to have my truck running good again! I had a CEL P0308 misfire cyl #8 and I was confused where to start - plugs and wires were new. The day I was going to take my truck to a shop I decided to check the codes again. Got P0302 misfire cyl #2 and #8. #'s 2 and 8 are on the same coil pack so I had somewhere to start! One new motorcraft coil pack from rockauto.com for $100 later (vs $150 from dealer) and I'm back on the road with no CEL's and no misfires!

The bad news is that the increased engine power is really showing the rear end's wear - it clunks now at high loads like 55 in OD and the like. My vehicles sure keep me busy.

 

Doesn't sound like the slip- yoke, -at those speeds, BUT, I would clean your output shaft and yoke with brake cleaner and apply a fresh (thin) coat of Teflon grease. It may assist (less stress).

What you need to do is change the rear end dif fluid and modifier. It has broke down enough to cause problems that will only get worse and more expensive if you don't do this. It's a common issue with these rear ends.

 

BTW- After doing all that, it may take 50 - 75 miles for the problem to go away. Just so you know.

 

Dang. I went camping overnight, and my truck ran pretty good most the night. I did get some clunking and clacking from the rear but the engine seemed to be running much better. 4x4 High and low both worked nicely.

The truck started missing big time on the way back home today. It got me home, but I got P0308 Cylinder 8 misfire again!!!

I am going to attempt to do a compression check in the morning to see what the internals are like. The truck has always seemed to have low power but I just figured thats the nature of the beast with the NPI 4.6 in a truck. Maybe it is just getting tired : /