Quote:
Originally Posted by AZKen
The fact that both gears have 9 teeth means nothing. They need to have the same pitch diameter, tooth form and other factors which you can not measure. The pinion gear needs to match the flywheel perfectly or all manner of noise, wear, mis-mesh and damage will occur. You need to use the GMC pinion.
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The gears are identical and mesh properly with the ring gear (and themselves)
The 478 initially had a coarser ring gear with the bigger 11 tooth Delco Remy starter, but I changed out the ring gear to match the 305. (191 tooth ring gear)
I measured the gear lengths, the GMC gear is 1/4" shorter than the Chevy gear.
Today I shortened the Chevy gear on the lathe. Quite a chore to because the one way clutch freewheels in the usual rotation of the lathe, meaning I had to cut with the tool upside down or from the other side (reverse direction). But the gear needed to be supported by the live center as well. Ended up slowly cutting off the bulk material with an angle grinder with the lathe spinning and the bed covered, making sure I did not introduce too much heat. Then used a CBN cutting insert to clean up the face. I made the chamfers/lead-ins with a Dremel tool. The tape is to protect the one way clutch from shavings/grinding dust.
The gear is through hardened so it should hold up.
Finished gear.
Converted GMC gear vs original worn out GMC gear.
Tomorrow I'm planning to modify the Chevy high torque shaft to match the GMC. It needs to be shortened, a new ring groove needs to be cut. The old ring groove will be sleeved as it sits in the bronze bushing now.
I must admit that I like to do these re-engineering jobs
By the way, I've seen rebuilt starters offered for the GMC V6 and I think the 366/427 big blocks that use the longer Chevy gear. Looking at how close the starter is to the dipstick tube makes me wonder if these starters fit properly, as they are longer than the original V6 starter. They use a different (longer) nose piece to compensate for the length of the gear. I've read one post where the starter indeed interfered with the dipstick tube.
Converted GMC gear vs stock length Chevy gear.