Under heavy acceleration it sounds like the drivers side cat is slapping the frame rail. Installed two new motor mounts and two new trans/t-case mounts.

Noise still there...

I crawled under and noticed the Drivers side Cat is a few millimeters off the frame rail. I know the tolerance is tight from the factory, but what is consider too tight?
Everything seems to be in order?

Any ideas?

Next step:
crawl under and have someone rev the motor in gear under load to confirm cat to frame interference.

 

With the initial inertia I reckon 5-10mm minimum clearance.

If you are going to crawl underneath with the engine running please ensure the handbrake is on tight and the wheels are chocked well as getting run over by an LR seriously affects your health, i.e no coming back

TIP: easier than that, stick some plasticine on the frame where you reckon the cat hits it and take the truck for a very short drive then checkout the plasticine. Two reasons, the initial inertia in gear is more and secondly it's much safer. Any young kids willl have plasticine some steal it off of them

 

Mine has about 3/8" clearance at the rear end of the cat. Unless the exhaust is way loose, even just a few mm should be enough to avoid any contact.

I had a Saturn once that had a loud rattle under acceleration. Sounded like a loose heat shield but turned out to the cat media had separated from the shell and was rattling inside the can. Ended up "fixing" it with a long drywall screw.

 

My 2001 had a rattle where the pipe hit the frame.

It was because someone rear ended the D2 when the previous owner had it.

I just bought steel rope.
I put the steel rope around the exhaust pipe.

Put the other end around a cement anchor for a light post in a shopping mall.

Went into low range.

Then carefully put on the gas.

The steel rope snapped.

But I must have gotten the pipe pulled out a bit as it did not rattle any longer.

 

interesting...

 

Likely need very little adjustment. I would stick a crowbar in there a nudge it away from the frame a little. If enough room stick a piece of flat stock on cat to protect from damage. It really shouldn't take much.

 

The heat shields on the D2 TD5 are notorious for loosening and rattling so I had to fix mine some years back.

Also the filling/baffles in the tailbox worked loose but was replaced under warranty when near new.

 

X1 ............. check the exhaust mounts if all OK then stick a pry bar between the frame and cat and ease the cat away but as already stated ensure you protect the cat from damage.

 

well, I finally found time to climb under and inspect further. The cat was definitely contacting the frame under load. I was able to gently persuade the cat marginally away from the frame rail with a little help from a pry bar. The tolerance is still tight, but a test drive proved my "pry-bar" technique successful.

something to note while prying between the cat and frame rail - I swore noticed the frame rail flexing. It's possible especially considering I had removed the horizontal frame support "cat-protector" that spans the drivers side to passenger side frame rail. It's got me thinking, I should consider re-installing it.