Picked up a 1970 GMC C3500 dump truck that needs some TLC

[Stimw]

It was the 10.00 x 20 Dayton rims that came on the F700 of our that we replaced with the one piece radial tire Dayton rims pulled from wrecked school buses. Locally they charge more for mounting the bias tires on the split rim Dayton wheels. Many still run them on older equipment. China imports the tires to fit this old Dayton rim. Dayton rims can be changed by hand if needed because with the nuts near the tire vs near the axle not as much torque is required to attach/remove them. To mount new tires on the Dayton radial tire rims you will want tire mounting equipment. They have a valley in the rim for the bead to drop into when mounting the tires to the rims. The split ring bias tire rims are not v shape.

The one piece rims have 22.5 tubeless or the larger are 24.5 tires that won't fit the older rims.
They do mount up without problems with lub and a tire hammer. The hard part is getting the bead to seal. They use those Cheetah Air Tanks that give a heavy blast of air to pop them up on the rim. Or some gas and a match!!!
A lot of people got hurt when Ford came out with a 16.5 rim for 1 tons and they got put on a 16" rim. When they aired them up they would blow off the rim!!

 

[Gale Hawkins]

Yes they are tubeless radials. Since ours were mounted tires pulled off of a wrecked school bus they were already aired up and ready to go. I gave the the tire shop our old pulled MH tires which he sold to another MH owner so he removed the old split ring wheels with the bias tires and put on the set of six radials (one piece rim) for me at no charge. I sold the six mounted tires pulled to a big truck tire service company for $100 for all of them and two where brand new. The owner did not want them at first but when I said $100 he got up in the truck and looked at them and handed me a $100 bill and I went home happy to be rid of something I could not pick up.

Now when I need service I will be able to find it and tires to fit these rims OK.

 

[pclausen]

Stopped by Autozone and picked up a 6 lug spindle nut. It was $20, but they have this program where I can return it anytime for a full refund. Same deal I did with the ball joint press.

Here's all the loose pieces after getting them off.

Here's the axle with the drum removed

And the monster drum itself

And the locked up wheel cylinder.

I made the (obviously bad) assumption that the rear end had recently been swapped/serviced when I got this truck based on the new rear bolts and brake lines. I'm going to pull the rear cover and inspect everything and replace the leaking gasket. I'll also do something about the brake lines. It sort of looks like work in progress by the previous owner.

The axle is a Dana 70HD, which I looked up and it has a 10,000 lbs rating. It was used from the 70's through 1985 by the big three, and was then available as an option all the way through 1994.

I don't think I'll have any problem finding a replacement wheel cylinder for it.

 

[Gale Hawkins]

You are making progress. That rear end came from a junk yard I expect since it is labeled 410 ratio or least the cover did and perhaps the gears themselves if the entire rear end was not swapped out.

 

[Stimw]

Love the Pics!!!
You even have self adjusting brakes!
What did the bearings look like?

 

[ultrarunner]

Looks much better than I thought it would be with the drum off.

Going through the brakes and suspension will make it a lot more reliable and work ready...

I'm still amazed at how inexpensive so many parts are for older american iron.

Never would have thought new AC/ Delco wheel cylinders for $6 would be in stock for my 85 3/4 Chevrolet.

Only wish my truck would be smog exempt... still have to take it in and most likely forever in my State... 1975 is the cut off.

 

[Kioti guy]

I used to have a 1976 chev c class motor home that I used as a tow vehicle for my race snowmobiles. It was a 3500 dually. Approximately 6 years ago I received a "Recall" notice on it saying that if it was still using the "Firestone" split rim wheels to immediately cease using them and to have them replaced.
I always thought if I was getting a recall for a 30 year old product it must have been an incredibly dangerous design that was likely still injuring people even then.

 

[pclausen]

Got the new wheel cylinders installed

The bearings in the drums appear ok both visually and when rotating them. However, the seal on the right side drum appears to be leaking very slowly. Nothing on the pad surface, but maybe I should change it. How hard is that to do?

I popped the rear cover off. Turns out there is no drain plug on these axles, so the only way to change the oil is to pull the cover or suck out the old oil. It was nasty.

Looks like it has been rebuilt before judging by the stamps and also the condition of the cover surface.

Some surface rust on the inside of the cover. I got the loose stuff off at least.

All back together using a Felpro gasket instead of just sealant as was the case before.

I'm trying to figure out what to do with this mess. There are no tabs or anything on the axle for me to attach this too. Perhaps they make diff cover bolts with a secondary thread that I could attach these to? Or perhaps a clip of some sort to slip under one of the diff bolts?

Also went ahead and had the rear wheels balanced. This one in particular looked like it could really use it!

 

[Stimw]

You need to remove the self adjusters and clean with a wire wheel and lub the threads and cup end. They adjust every time you hit the brakes when backing up but stop when adjusted properly.

One easy way to install a wheel seal is line it up and put a block of wood over it and knock the seal into place.
I have installed the large (semi/truck) wheel seals by tapping them to get started then tapping them into place with a punch when I didn't have a seal knocker. But that type of seal is not flat on the back.

 

[pclausen]

I found this excellent article covering the Dana 60/70 rear axle/break job:

A Boy and his Jeep » Dana 60/70 Rear Drums

Guess I'll be heading back to NAPA in the morning for more parts.