99 CAT clogged?

99 4x4 vin w
Starts and idles fine..when I give it throttle it feels like im pulling a train.
The guy at the shop said it probably a clogged converter.
I hit it with a rubber hammer ,and it rattles alot...Temperatures with an infrared heat gun read 457 at the cat and 137 at the beginning of the muffler....after a few minutes of idleing.(Engine runs about 195 ish)
Is it safe to start replacing stuff..starting with the cat?
No engine codes thrown.
TIA
CS

If the cat rattles you may have 2 problems.

1. Yes you can replace the cat at any time. They are typically good for 100,000 miles on average.

2. The cat is made with a monolith ( ceramic like ) material with small channels where the exhaust is forced through to have as close contact with the catalyst as possible. Sometimes this material just plugs up with deposits from the unburned fuel and oil vapors in the exhaust. Some times it will actually fracture and come apart in the converter. Hence the rattle you are hearing. These pieces of catalyst can be blown back farther into the exhaust system and plug the pipes and mufflers.

When you replace the catalyst, you might do the hammer test on the rest of the system and see if you have any rattles back there also. Unless you have a stainless exhaust system, it is probably time to change it anyway so you won't have to go back and break the system down a second time.

To test for a plugged cat do a back pressure test or engine vacuum test
Check engine vacuum at idle and at 2K rpm.
If vacuum drops at 2K rpm you have exhaust blockage.

Here is an update :
The truck felt like it was pulling a train..would hardly get up to highway speeds floored!
Removed the cat punched it out ,and reinstalled and VROOOM!
more power then ever before...Maybe that thing has been partialy blocked for awhile.
BIG difference in power!
Thanks all!
CS

You are welcome.
And thanks for letting us know how it went.
But you need to get a good cat on it.
No cat may stir up more problems.
Good Luck
MT

Yes!!! If there is an O2 sensor behind the cat, it may send a signal to the computer that you are running out of range of allowable emissions and it may adjust the entire system to compensate for this condition. Could decrease engine efficency and affect power.