LB7 Alternator Options in 2023

[sneaky98gt]

After 20 years and 250k+ miles of faithful service, it appears the alternator on my 2003 is giving up the ghost (I'm starting to sporadically get the "Battery Not Charging" message on startups). I'm curious what the consensus is these days on replacement alternators.

I've learned the hard way on previous vehicles to A) Not buy reman electrical components, and B) Only buy OEM electrical components. I was going to do the same thing here, but it's turning out to be trickier than expected.

There's not a great OEM option. AC Delco has two tiers (OE and Gold). The OE (highest) option for a 2003 is extremely expensive, and doesn't seem to be available except at some oddball websites. The Gold is readily available (including on Amazon for <$100), but is made in China, and well....meh. Not a fan.

I've also heard that alternators from the LBZ will also fit. I can find the AC Delco OE / "GM Genuine" version (which, as a bonus, is the upgraded 145 amp) for <$200 online and <$300 in stores, which is made in Mexico. Still meh, but less so than China. Can anyone confirm an LBZ alternator would work on an LB7? Pictures have them looking very similar, but they definitely have different part numbers.

Or is there another option behind door #3 that I'm missing? Priority is longevity / durability. Secondary would be availability at local parts stores (for ease of warranty replacement on the road, if needed).

Thanks!

 

[2004LB7]

I've have good luck woth AutoZone replacement alternators. Never have one fail early. Cheap too. Lifetime warranty???

 

[Bdsankey]

I've had very good luck with DC Power alternators.

 

[1FastBrick]

An LBZ alternator will work, However you will need a longer belt.

 

[bearwolf50]

I replaced my stock alternator with a XDP High Output 220 Amp Alternator XD224 5 years ago and have no problems.....

 

[kaylabryn]

On mine I just bought and replaced the Regulator/brush assembly from a local Alternator shop. Did that around 215K, now have 335K. On mine when it was failing I could smack it a few times and it would charge for 30 or so miles then drop out. Was able to milk it back home from a trip to San Diego, just took a little longer. I think at the time the part was $50 ish.

 

[silvrmax04]

20 yrs and 250k miles is a good run. I would buy the same one you have on there or have it rebuilt with Oem parts.

 

[turbovan]

Put the 120 amp unit on. I've had good luck with Wilson and AC Delco. Bosch are pure junk.

 

[sneaky98gt]

Quick update.

I did consider rebuilding the alternator, but I had an early failure the one time I did that myself some years ago. Likely operator error, but it's had me a little gun-shy, nonetheless.

The USA aftermarket pieces seem really nice, but they're way overkill for what I need, especially considering their price.

I wound up putting in the "AC Delco OE" / "GM Genuine" 145 amp unit from an LBZ. Part number 22781131, $181 shipped from Amazon. As you'd expect for a 145 vs 105, the body is a little bigger overall, but the pulley height is only about 1/4" taller. My truck calls for, and has installed, a 117.7" HD Gates belt, and it still fit on with ease. No need at all for a longer belt.

New alternator also fixed the "Battery Not Charging" message. I'm thinking the alternator may have been going bad, or at least only had marginal output, for a good while. I've noticed for several months that the truck wouldn't crank over nearly as fast as it used to. I'd just assumed that it was the colder weather. It's been cranking noticeably better all weekend since replacing the alternator and driving it a bit, including a cold start in the mid-20s this morning.

 

[Bdsankey]

Quick update.

I did consider rebuilding the alternator, but I had an early failure the one time I did that myself some years ago. Likely operator error, but it's had me a little gun-shy, nonetheless.

The USA aftermarket pieces seem really nice, but they're way overkill for what I need, especially considering their price.

I wound up putting in the "AC Delco OE" / "GM Genuine" 145 amp unit from an LBZ. Part number 22781131, $181 shipped from Amazon. As you'd expect for a 145 vs 105, the body is a little bigger overall, but the pulley height is only about 1/4" taller. My truck calls for, and has installed, a 117.7" HD Gates belt, and it still fit on with ease. No need at all for a longer belt.

New alternator also fixed the "Battery Not Charging" message. I'm thinking the alternator may have been going bad, or at least only had marginal output, for a good while. I've noticed for several months that the truck wouldn't crank over nearly as fast as it used to. I'd just assumed that it was the colder weather. It's been cranking noticeably better all weekend since replacing the alternator and driving it a bit, including a cold start in the mid-20s this morning.

Typically when you don't change the belt tensioner does not ride in an ideal location meaning it is towards the max of it's adjustment.

Is your tensioner fairly close to center of it's range of motion?

 

[sneaky98gt]

Typically when you don't change the belt tensioner does not ride in an ideal location meaning it is towards the max of it's adjustment.

Is your tensioner fairly close to center of it's range of motion?

It's nowhere near the max. It actually appears very close to dead nuts in the middle, though I'd prefer tighter if I had the choice.

The alternator (with a ~180 degree belt wrap) sitting 1/4" higher dictates that the tensioner (also with a ~180 degree wrap) must swing about 1/4" further out. With the tensioner arm length at around 3.5", that only comes out to about 4 degrees. With an easy 30+ degrees left in the tensioner, it's a non-issue.

 

[1FastBrick]

I bet that belt is stretched.

The 145 amp Alternator calls for 119.5 Thats originally why I mentioned you would need a longer belt.

If the one you have works, run with it.

 

[sneaky98gt]

I bet that belt is stretched.

The 145 amp Alternator calls for 119.5 Thats originally why I mentioned you would need a longer belt.

If the one you have works, run with it.

It's possible, but I doubt it. It's a 1-year-old heavy duty Gates fleet belt with 12k miles. I went through a dozen+ belts on my old supercharged car, and they never stretched any significant amount before just breaking.

I saw the 119.5" spec for an LBZ with a 145 alternator (as well as the 118.7" spec for the LB7 with LB7 HO alternator), so I went ahead and bought the 119.5" and had it ready in case I needed it. With the existing belt going on as easily as it did (seriously, not even kinda close to too tight), I quickly realized the 119.5" would be too long. Sent it back.

When I was researching around before posting here, I came across a couple of old posts confidently stating that an LBZ HO alternator would fit right on an LB7 with the factory length belt. But they were older posts without much corroboration. I'd now say it can pretty safely be confirmed.

At the end of the day, the LBZ alternator only measuring 1/4" taller tells the story. Worst case scenario is needing a 1/2" longer belt.

 

[ZappaCoop]

It's possible, but I doubt it. It's a 1-year-old heavy duty Gates fleet belt with 12k miles. I went through a dozen+ belts on my old supercharged car, and they never stretched any significant amount before just breaking.

I saw the 119.5" spec for an LBZ with a 145 alternator (as well as the 118.7" spec for the LB7 with LB7 HO alternator), so I went ahead and bought the 119.5" and had it ready in case I needed it. With the existing belt going on as easily as it did (seriously, not even kinda close to too tight), I quickly realized the 119.5" would be too long. Sent it back.

When I was researching around before posting here, I came across a couple of old posts confidently stating that an LBZ HO alternator would fit right on an LB7 with the factory length belt. But they were older posts without much corroboration. I'd now say it can pretty safely be confirmed.

At the end of the day, the LBZ alternator only measuring 1/4" taller tells the story. Worst case scenario is needing a 1/2" longer belt.

Writing in from 2026

Found this post and purchased part number AC Delco 22781131.

I had very similar scenario. 2004 LB7. I was replacing my stock 105A. I wanted to upgrade to 145A. Similarly, I had just replaced my belt with a gates fleet unit, p#K061177HD, about 7,000 miles ago.

Wanted to write in and confirm, this is a direct swap. You do not need a longer belt. On my truck, the indicator mark is exactly within, just past a “new” belt. I’ll post a photo.

Thanks for posting this! Hope this Helps someone else.

 

[Bdsankey]

Writing in from 2026

Found this post and purchased part number AC Delco 22781131.

I had very similar scenario. 2004 LB7. I was replacing my stock 105A. I wanted to upgrade to 145A. Similarly, I had just replaced my belt with a gates fleet unit, p#K061177HD, about 7,000 miles ago.

Wanted to write in and confirm, this is a direct swap. You do not need a longer belt. On my truck, the indicator mark is exactly within, just past a “new” belt. I’ll post a photo.

Thanks for posting this! Hope this Helps someone else.

The statement above in bold is not correct. It was a direct swap for your truck. Some tensioners don't have enough motion, some belts are too tight and won't go on etc.

I have had trucks where it is NOT feasible to just swap the alternator in. This is my experience over 100s of trucks. I'd say roughly 30-40% of the time I'd have to change the belt. I'm not saying this to be a dick or a jerk, just to clarify for the next person who stumbles upon this post to ensure they're fully informed.

I'm glad it worked for you tho!

 

[Chevy1925]

The statement above in bold is not correct. It was a direct swap for your truck. Some tensioners don't have enough motion, some belts are too tight and won't go on etc.

I have had trucks where it is NOT feasible to just swap the alternator in. This is my experience over 100s of trucks. I'd say roughly 30-40% of the time I'd have to change the belt. I'm not saying this to be a dick or a jerk, just to clarify for the next person who stumbles upon this post to ensure they're fully informed.

I'm glad it worked for you tho!

So what belt are you changing to? Would pretty much solve this whole discussion

Fwiw, ive done this on mine and 4 other trucks at the shop. Drops right in with either the hd belt or regular belt and a gm tensioner.

 

[Bdsankey]

So what belt are you changing to? Would pretty much solve this whole discussion

Fwiw, ive done this on mine and 4 other trucks at the shop. Drops right in with either the hd belt or regular belt and a gm tensioner.

HD belt (119.5”).

I took the post I quoted as him claiming it’s a direct swap with no belt change for everyone.

That’s what im disputing.


Sent from my iPhone using Tapatalk

 

[Chevy1925]

HD belt (119.5”).

I took the post I quoted as him claiming it’s a direct swap with no belt change for everyone.

That’s what im disputing.


Sent from my iPhone using Tapatalk

So a 601187.

Its not a big deal. Pretty much clarified now