Weird Surging

Posted by Redhexagon On 2024/2/6 18:54:21

My 1955 Patrician with a 3.54:1 axle surges while under heavy throttle at speeds between 35 and 80 mph. It seems to usually occur while in high gear converter drive, but I have felt surging while in direct drive as well. I have never felt it surge in low gear. It's a slow surging. You don't hear it, you feel it. The car just sort of slowly lurches forward and back.

Climbing a long, steep grade at 65 MPH and roughly 3/4 throttle makes it surge. I do not know if the converter unlocks for that. If it does, I don't hear or feel it. I'm pretty sure it just grinds up in it in direct.

Rolling heavy into the throttle at 50 mph unlocks the converter and it surges the whole way on up to 80 MPH whether you keep the throttle steady or go ahead and floor it after you reach 60 MPH (flooring below 55 mph downshifts to low...don't do that). Again, I cannot tell if or when the converter locks at those speeds.

The engine has good power even while surging. It will continue pulling hard. It's not like the surging that I have experienced in other cars due to ignition or carburetion problems where they fell flat on their face if you opened the throttle more. I do not hear any misfiring. The engine feels and sounds strong, but you can feel the car surging.

Moreover, it does this regardless of the outdoor temperature. It is the same on a 20-degree day as on a 90-degreee day. It's not a form of vapor lock.

Sometimes when it's surging you can let off the throttle partially then roll back in and it's better.

I have:

1. Replaced the fuel pump.
2. Replaced the fuel line between the pump and carburetor.
3. Replaced the fuel filter.
4. Blown out the fuel line between the tank and fuel pump to make sure it was not leaking or restricted.
5. Checked the rubber fuel hose at the pump.
6. Rebuilt the carburetor (Rochester 4GC).
7. Rebuilt the engine ignition system. Coil, points, condenser, wires, plugs, all of it.
8. Driven without the gas cap in case it was sucking a vacuum.
9. Changed the transmission fluid (Type F), adjusted the bands, adjusted the shifter linkage, and adjusted the throttle linkage.

Not one of those things has altered the surging even the slightest bit.


I don't know. I'm starting to think it might be the transmission slipping, but I don't get any of the "groan" that people describe when their lockup clutch is going out. The lockups that I hear at lower speeds are always crisp and clean, but I cannot hear or feel what is going on with the clutch at higher speeds.

I'm at the "get over it and live with it" stage.