Friend of mine has a 26 coupe. When driving it, it makes a thunk-kathunk sound when slowing down or when braking. It's really noticeable when using the brake pedal. Sounds like coming from the transmission, but I cannot tell. Nothing else on the car seems amiss except the band springs are not seating against the ears properly. (They might be worn).
He also said it didn't do this when he got it, but has just recently started making these noises. I drove it, and it sounds like what I said plus a sound like grinding coffee.
The grinding sound is only when the brakes are applied or when the reverse is engaged.
It won't hurt to check the rear end oil. See if it is grey from pulverized babbit? Could be remains of the thrust washers grinding in the ring and pinion.
The sound travels.
Yes. We're going to check it out next time I meet up with him. He's not currently driving the car.
I was thinking the universal was at fault to0 but it doesn't make that noise when pulling away, only when slowing down.
Ninety percent probability a thrust washer has failed. Ten percent split between pinion bearing, U-joint, triple gear pin in transmission, other unlikely transmission or rear end bearings or gears.
If it is not known for certain that brass/bronze thrust washers were used inside? Take the rear end apart and check that first. If it is absolutely certain that two brass/bronze thrust washers were properly installed (how many times have I heard that and it turned out to be wrong?), then further diagnostics may be necessary. Even if? Pulling the rear end first is still usually the easiest way.
As discussed on another recent thread. Please be careful with stands and blocking! I don't want to lose any friends to a falling car. And I am not there to throw a spare tire underneath.
Jack up the rear axle...both wheels off of the ground. Push and pull on a rear wheel while someone watches the other side. If the "innerds" are moving back and forth (side to side of the car) about 1/4", it's probably the thus washer. Also, if the passenger side brake drum shows signs of serious scraping, that is another sign of a bad thrust washer.
I had similar symptoms when a tooth broke off the pinion gear. Barely an audible click when under load, but a real growl on trailing throttle/braking.
Allan from down under.