Vibration Diagnosis.

Hello!

I have a driveline vibration in my RR, I was wondering if you guys might have ideas.

The car is a 1974 Road Runner, 318 4-speed.

My dad took the car, brought it back with a nasty vibration. the vibration is not speed dependent, seems to be engine RPM and load dependent.

First thought was clutch, so the flywheel was resurfaced and the clutch replaced with a diaphragm style one from advance auto--not the best quality, gonna swap that. This did not fix it, the car still vibrates like crazy. The vibration is most noticeable in the shifter, and in the clutch pedal.

Any tips for diagnosis would be appreciated. I have had the car in storage for 2 years and am missing it. I just pulled her out of storage this weekend.

bad driveshaft or bent at yoke . check carefully

I will check that.

To be more clear on the vibration, it happens in every gear, regardless of speed. The higher the RPM's go, the worse the shaking is. It's incredibly dependant on engine speed. as you go through the gears the vibration picks up before each shift.

Check the bushing in the flywheel, make sure its not hogged out.

What they said. Check your U joints. If you think it's the driveshaft, a cheap way to check is to use a large hose clamp. Tighten it around the shaft and take it for a spin. See if it's better or worse. Move it around the shaft so the worm is in a different position (3, 6, 9:00) Also you might want to check your timing marks to see if the balancer has slipped

I will check those things, thanks!

If the input shaft on the trans shows visible wear near the pilot bushing, could that be the cause?

When the new clutch went in the pilot bushing was replaced. The old pilot bushing was almost worn through on one side, it was paper thin. The input shaft on the trans showed visible wear on the part that went into the the bushing.

Sounds like the bellhousing isn't centered. What you need to do is check it with a dial indicator (which necessitates taking it all apart) and see how far off it is. There are offset dowels that go in the block in place of the straight ones. I probably have several input shafts if you need a replacement

The trans is coming out, I will probably pull the engine at the same time.

I want to tackle a transmission rebuild, and while it is out I was planning on checking the centering of the bellhousing.

I will need an input shaft, I didn't like the amount of wear on mine at all.

Not that I want to talk you out of maybe buying an input shaft, but IF the wear is confined to the very front of the shaft (up where the bushing is) then there is another way that would allow you to use the same shaft. There is a roller needle bearing that fits in to the centering ring for the torque converter. And it's a factory piece

Along with the obvious checks mentioned earlier, and as long as you are checking drive line stuff, check the motor / tranny mounts and drive line angle. Throw about 1/4" of shim under the tranny mount to raise the tail shaft and see if it makes a difference. The angle of the output shaft depends on three points to be correct and you shouldn't have any deviation in the horizontal plane.

By the way, I knew a guy that never ran a pilot bearing and there was no seat of the pants detectable vibration on his car. Hardly a recommended practice, but it may not cause enough mass displacement with the clutch engaged to cause a severe vibration. It will, however, be enough to cause rapid wear on the input shaft bearing and other tranny components over time.

Pulled the engine and tore it down, this is what we found (knowing full well it wasn't gonna be pretty)

Two cam lobes wiped clean off on two different cylinders. Not "hey ,these cam lobes look kind of nasty." wiped, but "Where'd my cam lobe go!" wiped.

New engine goes in today. I picked up a dial indicator, I'm gonna check to make sure the bellhousing is centered on the new block, but I'm thinking the cam has it. The thrust face on the center main bearing was missing some chunks as well. We're just going to overlook the bits of cam embedded in the mains, along with the complete lack of bearing surface.

We'll find out today. New engine is going in.

The old engine ran like utter crap, but still better than one might expect considering what was going on inside of it. It had been running badly for a while, I'm thinking the vibration manifested itself once the valves on two cylinders no longer opened at all, essentially turning them to dead weight. The new engine going in is another 318, the more ambitious plans are waiting until I am at school and have access to machining equipment. We got a 302 headed roller cam 318 to play with for now, but before spending any money inside this one we are just gonna toss it in (with my 4v carb/intake) to verify the vibration was confined to the engine. Pretty much all you will see me do to this one is shave the heads down to bump the comp ratio up, and throw some cam at it. I already have a weiand stealth and eddy carb to throw at it.