What have I gotten myself into - chevy axles

[robo]

I bought a chevy dana 60 and 14 bolt, supposedly from a cucv, for $300. I've read enough here to know I need to do rear disc swap, and the tear down has begun. But some more questions for the gods our forum:

1. For rear, what is the required rim backspacing to get end to end length somewhat close to stock? I seem to recall our rims have 5" backspacing, so I'd need like 2" or 3" to even out the short 14 bolt? My 14 bolt is about 70.5" overall.

2. Does the front need to be spring over? It seems most here have done it that way, but is that the path of least resistance? If front is spring over, do I need blocks under rear springs to level it out? Anyone got pictures of their front setup as the rear seems the most straightforward.

3. I'm running the corvette master for braking, but do I need to change it out if I'm going to run the discs in rear, or will I need to plumb an adjustable proportioning valve in the rear line?

Thanks!

[oskarkat]

Seems like you got a good deal on the axles. I'm interested in doing this swap myself but the cost of the axles has kept me on the fence. You're asking great questions and I'll watch this thread with interest. These guys know a lot, so you've come to the right place for answers.

[Barrman]

Spring over on front not needed. Spring under is actually an easier deal.

I have no idea on back to stock back spacing.

The "Corvetter" master cylinder is from a 1976 disc/disc non power brake vehicle. Which is exactly what you are going to have when you are done. The M715 originally being a drum/drum truck with no valving. You can put a valve in the line to the rear brakes and adjust it to your liking. However, you probably won't need it.

[bluesman2a]

1. For rear, what is the required rim backspacing to get end to end length somewhat close to stock? I seem to recall our rims have 5" backspacing, so I'd need like 2" or 3" to even out the short 14 bolt? My 14 bolt is about 70.5" overall.

2. Does the front need to be spring over? It seems most here have done it that way, but is that the path of least resistance? If front is spring over, do I need blocks under rear springs to level it out? Anyone got pictures of their front setup as the rear seems the most straightforward.

3. I'm running the corvette master for braking, but do I need to change it out if I'm going to run the discs in rear, or will I need to plumb an adjustable proportioning valve in the rear line?

I'll agree with Barrman here.

I run CUCV axles, have 4-wheel discs, and run a corvette master, so I know what you're talking about.

1) Not sure what BS I'm running, but it was nothing special (they were off-the rack at 4 wheel parts), I don't believe it was 5" though, more like 2 to 3.5 or so and the outside of the wheels are about right at the fenders, looks good.

2) no, mine is spring-under in the front. You just need to build a perch for it underneath and cut the web off the chunk where it gets in the way. If you do this, the truck will be level, no blocks required.

Here's a link to most of my setup:
http://s270.photobucket.com/albums/j...M-715%20Axles/




3) I run the corvette MC with mine, no prop valve, straight plumbing, no problems.

One other note here: I'm not normally a fan of Blue Torch stuff, but in our case, their 14-bolt brackets work nicely. You will need to clock the calipers down so they don't hit the spring-packs, the BTF brackets allow you lots of options.
http://bluetorchfab.com/store/produc...products_id=89

[robo]

Thanks - pics definitely help! It looks like you used about 1" pipe for spacing the rear holding brackets. Is that for calipers to clear the springs? I thought most kits already came with spacers or are built so no spacers are needed? Looks like a lot of metal to grind off the front housing. All I got is a die grinder, so I'd better stock up on lots of blades!

Utterly amazing how simple a 14 bolt its. I took the cover off but can't tell if it has a detroit locker or gov locker - any ideas?

On a bad note, I broke a stud in my 350 head while trying to swap valve covers and putting in victor intake manifold. Looks like my priorities have temporarily shifted to getting the beast functional again - darn. Maybe it's destiny that I just put in the 454 a fellow has up the road...

[bluesman2a]

It looks like you used about 1" pipe for spacing the rear holding brackets. Is that for calipers to clear the springs? I thought most kits already came with spacers or are built so no spacers are needed? Looks like a lot of metal to grind off the front housing. All I got is a die grinder, so I'd better stock up on lots of blades!

The spacers are included with the kit from the manufacturer. They are to center the caliper on the rotor.

On the housing, I took a little more than I needed to, I was running the plasma cutter so it was easier to clear it back then just grind to smooth.

[scottsmyth]

Is there a particular reason everyone seems to run a corvette master cylinder? I used one off a 71 dodge pickup, haven't tried it yet but I think it will work.

[robo]

I believe the corvette master cylinder had one of the largest diameter diaphragms to push fluid to stop our brakes. It is also readily available and is a direct bolt-in. Search under master cylinder and you'll find the reasons better stated than what I laid out.

[bluesman2a]

X2 what he said + the corvette MC is the cheapest bolt-on option.

[Barrman]

A little Zone history here. A former member, Tom, aka Spicergear, bought a truck that had no engine, transmission, tcase or brake master. The way he mounted his 427 Tall Deck/3053A M35 transmission is where the JP magazine article came from. It is also were the term "spicer plates" for the motor mounts came from. Tom wanted better brakes so he went looking through parts catalogs. Since a stock truck is drum/drum, he was looking for a twin piston master that had the same size bores at both ends. The bigger the piston, the more fluid it pushes. The 1976 Corvette was the last model made with an option of no power brakes. The cars were disc/disc. So, the non power mc had huge bores that were the same front and back. That is what Tom bolted on. He added Hydroboost later on to make it so the truck would lock up the tires at any speed with a toe twitch. As it is with no power assist, the stock drums front and rear will lock up the tires with a heavy leg push. I have the same mc on my truck.

By the way, the truck Tom was building he named Velvet. Tom and another former member named Barry took Velvet to top Truck Challenge in 2005 and did very well. Current members Doug and 40 Grit helped out with that effort.

Having written all of that. I am currently having trouble with my corvette mc holding fluid in. Agengr has had continious problems with his holding fluid and actually pushing fluid. I am going to pull mine apart again and see if new rubber makes it want to keep the fluid inside. I have heard other reports of basically bad quality when it comes to the Corvette mc's.

I have driven other trucks that have Wagoneer master set ups, J truck set ups, Cherokee set ups, Ford truck set ups swapped over. They all seem to work. I will add that the smaller the mc bore, the less pedal effort it takes. I drove a truck beloning to Kwai through traffic in Houston a while back and was enjoying the "power brakes" that let me keep my heal on the floor and just push with the toes to stop. I asked him what kind of booster it was and he started laughing and calling me bad names. No booster, just a small bore small truck master.

Whatever you use, make sure you have no leaks of any size, one push of the pedal stops all 4 wheels and that the back won't lock up a hair sooner than the front causing you to swap ends.