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Gearing for School Bus Paul 10-17-03  
I just bought an '83 GMC/Bluebird schoolbus with a GMC 366 "industrial" engine and a 4-spd transmission. Does enyone have any suggestions on how (or if) I could re-gear this beast? Right now it's running around 4,000 RPM at 65mph, I'd like to bring it down to a more (quieter) rpm range.
Re: Gearing for School Bus John the busboy 10-20-03  
First you must determine what type of drive axle you have. Our bus had a Rockwell H-172. The ratio was 6.14.

Then you need to shop around and see if faster gear sets are available. The wrecking yard that handles heavy trucks is a good place to go. So are transmission shops that only do heavy trucks.

If you can't find a faster gear set, then you have to look for a replacement drive axle. This is what we did. Our bus has hydraulic disk brakes and it took a few trips to the salvage yard before one turned up.

We now have a 4.11 drive axle. Makes a big difference.

Gear sets for the H-172 are pricey. We got the whole axle for about the same price as a 4.88 carrier.

The new axle is just a bit wider than the old one. So far the tires haven't rubbed against the wheel well. Our tires are oversize, so if it does become a problem, our next tires will be a little skinnier.

John the busboy
Re: Gearing for School Bus ron 9-12-05  
Sounds like you have a 7.17 ratio in your 83 gmc i have a 85 gmc same problem
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