1979 GMC Sierra Pops Out of 2nd

1979 GMC SIERRA
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JACKINCOLORADO
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  • 1 POST
I have a '79 GMC Sierra 4x4 with a 4 speed manual tranny ( Low-1st-2nd-3rd ). I would appreciate a little help in learning just how to adjust the shift linkage in my 4-speed. It pops out of 2nd gear.... All other gears hold just fine, only trouble is with 2nd. I couldn't say what make of tranny it is, so if that is an issue, please let me know how to tell, so I can take care of this irritating problem! Thanks for the help!
Sep 11, 2006 at 1:13 PM
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BURRBRIAN
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  • 158 POSTS
Unfortunatly, what you are saying sounds like it's not the linkage adjustment but possiby a bad sychronizer in 2nd gear. Does it pop out running easily down the road or just when you are under accelleration? If you are out of adjustment on your linkage it could be pulling it out of gear but doesn't seem too likely. Have you tried to hold the shifter in gear? Does it "kick" the shifter back to nuetral even if you are holding it?
this would lean towards the gear sychronizer. Hate to be the bearer of bad news [ if I am] but check it out before you ruin 2nd all the way. Luck and lots of it! :shock:
Sep 12, 2006 at 12:20 PM
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BURRBRIAN
  • ✓Experienced Mechanic
  • 158 POSTS
If it isn't engaging as fully as the other gears you might try adjusting the stop on your shifter. On a 4-speed it should be the front one towards the pass. side Back it off intil you can feel it go into gear without having to apply pressure to make it go completely in. If it still jumps out at this point you will have to see wether it is the teeth on the gear or on synchro. What really bites is ussually the part isn't costly- it's the labor! But if you like the tranny that much the more it jumps out like that the more damage is likely to be done. Bypassing 2nd will work for a while as long as it doesn't put too much strain on your motor.Hope turning some nuts and bolts will do it for you! :P
Sep 13, 2006 at 10:45 AM
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Suggested Repair

Check whether the shifter is forced back to neutral while held in 2nd, which points to a worn 2nd-gear synchronizer or gear teeth rather than linkage. If engagement is incomplete, back off the front passenger-side shifter stop until 2nd engages fully without extra pressure. If it still pops out, inspect the synchronizer and gear teeth before further damage occurs.

Conversation Summary

The owner of a 1979 GMC Sierra 4x4 with a 4-speed manual says it pops out of 2nd while the other gears hold. The expert says linkage misadjustment is less likely and a worn 2nd synchronizer is more probable, especially if the shifter kicks back to neutral while held. They also suggest backing off the front passenger-side shifter stop so 2nd engages fully, then inspecting the gear or synchronizer teeth if it still jumps out, since continued popping can cause more damage.

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