New Shoes and Hub too Tight

[SturmTyger380]

I am new to the M35 trucks and my son and I have been rebuilding his brakes. We have new shoes and have the rear axle done. With the new shoes the hubs fit really close and have to be lined up just right to go on.

I am working on the drivers side first rear axle. I have the shoes on and adjusted the bottom adjusters to where I think they are in most.

The top adjusters are turned so that they are at the in most position. With the return spring on the shoes are not pulled back all the way to touch the adjusters. I am guessing the new slave piston is holding them out. I can put a hold down strap around the shoes and cinch them in but I can't leave that on and when I release it the shoes move back out.

How can I get the shoes retracted more so that the drum will go on?

 

[doghead]

Open the bleeder?

 

[SturmTyger380]

We have not connected any of the hydraulic lines. We plan on purging the lines last thing before we connect everything. There is the plastic plug in the brake line hole of the cylinder. I had not thought that it might be tight enough to keep the pistons from going in. Hummm...... will have to check that out. If that is it I am going to feel stupid.

 

[clinto]

Doghead's method will work, I've used it before when I ran into your problem.

Also, you can verify you are correct on the bottom adjustment by removing the access plate from the outside of the drum, rotating the drum down to the bottom of the shoe and watching the bottom of the shoe move in and out as you turn the lower adjustment anchor.

I am sure you've read the TM and know the specs for the shoe clearance. I have occasionally had new shoes that were so thick that you couldn't get the proper clearances, if you do you'll just have to get it as close as possible.

Another trick is to get the shoes compressed down and have a helper ready with the drum-get them right, then throw the drum on before they can expand back out.

 

[Tow4]

+2 on the bleeder or pull the plug out of the wheel cylinder where the brake line fitting goes so trapped air can escape if you haven't hooked up the brake lines yet.

Brake shoes should not make contact with the brake drum unless the brakes are applied. There is a clearance spec in the TM, I think around 0.020. The springs should have enough power to pull the brake shoes into the adjusted position clear of the brake drum.

 

[SturmTyger380]

Well that was interesting. I loosened the bleeder screw cause that would let air out and less dirt inside. Then I used the strap around the shoes to pull them in. Well they moved in some but not enough to allow the drum on.

So I started fiddling with the bottom adjusters. I had them rotated so they where in as far as they would go the first time but there seems to be a point where they start to move back out just a little and then top of the shoe moved much closer to the cylinder. Hard to explain but it worked and now the drum is back on, all adjusted, axle back in and the tires back on.

Alan

 

[peashooter]

The top adjusters are turned so that they are at the in most position. With the return spring on the shoes are not pulled back all the way to touch the adjusters. I am guessing the new slave piston is holding them out. I can put a hold down strap around the shoes and cinch them in but I can't leave that on and when I release it the shoes move back out.

How can I get the shoes retracted more so that the drum will go on?

I'm dealing with this same issue now (new shoes and new wheel cylinder not yet hooked up to hydraulics). I'm replacing every bit of brake components so haven't got the hydraulics all installed yet. The new shoes are just too tight regardless of how I adjust everything. It's like the wheel cylinder is holding the shoes open too far.... Does the hydraulic system pull the wheel cylinder pistons in when not engaged? Just trying to figure out if I need to finish the hydraulic system first to make things work right or what? The new shoes are just too big at the moment. Would like to finish this front axle overhaul before moving on to the hydraulic stuff but can't get the drums on and when I do, I can't get them to turn

 

[DieselBob]

Does the hydraulic system pull the wheel cylinder pistons in when not engaged?

No. The only thing that retracts the shoes to the rest position is the return spring. One thing to remember is the bottom anchor pins are eccentric and not only cause the bottom of the shoe to move closer or further away from the drum but will also kick the shoe up or down depending on which way you are turning it. If one or both of the shoes is out of vertical alignment that could cause the drum not to fit correctly. Just something to check.

 

[SturmTyger380]

Even though my slave cylinders were new opening the bleeder screw did help. The drum has to not have any angle to it when you go to slide it over the shoes. I still had one very tight one and that position gets hot so I might have to go back in that one.

 

[rosco]

There should be virtually no reason to move the shoe anchor pin. That said, refer to the TM to re-adjust. Then everything in there should be clean and move freely. Like the shoes on the anchor pin, and the adjusters (these should have some drag). They should be (for re-assembly), adjusted all the way in. When re-assembling, the drum needs to go on absolutely straight, or it won't go on. Most of the problem there is that its heavy, and your vision is obscured, by the drum assembly itself. And also, leave the bleeder open too. I like to leave (on the rears), the duals on the drum/hub. Its less work, not taking the duals off. There are two ways to do this: Use a little jack w/casters & lift arms, designed to to do it if your rich(a pallet jack will also work, if your semi rich), but you need a hard surface to roll them on (maybe the Walmart parking lot, if your going to be fast). If your not rich, use a piece of cardboard or plywood, grease it up good right under the tires, take the load off the assembly with an axle jack, and just slid the assembly off the the axle & roll it out of the way. Two jacks work best, one on each end of the axle to keep it level. THEN, re-do the brakes, etc, and don't move the jacks, and it should go back on with a min. of fiddling.

 

[peashooter]

Yeah just a reminder, I used the tm, have them adjusted in as far as possible (including bottom eccentrics), got the hub on twice with bearings but it was too tight to turn without using a leverage bar. Tried adjusting more but can't get any gap on both top AND bottom. New brake cylinder isnt hooked up to hydraulics yet and no plug in the port... bleeder screw isnt open but fluid port is wide open). I might end up cutting the slots deeper in the wheel cylinder push pins so the shoes can close in a tad more.