops on my way home from work...I'll stop by tomorrow and see if I can't get them to do me a favor and press the teeth on.

Here's a shot of 2nd Gear for a reference.


Here is the old 2nd Gear Dogteeth. The points look a bit rounded.


And here is the new dogteeth...points are nice and sharp.


Randy

[UTKarmann_Ghia]

Nice work Randy. I put my dog teeth + gear in my vice with a shop towel on each side and easily pressed them on.

[rcecale]

Well, the vice idea just wasn't working for me. Picked up a real fancy one with 360 degree swiveling 5-inch jaws, nice looking addition to the shop!

Anyway, it just wasn't gonna do the trick and I surely didn't want to mess anything up. So, I dropped them off with my local mechanic on my way to work this morning to be pressed on. He had them ready for me by lunch time.(Thanks Reggie! ) Picked them up and they are ready to go. No pics yet, but I'll grab a few tonight when I get back home and back into this project.

Randy

[rcecale]

First Gear:


Second Gear:


I've noticed that the point of the dogteeth is offset on first gear and centered on second gear. I'm assuming these coincide with the offset and centered points on the teeth of the slider. Is this correct? And why the difference?

Randy

[rcecale]

The "stack-up" on First Gear, before I put the circlip on:


Randy

[ischmitz]

There was a modification to first gear at some point. I belive in model year 76 was the switchover to asymetric first gear dog teeth. Maybe the reason is that you downshift or upshift into 2nd and higher gears but hardly ever downshift into first. So first is optimized for when you put it into first from neutral. Just a guess.

Ingo

[Grady Clay]

Randy,

I keep intending to chime in about this.

Please disassemble 3-4-5 syncros and inspect all the parts. You also get the chance to clean any debris out. Considering the devastation from first gear, careful inspection is warranted.

If nothing else, you can turn the syncro rings. You can also swap third gear syncro for fifth.

Let me know if you need anything else from me. I’m available.

Best,
Grady

[rcecale]

First Gear...looking so much better than when it came out!


Randy

[rcecale]

Second Gear...ready to go!


Randy

[john walker's workshop]

be sure to point the assymetrical teeth on the 1 and 2 shift sleeve toward 1st gear. it goes on either way, and it wouldn't be the first time that mistake was made.

[rcecale]

Forgot this one...for a reference.


Randy