The Stovebolt Site Forums The Parking Lot Big Bolts 2 speed axle vaccum to manual conversion

Is there anyone that can point me in the right direction of what I need to convert from a vaccum to manual shift on my 59 3600 2 speed rear end? I am swapping to a turbocharged diesel engine and it would simplify the swap if I don't have to install a vaccum pump just for the axle actuator. Thanks.

The next generation of two speed axles used an electric motor to make the shift, I don't know of a conversion kit but there may be something out there. The task force 2 tons and 2 1/2 tons could be ordered with an Eaton rear axle, those were electric shift.

Just a note that your 1959 "Viking" isn't a "3600" Series truck. "3600" Series (actually identified as Apache 36 for 1959) is the designator for a 3/4 ton truck. The 1959 "Viking" trucks were either 40, 50 or 60 Series trucks (40 Series = 1-1/2 ton, 50/60 Series (Special) = 1-1/2 ton, 50/60 Series = 2 ton, 50/60 Series (Heavy) = 2 ton).

For some original detailed info on your truck (which ever series it is), you may want to read through this original 1959 Chevrolet Truck Engineering document. It will shine a lot of light on information on your truck.

There is no such thing as a "manual" shift 2 speed axle- - - -at least not one that's been made since the 1930s. They're either vacuum or electric shift. You would need to swap the complete axle assembly to an electric shift type if you can locate one, along with the electrical components to make the conversion. Then there would be the problem of finding an axle with compatible high and low gear ratios for the Diesel engine's torque band and the number of speeds of the transmission you'll be using. It will be completely different than the gas engine you're replacing.
Jerry

Dan, I'm sure he would get more responses if this was moved to the "Big Bolt" forum.

Thanks for that suggestion Craig. Moved to the "Big Bolts" for better visibility and more discussion for the topic.

A electric vacuum pump system wouldn't be that difficult to install in the chassis if you have a small reservoir and a vacuum switch set to around 30inHg.

Presumably the actuator could also run on low-pressure compressed air, maybe 20-30 psi. Don't put too much air in or the actuator will blow up.

You could try a short stroke, dual-actuating hydraulic cyilinder (those would be found in automation suppliers) since I presume you would be running hydroboost brakes with a diesel engine. Your valving would be through a electric solonoid valve with a switch on the gearshift. That conversion would have to be a customized job where you take the actuator and replace the vacuum pancake with a hydraulic cyilinder.

Go to the wrecking yard and find a 99 or newer Ford Diesel. They have a small electric vacuum pump and plastic reservoir that would probably work to supply vacuum to the actuator. Or you might look for a fuel/vacuum pump. You'd still need a reservoir of some sort.

Cadillac had a V6 diesel engine back in the 1980s that had a belt driven vacuum pump. They're pretty scarce, but they used the same vacuum pump device that the V8 diesels had. One of those things and a small Freon tank for a vacuum reservoir with a one way check valve would work well with the original rear axle.
Jerry

As infrequently as you'd probably shift the rear axle, a little electric pump with a large enough reservoir would work. The belt driven vacuum pump would likely be overkill. They had to support vacuum brake boosters so plenty of volume was needed.

The belt drive pump for the 6.2/6.5 Detroit GM diesel is still available through most parts houses. That pump was used only for the turbo wastegate, the diesel trucks all had Hydro boost brakes. I would probably use an electric vac pump for simplicity, you may not need a reservoir due to the diaphragm and control valve not wasting vacuum.

'97 and earlier Ford Diesels used vacuum boosters. Ford went to hydroboost in '99.

Here's a pump- - - -just needs the proper pulley to match up with the belt system on the engine:

www.ebay.com/itm/306335980546?

Jerry

How about an electric pump for less money?
Link

The older T150 and subsequent T170 rear axles used the same vacuum shift housing assembly, I have actually changed between them. Since the later T170 could be had with electric two speed shift, and it was not an uncommon swap back in the day to go from vacuum to electric.. I'd say your probable T150 axle could be made electric, you'd just have to find a later electric shift motor/housing and associated switch gear.

The bigger issue is finding parts for that T150. It's a great old axle, til it needs bearings and the larger diameter (IIRC from back in the '90s when I did this dance with my own bus) differential side bearing race has to be fabricated, because they do not exist. It's also pretty much impossible to find a taller ring and pinion for it.

I like the idea of the two speed rear axle, I think it's more versatile than merely an overdrive, while being a whole lot easier to use than a Brownie. It is even possible to buy a brand new two speed Eaton rear axle of approximately 17,000lb capacity. Then you would have an axle that would last til the sun burns out and if not, you could get parts for it.

When I switched out the old T150 axle under this bus for the newer T170, you could still get parts for said T170 at the dealer-it was the modern option. Now, 30 years later.. it isn't.

If you are installing a turbo Diesel, the two speed you have will be way too slow. And the vacuum shift was nothing but trouble in its day. Find a two speed that was behind a Diesel in the first place. I was a licensed salvage dealer for many years. I have been selling a lot of scrap, but I may still have some. They are getting pretty difficult to find.

What would you suggest as the new modern option, that would be somewhat adaptable to our old trucks? I've heard of guys using an Isuzu rear axle but I've never seen one done myself.

I suggested the new Eaton because I see it in their catalogs, however that would be the expensive option! Although you'd never have any trouble with it, again. And also rear disc brakes.

Any axle from the salvage yard can be swapped in if you ensure the GVW are similar, the springs have a similar contact point, and the driveshaft has a universal joint that can fit (a machine shop can do that for you if it needs to be done)

a lot of diesel medium truck brakes are either hydroboost or air-over-hydraulic, so interfacing the brakes won't be an issue.

An Isuzu axle might not be a bad idea as that will also address the issue of rims and tire availability that plagues the older medium-duty trucks.

Chevy trucks where manual shift 2 spd. up to 1946.

Don't forget to address control of the 2-speed adaptor on the back of the speedometer...it keeps the speedometer calibrated when in HI or LO range.

Mike B