gearbox mounted compressor

[Jacques Reed]

Hello Harle,

Just checking my Ford Parts list and there were two types of compressors made for the CMP trucks.

One was Outboard Marine or Saylor-Beall and the other one was Webster- ( your compressor type).

The Outboard Marine type had 3 screws retaining the cover and yours has 4.
Part No. 19947 located at your open cover hole is listed as "Fitting- Lubricator (Webster)"

It may be the type as used on the clutch throwout bearing on the transmission housing but I am only making a guess. Perhaps someone else can confirm what that lubricator was.

Hope this helps.

Cheers

[Jacques Reed]

Hello Harle,

Further to previous post: I believe your concern is leaking at the shaft where it goes into the bottom of the compressor.

If the shaft and/or bronze bushing are not worn, there should be little or no leakage into the compressor base. The viscosity of the transmission oil would also help to prevent leakage. The problem arises if either the shaft or bushing are worn and then transmission oil will certainly pass.

When manufactured, the clearance between the shaft and bushing would most likely be a precision running fit which allows for smooth rotation with minimum play between the bushing and shaft. If sloppiness between the shaft and bushing exists then it would require the bushing to be replaced and reamed to the correct size for the required fit. Most often it is the bushing that wears due to being the softer material. Ford distributors are a good example of this.

If your compressor has seen a lot of use then new bushings would be the way to go or just monitor for any leakage and then decide if the bushings need replacing.

I had a look at a picture of a Webster type transmission mounted compressor that I once had and it too lacked the fitting at the bottom. Wonder if the parts book is accurate?

Cheers,

[Lang]

I just had a look at my box of pumps. I have about 8 of them Chevrolet and Ford. No two are exactly the same and none of them has a name plate. Some cast iron and some alloy.

The plug in the bottom is just a hole for an oil can. Most have a right angle fitting with a little tin flip lid. The one in question has a spring loaded tin lid but coming straight out.

I think so long as there is about an inch of oil in the bottom all will be well as that is the height of the tin lid oiler. If gearbox oil does come along the shaft it can not fill the pump crankcase as it will just leak out the oiler fitting to maintain the correct level.

Quite apart from that there would not be a CMP in ten thousand that used its air pump sufficiently to wear it out when you consider early air brake trucks had similar compressors running continuously for thousands of hours.

Just an observation in my collection are two pumps mirror image to the CMP ones. This gives the option of fitting a pump with the head forward or back to clear chassis rails etc or on the opposite side of the gear box (does not matter which direction they turn) so a winch or hydraulic/mechanical tipper power take off can go on the other side. I had a Dodge WC53 with a winch take-off one side and a compressor identical to a CMP model on the other.

Lang

[Lang]

blitz pump oiler

Here is the oiler on 3 of my pumps. There are two which have no place for an oiler. I looked in the Chevrolet book and they say no maintenance on the pump because it is lubricated from the gear box. In other words they expect oil to go through the bush into the pump crankcase. If it goes higher than the gearbox oil level it will track back into the gearbox by gravity.

Lang

[Mike K]

Were the earlier cab 11/12 vehicles fitted with air pumps ? I ask because my C8 has a tapped hole and plug in the floor where the pump on/off rod would normally be located . I looked into fitting a pump in the C8 but its not easy, because there is a cross member in the way that fouls the pump . Not sure about the larger types 15 cwt and so on.

[Grant Bowker]

I have always understood that Chev pumps mounted on the left of the transmission and Ford on the right, both pointing to the rear. I haven't tried to see if the gears would mesh correctly if pumps are swapped from side to side.
In the Canadian context, and for Chev cab 13, there is only one threaded plug / opening in the floor to reach the pump's actuator shaft. Again, I haven't run a trial to see if all pumps would line up.
I believe all Chevs used very similar transmission mounts. At least the C8A, C15A and C30 up. I'm not as sure about the 2 wheel drive C8 and C15 but would guess they used similar bellhousing and thus mounts so would all suffer similar clearance issues. The 270" engines were mounted differently, whether in C60X or armoured vehicles but locations were similar.

[Lang]

Grant and Mike

Maybe the C8 could have a Ford pump fitted because it would face the opposite direction and possibly clear the obstruction.

The hole pattern and gears appear to be standard SAE dimensions and direction of rotation makes no difference.

Lang