Yes, that old GMC was nice to see and not a common one, however I didn't set out to bring home that much of a project. If I had any money, more time, and plenty of garage space there are a whole lot of trucks I'd love to have..
Back to work on the 51 GMC.
loading and unloading it form the trailer I noticed the left rear brake was dragging pretty hard and the first thing I did to the truck once home was pull that drum, inspect, and back off the shoes.
On our trip to DB mentioned above we noticed a slight smell of brakes and stopped to check them, a few warm drums but not hot, we kept driving the few more miles to home.
Time to really go through and adjust everything by the book.
First I thought if more than one warm drum it could be MC is not relieving pressure, not getting full return stroke.
That adjustment is covered in the manual here
http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0508.htmAbout 13/16" between pedal bar and the floor board. Mine was too tight and this adjustment solved the dragging brake problems.
Also wanted to inspect all the brakes just to see what I had. The rear drums come off after removing the wheels and two flat head screws. The shoes looked pretty new and thick and the drums clean, smooth, and no lip.
Drum PICTURE Shoes PICTURE Right rear wheel cylinder was wet, it was leaking but had not soaked the shoes. I pulled the pistons and cups out to inspect.
Wheel cyl. PICTURE There was a small amount of crud and discoloration but no serious pits. Measured the bore and the piston and found about 0.007" clearance which is about double the suggested amount.
See manual here:
http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0526.htmAt this point I figured nothing to lose by honing it and putting new cups in; the piston and spring were clean.
I realize it will be out of spec and honing only increases the clearance but I estimate the cup will take up the slack and won't give any trouble. Also on my mind are plans for a different rear axle and not wanting to spend a whole lot of money on these brakes that I don't need for very long.
I'm all for doing things right the first time and try to always think about safety. In this case I weighed those values with what I expect out of these brakes and the cost. Had I intended to keep this axle/brakes I would have had the cylinders stainless steel sleeved (I considered doing it myself, even looked up
thin wall seamless SS tube ). New cylinders run about $80 plus or minus some at NAPA, sleeving should be cheaper. New 1-3/8" cups at NAPA are $2.16 each.
After searching and searching the shop for my wheel cylinder hone I gave up and bought one the next day, some day I'll have two...
This job was simple.
First remove the top brake shoe spring with a set of brake spring pliers, flop the shoes out but still attached.
Next put some rags under the wheel cylinder, pull the adjusters, push on a piston to pop the other out, catch the fluid and remove both pistons, cups, and spring.
Then with cylinder hone on cordless drill hone the cylinder just enough to mostly clean up. I used some diesel in a squirt bottle to lubricate and flush while honing, not sure if that is right nor not but seemed like a good idea and it worked well.
Finally wash out the bore with brake clean as well as the pistons and spring. Reassemble with new cups lubricated in brake fluid.
One last thing about that right rear brake before reassembling.
The parking brake cable is missing a support bracket where it enters the backing plate and has damaged the cable sheath causing the cable to stick.
PICTURE While I order new parking brake cables I disconnected this one from the link inside so it won't cause the brake to drag. The other cable is in fine shape and works well on the left side.
Anyone purchased cables from
Inline Tube? They list cables for the 1 ton as original or stainless for $75 or $85 each, which is a little strange as the front page shows $39 or $49 as general pricing and these cables seem pretty normal, not special. I have not yet called for details.
Now on to the front wheels/brakes.
To get to them the whole hub must be removed. I elected to just remove the hub cap, cotter key, and spindle nut; Then pull hub, drum, wheel, and tire all together. This is faster and simple if you can be careful with the seal while doing it.
Front brakes looked similarly nice, good thickness on the shoes, clean drums with no lips, cylinders looked recent, no troubles at all. Even the ball wheel bearings looked like new (they may be?).
Here is the service manual on adjusting wheel bearings which is important to check because I'm more familiar with tapered roller bearings than I am ball bearings for this application.
http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0307.htm (and the next page)
Torque to 33 ft lb and back off one flat (1/6th turn) and no more than 1.5 flats to fit cotter key.
Next post is master cylinder rebuild and brake adjusting,
Grigg
