Hi Don -
I have a 1991 LS400 and have changed the alternator a couple of times, the last time being 2 or 3 years ago. It is not a very difficult job but it is a little tricky. It does come out from the top. First, remove negative battery cable, the plastic ducting and fan belt. Note: draw a diagram of the fan belt/pulleys before removing. You might have to remove the fan, however, I don't remember doing this. Next, remove the 14mm bolts with a long arm ratchet/socket setup to get leverage to loosten the 2 bolts. Next, slide the alternator off the top bolt. It comes out pretty far and you may need to remove the upper radiator hose or move it gently with your hand while pulling on the alternator. Finally, when you have enough clearance, you need to remove the feed wire and rear connector before carefully, as not to bump the radiator, pulling the alternator straight up and out. Remember, it's a tricky job but it's not hard. I completed the whole job every time in no more than 1 hour.
I hope this helps.
Wednesday, May 20th, 2009 AT 11:11 PM