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Aero Cruiser Brakes and 
Brake Upgrade
George Kinnison

At the Vegas Rally, (1994) a number of new members expressed concern about their brakes. Since these new members had not attended a "Tech Session" they were not aware of the brake upgrade I have recommended for sometime. As we continue to receive new members, this will be a common subject, so I decided to write a paper for distribution. 

When Gardner Pacific manufactured the Aero Cruiser they had a subcontractor provide the fames.  From 1988 to mid 1990 the frames were made by Vironex, a California company. From mid 1990 trough 1992 the frames were made by LGS, an Indiana company. Both companies obtained the front components from Chrysler (Chrysler warranty did not go aft of the transmission). Chrysler identifies these parts as a Dodge 350 one ton (4000 pound axle with 12" disc rotors and 5/8" wheel stud bolts in a 8 bolt pattern). 

The differential running gear was provided by Spicer and manufactured by Dana. Identified as a Spicer H-60 single wheel application (they did not provide the rear brakes). The Spicer H-60 may also be found on Ford and GM. 

The rear brakes were assembled by the frame manufacturers. They used a standard Budd brake drum (3-1/8" X 12") but placed only a 2-1/2" brake shoe positioned by a 7/8" hydraulic brake cylinder. The hub was fitted with a 8 bolt pattern using only 1/2" wheel studs (1/2 ton application). 

The result was a hybrid system where the front brakes and back brakes were mismatched. The proportioning valve, which was furnished by Chrysler for the front system, would shift the braking load from the rear brakes to the front too quickly and the back brakes did not share the proper work load. This created excessive use of the front brakes and heated them excessively which eventually warped the rotors. 

Another factor was that rear brake automatic adjusting device does not work very well due to infrequent backing up and that allows excessive brake shoe clearance. This aggravates the situation with little or minimum rear braking at best. The strange thing about this hybrid system is that all parts are standard Chrysler parts. It could easily have been a standard system. 

A major improvement can be made to your Aero Cruiser braking system by upgrading to a standard system. Have the rear brakes match the front brakes. Since the rear drums will be removed you can also match the lug bolts and upgrade the 1/2" studs to 5/8" studs (your lug wrench would then be the same size).
This upgrade consists of the following:
  • Remove rear drums and machine out the old 2-1/2" shoe wear pattern.
  • Press out old 1/2" wheel studs, drill out for 5/8" stud and press new studs in.
  • Part numbers for 5/8" studs:  Dorman -610-20 or NAPA (Balkamp) 641-1297.
    Note 1: Don't forget the Lug Nuts.  See Lug Nut Tip for Chrome 5/8-18 RH thread, 7/8, 60 degree nuts for aluminum wheels.  
    Note 2: My mechanic says replacing the studs is optional and not really needed.  In fact the 2006 and later Dodge Ram went back to 1/2" nuts and studs except for the Mega Cab.  
  • Replace 2-1/2" brake shoes with 3" X 12" brake shoes.
    Part numbers: Raybestos 314 (semi-metalic) or NAPA 358R.
  • Replace 7/8" wheel cylinders with 1 1/8 cylinders.
    Part numbers: Raybestos or NAPA 36057 & 36058 (left & right)
  • Replace proportioning valve with 1 ton application (if need be) 
    Part number: Chrysler 4293184
    Note 3: I checked with George and he told me that when he upgraded his brakes he did not replace the proportioning valve at first.  After making several hard stops while test driving, he checked the brakes and found that the front brakes were much hotter than the rear brakes.  He changed the proportioning valve and test drove it again.  This time he was satisfied with the braking front and rear.  He told me that our Aero Cruisers have a 3/4 ton proportioning valve installed in them and it should be replaced with a 1 ton proportioning valve.  "They look the same," George said, "but they aren't".  

    I checked with the local Chrysler dealer and had them look up the part number for the proportioning valve used in the 1989 3/4 ton and 1 ton pickups.  They both have the same part number: Chrysler 4293184 which George says is the correct one to use.  To satisfy my curiosity, we also checked the 1/2 ton pickup and found it uses a different one, the same one used in Dodge cars.  

    So do you change it or not?  It's list price is $195 but you can normally get it for $140 to $160 depending on how hard you push the dealer.  The other consideration is the labor costs to change it out and purge the brake lines again after the initial brake job is done?  

    My mechanic said it wouldn't make much difference.  If we don't change the proportioning valve, only the rear brakes are involved.  If we change it after, then both the front and rear brakes have to be purged, but that is a half hour at the most.  The cost of swapping the proportioning valve is the same in any case.

    What is a proportioning valve used for?  It has 3 basic functions:
    • In our rigs it splits the hydraulic pressure 60% to the front "Disk brakes" and 40% to the rear "Drum brakes".  Note:  The master cylinder has a part in this also. 
    • It monitors the hydraulic pressure between the front and rear brake circuits looking for an imbalance.  If an imbalance occurs, the brake light comes on.  This could be because of worn shoes or a loss of hydraulic fluid, or any number of other reasons.
    • It monitors the brake pressure to the rear wheels and relieves (lowers) the pressure if it gets too high to keep the rear wheels from locking in a panic stop situation.
    For a more detailed explanation do a search for "proportioning valve" on the Internet.  I found several good detailed explanations.
    Notes added by Tom Heald 6/09/09
  • Purge out old hydraulic fluid and fill with new fluid.

These changes will make your Aero Cruiser's brakes the same as the standard Chrysler/Dodge 350 one ton pickup's braking system. You will notice considerable reduction in your brake pedal pressure as well as immediate deceleration as you apply the brakes.

Update: Here is a breakdown of the cost for upgrading the brakes on my 1990 23 foot Rear Bed model in 2009.   When replacing the right rear wheel cylinder with the large 1 1/8" cylinder the mechanic found the brake line ended up too close to the air bag so he relocated that brake line.  He also remanded that I replace the springs and clips used in the rear brakes and the rear wheel grease seals for the rear axel, which I did.   I did not replace the proportioning valve or the rear 1/2" wheel studs which would have added considerably to the total cost.  

The List Price in the table below is what you would normally be charged by the mechanic, the Net Price is the cost if you provide the parts yourself and the mechanic installs them for you.  I found the best overall price at Napa Auto Parts after shopping around, but that changes all the time.  They also charged a "Core Charge" for the Brake Shoes which I did not include because it was refunded.  

The rear brake shoes were not worn much at all and the wheel drums did not have to be turned.  This is surprising as the coach has 50,000 miles on it!   I guess the front brakes were doing all the work.   I hope the new brakes take on their fair share (40%) of the load.  They should, with the new 1 1/8 inch Wheel Cylinders and larger 3" Brake Shoes.

Part Number Description List Price Net Price
UP-358R 12" by 3"  Brake Shoes (L&R) 92.93 57.32
36057 1 1/8 Wheel Cylinder (R) 19.27 10.50
36058 1 1/8 Wheel Cylinder (L) 19.27 10.50
2243 Maxi Pack (springs & clips, R&L) 24.06 13.29
475458 Rear Wheel Seals for a Dana 60 rear axel (2) 69.70 53.98
DOT-3  Brake Fluid (1 Pint)   4.15
202X3 3/16 Flare Union   2.42
813-1203 Brake Line   3.98
Labor Remove and replace rear brake shoes, springs and wheel cylinders.  Fabricate new brake line for right rear cylinder, bleed and adjust rear brakes, road test.   539.00
Tax  California 9.5% Sales Tax   66.04
Total      $761.18

Keep on Cruisin', Tom Heald

Do It Yourself:   
Here is a step by step for you to upgrade the brakes yourself:

I just did entire rear brake upgrade today! It took 3 ½ hours per side. This is what I did:

1) Remove the wheel

2) Remove the 8 nuts and pull the hub out.

3) Find the tab that’s keeping the outer hub nut locked and using a screwdriver and hammer, bend it back out of the way

4) Remove the outer hub nut – this is big – about 2 ½” diameter. It didn’t require a socket or anything special– on the left side I used a pair of pump pliers, end-on, coz you can only get the tips of the pliers on the nut – and with a little force it turned! On the right side it was tighter, so I used a steel drift and my hammer and gave it a few persuading blows in the correct direction at one of the points of the nut and it turned – switched to the pump pliers and it was off easily.

5) Pull out the locking tab washer, revealing the inner nut – same size as the outer one – mine was easy t turn – on both my both wheels it just took a little twist with the pump pliers and the inner nut turned.

6) Pull off the brake drum – as you do so expect the wheel bearing to plop out in a big pool of semi-liquid grease, coz it will, so have a pad of newspaper down on the ground, between you and the axle and the bearing will drop onto that.

- By the way – lots of grease is going to appear from this point on. You need to have a sheet of cardboard or several pages of newspaper laiddown and you’re going to place the brake drum face-up on that, so that you can see inside the drum. Grease – lots of it – will ooze out of the hub onto the newspaper.

7) Now clean all the grease of the stub axle and you’ll be looking at nice, shiny steel.

8) TAKE A PHOTOGRAPH NOW – BEFORE DISASSEMBLING ANYTHING! using your smart phone or digital camera. That will be VERY handy later, when you're trying to remember what it all looked like and where everything goes.

9) Now undo the four nuts holding the brake assembly onto the axle – dead-simple, coz you don’t need to be trying to hold the bolts from behind so they don't turn because Chrysler sis a neat thing – they gave the bolts a single flat side back there, so they don't turn while you’re undoing the 4 nuts.

10) Now you can pull the entire brake backplate toward you a couple of inches at the top– it’s still fully assembled, with brake shoes, springs and all that stuff – and if you look over the top of it at the brake pipe you’ll see the brake bleed nipple (3/8” wrench takes that off). Once you have that off you can get at the brake pipe nut easily and use either a wrench or carefully start it turning with vise grips, finish off with your 3/8” wrench.

11) Now the entire, fully-assembled brake backplate is almost off – you just need to unclip the handbrake (foot brake) cable – takes about a inute and you’ll have the entire thing in your hands   
- Total time taken to this point = only 30 minutes, including removing the hub cap and the wheel.

12) Take the brake assembly over to a convenient table or bench and TAKE ANOTHER PHOTOGRAPH with your smart phone or digital camera!!

13) Now you can do your brake swap without straining your back having to stoop down – it's so much simpler and easier. Once you’ve removed the springs – about 6 of those, and the shoes, you can flip it over and remove the two ½” bolts and with a little tap, the old slave cylinder pops off.

14) Install your new cylinder and reassemble the whole thing, hang it on the axle and bleed the brake cylinder right there – dead-easy! Do that before you bolt it onto the axle, so you can easily reach the bleed nipple. 

15) Ok – now bolt it onto the axle with the 4 bolts, hook up the handbrake
cable again.

- By the way – oddly you’re going to find a lot more slack in the handbrake cable ! These new shoes are set somehow differently, so once you’re all done upgrading both sides’ rear brakes then you’ll need to take up a whole lot of slack in the handbrake cable by adjusting it at the front.
16) Now for the brake drum - take a good stiff wire brush and seriously scrub at the inside of the brake drum. (Make sure you ware a dust mask to keep the asbestos dust out of your lungs.)  – the inner part where the old, narrow brake shoes didn’t track. On mine I was REALLY lucky, coz after wire brushing it and then using 300 grit sandpaper on it, it was nice and smooth and I crossed over that line, a few times with my finger nail – from the shiny, worn surface to the newly-sanded surface and back again. There was NO difference in height. In other words my rear brakes hadn’t worn ANY material off the drum. No wonder the rear brakes on mine hadn't been doing any work!  If you do find a difference in height then you’ll need to take the drum over to a brake shop and they’ll turn it on a lathe for you and cut the unused ¾ “ to equal the rest of it - same diameter, in other words.

IMPORTANT NOTE: between the brake shoe ends, at the bottom is the automatic brake adjuster. It is a gadget that is a bolt inside a threaded sleeve. Make sure that when the cable that operates it pulls it, that it does indeed increase the distance between the shoes.  Guess what I found on my rig?!!! – the left one did indeed tighten the brake adjuster by one click every time I pulled on the cable – the right one had been installed backwards and every time you pulled the cable it LOOSENED the brake!!!!!! The shoes on the right side had virtually NO WEAR as a result!!.

You know how we’re supposed to back up and then jam on the brakes, repeat a few times and that’s supposed to adjust up our rear brakes? Well that causes a pull on this steel cable, which makes a little ratchet assembly unscrew the bolt from its sleeve a bit and that moves the brake shoes apart.

Not in my case – it was doing it the opposite way on my right rear wheel.

Anyway, I hope the above helps you – it’s not hard to do it and I’m so glad I didn’t entrust a shop to do it – I doubt they would have spotted the backwards-working brake adjuster and I would have ended up with useless brakes again after all that work. 

Here’s a link for a regular Dana 60 brake overhaul – it describes everything but he doesn't remove the backplate, which means his version is much harder on your back and you knees. Also of course he’s not upgrading to wider shoes but otherwise it's the same.

All the best! 
Jeremy MacDonald
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