I've heard of the Grand Cherokee alternator being put onto the XJ's. All the write-ups I've seen have the alternator at the top of the motor. I have an 89 and its on the bottom. Would this still work? I need a bigger alternator.

 

Yes it works. The writ ups you have seen are for TJs and YJs

 

i have read that a 136 amp alternator out of a 98 grand cherokee with the 4.0 l engine is a direct bolt in for the xj's just have to rotate the black holder on the back of the alt. for the charging wire im looking to do this as soon as i get the money to head to the jy click the link for more info

http://www.bc4x4.com/tech/2004/jeepalt/ alt up grade

 

No, it will not work.

The ZJ/WJ alternator is a Nippondenso, with the voltage regulator inbuilt into the PCM. The 1990 and earlier XJ uses a Delco internally-regulated alternator (1984-1986 was the 12SI, 1987-1990 the CS130,) and that means you won't get anything out of the ND when you wire it up - unless you manage to feed full system voltage to the field coils (then you're going to blow electronics.)

Upside? Delcos tend to be hardier than ND units anyhow - and any competent shop can "upwind" for you. You can get up to 100A application-specific and "off-the-shelf," go to an alternator/starter shop for more. You can also click the link in my sig and check out San Jose Generator - he's the shop I've been using for a number of years, and his pricing is reasonable (and Rod does damned good work. I wouldn't recommend him if he didn't!)

Nota Bene - if you go past 100A on your alternator's rated output, you will want to upgrade your mains wiring as well. Again, click the link in my sig for information on that (the OEM wiring is rated for up to 100A, and at 40-50% duty cycle. Exceeding either or both of those limitations will likely blow the fusible link in the alternator output circuit - and how long you stay running after that depends on your battery.)