Alternator Pulley Sizes
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Trailering
Joined: May 2003
Posts: 22
Likes: 6
From: Arizona
Alternator Pulley Sizes
2003 - 6.0 - 127k single 110amp alternator
I replaced alternator around 60-70k with stock reman. Changing alternator now just for preventative measures.
I have had no electrical issues or additional amp needs.
Going to install a 2005 6.0 upper 140amp alternator
Reading about using an overdrive pulley I'm a little confused.
As far as I can figure the 03 and 05 6.0 have the same size crank pulley
The stock 03 110amp appears to have a 64mm pulley
The 05 upper 140amp appears to have a 70mm pulley
I also have an overdrive pulley 58mm
Seems normally one would overdrive the 110/64mm with the 58mm pulley.
Dropping the 140/70mm to 58mm seems to be a pretty big drop in size
I'm thinking of just replacing the 70mm with the 64mm
My "ruff" calculations (not sure of accuracy)
58mm 3.55 to 1 / idle 670rpms = alt 2,378 rpms / at engine 4,500rpms = alt 15,975rpms
64mm 3.22 to 1 / idle 670rpms = alt 2,157 rpms / at engine 4,500rpms = alt 14,490rpms
70mm 2.94 to 1 / idle 670rpms = alt 1,969 rpms / at engine 4,500rpms = alt 13,230rpms
Thoughts? Overthinking it?
I replaced alternator around 60-70k with stock reman. Changing alternator now just for preventative measures.
I have had no electrical issues or additional amp needs.
Going to install a 2005 6.0 upper 140amp alternator
Reading about using an overdrive pulley I'm a little confused.
As far as I can figure the 03 and 05 6.0 have the same size crank pulley
The stock 03 110amp appears to have a 64mm pulley
The 05 upper 140amp appears to have a 70mm pulley
I also have an overdrive pulley 58mm
Seems normally one would overdrive the 110/64mm with the 58mm pulley.
Dropping the 140/70mm to 58mm seems to be a pretty big drop in size
I'm thinking of just replacing the 70mm with the 64mm
My "ruff" calculations (not sure of accuracy)
58mm 3.55 to 1 / idle 670rpms = alt 2,378 rpms / at engine 4,500rpms = alt 15,975rpms
64mm 3.22 to 1 / idle 670rpms = alt 2,157 rpms / at engine 4,500rpms = alt 14,490rpms
70mm 2.94 to 1 / idle 670rpms = alt 1,969 rpms / at engine 4,500rpms = alt 13,230rpms
Thoughts? Overthinking it?
Lead Driver
Joined: Jul 2004
Posts: 6,951
Likes: 512
From: Foothills, CA
I ordered our truck with what was at the time called the High Output single alternator - the 140. I've been running the 58mm for a number of years now and you do see a slight difference in voltage down low. I recommend the combination... As a little tidbit: the 6.4s normal alternator was the 140A...
Mountain Pass
Joined: Aug 2019
Posts: 167
Likes: 50
From: Miami, FL
I replaced my stock pulley with a 58 mm overdrive one a couple years ago. I did notice an improvement in output (Amps), particularly at idle. I rarely run above 2,000 RPM for any sustained period, so I was more interested in output on the lower RPMs.
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