Herding Goats

Thanks for the link @Sam Buchanan. I was struggling with the search and seemed to be only pulling up posts about rear seal leaks. I read through your thread and that does seem like the place to start. Thanks everyone for your thoughts on the gasket's mystery purpose. It does not seem like that would be the cause of the leak, however we will likely put one in. Nothing to do now but pull the transmission out and have a look! Thanks for background info, will report back.

Thanks everyone for the additional ideas and resources. I love these old tech papers @Scott in ct! @MBF I think this may be the same vehicle we're talking about. A friend of a friend! I'll send you a message.

Hi all, my friend's 1939 Chrysler Royal has a leak in the front of the 3-speed manual transmission. When we jacked up the back of the car to work on the rear axle grease seals, oil dripped from the mating surface of the bell housing and the front face of the transmission. With the car back on level ground the leak has stopped but we'd like to get to the bottom of it. The transmission was recently rebuilt and installed without the gasket between the bell housing and transmission. Would this be the obvious culprit of such a leak? Anything else to look for? Curious if anyone has experienced a similar problem or what that missing gasket is supposed to seal. Thanks for any ideas!

Hi all, been a while and we still haven't fond the problem, but I thought I would post an update. Despite the noise the truck has been used a fair bit and now the noise only occurs at idle. We've gone through pretty much everything in the bottom end and even explored the clutch as that was a recent change. Our latest working theory is a sticking valve. So we will be digging into that. Will report back!

Hi Merle, that is a very good question. I think best have transmission in neutral and not to step on the clutch when starting, but I digress... I wasn't the one starting it, so this will be added to the list to check out. I do know pushing in the clutch after it is running did not change the noise, however agree the cutch is where we need to look next. We haven't been over to work on the truck as one of the guys got covid for the holidays, but will be soon and I'll report back. Thanks everyone for the great ideas and happy New Year!

Speed increases with engine speed and matches crank timing.

Thanks all for the great feedback. The timing about the knock and oil pressure may be more of a coincidence than a direct relation, just to say it doesn't seem to knock immediately upon start up, but a couple seconds later. One new piece of info (which I wish I'd known earlier), is that the knock developed after the clutch was replaced, which was very soon after engine installation as the first new clutch was slipping. So it looks like we have to cast a wider net. We will be back at it again soon, explore the above suggestions, and report back!

Hi all, new member here. Wondering if the unusual problem with my friend's truck is anything specific to a 251. The background: His crankshaft broke in half under the #5 connecting rod. He sourced a replacement crank and had the engine rebuilt by a local builder. It runs well but as soon as the oil pressure comes up (a couple of seconds after start) it has a knocking sound at idle which does not go away as rpms increase. Oil pressure is about 20 at idle. Removing #4 plug wire changes the noise, but does not eliminate it. No change with the clutch in or out. Pulled the pan and rod and main bearings look ok. He drove it short distance (brave or foolish?) and the noise disappeared. Turned off engine, went in a store, came out, restarted and it reappeared. It's got a couple of pretty experienced guys stumped. So asking the experts here if there is anything specific to these engines that should be looked for before the engine gets pulled back out. Thanks!