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Popping Out of High Gear

Discussion in 'The Garage' started by prossett, Jan 6, 2006.

  1. prossett

    prossett 1/2 ton status

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    Lost the use of 2nd gear while out on a long desert run... :(

    1983 Jimmy, 4spd manual gears L-1-2-3, will drop out of 3rd (though it's marked as 2nd on the stick - OK, it's the gear up to your right). I can hold it there sometimes, but other times it kicks out. Otherwise running through the gears is smooth and when stopped there's nothing that would indicate a problem. Clutch works fine.

    OK, so the solution?

    I'm thinking of maybe the transmission mounts? They look fine, but maybe re-tightening?
     
  2. diesel4me

    diesel4me 1 ton status Premium Member

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    oh-oh...

    Sounds like a snap ring broke..it was a fairly common dilema on the SM465's in the 70's and 80's..the snap ring that holds 3rd gear(or "second" if the knob says "L-1-2-3") onto the mainshaft of the tranny..it requires a complete removal and teardown to fix..:( --unless someone else knows an easier way..

    Could be a synchro too,or chipped teeth on the gears,but you'd hear them crunching most likely..

    I saw some things in J.C. Whitney's catalog many years ago to fix this problem..they looked exactly like 2 peice shaft collars ,with the I.D. machined with a "step",just the same width as the snap ring was..and supposedly you could install them thru the PTO covers on the tranny,without having to pull it,though I bet it wasn't fun to do..they were only around for a year or so,then they dissapeared..not sure if they didn't work out,or what..maybe someone else here has more info??? ..(or a cheap tranny 4 sale!) :crazy:
     
  3. prossett

    prossett 1/2 ton status

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    Aw Man... that's bad news for me... heavy bad news. :(

    No chance of alignment issues? Replacing motor mounts and/or tranny mounts?

    It's a long way to ship a tranny to here!!!

    I didn't mention that it happened kind of gradually (sorry, I tried to give full details) one day it popped out once at speed on a hard track as a result of a hard bump, then it continued fine. The next day it popped out 2-3 times also when I banged over something, then it started happening more frequently and when accelerating, now it won't stay in gear more than ten seconds when accelerating, but will stay when decelerating.

    Would you reckon it's worth giving the mounts a shot first? It's way cheaper for one, plus I can do that myself.
     
  4. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    deffinetly a common problem, if i remember correctly, its a worn syncro. you can buy a rebuild kit on ebay for like $125, not sure if they will ship it there or not though.
    if they won't i think i can get a rebuild kit for it, not sure on the price or shipping, but i would be willing to ship it to you. email me, its in my profile.
     
  5. diesel4me

    diesel4me 1 ton status Premium Member

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    Pray??

    Seeing its not MY truck,you could be lucky,and have it just be something fairly easy to fix,like the shifter itself being too sloppy,or worn shifting forks inside the tranny,which can be fixed in the truck IF yours has an unboltable floor pan "hump"..(or your handy with torches or an air chisel!:p: )..other than that,I'd say start using first and third,and skip second gear if possible..

    I'd say motor or tranny mounts would make it pop out of other gears,and you'd have other issues too,like hearing the fan hiting the fan shroud..but anything is possible,wont hurt to check them out,and see if any bolts broke or fell out of the crossmembers too..good luck!..:crazy:
     
  6. big83chevy4x4

    big83chevy4x4 3/4 ton status

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  7. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Syncro rings have absolutely nothing to do with gear popouts. If your gears don't grind when you try to shift, they are working correctly.

    There are 3 things that can be amiss here. Two are easy fixes, one is not.

    By far the easiest thing to fix is a sloppy shifter. They have two welds on them that break, a couple small o-rings that wear out, and a pair of roll pins in the tranny top wear out, and start to back out. These all reduce the amount of gear engagement you get when you try to shift it into different gears due to the amount of slop they introduce into the system.

    You can check on these by taking your shifter boot off, then grabbing the little "ball" that sticks up out of the top of the transmission (while it is in neutral!) pushing it in, and turning it counter-clockwise. It should then pop up and out. You can then grab the shifter, and pull it right out of the transmission.

    Take a look at the bottom of it. You should see the welds on the round part with the little slots in it. If you see any cracks in either of the welds, they need to be re-welded back together.

    Now, this next part varies depending on the shifter, but some of the older ones had an o-ring in them to help with spacing. It will probally be worn down to be flush with the tip of the shifter (which shouldn't be worn down BTW). Mine was a newer one, and had a solid injected bushing for the whole thing, and didn't use any o-rings. It did have the cracked welds however.

    Next, take a look at the little roll pins. Make sure that they are all the way in the hole. If one is broken in half, or backed out, then get some hose clamp to hold them in after you re-install the shifter.

    Second easy possiblity is worn shift forks. They have a nylon / or teflon coating on them that wears out with time, and will cause the gear not to get proper engagment. To check them, you'll need to remove the top of the tranny. If you've got a removeable hump, this should be a relatively straight forward job. First, put your shifter back in, then put the truck about half way into reverse. This lines up the reverse shift fork to slide out without hitting any gears on the way up. Undo the bolts that hold the top on, then using the shifter as a handle, lift it straight up. You'll understand immedately how the tranny works after you get the top off. Check the tips of the forks to see if there is any coating left on them. If it is down to the bare metal (check the low gear fork, since it doesn't get used much, it usually has most of the coating left) then you'll need to replace the forks. They can be bought new, but they are not cheap.

    Last thing, is that your countershaft's snap rings are loose / broken, and are allowing the gears down there to walk forwards or backwards. To fix that, you need to remove the mainshaft, then the countershaft, and put a steel sleeve inbetween to replace the snap rings, and prevent the gears from moving around.

    Hopefully it is just shift forks, a broken roll pin or something. If not, best of luck to you :S I can imagine getting a 200 lb tranny shipped to the middle east will not be cheap!
     
  8. prossett

    prossett 1/2 ton status

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    OK, thanks guys.

    So, the mounts would affect all gears, huh? Shame, I can uncross my fingers now...

    Sloppy shifter sounds about right. The gears do not grind and they move smoothly, but there is a lot of play in the shifter, so much play that it could be in neutral in any gear, and you have to know exactly where the gear is to insert it properly.

    This quote I have copied and printed out and I'm taking it down to the garage with me: "You'll understand immedately how the tranny works after you get the top off." :haha:

    Thanks again, I'll post pics as I work through it and hopefully I can get my beast back in service soon.
     
  9. prossett

    prossett 1/2 ton status

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    OK, so SierraClassic's instructions were spot on - and I might have lucked out.

    The welds checked out ok...

    [​IMG]

    but it seems the o-rings or injected plastic have disintegrated long ago...

    [​IMG]

    This means that hopefully new rubber will fix the problem!

    If not, it's going to be tough 'cause the tranny does not open from the top.
     
  10. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Yes the tranny does open from the top. It's held on with 8 or 10 bolts...

    Rene
     
  11. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Yep, tranny opens up from the top :) Gotta put the shifter back in, and stick it about 1/2 way into reverse though.

    You'll see what I mean about just how simple these transmissions are after you get it apart though. I was expecting it to be something like an auto, which it totally isn't :)
     
  12. 79k20350

    79k20350 3/4 ton status

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    real easy to work on, but i doubght that that oring was the problem, i can almost gaurantee that it is the snap ring for 3rd gear. www.anaheimgear.com carries a sleeve to replace the snap rings. it will completely sovle the problem and is $13
     
  13. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    While I agree this can be a big problem if the snap ring breaks, I'm not a big believer in snap rings being able to flex enough to allow a gear to pop out. You can check them by taking either PTO cover off, and taking a look at the condition of the snap rings from there (make sure you drain the fluid first though!)

    I'd tend to say his problem, like in most 3rd gear popout cases, its probally gonna be worn shift forks...
     
  14. prossett

    prossett 1/2 ton status

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    Well, I'll soon find out. Thanks for the link to anaheimgear.com I hope they'll ship overseas if I need them.

    As for opening the top, I should have explained that since my rig used to be auto and was converted to manual gears some time before I bought it, it seems to me they cut a hole into the floor for the shifter to fit through, and therefore I need to take the tranny out to open it from the top.

    Right now I'm trying to find those rubber/plastic bits for the tip of the shifter... to give you guys an idea of what this means, here's a pic of one of the local mechanics....

    [​IMG]
     
  15. Jagged

    Jagged 1 ton status

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    Prossett ain't lyin bout them mechanics. Seen them places myself.
     
  16. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    go to the hardware store and get a thick O-ring that fits in the groove. i don't remember the size off the top of my head, but there was a thin and thick oring the same size.
     
  17. prossett

    prossett 1/2 ton status

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    Any old rubber o-ring? No problem with the gear oil getting to it?
     
  18. 79k20350

    79k20350 3/4 ton status

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    nothe grease/ oil will not affect them. they'll be fine.
     
  19. prossett

    prossett 1/2 ton status

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    Well, got the o-rings, and the slop is clearly gone - but same problem...

    Looks like I need to drop the tranny and look at the shift fork.

    Man, the only thing that's keeping me going is just how great it feels to own and ride a great rig!!! And drive rings around newer, more expensive SUVs!!! :)
     
  20. prossett

    prossett 1/2 ton status

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    OK, just so this can help some other guy, I hooked up with a buddy who knows trucks some, and we set to find the top access through the floor panel - yes, it's there. We had to rip out carpet and soundproofing, and remove seats and the centre console, but there it was, still with the factory seal.

    As Sierra Classic and the guys said, you can take the top off the gear box by placing the stick half-way into reverse, and look inside the gears. Definitely worth doing before dropping anything!

    In fact, in my case, the gears look perfect, but the shiftforks are clearly used up badly. Tomorrow I go looking to replace them, and if that solves the problem, thanks to ColoradoK5 and my buddy, I've just saved myself a major hassle!!!

    I was about to drop the transmission and take it in to a garage nearby... no doubt they would have welcomed me by cackling and rubbing their hands together.

    SierraClassic, my respect. You know your stuff.
     

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