Alternators?

Chris · May 17, 2012

I have the 105. I have a clutch fan and a stereo system. While looking for larger alternators I found 145's and 160's which came on what? I also plan on changing to electric fans with overdrive pulley on the new alternator. But advice? Or info?

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Lv1G6He3V2 · May 17, 2012

I did the alternator upgrade recently on my 5.3L. The pulleys are the same size but the casings may differ; larger casings require a longer belt. Someone said the bigger alts came on vehicles with plow options.

Overdrive (and underdrive) pulleys change the speed by changing the pulley diameter; I think this requires a different belt size. If you are getting the Blackbear pulley then you should ask them what belt size goes with it, and they will need to know what casing your new alternator uses. I don't know the casing details but if you need to search, the model numbers look like CS-1xx. The seller/rebuilder should be able to tell you.

You can check your belt size by looking for the part numbers; one of them will have a 4 digit number at the end. My factory belt # ended in 2345 which means it was 2345 mm long, or about 92.2 inches. For the larger casing someone provided a belt number that was 93.0 inches. Most aftermarket belts end in inches, e.g. 4060922 and 4060930. There are some minor variations in size for different engine sizes and options so my numbers may not work for you.

Both the belt and alternator replacement are easy.

- Before starting, verify serpentine belt diagram on radiator shroud is readable.

- Disconnect battery negative wire (3/4" wrench), disconnect alternator positive wire (10mm wrench).

- Use screwdriver to remove air intake hose from throttle body & and airflow sensor.

- Grab a 15mm wrench or socket and use it on the tensioner pulley's nut; while holding wrench with one hand, remove belt with the other hand.

- Use the 15mm wrench to remove 2 alternator nuts and a pry bar to loosen alternator from engine mounts.

- Reinstall parts in reverse order. For serpentine belt pulley order, see diagram on radiator shroud.

The only tricky part is finding enough room to remove/install the belt. Fan shroud and clutch fan removal would really help but are not necessary. If you do the e-fan conversion at this time, you will be removing the fan shroud and clutch fan anyway. (I'm inexperienced so I'm doing the e-fan conversion later LOL.) I read that the clutch fan bolt is a pain to remove: hammer + wrench ought to work.

I'm pretty sure upgrading the alternator requires the "big 3" upgrade. More amps -> additional wires. You add a wire from alt to battery positive, another from battery negative to engine block ground, and one more from the engine block to the firewall ground. I used 4 gauge wire which I think can handle up to 200 amps safely, and 3/8" eye connectors. GM battery post extenders gave me extra connections on the battery. Just remove the old cables, pop the old nuts out of their rubber shells, and bolt extenders on. For both engine block connections I used the two bolts for the painted metal bracket below the alternator mounts; on someone's advice, I slid the eye connectors on under the painted surface, not on top of it.

There are two sizes of e-fan assemblies, which correspond to the 28" and 34" radiators. I think Blackbear gives out fan details if you buy fan harness/tune from them. If no one tells you what to get, you can check radiator size by measuring the distance between the radiator bolts. I have the 28" which is apparently harder to find bolt-on e-fans for. 03-04 tahoes used e-fans with 28" radiators. All (?) GM trucks 05+ used e-fans with 34" radiators. LS1/LT1 fans are said to work but I've heard they do not look factory.