Synchro Question!

[PToombs]

I pulled the 'rag back out today to fix the 3rd gear problem. It won't go into 3rd when cold, it just grinds unless I double clutch or shift it slow. Once it warms up it shifts ok, even good. I pulled the trans apart and inspected the synchro and all the other related stuff, and it all looks good. I expected to see the synchro worn bad or damaged or something. The only thing I see is the little pointy teeth on the gear itself are slightly rounded. If I didn't look real close I wouldn't have even noticed it.
So, is that the problem? Or is it something I'm missing? Any tips or bright ideas are welcome at this point.

[bmoeller]

Damn, you've had trouble with that one! Wish I had some insight.............

My guess is, though, if they are wore more than the rest, they probably are part of the problem at least. Seem to be having a top cover issue with mine (2nd and R).

[oldestof11]

How is the shift fork?

[PToombs]

Looks good. It never did this with the old synchros, after I changed and put in the new ones from ZBag and drove it a little over a year it started. I'll double checl to see if the fork is bent, but it looked good at a quick inspection.

[ellis93]

Mr Pete have you measured the clearance between the synchro and the gears matching teeth? A couple of .001 will make a huge difference. You can compare it with one that is known to shift nice.

[ellis93]

Oh......I also have the shift dogs for that hub too, if you need them

[PToombs]

I measured it and the one for 4th, and they both measure the same, thickness, ID, how far they sit down on the cone, etc.
I think it was the dog shifting that screwed it up!

WTH are the shift dogs?

[oldestof11]

3 little spring loaded teeth iirc.

[ellis93]

Pete they push on the synchro before the collector ring hits them and keep pressure on the synchro while the collector ring engages the gear teeth.
They look like this

I've extra

[Mark Nixon]

The "teeth" on the gear are referred to as the "clutching teeth", not sure if it matters what they are called, though.
They do have a function, which is to pre-engage the slider ring to the gear before it locks to the hub and gear.
That the engagement changes with temps tells me you might still be just a smidge tight on bearing preload.

I'd almost bet that above 70* it probably wouldn't make noise one.

Damned Getrags and their pre-load, anyway.

Mark.

[PToombs]

Ellis, the dogs are ok. I was careful not to shoot them all over the floor like the 1st time I took it apart. When I was putting them back together the wife took the kids and left for the day. I was a little upset about the way they were going together......

Mark, fockin preload! You know, now that you say that, the last time I had it apart I adjusted the shims a little. I didn't think I did the main shaft, only the counter, but I may have. I'll check it again. Maybe I'll set it .001 or 2 loose this time instead of at 0. I'm almost to the point of looking for an auto for it. Now you know I'm getting fed up!
I was beginning to wonder if it might be the oil, 50w synthetic. It just seems like I have been having more problems since I went to that from 15-40 engine oil.

Mark, thanks for the input. I was hoping one of you guys with more time inside one of these things would chime in.

[Mark Nixon]

Watch going to clearance instead of pre-load, this is actually why they will start to grind when the pocket bearing goes.
When that happens the mainshaft starts to "float", then the synchros get canted around and start to grind.
In severe cases of mainshaft float, when the mainshaft moves fore-to-aft, the tranny literally will pop out of gear on deceleration or light acceleration and some people blame it on the shift cover assembly, change it and have no improvement whatsoever.
In some cases mainshaft float will also make the cover bind (Miss gates) between 2nd and 3rd or 4th and 5th gears, any time you pass between gates.

All of this is at least initially linked to that stupid pocket bearing going to schit.

Mark.

[bmoeller]

Watch going to clearance instead of pre-load, this is actually why they will start to grind when the pocket bearing goes. In severe cases of mainshaft float, when the mainshaft moves fore-to-aft, the tranny literally will pop out of gear on deceleration or light acceleration and some people blame it on the shift cover assembly

Hmmmmmm. Wonder if that is my problem with 2nd and R................... No grinding, though.

More than likely, the trans has to come out to check/adjust preload? Shims? Never been in one.

[Mark Nixon]

Bryan, certainly, they can pop out and you woudn't hear a grind one, which means it's probably just starting to decline.
In a perfect world, the tranny shouldn't pop out of gear, EVER. So much for perfection.

As a rule, if the input has notable "wobble" when you try to deflect it, odds are great that the pocket bearing is hashed, which generally means it needs at least an input.
On a 4wd, it's really easy to see how out-of-tolerance it is, drain it (of course) then just stand it up on the rear flange with the output over a hole or something, then try to feel the play, or use a magnetic dial indicator to check it at the input.
Generally speaking, if you can FEEL play, it's likely pretty hacked already.

When lying horizontal, a seriously bad one will pivot, or "see-saw", meaning that when you push the nose of the input down, it'll push back.
I've lucked out and only had to re-shim a couple, but it's very rare.
Usually it needs at least a new input, but a re-bearing is always good insurance.

Put it this way, I NEVER buy a Getrag as a "good" tranny if the input wobbles or see-saws.

Mark.

[bmoeller]

Thanks Mark. Kind of what I was afraid of. May need an input for 5600 as well. Nose is worn where the bearing was. Need to sell some more parts I don't need, I guess...............