2 speed rear

[adamanderr]

anyone know anything about 2 speed rear ends. do they sit in conventional rear axle housings or other. are they adaptable to any transmission? etc. etc.
thanks
adam

[the_experience03]

In many cases the 2 speed third member can fit into a standard housing. It really is just a matter of what the axle manufacturer (Eaton, Rockwell, Spicer, etc) offered in that particular model of axle.

As far as transmission compatibility it really doesn't matter. The transmission doesn't care what's behind it and the axle doesn't really care whats in front of it. More commonly the two speeds are found behind manual transmissions, but they are also seen behind automatics in some cases. Allison gives instructions for shifting them in the manual.

Most two speeds are electronically shifted, but I suppose it is possible to find one that is still vacuum shifted. Electric is going to be easier to deal with, especially if you have a diesel bus.

[Xtevan]

I looked around a bit and found this page.

http://www.roadranger.com/Roadranger/pr ... /index.htm


Model # Ratios
19065T 3.55/4.83, 3.70/5.05, 3.90/5.32, 4.11/5.61, 4.33/5.91, 4.56/6.21,
21065T 4.88/6.64, 5.29/7.21, 5.57/7.60, 6.14/8.38, 6.57/8.96, 7.17/9.77
22065T

23082T 3.70/5.04, 3.90/5.31, 4.11/5.60, 4.33/5.90, 4.56/6.20, 4.88/6.64,
26082T 5.43/7.39, 6.17/8.40, 6.67/9.08

the first two digits of the model # are rated capacity

I wonder how conservative the load rating are, my bus unconverted and empty is 17K lbs, I suspect a new one would cost way more than the bus.

Steve

[Elliot Naess]

Hey, that's a good site to learn stuff! But it appears to be all current production specifications, and I don't see my Spicer J-190 rear axle from 1992.

However, I see that Roadranger, Dana, Eaton and Spicer are all in the same "family" of brand names, and that could be useful to know.

My guess is that the best place to find out what two-speed "pumpkin" will fit an old axle, would be a truck wrecking yard, or a truck gear/driveline shop. Those are the folks who work with this stuff every day.

A great many of us have a Blue Bird TC 2000 or AA. Do we all have the Spicer J-190? If so, it might be worth some research time to find out what we could swap in.

My stock ratio is 4.78. One ratio on each side of that would give me both highway-speed and better starting-on-a-steep-hill gears.

[adamanderr]

bump this seems to be going in the right direction

[wtd]

If you have an Eaton rear and it has this round access cover doohickey, next to the shock on the left

it's a 2 speed housing. They made single and 2 speed rears using this same housing.
I've heard that some were equipped with 2 speed rears, they were just set at one or the
other at the factory as required and weren't shiftable. Don't know how true that is. This
particular one on my Thomas is a single speed rear in a 2 speed housing.

[adamanderr]

What does the "family" of brand names mean for interchangibility?Or does it mean they're all the same maker? someone told me they only make two types of splined connection coarse and fine, can i assume that they did'nt meant diameter is always the same?

[Elliot Naess]

By "family", I meant that those brand names all appear on the same web site, suggesting that they are all owned by the same corporation, which may mean that many components may be interchangable between brand names -- like you may find a Chevrolet engine in a Buick; all GM "corporate" stuff. Yes, we need to learn more about this!

[bdavis441]

I'm interested in this also. One thing I learned from looking at old grain trucks with 2 speed rearends was the two speeds were something similar to our buses and LOWER. I don't know if they can be redone with higher gears or not. Be nice to find out.

[Elliot Naess]

So... I just picked up the telephone and asked a major truck gear shop, Acme Truck Parts in Stockton, CA. The man said: Furgeddaboutit.

There is no two speed pumpkin that will fit in my Blue Bird's Spicer J-190-S axle housing, so the entire axle assembly would have to be changed. And the two speed units are not really suitable as highway overdrives, since they are intended for off road and other slow work, with one highway ratio and one "crawler" ratio. Typically, the ratios are around two points apart, such as 4.5 and 6.5. My bus is 4.78, so I would not gain much highway speed.

With a gasoline engine, the situation would be different. Gasoline engines spin faster, and have normal rear end ratios around 6 or 7. So a two speed would provide an overdrive. (And the one school bus I have seen with a two speed rear end was a gasoline engine bus.)

But even if the ratios in a two speed would suit you, the reliability would not, said the man at Acme. Those things are not meant to be shifted on the fly. Yes, people do it all the time, but they also break those units a lot. This matches what I have observed over the years in delivery and construction trucks.

So there. Now we can sleep in peace. One thing we won't have to spend money on!

I'll be installing a tach and experimenting with engine RPMs soon, and will report -- probably in the Millicent thread.

[GoneCamping]

It was suggested to me to switch over to a 2 speed rear, but to be honest I don't think it's anything I want to try. I am however considering a change in gear ratio to improve fuel & speed performance on the hiway...

[Elliot Naess]

...change in gear ratio...

Once you have an accurate tachometer in your bus, you'll enjoy playing with this online calculator: http://www.idavette.net/tech/ratioc.htm