The Stovebolt Site Forums The Shop Area Driveline Conversion from mechanical brakes to hydraulic brakes - 1934 1-1/2 Ton

Hi i have a 1934 1 1/2 ton truck. I am in Australia and I am looking into how to convert the mechanical brakes on the truck to hydraulic any information on how to do this would be appreciated thanks

Welcome back sir! I did a bit of searching through Stovebolt and only found a few tidbits that might be pointers toward answering your question.

This early post talks about when Chevy first introduced "hydraulic brakes". Seems 1936 Trucks could/would be a starting point to see about what was used on those trucks.

A peek through the web found a similar discussion in another very long ago conversation on a 1934 1-1/2 Ton truck. Again, really only a pointer to when Chevy began installing hydraulic brakes.

Perhaps some of our fellow Bolters into Early Bolts will come along and share further info or suggestions.

If it's of any help, here are links to the Chevrolet Truck data PDFs for 1934 and 1936 that may prove useful when trying to come up with a solution to your conversion. These documents contain engineering data and specifications to a certain extent that may help you out.

It might be worthwhile to investigate a swap to a complete rear axle assembly from a Japanese pickup truck- - - -including the brakes. The lug bolt pattern from several Nissan, Toyota, and Mazda pickups are the same as the 6 bolt Chevy lug bolt pattern, which will allow you to bolt the original wheels onto the newer rear axle. The track width should be very similar to an early Chavy axle. The Japanese rear end might have a more highway-friendly gear ratio, also. Then you'll only need to deal with a front axle conversion to hydraulic brakes.

If you want to keep the original torque tube type rear axle, it might be possible to simply fit the hydraulic brake backing plates and drums from the Japanese vehicle to the Chevy axle with some creative adapting.
Jerry

Great advice, Jerry. I'm not sure how different the '34 is from the '31 or my '27 (both trucks I am starting to understand *slightly*)... but it seems to me that any kind of upgrade to juice brakes will require just the sort of out-of-the-box thinking that you've described.

Maybe Dean ("Rustoholic") will chime in with his insight on this ...

My grandparents owned a couple of 34 Chevy trucks, dual rear wheel rigs set up as tractor-trailers to haul beer from St. Louis and Milwaukee back to Nashville. Mechanical brakes on the trucks, and NO brakes on the trailers. Eventually, Grandpa converted both trucks to vacuum-boosted mechanical brakes! Still had no way to brake the trailers!
Jerry

Thanks for the information i will look into all of the suggestions put foward

AS Jerry said there were vacuum-assisted mechanical brakes in the 30s. I have seen one like that and it had a valve to port vacuum to vacuum trailer brakes. I drove old gas-pot semis with vacuum-over-hydraulic brakes. The vacuum cans were huge compared to air cans. Bear in mind that excluding the air can, air brakes are mechanical (think about the S-cam linkage or, heaven forbid the wedge type. Air cans come in various sizes. One might be able to convert the system to air brakes rather than hydraulic. That would require an air compressor, tanks, a treadle valve, some sort of spring brake release valve....

Naa that's getting way too complicated. I don't see why vacuum-assisted mechanical wouldn't work well if you could find the parts. The Model A crowd argue that mechanical brakes in good shape are as good as hydraulic brakes. Oh, and a lot less trouble on a rig that sits most of the time. The brakes on my old non-hydraulic motorcycles never give trouble associated with sitting around un-ridden. The hydraulic ones in a damp climate are a constant pain in the pittuti unless you ride them all the time.

With a little tinkering, an air brake chamber can be converted to work on vacuum. I've done that to operate the clutch linkage when running a PTO powered winch.
Jerry

Just an aside for a moment ... I am far from getting my mechanical braked vehicle on the road so I have no personal experience driving with mechanical brakes.

Is it safe to assume there is more to this question than we've been told? I ask because I'm wondering if its worth the trouble to do this for a vehicle that, with all other things remaining the same), will not get driven much or far, will never see 40 MPH and probably won't get loaded very heavy.

Bottom line is that I think converting the OP's vehicle to hydraulic brakes makes sense if the rest of the truck is being heavily modified, as well. If not ... There is no "standard" way to do it. It probably won't be easy and in the long run will only be a marginal improvement over the original system.

Food for thought and like I said, if there's more to this than we've been told ... and this is a reasonable upgrade ... then we're talking unique situation with little or no existing documentation to guide you -- You can be the first!!

John

My experience with Model A brakes is that most of them have worn tracks that the rollers run on, so the wedge that expands them can't push the shoes apart. I solved that issue by welding the tracks on the backing plates with a carburizing flame on OA (kind of by accident) and machining them smooth again. But they were too hard to cut them on a mill, so wound up grinding them smooth. Then my brakes were "adequate". The emergency brake on the Model A used a toggle type linkage to expand the band, and it was very effective. Easy to lock up the rear wheels.
It totally would depend on the design of the mechanism whether mechanical brakes should be restored to original condition or replaced by hydraulics.

John, he might be asking if there is a later model Chevy bolt on stuff. Similar to what Model A guys do. Where, I think, you can take juice brakes from a 1940's Ferd, just about bolt them on to an early 30's Ferd, plumb them, and be on your way. It's possible even the master assembly bolts in. Old Henry not wanting to do much engineering to save costs. Things like changing spindle bolt patterns, etc.

You know me. I'm of the mind that if you are going to upgrade, why not get the latest and greatest. Everyone one and their mom makes parts for the 9" rear axle. And there is also a bunch of choices for front axle/brake upgrades. How deep down the rabbit hole do you want to go would be the only question you need to ask yourself. Restore or daily driver, etc.

Psmith, can I ask why you want to make the change? Are you upgrading the rest of the drive line? If leaving the truck stock the mechanical brakes should work fine. They are the S-Cam type just like the Air Brake big rigs use today, except they are mechanically activated.

One advantage is mechanical brakes require less maintenance over time...let the truck sit for a year or two and as long as the shoes don't rust to the drums they will still work...can't say that about hydraulic brakes.

Mike B

Mark -- Exactly. Thank you.

Mike B, you, too.

There is an urge to upgrade a lot of the equipment on these old trucks that I think is misguided. Many but by no means all of the factory "upgrades" over the years were done for manufacturing efficiencies or cost saving on parts from suppliers. The process goes on today. But there was a time when the corporate brass listened to the engineers rather than the been counters.

As an example take the chassis components of a 1-ton pickup: Frame- also used on short wheelbase 14,000 gross 1-1/2 ton; Hydrovac - standard on 2-ton optional on 1-ton; Brakes - 14" rear 12" front; Springs - 2 stage with optional overloads.

I ran the factory setup for many years and never overheated the brakes. In 200,000 miles I've changed the shoes once and never ground the drums. I and many other owners grossly overloaded these trucks, as the factory apparently knew we would, with rocks, sand and gravel, cordwood, wet topsoil, barrels of motor oil, etc. One time I scaled out of the rock quarry with 13,700 gross. White knuckles on crowned rough road but no lasting ill effects.

What got me to install a hydrovac was a trip through Vancouver weekend traffic with a camper and pulling two motorcycles on a trailer. By the time we got out of the city my right knee was pretty sore. At 65 years old in retrospect that wasn't too surprising.

In the thirties, the roads were nowhere near as good, the hills steeper, the potholes deeper, the washboards just at tall but many more miles of them and the loads often exceeding the ratings of the trucks. For hobby trucks, used occasionally on much better roads and seldom loaded near capacity, I think the original equipment usually is sufficient. That is unless you just can't get replacement parts, like, say, Huck brake drums. Fast city or suburban traffic is another matter and maybe we just have to drive slower with an Ag. Equipment Triangle on the back.

First thanks for all the reply's and help on this there are a couple of reasons i am thinking of the upgrade one is at the moment i have not been able to get the adjustment right on the mechanical brakes so i thought for better safety the upgrade may help . I have spent 3 months trying to adjust these brakes and had 2 brake shops try but to no avail at getting them right .

My guess is the brake shops are accustomed to working on disc brakes or Bendix. From what I've read from the Model A guys, there is lots that can go wrong besides adjustment: groves worn in the backing plates, worn actuator bushings and frozen rusty parts, loose anchor pins, etc.,etc. My own experience confirms this. On Bendix drum brakes they wear grooves the backing plates. Hucks seem to be less prone to such wear issues but rust can be an issue. I wonder if Huck made the mechanical brakes on 30s trucks. I have an old book. I'll go look.

Were they using the 1934 Shop Manual to make the adjustments?

What are the issues/symptoms now?

Mie B