Alternator Question

So my alt is going out on my 92 4.0 and I figure I should get a small upgrade while I'm putting a new one in. My question is would an alt from a 4.0 zj be bolt in? I know the v8 ones require grinding the brackets but I have been reading conflicting answers about the 4.0 swapping directly over.

You can have a local rewind your stocker and get some more power out of it. Going rate last time I checked was approx. $.75-1.00 per amp.

Factory put in a 90 amp in most XJs and even aftermarket replacements usually bump it up some. Most of the time I see them bump them up to 115 or a little higher. But you might be able to get a local place to rebuild it for cheaper than a replacement costs since they are very pricey these days. The ZJ 4.0L is more than likely not a real upgrade but don't quote me on that.

One of the auto parts places online was selling a zj one with a 4.0 for about 100. Said it was a 120 amp model. Same price as a 90 amp xj 4.0 replacement so I was curious if it would bolt in before I grab a 136 unit and spend a day grinding.

Different year XJs also have different belt routing than others. I know it matter for XJ water pumps since some belt routes have the pump turning clockwise and the other route having it turn counter clockwise. Might want to make sure this isn't the same for the alternators since that may affect whether the ZJ alternator will work.

Ben824 said:

Different year XJs also have different belt routing than others. I know it matter for XJ water pumps since some belt routes have the pump turning clockwise and the other route having it turn counter clockwise. Might want to make sure this isn't the same for the alternators since that may affect whether the ZJ alternator will work.

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Earlier models do not have a tensioner pulley, but use the PS pump to adjust the belt, which sucks IMO. But otherwise pretty close. If the ZJ 4.0L bolts in that should like a good idea. Unfortunately I'm stuck with a renix.

Well the zj 120Amp from a 4.0 was not bolt in. It did require modification of the brackets but was easy enough to do. Make sure you swap the isolator from the old one and everything else should connect just like the xj one once the bracket has been clearenced. If you are planning this might as well go up to the 136 unit. I needed to be back on the road ASAP and parts store didn't have one in stock at the time.

Forceful Llama said:

One of the auto parts places online was selling a zj one with a 4.0 for about 100. Said it was a 120 amp model. Same price as a 90 amp xj 4.0 replacement so I was curious if it would bolt in before I grab a 136 unit and spend a day grinding.

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You have to be smarter than the average bear on some of this stuff. One number at 12v can be another number at 14v (when the alternator is actually generating voltage). Try to see what voltage they're using for the numbers (many don't say), failing that do the numbers in your head and if they are not multiples then maybe they are different. Physical size is another good way to tell.

Anyway, in this case its easy: the ZJ with 4.0 used the same alternator as ours, it was the 5.9L V8 that had the big alt. See this image for the application listing. http://i183.photobucket.com/albums/x57/UrsusMorologus/vdn11361204.jpg

Forceful Llama said:

Well the zj 120Amp from a 4.0 was not bolt in. It did require modification of the brackets but was easy enough to do. Make sure you swap the isolator from the old one and everything else should connect just like the xj one once the bracket has been clearenced. If you are planning this might as well go up to the 136 unit. I needed to be back on the road ASAP and parts store didn't have one in stock at the time.

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HA! I just did this yesterday... was pissed. Thought I had the wrong alternator since the plug didnt match up after I swapped it over from the old one. Had to cut a hole in the back cover plate. Not to mention grinding down a crap load from the bracket. Didnt seem like anything went right until we started it up and ran like a champ.