Majestic9C1

iTrader: (19)

Just an update, My Junkyard 2 wire Truck alternator has been going strong for 2 years now

00pooterSS

iTrader: (40)

Another happy customer, lol.

89ROC-Z

iTrader: (11)

WOW... put that junkyard alt on and there's a steady 14 volts all the way to 5k!

Just to be safe, I want to put a 3.5" alternator pulley on but haven't found one yet. I think that would help make them last longer.

Anyone know where to get one?

Edit: https://www.summitracing.com/parts/krs-krc40150600 should work. With the stock 2.2" pulley, at 1000rpm I've got 3200 alt rpm. with a 3.5" pulley I'll have 2071 alt rpm.

89ROC-Z

iTrader: (11)

I'm going to bring my old alternator to the local shop and pick their brain on it. He said that the diodes could be bad, and he might be able to put different parts inside to make it live.

Will update with what he finds out!

00pooterSS

iTrader: (40)

If you're not running an overdrive crank pulley leave the alternator pulley alone. I spun mine to 6800 rpm daily for a long time and the two owners after me of my car did too with 0 alternator issues (this was over a period of roughly 4 years and roughly 40 thousand miles until the car was totalled, the car went all over the country and got raced a lot too). Others that have used the used truck alternator haven't reported any failures either so no need to fix what ain't broke on this one. And if you use the larger pulley you'll likely start having charging issues at idle and create problems you didn't already have.

Be interested to see what the builder says, hopefully he can source some quality internals for it. That seems to be the issue with the remans, they use low quality diodes etc.

G Atsma

That has to be it, I mean, how complicated is an alternator? Mechanically stone-simple. Electrically not much more than that. Armature and field windings. PLUS diodes. BOOM!

00pooterSS

iTrader: (40)

And I bet near 100% of the remans just have new bearings and diodes, the ones that just got new bearings only are the few that survive is my guess. I highly doubt the remans are getting fresh windings or complete armatures. So the "new" ones use new armatures and all but still fail in the same pattern failure manner. So the common denominator here is diodes. Unless i'm forgetting a component in my haste to leave work.

G Atsma

Naw, I think you nailed it! Stinky diodes....

89ROC-Z

iTrader: (11)

I have the stock 7.2" crank pulley. I believe the alt will spin around 20k in this form. With the oversized alt pulley it should be 16k. You're confident the junkyard kg3 handles that kind of rpm without issue?

Didn't get to the electric shop today, but will update with what re recommends!

00pooterSS

iTrader: (40)

Me and everyone else in this thread that has switched over to a used kg3 with stock pulley size on the alt and on the crank have had zero issues. That's all I can tell you. I don't know of anyone that has checked the max rpm speed the alt can handle and honestly you're the first one to bring it up that has used the kg3 so I have no idea what a safe pulley speed is.

If all of your other alternators handled those pulley sizes, why wouldn't this one?

I also spin my truck up to 6500 rpm damn near every day of the week for the past few years with a kg3 on it. The camaro saw 6800 rpm daily for years. So that's all I got as for being sure.

G Atsma

Alternator life at high RPM comes down to two things; balance and GOOD bearings. Armatures by nature should be very well-balanced IF free of crud, so that narrows it to GOOD bearings. I don't know if truck alternators are made with any better bearings than the auto ones, but they do seem to hold their own at speed.

the crowing

My alternator died. Went looking all over the place for a kg3 alt and nobody at the junkyards have them. Looks like I'm just gonna buy a pepboys pro start truck alt.

wph351

iTrader: (3)

Lkq has tons of them. Mine was like 55 bucks shipped to my doorstep.

455GTO

iTrader: (18)

I finally went with the 3.5" alternator pulley along with my "truck" alternator. I killed every new truck alternator after taking it up to 7000rpms with the stock size balancer and like the above poster mentioned, its too much rpm for the alternator. Granted these were new units and not pull offs from used trucks but they were the large case 145amp units. I guess some people are just luckier than others. I have killed 3 Fbody alternators and 3 truck alternators ever since i took off the under drive balancer and i dont think its a coincidence that the new ratio of alternator to engine rpm is the issue... If anyone still has high rpm issues with the truck alternator I would at least consider an under drive balancer or a large alternator pulley.

My idle RPM is 1000 and have full charge at idle.

00pooterSS

iTrader: (40)

Decent advice, but I had the exact problem you did until I went to the used alt. I killed every single one of them with RPM, the ones that didn't take a **** right out of the box anyway. The couple that lasted a couple weeks died the second I took them to 6800. Put the used alternator on and never had an issue again, and it saw high RPM very very frequently.

If you had used the used alternator you wouldn't have had to swap pulleys.

So it's not really that it's too much RPM for the alternator, it's too much RPM for the crap alternator, the good ones (used OEM) take it.

the crowing

Just ended up buying a prostart alternator 102 amp. It has Delphi engraved on it. So hopefully it's a good 1. So far so good. Voltage with car on, ac, lights, and radio showing 14.2 volts when I tested it with my multimeter. I don't know how people are swapping these in 15 mins or so. People must have spaghetti arms and fingers. After cleaning my grounds and installation of the alternator it took me 2 hours. Definitely a pita. This alternator better last 10 years.

00pooterSS

iTrader: (40)

Hate to say it but it's rebuilt so the quality delphi stuff is likely gone. I'm not exactly sure what process you went through to change the alternator but if it was your first time then I can see it taking a while, but after you do it a couple times it's super easy. I've always felt it was super easy from the first time, but I'm a tech by trade so this is what I do for a living.

Hope it works out for you, I have no idea what a 102v is so I don't know if you got the truck alternator or the F body alternator. If you got the f body alternator I'd say you need to be prepared to change it in roughly a week or two. Seems to be the standard with rebuilt/"new" f body alternators

the crowing

Yes first time doing it. I took it off fairly easy but installation took longer. I'm sure I'll get to it quicker the next time. Yes I got the f body one. I meant to say 102 amps just updated post. I was hoping to find a truck alternator but nobody had any and I was impatient to order one online. If I find one at a salvage I'll buy it cus a day later now my belt is screeching. Everything looks aligned. Plus it wasn't doing this since new alternator went on. The noise is embarrassing driving around. My voltage is great though.

MY_2K_Z

iTrader: (1)

Yep after smoking countless alternators I finally put a used truck alternator in and all my problems are gone. FYI I got 250 miles with 4 reman alternators, they are garbage.

00pooterSS

iTrader: (40)

Thanks for the feedback man, glad the thread helped.