Accessory drive for 4104 with 671IL

dtcerrato · January 15, 2017, 10:38:11 AM

Does anyone know the part #s for the accessory drive needed to change from the original gear driven generator to a belt driven unit? There are so many variations out there its mind boggling...

luvrbus · January 15, 2017, 12:11:35 PM

I'll try and find you a group number, it is hard to find you should have a picture in your manual I think in section 1.7.7 page 3 showing the correct drive.I have 5-6L71's with extra parts coming from Slidell LA there might be a drive in the parts or on a engine I could send you.I have a shelf full of the drive gear just no 5.5 pulleys

dtcerrato · January 16, 2017, 05:46:17 AM

The manual shows the generator drive gear which is 21 teeth (as mine is) - but it's offset from center to mesh with the 31 tooth gear in the 671 gear case - so at 1750 engine rpm the generator shaft turns at 3000 rpm. All the accessory drives I'm finding have the 21 tooth gear "centered" so as not to mesh with the 31 tooth gear in the 671 gear case. I was tempted to modify the generator and use the housings and frame with a fabricated pulley but was considering a little cleaner look. I'd be interested if you come up with any parts that would work. I found brand new accessory drives on Ebay with the 21 tooth gear centered for $69 - cheap! but the missing link is the space between the 21 & 31 tooth gears... Thanks for the response.

luvrbus · January 16, 2017, 06:09:35 AM

Most belt accessory drive are centered you toss the planetary gear and install the flat gear drive and use the pulleys on the alternator and drive to achieve the rpms needed for the alternator around 6 to 10 rpms depending on the alternator manufacture.I have never seen a planetary belt driven accessory drive on any Detroit fwiw

daddysgirl · January 16, 2017, 08:29:43 AM

"I have never seen a planetary belt driven accessory drive on any Detroit fwiw"

Isn't that similar to the Epicyclic drive? If so, I don't think I've ever seen one on an engine that wasn't enclosed?

dtcerrato · January 18, 2017, 04:42:26 AM

The original DC positive ground Delco Remy generator on our 4104 is direct drive from the gear housing on tranny end of engine. The gear in the engine housing is the larger at 31 teeth. The smaller generator gear is 21 teeth & sits inside the larger one off centered so drive gear turns driven gear faster than the countershaft rpm. When engine turns 1750 rpm the generator shaft is turning at 3000 rpm. So the faster RPM needed to spin a belt driven alternator is partially achieved.

dtcerrato · January 31, 2017, 09:18:11 AM

Finally going forward on purchasing parts for our charging system upgrade.
We're going negative ground with the bus & a 200 amp Leece-Neville.
Using the original Gen. converted to an accessory drive.
Decided to go with converted Gen because the drive ratio is already @ 1 to 1.72
An additional ratio achieved with pulleys is 1.9 thus total ratio = 3.62
RPM range @ the new Alt. = 2400 rpm (idle) to 8400 rpm (top speed)

dtcerrato · February 23, 2017, 09:26:33 PM

We got her done. Sure is nice to see battery voltage over 13 at idle. Everything looks good. We hooked it up in positive ground mode to get it operational. We have the option to convert to neg. grnd. later on. Will probably need to tighten the belts soon as the paint wears off the pulleys & the belts seat. I noticed quite a bit of gear lash but most of it disappears at operating temp.