So, do you mean the synchroniser shaft bushes or the sensor bush??[/quote]
the shaft bushes

Thanks, I have ordered a new shaft and Sensor from rockauto.com as advised by someone on the forum and it is only US$79 to my door for the whole lot. Hopefully as well as fixing the noise it will also fix the slight hunting I have on light throttle. "Available from www.rockauto.com, Search catalogue with part numbers or search Ford - 2000 - Explorer - 5lt 302 V8 - engine - camshaft synchronizer. This will lead you to the Dorman 689-101 - $us41.95"

Well the synchroniser arrived from USA only four days after ordering, it is made in China and I had a bit of problem fitting it as the the 23mm long shiney shaft bit under the gear jammed in the oil pump guide hole. After a little bit of filing and emery, mainly on the bottom edge of the step down to the black part of shaft) it fitted in ok and now the noise is gone. The "hunting" problem was still there, but I am not sure if the sensor position was wrong before I played with it as the old sensor was at approx. 7pm anyway, instead of 6 pm (as reqd. by the workshop manual instructions). I then set it to approx 5pm as couldn't put it to 6pm and the car runs ok but maybe down on power (hard to tell as is raining at the moment, so hard to put foot down). At the 5pm position the hunting maybe be gone or only slightly there, will have another drive when dry. The sensor picture in the workshopmanual seems to line up closer to mine now that I alignment tool is set to approx 5pm.

I remember replacing synchronizers ( product recall ) in the OHC V6's in the Explorers. The original ones had 1 oil feed hole, and the replacement ones had 8 oil feed holes. The synchronizer also ran the oil pump.
The old ones would seize up, and the engine would blow, no oil pressure.....hence " Exploders ".
That was nigh on 15 yrs ago now.

Well my sychroniser was at the wrong postion to start with. When I said you had to pick either 5 or 7pm, it is really closer to 5.40 or 6.20 pm positions. I had a look at another 5litre and approx. 5.40 is the correct spot, which lines up with the workshop manual picture as mentioned before. The hunting is still there(maybe a liitle less), so that is another problem. So someone working on the car in the past put it back in wrongly, maybe when fixing the common 5l problem of leaking intake manifold? Anyway the chirping noise is gone and the engine is running a bit smoother.