Trailer hitching at 3000 rpm

I am having problems with my 92 B2200. When I'm driving and the engine gets up to 3000 rpms the truck starts jerking, or trailer hitching pretty bad. It doesnt happen under 3000 or when I'm accelerating hard or coasting. At first I thought it was the differential because the spider gears are trashed and there is a lot of lash. Now I'm not so sure. Has anyone else had this symptom? Any help would be great! Thanks.

sounds like your pulling in air somwheres. try cleanin out your egr, it might not be closing all the way, spray starter fluid or somthin around your carb and intake and if you have a leak, the fluid will get in there and you will here an rpm change and youl find the leak that way if there is one.

If it were your ring and pinion it would have a clunk sound and VERY distinct!Not only would you here it but,would feel the truck have a hard metal jolt.I have had this and replaced my r/p busted gears.Anyway checking the egr is easy and has 3 ten mm bolts,one vac line,one electrical plug.Remove and note the gskt position on this,and clean with carb cleaner and a toothbrush and remove the carbon buildup.Reinstall and making sure your carb is clean and linkage is FREE moving and lube with graphite powder and or liquid wrench(my choices) on the cables and hi idle kick down arm.Unless you some blockage from your charge air filters(inside air cleaner) from charge air hoses(3 of those) on top and or maybe blocked pre -cat convertor below exhaust manifold or blocked up cat under the truck.Any air restriction would choke truck or cough it.I do not want to over load you with info but,just some suggestions that may OR may not come into play.Sounds like it has a hiccup and EGR may be the real problem with those rpms since it fits the idea.