Doh! J-20 Rear Wheel Cylinder bolt sizes

[Bob Barry]

Well, you learn something new every day...

I'm redoing my J-20's brakes, stem to stern, as its life as a plow-truck was not kind to the lines or to the components.

Replacing the rear wheel-cylinders, I decided I should replace the old bolts, as I had lost one and the remaining three ranged from crusty to crustier.

So off to Lowes I go, wheel cylinder and old bolt in hand. The front caliper banjo bolts, as well as the bleeders, are now metric, so I'm looking at the metric bolts, M8 seeming to be the right diameter, but the 1.0 pitch is too fine. So I try the 1.25 pitch thread; *still* too fine. The thread-pitch on the M10-1.5 bolts seems to match, so I start looking for some M8-1.5 bolts. They don't have them.

Nor does Autozone.

Nor does O'Reilly.

Fastenall doesn't open until tomorrow.

So, I give up, have dinner and get ready to settle in for the night, and start researching on the internet these metric-thread bolts that are all new to me.

But nobody mentions the M8-1.5 size.

Anywhere.



Huh.

Could it be?

Out to the garage, where I have plenty of standard-thread bolts.

And sure enough; 5/16-18 it is.

So off to Lowes, who has plenty of grade-5 5/16-18x3/4" bolts that I can grind the tip down to the proper 5/8" length tomorrow morning.

So *some* aspects of the 1987 J-20 braking system are metric; the attaching bolts for the rear wheel cylinders are *not* among those parts.

[babywag]

Any parts store "should" have banjo bolts...or be able to order them.
GM D52 calipers used on millions of vehicles.
pretty sure they're 10mm for metric calipers.

[Bob Barry]

Yeah, those banjo-bolts are metric.

I forgot to mention the reason I thought the wheel-cylinder bolts were metric in the first-place is that they took a 12mm wrench to remove.

Turns out, they're 1/2"", just rusted down to 12mm.

I have *never* had such tight confines for a backing-plate, however! That 8200GVWR spring-pack blocks access to those bolts, the brake-line and the bleeder. I had to screw the brake-line in to the wheel cylinder before bolting it up.

[J20 project]

Bob and weave...just has to happen these days.

J20

[Bob Barry]

All done with the brakes!

Went from this:



and this:



To This:



after a LOT of degreasing and de-rusting.

Now to adjust the parking brake and maybe do a final bleed, if necessary, tomorrow, so I'll be able to drive it safely for the first time.

[chubbinius]

Holy smokes, that's quite the difference! Looks good all cleaned up and with the new parts.

My 70 Wagoneer has drums all around...hoping it won't be quite so scary-looking when it comes time to do them.

[babywag]

Gotta love the rust belt...I've seen worse drum brakes, but not by much! haha

Seen and refused to work on several plow trucks back when I was wrenchin' in MN...
Too unsafe and told owners to retire them before they hurt themselves or some other poor unfortunate soul on the road.

[Bob Barry]

Brakes are bled and feel good.

Now, to find out why the (+) Feed to the choke on the 2150 is dead.

My neighbor's boy wants to learn how to work on cars; I told his dad to just send him over any Saturday, as there will *always* be something for me to teach him to fix on the J-20...

[jpcoutts]

I remember working on those wheel cylinder bolts, and the brake line behind those spring packs! I was very satisfied when I got it all done and back together! Mine weren't as worn as yours, just way more rusty and even a few cob webs from sitting for several years.

[Bob Barry]

I remember working on those wheel cylinder bolts, and the brake line behind those spring packs! I was very satisfied when I got it all done and back together! Mine weren't as worn as yours, just way more rusty and even a few cob webs from sitting for several years.

Yikes! Yours were worse than this?



I thought I had it bad!