sm465 bomb, update: tranny out, need your help sm465 guru's..

[stevos67k20]

hey guys i just gernaded my sm465 and its really bugging me, heres why:

i was accelerating in third (or second on the shift knob) gear very hard and it banged real hard and my engine spun like crazy . its a low rpm 454 so that wasn't so hot.

so i shifted in to 4th (or third on the knob) and kept driving. i parked. it was fine. and i drove home a few hours later. it was fine all the way home though all gears. note: i did not use the tranny to slow down, just the brakes.

right in front of my house i was down shifting from 4th (3rd on knob) to 3rd (2nd...) gear to slow down. i drive my truck alot and am very familiar with it and i knew it was fully in gear, anyways it rattled/grinded like crazy, i couldn't let the clutch out fully.

so i go "crap" and switch to 2nd (1st on knob) and it rattled/grinded like crazy also. ?????? how could this be? ive never had a problem with 2nd gear. its like 3rd gear took a crap and took 2nd gear with it, is this possible? i didnt drive more that 6 miles after the 3rd gear showdown.

a few hours after i parked it i went out to see if it fixed itself while it was parked. i put it in 1st gear, it pulled forward, 2nd gear:rattled/grinded, 3rd gear:rattled grinded, 4th gear: pulled forward.

today i opened the top cover of an sm465 and ive been doing some research on it, enough to know that the 3-4 and the 1-2 gears have two different shift forks. any ideas on what could of happened? no i havent looked at it yet. if 3rd gear got screwed and 2nd gear did too, then could it be a deeper problem than worn shift forks, weak snap rings, or bad synchros??

i have a random question about synchros, in the sm465 i pulled out, it had square syncros but had beveled ends on the shift coupler..?(slidy thing) side. is this the "diamond type" synchro? it looks like they were cut that way, does this mean the trans mission was rebuilt?

i know this thread is long but transmission problems require a good description and information that might help. thanks chevy bros

 

[u2slow]

If you have the top off and can't see any visible carnage, you probably blew up the clutch.

I was so skeptical on mine that I slid the collars to pick a gear, and then ran the engine with the top off.

 

[stevos67k20]

UPDATE: More info

hey everyone, i have a few questions regarding my sm465 that got jacked up. obviously i searched and could find the answer i was looking for.

so i pulled the trans out after pulling the top cover and notinving third gear slides on the main shaft and the shift forks were showing shiny metal. i also noticed fine metal power kind of shavings in between the third and fourth gear.

so thats why third gear isnt engaging, cuz its sliding on the main shaft. second gear is also sliding on the main shaft. i under stand that once yo9u take the adapter housing off the mainshaft has about an 1/8 inch of play i the whole case. i am not confusing this with gears sliding on the main shaft.

the output splines look suprisingly good on this main shaft. can i still use this main shaft for a rebuild?

i also have a question about the "UPDATED 3RD GEAR AND 3-4 SLIDER" is this what fixes the 3rd gear pop out? i have seen very little info on this during my research. why does this help? i also have seen the spacer used between the 3 and 4 gears on the countershaft, i think i am gonna get those. any ways thanks in advance, if you have any questions let me know.

 

[5280k5]

The updated 3rd gear has the teeth cut at a different angle making it more difficult to disengage(by itself), doesn't affect engagement though. Third gear itself is held in place on the mainshaft by a snapring that gets weak or can even break and will allow the gear to move around which is typically the cause of the infamous 3rd gear jumpout. The spacer is installed in between the gears and holds them in place under load. This spacer is not a guaranteed fix as I learned when I tore my tranny apart to rebuild and found it had the spacer already but still jumped out of 3rd gear. Between the spacer, new designed 3rd gear & synchro and replacing the springs for the shift rail detents it finally was fixed. I purchased a master rebuild kit from a local tranny parts place and it had everything I needed and was only about $200 bucks.

Good Luck!

 

[tattedmike]

i was reading an old post because i am dealing with my 3rd gear jumping out but i cant see to find the updated 3rd gear, the spacer, or the diamond cut synchro. i was just hoping that maybe you could guide me in the right direction as to how to find these parts. thank you in advance if you are able to help me locate them!

 

[5280k5]

i was reading an old post because i am dealing with my 3rd gear jumping out but i cant see to find the updated 3rd gear, the spacer, or the diamond cut synchro. i was just hoping that maybe you could guide me in the right direction as to how to find these parts. thank you in advance if you are able to help me locate them!

The place I used here locally in Denver was A-1 Transmissions, 303-623-1401. I know there is also a place out in California, Anaheim Gear that sells this stuff. Hope this helps out.