Scenicrusier Rear Axle

DandM · April 25, 2019, 04:48:44 PM

I'm planning on removing my engine and trans in by Scenicrusier sometime this summer/fall as I need to do rear most bulkhead repairs. I also want to build a new engine cradle, degrease the engine/trans and do a reseal. While all this is out of the bus it would seem to be about the best time ever to replace the ring & pinion. I believe it has the original 4/11 set. I would like to find something in the 3/90 range. I really don't know what ratios were/are available. Can anyone chime in here on GM ring/pinion sets and their fitment? Who would be a good source? I live near Salina, Kansas. Something in this area would best. Thanks, Mike

Bill Gerrie · April 25, 2019, 06:25:24 PM

Mike
Think twice about the rear end. A 4/11 is a good choice. If you go to a 3.9 or so you will be dead on soft ground or slow on take off. Your top end will increase but you will pay for it on the bottom end.

kyle4501 · April 25, 2019, 06:46:21 PM

I may be mistaken, but I thought the 8v71 conversion included a 3.7:1 axle ratio. All of the ones that I have checked were.

Bill Gerrie · April 26, 2019, 07:30:12 AM

You might be right Kyle. I just know a Scenicruiser is a heavy bus and the lower ratio would slow it down on take off and soft ground.

TomC · April 26, 2019, 09:40:39 PM

I would replace that 4 spd with a 7spd overdrive. Why-because the 7spd is the most speeds you can get without having to plumb in an air operated splitter.
Course, I would just install an Allison HT740 and be done with it. Believe me the difference in performance is shocking, but of course less fuel mileage. Good Luck, TomC

kyle4501 · April 27, 2019, 05:31:47 PM

I didn't have any problems with the 4 spd as long as a BUS clutch was installed and the 8v71 was set at the greyhound hp (nice flat torque curve). A truck clutch was god awful on start- even on flat ground.

DandM · April 28, 2019, 01:30:17 PM

Where would I look for any rear axle ratio numbers? Is it stamped any where on the axle housing? Is there any place where a ratio tag plate would be bolted on? I have been under that area and just don't remember seeing one. Ideas? Mike

kyle4501 · April 28, 2019, 02:00:45 PM

I don't trust tags -
I jack up one side, mark the yoke, count driveshaft revolutions for 2 turns of the wheel - That is the ratio.