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Clutch Pedal "Thump" Sound

G

greg mgm

1/2 ton status
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Apr 6, 2005
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Location
Pine Cove (near Idyllwild) CA
My 78 manual trans GMC truck's clutch pedal makes a thump sound about halfway down. It doesn't affect clutch engagement, but I'm concerned something's about to let loose. I had my wife press the pedal while I was underneath, and I heard the "thump" from inside the bellhousing... unfortunately.

I'm no trans expert, but I know the clutch lever pivots and pushes on the throwout bearing, but if there's slop in the arm what's getting out of alignment? What's going to fall off if I don't repair this right away?
 
I dont think you are going to have anything just fall out of alignment. That fork is actually engaged on the throwout bearing and that bearing rides on the input shaft. A thump halfway down sounds to me like your throwout bearing may be wearing out and that thump is the noise caused from when the bearing contacts the pressure plate. Changing out one of those bearings can be a pain in the butt depending on what tools and skills you have.
 
It's hard to describe on a forum, but the thump is like the linkage or arm is out of alignment, then thumps back into alignment. Or something catches the arm halfway through the travel. When I moved the arm from underneath the truck, there was a lot of play in it....But not being a mechanic, I don't know how much play there should be.
We'll find out later today since I just dropped it off at a shop.
 
454k30 said:
I dont think you are going to have anything just fall out of alignment. That fork is actually engaged on the throwout bearing and that bearing rides on the input shaft. A thump halfway down sounds to me like your throwout bearing may be wearing out and that thump is the noise caused from when the bearing contacts the pressure plate. Changing out one of those bearings can be a pain in the butt depending on what tools and skills you have.
Click to expand...

Whats so hard about changing a throwout bearing besides taking the heavy tranny/tcase down?
 
thats what makes it a pain in the butt. the 205 weighs over 120lbs, and the sm465 is around the 190 range. I know it sounds simple but taking this thing down involves seperating the t-case and getting that out. You can pull the 4 large bolts out of the transmission to seperate it from the bell housing rather than pulling the transmission tunnel cover, but you still have to deal with safely getting that 190lbs thing out of there. Putting it back in can be a pain as well as you have to align the bearing without knocking it off the shift fork, get the shaft through the splines and finally into the pilot bearing. Its a pain and trying to do this job without the proper tools is foolhardy at best, as well as a great way to get hurt.
 
exactly my point. I've seen a few others try wal-mart floor jacks with scaring results.
 
next time we do one, i think we'll pull the trans cover in the floor and use a engine hoist from inside the cab.
 
YZEATER said:
next time we do one, i think we'll pull the trans cover in the floor and use a engine hoist from inside the cab.
Click to expand...
this is the best way to do it. if you hang it from the trans/tcase adapter (bellhousing removed), this set up hangs almost perfectly level, making install easy too.
 
Like 454K30 said, "depending on what tools and skills you have" ...I have plenty of skills, but no SAFE place to do the work. No garage, so work is done outside in the dirt (No level concrete area) Most of the time that's not a problem, but if it involves jacks, stands, or hoists, I'd rather send the work to the local shop. I REALLY need a garage!!
 
if you're replying to my comment, you probably could do it without removing the tunnel by going through the t-case shifter hole, but i'd recommend removing the tunnel. i believe all blazers had removable tunnels, but the other trucks i think may not be removable for all years. don't know the split on that one tho.
 
Yeah there's no rivets or bolts or anything on my k10. I'm gonna have to check out the tcase shifter idea. I do have access to an engine hoist!
 
i assume that this is with respect to the 87 mentioned in your sig? i feel like i heard somewhere that the split re: the removable tunnel hump was a mid/late 80's thing. my '83 blazer had a removable tunnel. i've seen a 71 chev pick up with a removable tunnel too - but again, i think the split may have been specific to the pick ups. not sure on that tho. :confused:
 
Yeah I've had that floor stripped and herculined it myself theres no removability to my tunnel... too bad too would make clutch jobs much easier.
 
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