[MudMagnetYJ]

1998 Jeep Grand Cherokee 5.9 Limited with a 5.9L V8. Only thing different is the pulley is 7 ribs, but your belt is 6. You can reuse the old pulley like I did, or just slip the belt on and not use the rib furthest from the alternator. I went from 75 amps to 136 amps.

Keep in mind, most part stores do NOT refund core charges from different vehicles. I got mine from Advance Auto where they all like me so there wasn't even a question. Rock Auto won't refund the core, so don't bother with them.

 

[roadyrob]

the 4.2 has an internally regulator, the newer ones wont work.
there are a few threads on using a big gm alt.
I bought one from DB Electrical
DB Electrical - High Output

I got the 105 amp, its been working great for about 1 1/2 years.

you need to upgrade the wiring, especially with the 140 amp.
if you have a serpentine belt you will have to change the pulley

 

[ed4banger]

Mean Green


1990-87* 4.2L(258) - MG Industries Inc.

 

[MudMagnetYJ]

roadyrob is right, I looked on O'Reilly and the stock alternator on the 2.5Ls and 4.0Ls does NOT fit the 4.2Ls. If the bolt pattern is the same, you may be able to do some modifications.

Here is a writeup. How many amps is your current alternator? Mine was 75 but some come with 90 amps.

 

[Nubby55]

They are way not the same, on my Alt. I bought a kit that changed out every thing inside the old Alt., accept the Rotor and now it is a 90Amp. Alt., that was the low cost way of getting more Amps. for not much money, plus I had a bad bearing to replace anyway and it was all in the kit from eBay.