SM 465 stuck in 4th

[Adambomb]

Hey I have a 1970 gmc 4x4. I was driving to the city today and went to downshift at a light, and it wouldn't come out of 4th.. Its just stuck in there, the clutch is working still, but I reefed on the shifter and it just wont come out.. I still drove it home but, it was hell if I had to stop at a light and start in 4th.. oh well I got it home without a tow truck and luckily there was only 2 lights!!

I'm pretty sure its a sm 465 tranny.. I broke the roll pins for the shifter a few months ago and couldn't find the pieces of them. I ran a magnet inside the hole but came up with nothing, so I'm sure the pieces are in there still somewhere..

Any suggestions? Would a piece of roll pin be blocking it from shifting?
Also if I have to remove the tranny, do you think its worth getting a more modern one with better gearing? The engine block I run is out of a 2000 Camaro already.

Thanks for any help or suggestions!!
Adam

[jjzepplin]

What roll pins do you speak of? You could try pushing the truck forward and reverse a couple times. Might try to jack up the rear end and put on jackstands, Then crank the engine in reverse rotation to try to dislodge the offender. Did you drain the fluid in the tranny after the breakage of said pins? I would glue a magnet to a copper wire and put a bend in it to fish around in the case from the drain plug to remove any pieces of pin.

[Adambomb]

hey thanks for the response. I really appreciate it.

The pins I mentioned are the ones on each side that hold the shifter from spinning around. One day on the way to work the shifter just started spinning, but that was over 3 months ago.. I made new ones with some stainless bolts ground down a bit to fit the slots in the shift ball.

I fished around pretty good with my magnet. Its one of those flexible ones so I got it right down to the pan I think.. I just figured any pieces where just sitting in the pan below.
There was no pinging or grinding at all. I did try to roll backwards with the clutch in and shift out, but she's really stuck.. Maybe I'll try to jack it up like you said..

I took a photo, you can see the 3rd/4th rail is forward, I tried prying it but it won't budge..

thanks again!

[jjzepplin]

Did you try to move the other rail? If they are both not centered "Neutral" One can get stuck.

[Adambomb]

Ya thanks tried to move the other rail but it doesn't budge.. the 3rd/4th rail wiggles like a 1/8th of an inch but that's it..

I guess tomorrow I will try to jack up the back and spin it in reverse, if that doesn't work I guess I'll peel the carpet back and try to remove the top piece of tranny..

Thanks again eh!!

[Adambomb]

Well I got it to pop out of gear finally. I drained the fluid, opened up the 2 side inspection plates an ran a magnet around in there and collected some chunks of shtuff..
Then I put the rear end on jack stands. my friend turned the wheels in reverse while I pushed on the shifter. POP! back to neutral..

I then decided pull the top shifter cover off to inspect the gears.. Everything looks fine in there.

Cool to see how this tranny works, I will probably rebuild it one day soon.

Thanks
for your help!

[jjzepplin]

Glad to see you got it working. Those trannies rarely need rebuilding and don't usually have any issues. Tough trans. You may want to get a magnetic drain plug. My Saginaw has a magnet inside it that I would not have seen if I did not rebuild it.

[kwmech]

A lot of them had magnets in them from the factory. If the covers are still off you may find it towards the front if you root around with your hand.

[Adambomb]

well I got the top plate back on and filled it up with some new 90wt gear oil..

It felt good to shift into all gears turned with the truck turned off,
but when I fired it up, not so much...

Even when the shift rails are all lined up and its in neutral with no gears selected, I let out the clutch and its definitely in reverse.. It starts to creep backwards as I let out the clutch in neutral.. None of the forward gears make it go forward..

I am thinking something isn't lined up inside there? Any ideas? I am beyond frustrated..

I guess its time to take it apart again, GRRR.. glad I left the floor hatch off..

[Adambomb]

Got it.. I guess theres just enough room for the reverse shift fork behind where its supposed to go, pushing the gear all the way forward.
That reverse gear is tricky to keep in place while putting the top cover on..

Anyways, I keep posting my progress, or lack of, because I've learned alot from these forums.. Hopefully someone can learn from my mistakes as well..

[OrrieG]

When I was in college I lent my truck to a guy and forgot to tell him to always keep pressure down when shifting, the pins were good but the housing that hooks to them sheared off and I had little time and money to fix it. About an hour later I get a call in a blind panic, he had shifted into 4th and pulled the handle out of the trans. This was long before cell phones, he was calling from a phone booth, I told him to just shove it back in pointed to where 4th would be and it would be fine. Took him a couple of tries but made it back to my place. No one ever asked to borrow it again after that. I eventually just ran some wire of strapping over the top and around the trans and drove it for another 5 years until converting to the current drive train.