99 EXP EB Jerking when going up steep hills

It started when going up steep hills the truck would jerk and I would hear this thump. It feels like something is banging under the truck. Someone said I may have a bad tooth on the differential gear. Any ideas? What size gear is on a 99 EXP EB?
Thanks for any ideas.

How long since the spark plugs have been changed? Sounds more like an engine misfire.

Check the universal joints on the drive shaft.

I changed the spark plugs about 1.5 yrs ago. I don't have any engine lights on. I checked the universal Joints and they are solid no play. Someone suggested that I check my ring and pinion gears. Does anyone agree with this.
Thanks for the two replies.

I do not think your problem is in the rear end. An engine misfire can mimic many things under load. If you can get a scan tool that will read Mode $06, you can find a misfire along with the cylinder that is causing the problem. How many miles on the truck? Have any of the coil boots been changed? Or any of the coils changed? Do the simple things first.

The truck has 215,000 miles. I changed 3 or 4 boots and coil packs about 2 years ago. I used a hand held code reader and it said no faults. Thanks for the info.

You really need a scan tool to access the computer to read the information it is giving you. An engine can misfire and not set a code. We see it almost daily. The scan tool allows you to look at the misfire counters for each cylinder and pinpoint the miss without a hard trouble code.

Ok thanks