After my 2nd alternator died in three years, I've decided to go a different route. After some research here and elsewhere, I went with the pre-1999 7.3 PSD alternator. Some people on here suggested a 6.0 Alt. Searching through the 6.0 board, some of them recommended the pre-1999 one. My stock alt was 115 Amps. The pre-1999 version was 130A. The case is bigger, and some say that helps it deal with heat better. Who knows, but I'm giving it a whirl.

The Alternator I was using before is a Bosch AL7555N (lifetime warranty). My pre-1999 one is a Bosch AL7526N (also lifetime warranty). New on the left, old on the right. Notice the pre-1999 version has a 6-groove pully. Pully swap is a must.


Slightly larger case diameter on the new one on the left.


The nuts came right off using an impact gun and a strap wrench. The threads do not appear to be the same from one alternator to the other. Not sure what this was about?


Correct gap from the face of the case to the pully.


New alternator with old pully has no gap.


It's pretty obvious the problem after comparing pully stand-offs side by side.


As close as I could measure, I needed a 3mm spacer. The shaft of the alternators is 17mm. The OD of the pully standoff is ~24-25mm. A 17x24x3mm washer is non-existent at any "normal" place you'd buy washers. I tried modifying an existing US washer but screwed it up (how do you hold it?). I then contemplated machining one of my own but ran out of time before heading out of town for a 3-week vacation. In the mean time I found some stainless steel "shim gaskets" on Amazon. The ones I got are 1mm thick, so needed three stacked. Pack of 20 shipped from China, so good thing I was on vacation.


I've got 17 of these "gaskets" left if anyone feels like giving this swap a shot.


The current 7.3 alternator has a 3G case, the pre-1999 version has a 6G case. Of course a wiring adapter is needed.


Found this on eBay:


You'll notice the new alternator on the right sticks out significantly more on the bottom where the arrow is.


The alternator was teeter-tottering on the mount where I marked in black.


Wore out a couple Dremel sanding drums getting this far. Not deep enough...


Now I have space between the alternator and mount.


I cheated by using washers between the alternator and mount.


I've got the @Sous "Be More Positive and Energized" mod from trying to fix issues with my previous alternator. Before even closing the hood I noticed that the Be Positive mod had deeply imprinted in the hood insulation. Luckily the attachment point for the positive lead standoff from the mod looked to be approximately the same distance from the center of both alternators, so with crossed fingers I gently closed the hood. No bulge! I pressed down on the top of the hood all around where the alternator is at. I could pretty easily flex the hood down 1/4" or more everywhere but at the alternator location. I might flex it 1/16"-1/8" there before contact. Maybe I need to grind down further to give myself a bit more margin as It's close...


I'll post updates once I get some serious time on this alternator.

 

Great pics and write-up!

 

Thanks for the write up! Mine just died so it came at a good time

 

Alternator swap still going strong. Voltage “regulator” on the new alternator is more inconsistent than the previous Bosch. Old ones (before the VR went TU) had a very solid 14.1-14.2V at highway speed. When the VR went bad I had voltage excursions up to 18V. New one fluctuates between 14.1-14.9V at highway speed. So far this hasn't affected anything that I can tell. Over 11,000 miles on this alternator in the last 9 months. That’s more miles than the last three years combined on my last two alternators.

 

Thank you for sharing

 

Wet cells have to be pushed to ~15 volts to properly Equalize them, and the OEM system can easily handle 16 volts plus w/o damage.

 

I'm a huge fan of installing an auxiliary charge wire between the alternator and the battery/s. For far too many decades I've seen factory wiring harnesses get "tired" and the voltage arriving at the battery is lower than what's at the post. Battery never gets it's full charge.