Trying to help clarify the problem with a question. Does a tick from the torque converter/flex plate match engine RPM? The tick frequency for the OP is only 1/2 engine RPM.

Recent experience with noisy valve train tick (frequency = 1/2 engine RPM), caused by loose rocker arm bearing cup. Not flopping around loose, but spins with a screwdriver loose, and easy to check. Sorry if I am being annoying, just trying to understand torque converter/flex plate failures.

 

Quite unclear what the stator rpm in the torque converter would be but likely less than engine rpm. Sounds like your ruled out valve train so torque converter is the only other option that makes sense.

 

I wondered if it was the TQ converter too but it drives totally fine. Part of me is ready to give up on this thing but part of me is determined to find the solution. I've watched a bunch of videos and it's the same sound they all seem to have and nobody has ever determined a root cause from what I can find. I wish the company that made the integrated LS swap was still around. I'd bite the bullet and go that route before I keep dumping money in this 4.6.

 

Well the sound they all make is the slipped liners, but with top hats that seems highly unlikely. If you need it to be reliable I can see the problem, otherwise I would keep driving it until the problem becomes more obvious.

 

Thanks for the response. A bit more to consider: Parked at idle in Drive, torque converter slip = 100% = stator not turning. Flex plate and rotor speed = engine RPM.

IMO valve train noise has not been ruled out yet. Could be a bent pushrod, for example or a couple other faults. A stethoscope (or long screwdriver to the ear) on the rocker shaft supports is an easy test to help pinpoint valve train noise.

Agree that continuing to drive is not a problem.

 

Thought I would follow up on this. Got the engine pulled out of the Discovery. Regardless of what was making noise, I needed to replace the rear main seal that was leaking. After getting it out and taking a closer look, it appears I have 3 cam lobes that are shot. I have no idea why just three but the Intake lobe for cylinder 5 was by far the worse. The lift portion was practically gone and there was a sharp hump on the cam. I am surprised it ran as good as it did. I talked with Woody at TWS and I am putting a fresh new valvetrain on it. I ordered a mild performance cam with their improved lifters, rebuilt rocker assembly, upgraded pushrods, and rebuilt injectors. I ordered the oil additive they recommended for breaking in their cams and will follow their procedure. Either I didn't properly break in the current cam or it is flawed on a few journals.

 

Well I am throwing in the towel on the Discovery. After all that work and money the noise came right back. Something must be wrong with one of the pistons or something else is that is totally confounding me. I could buy another cheap DII and swap a used engine in but in my mind that is just a ticking time bomb and more wasted money. I could buy a short block from AB for $5,500 or a long block for $7.5k but I just can't bring my self to dump any more money into this thing. It is in decent shape for it's age but not perfect. If it were an extremely nice example of one I might would do it. The only other option I would have considered is an LS swap but I really like things to function as they would stock and don't really have the motivation to figure out how to re-wire everything to play nice together. I'll probably just let it sit until I win the lottery I never play as it wouldn't even sell for what I just put in the valvetrain much less all the aftermarket suspension tires and wheels.

 

I'd just drive it till something happens in that case...

 

It's too embarrassing lol. Plus I don't really want to end up stranded if it does finally let go.

 

Sorry for your ordeal. Maybe just drive it now. Guessing the flex plate looked good when the engine was out. You did find the bad cam.

Actual oil pressure reading might tell something. Oil pump can be changed in the vehicle, if needed, and not too expensive if DIY. Low oil pressure can maybe cause cam failure too.