I have a 99 ex and have a roaring or grinding sound from the front end. I think it has something to do with the auto 4x4. When I go full born it will not have the sound but put it in a pull half throttle and the grinding starts, I ease off the throttle and it quites. What can this be and what can I do to fix this. Thank you for your help and any suggestion will be big help.[&:]




1999 exp eddie bauer awd stock. I have checked on chip.

 

Check the bearings and u-joints

 

I had these exact symptoms on my '99 Expedition with 65,000 miles. Mine was originally diagnosed as a bad torque converter and maybe a bad trans fluid pump also. The explanation was that at full throttle, the torque converter locks up transferring all power to the wheels. At half throttle, the torque converter can slip if defective. I had the truck in the transmission shop for a day and a half and the verdict was that the trans was fine but my engine was misfiring on a few cylinders under half load.

Long story short, the lash adjusters (hydraulic lifters) were wearing out. Under full throttle, the oil pressure is high enough to keep the lifters rigid enough that the engine sounded fine. At idle the valves were opening enough to run smoothly. The problem is most noticeable at half load. Fortunately you don't have to remove the timing chain and cylinder head, just the valve cover. There is a tool available that will hook under the camshaft and can pry the valve spring down a bit using any 3/8 drive ratchet wrench or breaker bar for leverage. A piece of pipe over the ratchet handle for more leverage helps. Once the valve cover is off, it takes maybe 30 minutes to replace alll 8 lifters and rockers per engine side. For each valve, use the tool to squeeze down the valve spring, then no other tools are needed. Use your other hand to slip out the rocker, pull out the lifter, drop in a new lifter, put one end of the rocker over the valve stem, and set the other end of the rocker over the end of the lifter. I had to rotate the crank around a bit to get the cam lobes pointing up, out of the way. There are two versions of the tool, but here's the one I needed:
http://www.etoolcart.com/browseprodu...--303-567.HTML

This seems to be a planned replacement item on the Triton 5.4 because they are so easy to replace and it dramatically restored engine power. I should have done this a year ago.

 

I had one that the nut on the diff inut yoke had backed off ???? customer stated he never had any work done it.. Anyway made a similar noise -- If it turn's out to be the Lifters as rpalm thinks make sure you look good at the bottom of the lifters incase you might have a cam problem !!!

 

My cam had almost no trace of wear. The rockers looked perfect too, but I changed them since I was replacing the lifters. You can't help but inspect the cam since it's SOHC. If there's any damage, you'll know it.