Hello all! This is my first to this board, so please take it easy on the newbie!

Ok!

First off I am an Area Field Manager for U-Haul. I drive a 96 Ford F-350 Panel Truck (AFM Rig), it's considered a Metro Rig as it has a short box with only 3 cabinets per side, and a bed in the back. Ah with most "Hand-Me-Downs" it was in need of plenty of repairs. Some of the things already done are, shocks (all around @ Meineke), head gaskets (@ Ford), EGR valve(myself), new head lamp assy (Myself lenses), New Alternator (Myself), New Battery (Myself), New Fan Clutch (myself), New Rims & Tires (myself), Brakes (@ Ford), new LED style lights on the box (Myself), & New Differential Gasket & Fluid. She still runs strong for a 96, but I have plenty work to keep me busy, she bounces around alot, and makes a TON of noise from the suspension. I have the bushings on order, it's one of my next endeavors.

My problem is, I have noticed that when the truck goes 60+ MPH, it tends of make a rattling noise. If I give it WOT, the noise gets very prominent. I have not been able to get rid of the noise. I have read a bunch of post on various forums saying that it's the catalytic converter. So I started to look into that. I noticed that there is a small backfire coming from the exhaust, nothing noisy, but noticable if you listen at the tail pipe. SO, I placed an order for a new Catalytic Converter, O2 Sensors and also for a New Muffler, as the parts that are currently on there look like they're stock. (Note the engine has 228K on it)

My question is, what would cause that noise? And why only after 60+ MPH?

The noise is like a rattling/bearing spinning noise. It's not a grinding. Any ideas?

 

Before dumping that much money to replace the cat and stuff, make sure the engine does not have an actual internal problem. With that many miles on it, I would be skeptical.

 

Hey thanks for the response. Well the reason we are spending the money into the truck is because it is a service truck for other U-Haul trucks in the area, and we won't likely see a replacement truck for another 2 Years, so we have to ensure it stays in good shape. There is definately an exhaust leak thought its not major, but I was advised to changed the parts as the service records don't indicate that parts have been changed in the last 5 years. So those parts are a go.

Anything that you would suggest checking, that would give me that kind of problem?

Also! One thing I forgot to mention I'm randomly getting a Check Engine Light, as I get the light, I notice the Temp Gauge goes up to about half, and then promptly returns to the "N" in Normal. Any ideas?