Around 2000 rpm the engine does not feel as smooth as it should. Power and responsiveness are good.

The flywheel is an aluminum Scheifer unit. I am suspicious that I am dealing with a flywheel balance issue, or perhaps pressure plate/clutch balance. The input seal to the transmission is leaking oil, so I am prepared to do a teardown, replace clutch components, and have the flywheel balanced (assuming it’s in good enough condition to do so)—but I want to make sure I have covered the other reasonable possibilities before diving in.

Any suggestions for what else I should check?



1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

I am not an expert by any means but whatever you do, when you have it all apart, if there is some way to evaluate the input shaft I would try to do that.  I had to replace the tailshaft seal in my old '55 Fairlane..so I did.  Then a few months later I got a NASTY vibration that turned out to be the driveshaft so I got a new one and the same yoke wouldn't fit anymore.  Turned out the imbalance bent the tailshaft so I needed a different tranny...turned into a real rabbit hole situation.  

Short of taking the flywheel and pressure plate to a shop to have the balance checked, you might try cranking the engine up with the transmission removed.  Be sure the throw out bearing and arm are out of the way.  With the pressure plate still bolted to the flywheel, just determine if the same imbalance is present or not.  If the vibration is still present, then remove the pressure plate and clutch disk and run the engine again.  If the vibration diminishes and/or is gone, you’ll know it’s the pressure plate/clutch disk assembly is at fault.  If the vibration is still there, then it’s likely the flywheel.  Be sure to have the pressure plate also balanced to the flywheel when getting any of the pieces checked at a balance shop.

Lorena, Texas (South of Waco)

Ted, that is a great suggestion. If I end up removing the transmission I will certainly try it.

Today I had the car up on ramps and took another look at this vibration. I had noticed it around 1800-2000 rpm mostly while driving, but slowly increasing engine speed in neutral while stopped I found the vibration to be strongest at 1600. I tried disconnecting the vacuum advance to see if timing affected it and if so the effect was very minor.

Next I crawled under the car with it idling. I don’t have a flywheel dust cover, so I could easily observe the clutch assembly rotating. The flywheel itself appeared totally smooth with no runout or wobble evident at all at idle speed. The pressure plate housing was harder to be sure about because its shape is irregular. The element of the pressure plate that actually contacts the clutch disc did appear to be slightly non-concentric with the crank. I’m not sure if it was enough to produce my vibration.

The only other thing I can think of to check is running the engine with the belt removed to eliminate the fan, water pump, and alternator as potential causes—but I seriously doubt they are.

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

I WAS going to suggest checking the timing, as too much advance at that rpm could likely result in a subtle ‘rough running’ vibration (mine disappeared eventually as the points wore down). Lean fuel mixture might maybe also cause the same effect (?) 

6 VOLTS/POS. GRD. NW INDIANA

Four months later, I finally got around to removing the transmission.  So far, all I have tested is running the engine with the transmission removed.  The imbalance is still evident (unchanged, I believe).  I crawled up into the transmission tunnel with it running around 1600 rpm and didn't see anything irregular.  Crank, pilot bushing, pressure plate fingers, flywheel all looked perfectly concentric and smooth-spinning.
Hopefully tomorrow I'll be able to remove the clutch/pressure plate and see what effect that has.

One other thing I found is that my transmission doesn't have an input seal.  The one I bought is supposedly for a Warner T86, but I have the Ford transmission.  I guess the gasket must be the leak point up front.

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

Any chance at all for a simple miss fire. If your at a loss can’t hurt to check the plugs.

1955 312 T-Bird Warwick, NY

T86 transmissions do not have front input seals.  My '55 TBird has it's original top load T86 three speed O/D transmission. When I purchased it, the transmission had a leak in the front which I concluded was the front input seal.  After removing it, I discovered these transmissions do not have a seal on the input shaft.  I called Van Pelt and he told me BW used a spiral grove cut in the input to channel fluid back into the case. After further inspection, I discovered a plug missing in the front of the transmission. I installed the correct plug, replaced the shifter arm seals and have no further leaks.

A lot of people including myself found out the hard way that those transmissions have no input shaft seal after parking their cars nose down on a steep hill and oiling up the clutch disc. Something to remember!



"FREE SAMPLE"

From the diagrams I’ve looked at the Ford transmission has an oil shield behind the front main bearing to defect most of the transmission oil into the case. Other transmissions don’t have them I’ve had apart. I’ve never had a standard transmission apart with a front seal. There has always been a drain back cast into the Throwout bearing snout and an opening in the front of the case. The gaskets have always been thin. 

56 Vic, B'Ville 200 MPH Club Member, So Cal.