sm465 jumps out of 3rd sometimes, is this a worn shift fork, or a synchro? i've heard this is common on them after awhile, but haven't heard what the fix was.

On the 465 in my 76 Blazer it was the syncro.There are acouple different Syncro repair kits out there.The one I got had dogs like a lenco drag tranny or like a motorcyle tranny.I think it must be pretty common because when I went to get an overhaul kit the first thing they sked me was about third gear and did I want the syncro kit for it.I think you could probably ask eny tranny shop that does 465`s about itI think it was around $90.It`s been about 6 years ago so If I rembered right that`s what it cost. JB

it is the shift fork, but now that it is kicking out it has probably messed the shift teeth on the gear
so replace the shift forks and inspect the teeth on third gear to see if they are wrecked from partial engagement

the syncro is a brass ring that does not hold anything in gear
if your truck is a bit crunchy going into gear that would be a worn syncro

Call Tourist Auto is Salt Lake City.. they have done all the UPS SM 465 repairs in this area. There was a GM design problem and Tourist came up with a solution. Instead of a snap ring /circle clip on the countershaft ( which wears thin) .. they made a sleeve. I have pictures somehere..

Cost is $7.50 IIRC... might be worth a call

Tourist Auto... ask for Greg 1 801 364 5743
Nice guys and will take the time to talk


berg

i'll have to check them out, it shifts into gear fine. i will probably try to swap the top with another 465 i got that i know doesn't jump out first.

I have yet to see a countershaft gear come loose and have yet to have anyone show evidense of it happening
how can a snap ring that locates a gear on splines "wear thin"? nothing is moving.
even if it did come loose it would then have to contact the shift collar, which should leave an obvious witness mark as they are counter rotating

when you have the top off to swap inspect the shift forks to see how much plastic is left on them
also look at the condition of the engagement teeth on both the gear (easy to see) and the shift collar (hard to see)
I am pretty sure one of them will have damage from partial engagement
once you peel that bit of contact away it is done
but the root cause is not getting it fully in gear due to the shift fork wear IMO

They don't neccessarily wear thin, but they do break. It might be from impact. I have a 465 i need to rebuild because it has slop in the gears on the countershaft due to the broken snap ring. They do make snap ring eliminator kits.

I have a 465 i need to rebuild because it has slop in the gears on the countershaft due to the broken snap ring.

pictures please

gimme a day or two..........sorry. no digital offhand.....

I've read about replacing the circlips with a solid collar too. That's supposed to be the fix and yes, my 465 jumps out of third too. It only does it on deceleration when it's mostly coasting. I was going to fix it if I have a reason to take the thing apart. It's not a big deal most of the time.

these transmissions had a thirty year production run
IMO if there was a design flaw as simple as a snap ring that was too weak it would have been fixed by the factory

these transmissions had a thirty year production run
IMO if there was a design flaw as simple as a snap ring that was too weak it would have been fixed by the factory

The bevel cut angle of the gears pushes toward the clip...

MJ agree to disagree.
It fixed my 3rd gear from popping out on deceleration on a 77 Blazer and later on a sm465 going in a land cruiser. Clip was laying in the bottom of the trans when I got it.
MJ... no one is trying to convince you.... the information is there for and for a solid fix that takes the place of a clip on the counter gear... I'd do it everytime just for peace of mind.

*edit* from my info..
"There are two snaprings, they retain the input countergear and the third gear countergear. They wear and allow the two to walk, which causes the transmission to jump out of gear. These are replaced with a spacer bushing (p/n 14020811 from Anaheim Gear, essentially tubing as far as I can tell) like this.

http://www.anaheimgear.com/update.htm

I can forward more info/files if you want to beat a dead dog some more.!

these transmissions had a thirty year production run
IMO if there was a design flaw as simple as a snap ring that was too weak it would have been fixed by the factory

You sound like my Mother.

I have seen all the voodoo fixes
just never proof they fix anything
you show me how it knocks the shift collar off of third gear
I have a 465 disassembled on the bench right now so I can eyeball any part you care to claim hits the shift collar
if you can show me a shift collar with witness marks from third counter gear hitting it out of gear I will believe you
what i have seen is the worn shift forks on every 465. 3 at $65 each to replace, they do not get fixed during most rebuilds.

listen to your mother

Shit, no way. :D

these transmissions had a thirty year production run
IMO if there was a design flaw as simple as a snap ring that was too weak it would have been fixed by the factory

Unless they knew of this flaw and were making so much money on fixing what has been breaking that it wasn't in their best interest to fix it. Kinda like the cure for cancer.

Ok who fixed their transmission from jumping out of gear,and what was the actual fix.Mine is doing the same thing and would like to fix,but don't want to buy parts that I don't need.Thanks

Berg's going in the right direction. The part # cited is a GM # and they (GM) came up with the 3rd gear cs/sring fix. No smoke and mirrors here. Yes the cs 3rd gear will come in contact with the synchro collar.Worn shift forks are a symptom of something else--worn synchro hub teeth, 3rd gear clutching teeth, lazy driver hanging on the stick. I'm sure there are others that cause the synchro collar to push against the fork to cause the wear. Incomplete shifts caused by a loose or worn shift finger on the stick can also cause the same problem. You can detect the 3rd gear sring problem by just pulling the PTO cover and you are looking right at it and most of the 3/4 synchro. Knocks the socks out of pulling the whole trans.

these transmissions had a thirty year production run
IMO if there was a design flaw as simple as a snap ring that was too weak it would have been fixed by the factory

It was the factory that came out with the sleeve and new snap ring for the end of the shaft---about 15 years ago, or better. I've been installing them for at least that long.

Does GM still make this sleeve and do you know the part number that I will need to fix this problem.gaskets,bearings,seals, etc.What all is involved in doing this.Thanks

I want to see pics of the gears and shift clutches when you pull it apart.
I will bet the shift forks are the culprit.

Which is the easiest and cheapest to try?the sleeve or shift forks?

Just pull the PTO plate and you will know which way to go. No point in adding sleeve if s/ring is not wandering around and if you are running a fullsize you should be able to get to the cover from the top.

sleeve requires full disassembly including a press to remove the gears from the countershaft.
shift forks you have to pull the top cover off, which can be trickier then it sounds. shifter has to be half way into reverse to remove or install.