Not hard at all. There's a DIY on this forum on how to replace the alternator. If you've changed brakes on an x5, an alternator is not that much harder to do.

HAHA sorry to bring up a 3 yr old thread but I have noticed that under load so must be driving and not park or neutral there is this ratcheting noise/whine that only comes noticable when the rpm in 4th gear for example is around 3000rpm - 3200rpm i get that sound and ive been driving and have the heater off .....so im leaning to the aux pump but what about the guide rails?

Nice, I have it around 2500 RPM under load when going up a mountain. But had the same over years on my former Chevy Trans Sport. Never any troubles with that noise. Just let it whine :-)

Hope the best

I have a favor to ask.....I am starting to think that the timing chain tensioner (7) and guide rail (5) are worn out or on their way. There is also a upper tensioner (2) in the right picture. Now when i put my hand on the front black part of the engine not where the oil top is but down basically right above the chain on the valve cover when i have someone rev the engine slowly building rpms i can feel the chain to what feels like its hitting the valve cover but i would like to know if any one who has experiance with this can pitch in and for those that dont have any sounds would mind feeling the valve cover and see if you feel the same thing. THANKS!!!

OEM / Performance Parts for Audi, BMW, Mercedes Benz, Mini, Porsche & Volkswagen - ECS Tuning

When I had my 318 (M42 engine) it was the same setup as yours for the chain tensionner. On those engines, the hydraulic tensionner had a tendency to fail every 2 years, at least on my car.
It is item 9-10-11-12 on your diagram. For my 318, those parts were sold assembled, and called a hydraulic tensionner. It gets extended by oil pressure and pushes on the chain tensionner itself (ref #7). I don't know why for the X5 it comes as separate parts, but on my 318, the piston was easy to wear, and was then not pushing strong enough on the tensionner and you could hear rattles from the front of engine.
Maybe that is your problem. At least, it's a less expensive try than opening the front of the engine, and it takes 10min to change.

As a reference, here is the diagram for a 318. It is part #17
RealOEM.com * BMW E30 318is Timing and valve train-timing chain

Thanks Turbo Bimmer...I will look into that since i feel the chain when i rev so im a little concerned but also a factor is that on this board and so far i have not seen any one replace these rails on the I6 mainly on the V8s but i will look into replacing the hydraulic tensioner. on a side note the rattle has been located but not the exact cause. the link is to another thread were i was askin for possible rattle but i have definitly found its location just not whats causing it exactly.

http://www.xoutpost.com/bmw-sav-foru...ing-sound.html

Piece of cake. Check out how to's on the x5 on alternator replacement.

oh also if your doing your alternator might as well as change the oil housing gasket....
since you have to remove the alternator to do so...

Mine is making noise, im thinking tensioner by where the noise is coming from.

Sounds like a kenne bell supercharger, and the noise is from the bank 2 vanos area.