Ok, i'll try not to make this too longwinded. Last fall I swapped my th350 to a sm465. I got the donar out of a 1978 4x4 pickup. The clutch, flywheel and pressure plate were all very new/resurfaced. Right away, there was a slight vibration in the pedal, and I thought it might just be a little loose, so I tightened up the linkage, but the vibration was still there. BTW, it is a mechanical clutch, not hydraulic. I have put about 2500 miles on her, and now when I let the pedal out the entire truck shutters, no matter how I adjust it, and just driving down the road in any gear the pedal vibrates so bad I can't even hear the flowmasters. It also shutters really bad when I take off in 2nd gear. In low, it's ok though. I called a couple tranny guys and they say maybe I simply have the wrong flywheel on it, and I have to find out if the motor is internally or externally balanced in order to get the right flywheel. SO...how do I find this out, and does this sound like it might be the problem?

what motor? in donor and your rig

It's a 350 motor...pulled the numbers and found out it's out of a 75

After re-reading the previous response, I thought I'd better clarify. I have a 350 in my truck, came out of a 1975. And the donar was a 350 also, but I never pulled the ID numbers off of it to see if it was original to the 1978 donar. I wanted to add also that when I look at the clutch fork while running, it jumps up and down pretty good.

Sounds like you could have a shot throwout bearing. If its adjusted to tight, the throwout bearing will always be contacting the springs on the pressure plate and wear out prematurely. Also could just be a POS throwout bearing.

Also, you get what you pay for, and I had to replace a Checkers $125 dollar reman unit 4 months after I installed it because the pressure plate warped.

Centerforce, Ram and others are good clutch manufacturers.

Another problem you could be experiencing, and I have this too, is that the bearing retainer (the sleeve that the throw out bearing rides on that surrounds the tranmission input shaft) is worn out of round from years of use.

It causes the throwout bearing to not engage the pressure plate head on, but rather at an angle, making the pressure plate engage all crooked.
That part costs $22.50 new from Drivetrain Specialists in Las Vegas.

Could possibly be a warped flywheel. My old Z28 camaro had a really bad vibration when I bought it, especially when engaging the clutch, and when I pulled the clutch the flywheel could be rocked back and forth on the concrete floor. Even though it was just resurfaced (supposedly) It might still be warped enough to cause a nasty vibration.

I'm going to yard it all out soon, and I'll check all parts for warping/breakage. I just didn't know if I should be looking for a different kind of flywheel due to balancing issues.

you should be clear on all that

did you bother to put a pilot bearing in it?

is the bell housing tight to the block?
is the tranny tight to the bell?
is it a rebuilt/bigger piston/new crank motor?

the input snout may have busted, i have seen it on older jeep stuff not a 465.


a 350 fly wheel is a 350 fly for about 30years, so your donor 350 and the 84 350 wont make a difference. balance would only become an issue if you got i the fly wheel from a 400 or a newer 350.

did you bother to put a pilot bearing in it?

is the bell housing tight to the block?
is the tranny tight to the bell?
is it a rebuilt/bigger piston/new crank motor?

the input snout may have busted, i have seen it on older jeep stuff not a 465.


a 350 fly wheel is a 350 fly for about 30years, so your donor 350 and the 84 350 wont make a difference. balance would only become an issue if you got i the fly wheel from a 400 or a newer 350.

Yep, new pilot BUSHING, new throwout bearing. Tranny is tight, and it's just a stock bottom end, no performance mods internally. Hopefully it's something simple like a worn out fork. And I HOPE it's not a busted shaft!!

Wondering if you figured it out yet. i'm having the same problem. bought a 350, sm465, and 205 already put together and dropped it in the k5. i think my problem might be a bent clutch disc. if you dont support the tranny well enough while mating it to the motor it can bend the clutch disc......atleast thats what happened to my last vw. anyone have this happen with an sm465?

A set of busted motor mounts can also make the truck shake due to the motor not being bolted down tight when engaging the clutch.

I'm not real clear if it shutters only while driving? or also while parked?

if only shakes while driving could be U joints (or even brake drum/rotor/wheels).

I had a 4.3/700R4 do that once, turned out to be ceized u joint.

First I would double check the clutch adjustment, should be 1/2" of free play before engagement. Reading over your post again it makes me want to ask do you even have a return spring on your linkage?

If the above pisses you off check your tranny and motor mounts, lot easier to replace them than to pull the transmission/transfer case out.