new rear drums ??

[f.boyle]

Has any one gotten new brake drums for there spicer 70??How much?Are all the spicer 70's in our trucks 35 spline?Thank you for your help.

Frank

Put the hammer down

 

[AMikonis]

I just bought some. They were over $70 each at my favorite independent parts house. Plus the hubs have to be pressed out of the old and into the new, so they charged, I think $1. 50 a stud for labor. The shop guy said I could reuse the old studs, had to bring one drum back because it wasn't properly seated on the hub. To make a long story short I ended up with another new drum and I'm not still not sure if it's right - haven't had time to take it down again. New studs may be the way to go. Somehow, with a couple wheelbearings and new axle seals I'm into this one-axle brake job for $400 in just parts and machine shop labor(!) It costs to have this big stuff.

 

[JLEONARD]

I replaced the rear drums on my 91 last summer.

Went back to the parts store several times to get the right parts.

They all wanted the numbers off the driver's door sticker, but none of the parts fit. Door sticker said 5500 # axle, but the correct parts were for a 6200 # axle, so they said.

The drums had a raised hub.

Also the brake cylinders did not match either.

I am lucky that my son is in the auto repair busuness (Goodyear at the time, now on his own). Once he found out I had the wrong parts, he had his contact get us all the brake stuff possible for a Dana 70 so we could match things up.

We got all the studs out with his air hammer, and got everything back together easily with hammers and wood blocks.

Don't remember all the prices, but the total including a new master cyl and axle seals was about $400 with his discount. I can look exact prices up tonoght at home if you'd like.

I also bought an axle nut socket , 2 9/16 if I remember right. $15 at a heavy truck parts store (Fleet Pride).

For reference... .

Drum BD 60328

Wheel cyl (1" dia) WC 78974/WC 78975

Shoes PAB 357AR

Master cyl WAG F98896



Hope this helps. Good luck.

 

[Matt S]

Go with the 3" brakes and 1 1/8" cylinders. Our axles are 32 spline but 35 will work if you are rebuilding the rear.

 

[Midnite]

Are the 35 spline axles larger diameter, or are the splines just a tiny bit smaller?



Just curious,

Mike

 

[Matt S]

I believe the shafts are both 1. 5" but have a different spline count.

 

[Dfeland]

I believe that our shafts are 32spline. The higher number the splines then the larger the shaft. The front end has 35 spline into the carrier but little 30 spline stubs to the hubs .

 

[f.boyle]

I pulled my rear axle out the other day to change cylinders. I cpunted 2wice pretty sure I got 35??Thanks every one

Frank

 

[Hart]

part # for 1 1/8" wheel cylender is ?????????? and where do I find them. hanks for any info Jim

 

[CDegner]

Why 1 1/8" wheel cylinder?

Everyone keeps saying to go with the 1 1/8" wheel cylinders. Can anybody give me a reason to use the 1 1/8" wheel cylinder over the 1"? Don't say it applies stonger because that is not going to hold water with me. The master cylinder pumps a finite volume of fluid per stroke. If that volume is flowing into a 1" wheel cyliner, it is going to push the pistons out further (due to it's smaller volume) than if it is flowing into a 1 1/8" cylinder.



Can any one persuade me otherwise?



Carl

 

[paccool]

Carl,

I did mine a few years back. At the time I had a friend working in the NAPA store and I went to him cause he gave me a discount. Told him I wanted to up grade to 3" shoes and 1-1/8" cylinder. He looked it up and said my truck CAME with those size items. Some one said the trucks could have either size, so????



I think you need to consider pressure rather than volume when thinking about the size of the cylinders. Just like a ram for a wood splitter or anything else, a pump putting out 2000PSI will always put that amount out. The larger the cylinder diameter, the more force that 2000# of pressure is able to produce.



If a master cylinder can put out 2000# (I don't know what the real number is), a 1" cylinder will convert that to 1570 pounds of force. A 1. 125 diameter cylinder will convert that same 2000# into 1988 pounds of force.



Gad, I hope I'm right here cause I'll really get flamed if I'm not!

 

[cerberusiam]

Consider the following formula:



holding force = pressure x area





Given a constant pressure increasing the area will increase the holding force. In the case of the 1'' vs 1. 25'' wheel cylinders if the pressure is the same in the wheel cylinder the holding force will increase. However, throwing in Carls assumption that a finite volume of fuid is pumped then the holding force of a larger cylinder could be less than that of the smaller cylinder.



If master cylinder fluid delivery, pressure release, and whatever else is in there are not set a certain limit, you should expect to have a slightly longer stroke on the pedal to fill the extra volume required but you should be able to increase the holding force and braking by installing the larger wheel cylinders. We are ignoring the proportiong valve and RWAL valve but as a guess they should not affect the amount fo fluid delivered.



Just upgrading to the 3" shoes will increase braking efficacy by increasing the area applied to the drum. If the pressure variables also remain the same then the larger cylinders will increase it a bit more.



From personal experience if you mismatch the MC to wheel cylinders there are issues with stopping power. This generally only happens when you start swapping between disk and drum brake systems. Given the amount of fluid that is expelled during bleeding I cannot see how the MC would not be able to handle the extra requirements of the larger cylinder. Given that and it would not be cost effective to have different fluid delivery systems between the 3/4 and 1 ton versions of these trucks I suspect the only difference is the wheel cylinder and brake shoe dimensions.



About the only way I know to be positive is measure the output from a 3/4 and 1 ton MC and somehow verify the pressures obtained are close to each other. Lacking that information I say to each his own as long as the brakes work.

 

[JLEONARD]

Given that and it would not be cost effective to have different fluid delivery systems between the 3/4 and 1 ton versions of these trucks I suspect the only difference is the wheel cylinder and brake shoe dimensions.

I agree... . that's why the change to 1 1/8 cylinders for the "heavy" applications... must have been the most cost effective (read cheapest) way to deal with it. Costs go up big time for low volume items.

Jay

 

[Case500D]

Here goes an attempt to explain what has worked for me. I have done the rear brakes on both my trucks in the past year. I tow quite a bit and am hard on brakes in general. I went back to drum brakes on the W-250 because the rear disks performed less than desired. I am running 1" wheel cylinders and 3" shoes on both trucks. The dually has the RWAL valve removed, the 3/4 still has it. No difference in braking because of the RWAL valve. The reason I went with the 1" wheel cylinders is as follows. A MC has a set amount of fluid flow and pressure that it is capable of delivering. The 1. 125" cylinders are able to exert more force on the shoes, however it takes more time for them to react or fill. The 1" wheel cylinders bring the rear shoes in faster. On both trucks you can feel the rear brakes working with each stop. When I had 1. 125 cylinders on the W-250, I couldn't ever feel the rear brakes working unless I really got on the brakes hard. The fronts were doing most of the work because hey were already applied when the rears were just starting to come in. Both trucks can readily lock the rear wheels up in a hard braking situation. Towing is much better now that I know I have faster acting rear brakes.



Now for a bit of a sermon. When you do rear brakes, have the rear drums turned or replaced. I bet there isn't one guy out there who can spot an out of round drum by eye. If the drum is out of round, you loose a lot of effective contact area for the brake shoes. Obviously replace the shoes. Change the adjusters, springs, and adjusting cables (adjuster and small parts kit at NAPA). The adjuster cables will stretch over time and use. The last set I compared (new to old) had a 1/8" difference in length. Take the anchor bolt apart and make sure it works freely. If you don't do those things, then your efforts of a brake job could well be wasted. Dodge brakes are effective if they are setup right. It will cost some money to do a brake job, but like Andy and Stan said, you have to pay to play. Hope this helps some guys out.



Jeremy