Mystery Rattle above the Bell Housing.

My '71 SWB has developed a mysterious and increasing rattle. It sounds like a cup full of marbles in the general direction of the lower bulkhead. Here is info to eliminate (or tip-off) any ideas: The transmission was gone through by Great Basin Rover in Salt Lake City right after I bought the beast, about 3 years ago. I replaced the front propshaft with a new one from RN; drained and replaced fluids in the transmission and transfer case after maybe 700 miles; recently pulled all the floorboards (twice) while re-doing the clutch slave cylinder. The engine starts and runs smoothly, Shifting is good in all gears including the Fairey Overdrive, and stays in every gear during over-run (replaced third gear detent spring to fix that annoyance). The rear propshaft likely needs service - I get a gentle "clunk-clunk" when slowing to a stop. I doubt I have put more than 1500 miles on it since I've owned it, and the noise wasn't there, or was unnoticeable early on. I'm perplexed. I'm getting nervous about driving it, lest something falls out. I've read about 200 posts looking for anything similar, but nothing so far. Any ideas?

Does the sound change with engine RPM, or vehicle speed, or is it constant? Have you checked the valve train, and adjusted tappet clearances? There's not much else in that area to make noise, so my guess would have to be either valves, or clutch/flywheel. The speedo and speedo cable can make some crazy sounds too, if they're on their last legs - relatively easy to disconnect the cable at the transfer case and see if the noise goes away.

Maybe flywheel coming loose? I had a buddy said his girlfriends car wsa making an awful racket, turns out the flywheel bolts were coming loose. Also maybe the shield at the front of the tunnel is touching the bell housing? just spitballing, I know my Rover had the paint rubbed off there, although it was rusted out and not sitting right either.

The noise is only there when the vehicle is moving otherwise all is quiet. Speedo cable is new; This loosening flywheel idea is possible but terrifying, having spent my money on the tranny work about 3 years ago.....I'll pull out the floorboards and listen more closely. Thanks!

My series 2A made a concerning noise from the bell housing area, related to engine rpm, it turned out to be the Brass bushing in the flywheel was worn and needed replacing, but what a racket it made.