SM465 locking between gears

[Jordan Goodwin]

Haven’t driven the truck in 10 years, but working on putting her back on the road. When it was parked, we had an issue with the trans shifter occasionally getting locked between gears when shifting. It sometimes seemed to take forever fiddling with it to get it moving and into gear again. Any idea what usually causes this? I should mention the truck is an ‘85 K30, and my dear dad SWEARS there was a recall for this issue in that year. But many other things he has been convinced of on this truck have also not proven out… and as for me, I’m a total newbie just learning.

 

[Strick]

IF the floor unbolts from that truck it will make repairs much easier. You can gain access to remove the top plate with shift rail while still in the truck.
You can also start by pulling the shifter & inspecting both sides of the flange on it. I'd also pull the fill plug to check the fluid. You may want to drain it & fill with new oil as well.

HS

 

[Jordan Goodwin]

IF the floor unbolts from that truck it will make repairs much easier. You can gain access to remove the top plate with shift rail while still in the truck.
You can also start by pulling the shifter & inspecting both sides of the flange on it. I'd also pull the fill plug to check the fluid. You may want to drain it & fill with new oil as well.

HS

Thanks! I don’t think I can access the top plate through the floor, but I will definitely check, and I’ll check out that flange at a bare minimum. I already wanted to change the fluid, which was one reason I wanted to see what else I could look at before putting new fluid in.

 

[PrairieDrifter]

I would guess synchros are pretty well used up. The brass synchros are supposed to make the shifts smooth and seamless.

 

[vr1967]

Pull the shift lever and check for slop in the pins. (Circled below) slop in them will cause shifting problems.

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[OldBlue83]

Having something similar, will create my own thread if it's not similar enough. '83 K20, went for it's first actual drive in 19, almost 20 years the other day to make room in storage unit for the diesel so it could get some stuff done.

It shifts in and out of gears just fine, but 3rd it really wants to kick itself out (have to forcibly hold it into gear). Drove it  maaaybe 15-20 miles, each time it got into 3rd it seemed to stay a little better, but i didnt fiddle with it till about halfway home. Best approach seemed to be getting it into 3rd and getting on it to get it into 4th.

We are thinking it may just be a case of just use the thing and it'll sort itself out, but wondering what other things I can keep an eye out for or check to make sure I don't toast something. Thing drives like a dream, just the weird 3rd gear thing. Should also note it's still working some really crappy fuel out of the system.

 

[deman]

Having something similar, will create my own thread if it's not similar enough. '83 K20, went for it's first actual drive in 19, almost 20 years the other day to make room in storage unit for the diesel so it could get some stuff done.

It shifts in and out of gears just fine, but 3rd it really wants to kick itself out (have to forcibly hold it into gear). Drove it  maaaybe 15-20 miles, each time it got into 3rd it seemed to stay a little better, but i didnt fiddle with it till about halfway home. Best approach seemed to be getting it into 3rd and getting on it to get it into 4th.

We are thinking it may just be a case of just use the thing and it'll sort itself out, but wondering what other things I can keep an eye out for or check to make sure I don't toast something. Thing drives like a dream, just the weird 3rd gear thing. Should also note it's still working some really crappy fuel out of the system.

Popping out of 3rd is a very common problems with 465's - I think Novak makes an upgrade 3rd gear with an oil grove in it but I haven't heard how well it actually works yet.

 

[deman]

Haven’t driven the truck in 10 years, but working on putting her back on the road. When it was parked, we had an issue with the trans shifter occasionally getting locked between gears when shifting. It sometimes seemed to take forever fiddling with it to get it moving and into gear again. Any idea what usually causes this? I should mention the truck is an ‘85 K30, and my dear dad SWEARS there was a recall for this issue in that year. But many other things he has been convinced of on this truck have also not proven out… and as for me, I’m a total newbie just learning.

Jordan - I'd definitely drain the gear oil out of it and see if you have any brass in the oil. A good oil change might help things out - and remember to try to only use Mineral Based gear oil (Napa sells it) as the GL-3 and GL-4 (modern) gear oils are not compatible with the brass synchro gears (the oil is slightly acidic and will eat away at the soft brass). Once you've changed the oil, I'd try to get it in 1st or 2nd and drive it at a steady speed for 10-20 min to slosh the new oil up onto the shift rails at the very top cover of the trans and see if shifting doesn't improve.

If you do find brass or can see any chunks of metal inside the drain plug (there's a huge magnet glued to the floor of the trans right inside of the drain plug opening) then it's unfortunately time for a rebuild. But they are very easy to rebuild.