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What the hell did I just do

A

Aquafbody

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Bennett, Colorado
So first off we are talking about an 81 K5 with a 454 and sm465. I was towing my trailer and a couple of atv's last weekend and I kept getting "or what I thought to be" clutch chatter. No biggie right? Well as I was getting onto the highway I opened up all four barrels and the Blazer started surging, as I pulled off the highway I put it in neutral but when I tried to put it back in gear it i heard a grinding noise and my back wheels locked up. After a while I decided to try to move it out of traffic. If I start the truck in gear with the clutch in the engine lugs but when I release the clutch it WILL move in all gears but I can's shift gears. WTF?!?!?:dunno:
 
Sounds like pretty much what happened when I broke my sm465. I couldn't shift it but it would work move while in gear. I never did find out exactly what broke though since I just replaced it instead of tearing it apart.
 
Could be the pressure plate failed and will not disengage,or maybe the disc chucked the linings and they are jammed in the pressure plate..

It could be the transmission,but SM465's dont usually break too easily,or without warning...maybe a shift fork broke and went in the gears?..
I'd say the clutch is more likely to fail..
 
diesel4me said:
Could be the pressure plate failed and will not disengage,or maybe the disc chucked the linings and they are jammed in the pressure plate..

It could be the transmission,but SM465's dont usually break too easily,or without warning...maybe a shift fork broke and went in the gears?..
I'd say the clutch is more likely to fail..
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That makes pretty good sense, I'm not hearing any funny noises so I'm fairly convinced it's not the tranny like you said sm465 come in one ton's, however I was towing and under full throttle with a big block.
 
I think the notion that sm465s never break internally is a little bit exaggerated. I broke mine in the flatbed, the replacement I bought had a bad output shaft bearing, and the local kid I know that runs one in everything hes ever had pretty much feels the same way. General bulletproofness is pretty overrated.

Theyre strong dont get me wrong but not unbreakable.
 
In any case your pulling the trans. So let us know when you find out. Almost sounds like what happened to me when I broke one of the springs
 
Stomis said:
I think the notion that sm465s never break internally is a little bit exaggerated. I broke mine in the flatbed, the replacement I bought had a bad output shaft bearing, and the local kid I know that runs one in everything hes ever had pretty much feels the same way. General bulletproofness is pretty overrated.

Theyre strong dont get me wrong but not unbreakable.
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I agree that they can fail,anything can, if whipped ,or driven far enough..
I've seen a few that wouldn't stay in 3rd gear or pop out under a load,the infamous snap ring failure,and I had 2 of the 10 spline versions that ate the splines off the output shaft and that coupler that joins it to the transfer case..

A lot of these transmissions get wrecked when someone tried speed shifting them,or downshifting into the non-synchro granny low while moving,and grind off some teeth,which gets sent thru all the gears and bearings..also many get run too low on lube too..

The SM465 is probably marginal for a C-60 sized truck,but many had them and they held up pretty good...I'd say they were overkill for a 1/2 or 3/4 ton truck though,and should hold up well for at least 100,000 miles if not abused or neglected..
 
I fragged a clutch disc towing a 5200 lb trailer with my old K5. A bunch of those wave springs let loose and the clutch just felt weird, plus I had a new noise to worry me.
 
update.
I haven't been able to pull the tranny as the Blazer is sitting at my parents house. I am able to move it AND shift gears, It is still trying to bog down and die and when driving I hear a whirring sound. At this point I'm starting to think the throw-out bearing is toasted. What do you guys think?
 
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The throwout bearing only spins with the clutch pedal depressed,(provided the clutch is adjusted right so it has 1" of free play at the pedal)-so if your hearing noises with it out while driving ,it's most likely not the throwout bearing..

If the pilot busing in the crank decided to seize to the transmission input shaft it will make it hard to shift ,if not impossible,and make scary noises.but I've seen that only a couple of times in my life (and probably 100 blown clutches!)--the type with needle bearings seem to fail easier and more often,but most older Chevy's used a solid bronze bushing that rarely gives any trouble..(other than trying to remove it when your doing a complete clutch overhaul).
 
diesel4me said:
If the pilot busing in the crank decided to seize to the transmission input shaft it will make it hard to shift ,if not impossible,and make scary noises.
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Update, I figured it didn't do me any good to speculate and I was just going to drag it home from my parents. So I started it up and adjusted the idle to keep it from dying and limp it onto a trailer. Well.. it made some odd noises but otherwise drove ok. I got it home and started moving it to the garage and noticed the noise was gone. Huh so I drove it around my little town and hell it's fine no noises no shakes it shifts fine its normal again. Could a pilot bearing going out cause this?:dunno:
 
It is pretty rare for a pilot bushing to give trouble,but it is possible for the transmission input shaft to bind in the bushing and be spun ,so shifting will be difficult due to the tranny still turning,even with the clutch depressed..once you do get it in gear,you may hear squealing or grinding noises from the bushing dragging,still trying to spin the input shaft..

Have you even checked the 4 transmission to bell housing bolts?..if they are loose it'll sag,and let the input shaft drag on the pilot bushing and cause these symptoms..
Wont hurt to make sure its full of gear oil too..
 
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