Manual Transmission T56 | T5 | MN12 | Clutches | Hydraulics | Shifters

violently pops out of third (gallery)

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Old Aug 15, 2013 | 03:38 PM
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Default violently pops out of third (gallery)

So I bought the transmission from someone about a year or so ago and finally got it into the car, and driving and what not.

Everything seems to be fine, but then I notice that it violently pops out of third when the clutch engages, but only under normal/slower driving conditions. At high rpm it works fine.

Me being me, after the general anger left, I took it back out and tore it apart, using the shop manual and patience of course. I'll be honest, I get excited to tear things apart that I have never messed with before.

Here I am, I have the expertise to fix it and tear it apart, but my inexperience keeps me from knowing whether something is overly worn or out of place.

I always heard that the 3/4 shift fork is usually the culprit, so i included a lot of pics of that, and there does seem to be a few oddly worn areas.

Guys and gals, take a gander at my gallery and tell me if you see anything obvious out of place, or if there is anything indicative of my issue!

I can always take more pics, so if it will help you help me, I'm all for it!

LT1 T56

http://imgur.com/a/ocYLf

Thanks in advance!

Last edited by Tolley's94z28; Aug 15, 2013 at 03:54 PM.
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Old Aug 15, 2013 | 04:31 PM
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i could be the fork is bent, also if you look at the teeth on the synchronizer sleeve is there more wear on the 4th gear side?

mine was popping out of reverse and i had to flip the synchronizer sleeve, that fixed my problem. on yours you can do that because it most likely just pop out of 3.. you may have to replace the sleeve.
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Old Aug 15, 2013 | 04:46 PM
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Originally Posted by AKAFRED
i could be the fork is bent, also if you look at the teeth on the synchronizer sleeve is there more wear on the 4th gear side?

mine was popping out of reverse and i had to flip the synchronizer sleeve, that fixed my problem. on yours you can do that because it most likely just pop out of 3.. you may have to replace the sleeve.
How could I tell if my shift fork is bent, would it be apparent?
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Old Aug 15, 2013 | 05:55 PM
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There isn't much play between the shift fork and shaft, so I doubt it is a shift fork.

How can I tell if it is a bad synchronizer sleeve?
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Old Aug 15, 2013 | 07:38 PM
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I think I found the culprit!

There is excessive slack between the 3/4 synchro and 3rd, here are a few pics:

violently pops out of third (gallery)-imyabtf.jpg
Key separation when engaged in 3rd (don't know if this matters)

violently pops out of third (gallery)-cvhcxzu.jpg
This is where it sits on 3rd when engaged showing just how much slack there is. As you can see, it is barely on the teeth of 3rd gear, which would explain why it kicks out of 3rd during normal driving (not much area to grab)

violently pops out of third (gallery)-ailil0c.jpg
For reference, here is the amount of gap when 4th is engaged (orientation doesn't matter, the space the same)

Is this my issue? How do I fix it?
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Old Aug 15, 2013 | 07:50 PM
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Tear your synchro apart and check your keys. The synchro should go all the way over the engagement teeth on 3rd. You probably have a broken key.
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Old Aug 15, 2013 | 07:50 PM
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Originally Posted by AKAFRED
i could be the fork is bent,


They don't bend... thats a myth.
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Old Aug 15, 2013 | 10:36 PM
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The fork hole wallows at the shift rail.

While high-rpm could pull the synchro slider into the gear dog teeth somewhat at RPM due the hourglass shape of them, you need to assure the slider is going over the gear dog teeth fully. Is the synchro fully pressed on? Any compression evident on the fork pads? ANY wobbling of the fork on the shift rail - get a new fork. Wear at the shift lever bushing (under the shifter)?

The single cone 3rd/4th on these is simple; there shouldn't be much preventing a full travel shift.
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Old Aug 15, 2013 | 10:52 PM
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Originally Posted by jmd
The fork hole wallows at the shift rail.

While high-rpm could pull the synchro slider into the gear dog teeth somewhat at RPM due the hourglass shape of them, you need to assure the slider is going over the gear dog teeth fully. Is the synchro fully pressed on? Any compression evident on the fork pads? ANY wobbling of the fork on the shift rail - get a new fork. Wear at the shift lever bushing (under the shifter)?

The single cone 3rd/4th on these is simple; there shouldn't be much preventing a full travel shift.
There's no wobble between the shaft and the fork, or anything like that. I'm going to pull the synchro off Sunday when I have time, but I'm pretty sure it's something inside there that's the culprit.
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Old Aug 16, 2013 | 12:46 PM
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3/4 is on the short end of the main shaft right?

Because the gears in the picture are on the long side, but I haven't had any problems with 1st or 2nd!

Also, I noticed that the bottom left bolt hole was stripped, and top right bolt wasn't tight when I removed the shifter, could this have caused all my issues all along? (the other two were pretty tight though)

Last edited by Tolley's94z28; Aug 16, 2013 at 01:40 PM.
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Old Aug 17, 2013 | 01:55 AM
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3rd and the synchro, yes.

A loose shifter will keep you from fully shifting into gear, yes.
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Old Aug 17, 2013 | 12:30 PM
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Originally Posted by jmd
3rd and the synchro, yes.

A loose shifter will keep you from fully shifting into gear, yes.
Pop on over to my other thread and check out a couple videos that I posted, let me know if anything seems out of place!
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