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Rear Disc Swap

Old 08-24-2009, 10:21 PM
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booked*
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Old 08-25-2009, 06:28 AM
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Mine "rolls" a bit before it catches as well. I too also have to mess with it a bit more to make it grab better.
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Old 10-29-2010, 10:27 PM
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Rear Disc Conversion

Doing my '84 now and redoing bearings and the axle and seals n all while I'm in there. Not been done on this little beauty. Can I just remove the backing plate all together, in this case?

Thanks
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Old 10-29-2010, 10:59 PM
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Originally Posted by TruckeeToy View Post
Doing my '84 now and redoing bearings and the axle and seals n all while I'm in there. Not been done on this little beauty. Can I just remove the backing plate all together, in this case?

Thanks
hmmmm...i don't see any backing plates on rear disc set ups
when I do mine there won't be any...
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Old 10-29-2010, 11:07 PM
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lmao i think he meant can you take them off, without cutting them.

yes you can, but you have to have the bearings pressed out or whatever.

it's just simpler to cut the backing plates off.
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Old 10-30-2010, 12:47 AM
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nice write up, thanks.
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Old 10-30-2010, 08:10 AM
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Originally Posted by TruckeeToy View Post
Doing my '84 now and redoing bearings and the axle and seals n all while I'm in there. Not been done on this little beauty. Can I just remove the backing plate all together, in this case?

Thanks
Yes you can just leave the entire drum assembly off. I did this on my 81 and 90 when I did the disc conversion, I replaced the bearings and press collar as well. There is an inner seal burred inside all the stuff to, replace that as well. You will have to make a tool to get the old axle apart. You can look for a picture of the Toyota tool on the Toyota SPX website,they sell the Toyota service tools.
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Old 11-01-2010, 10:33 PM
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Re. drum brake backing plates

I ground off the backing plates but could have used Trailgear's Rear Axle Bearing Pockets:
http://www.trail-gear.com/rock-assault-axle-housing
They feature holes for the new nylock nuts and ss bolts Sky Manufacturing included with their kit (too bad I had to hunt down my own banjo bolts).

The axle housing bolts that I kept are just a touch too short for the adapter bracket. Guess I could weld them on on, then in 100,000 miles drill everything out and replace with the pockets. The nuts are only able to thread on about 2/3 of the way.

When first installing my kit, things looked askew until I cranked the lug nuts on to seat the rotor and compress the caliper piston enough. As for dimensions, Elvota, Yota, and bskey - you're right, the axle's width and twist can change the whole thing. I think my axle's torqued back some, and so I was barely able to get the upper caliper bolt in. Just barely cleared the springs.
You can see in this pic two things: the level of the caliper bolt with the leaf springs, and the reason that axle width precludes the placement of the brake line.
?action=view&current=AttachingDiscs005.jpg#%21oZZ2QQcurrentZZhttp%3A%2F%2Fs825.photo.jpg%26

I'll have to run it parallel the bracket and the springs:
Here's the overhead view:


Dang. I thought I was done with the grinder.
Do I need clips to keep the brake pads in place? The inner one has such a thing, but the outer pad floats and secures to nothing. It's just held loosely in place by the caliper body...
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Old 11-02-2010, 11:29 AM
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Before you break out the grinder...
Shouldn't your bleeder valve be higher than your brake line?
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Old 11-02-2010, 05:23 PM
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That caliper is upside down. The fitting is on the bottom bleeder ontop
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Old 11-02-2010, 05:31 PM
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I think you got the calipers in the wrong sides
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Old 11-02-2010, 06:12 PM
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Indeed.
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Old 11-02-2010, 09:50 PM
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Re. calipers backward

Thanks guys. Duh. Switched them up, bled the brakes, and just when I was thinking I was done and ready to see how the proportioning valve carried through, the new FJ80 master cylinder (from same prominent off-road shop in CA that messed up my axle bearing and seal kit order twice) failed. Leaking out the bottom. Can see the pinholes in the cheap metal seam on the bottom front end of it. Brake fluid everywhere - I originally thought it was from bleeding the MC. Not so. I'll save the sob story about how sad I am without my truck working for the company that's going to be sending me a new MC asap.

Last edited by DeathCougar; 11-05-2010 at 10:50 PM.
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Old 11-04-2010, 12:49 AM
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We'll never know what TruckeeToy said before he got the wambamhammer

anyway, your caliper doesnt look like my GM calipers. But heres how these particular ones should be installed

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Old 11-04-2010, 01:09 AM
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heck heres your caliper, same as elvotas pictured on the first page,

Name:  19.jpg
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interesting...seems like it should be flipped. I'm confused how this bleeds?
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Old 11-04-2010, 05:21 AM
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Bleeder goes on top as air rises in fluid. Bleeder is on top in that pic.

:wabbit2:
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Old 11-05-2010, 12:59 AM
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Well yea i understand that but still a strange design how the inlet is above the bleeder. Maybe my "style" GM caliper was a later model?

IIRC the data used to order it was an 82 Montel Carlo front calipers thru NAPA.

Last edited by drew303; 11-05-2010 at 01:01 AM.
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Old 11-05-2010, 08:25 PM
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Re. wambamhammer and FJ80 master cylinder

Thanks guys. Duh. Switched them up, bled the brakes, and just when I was thinking I was done and ready to see how the proportioning valve carried through, the new FJ80 master cylinder (from same prominent off-road shop in CA that confused my axle bearing and seal kit order twice) failed. Leaking out the bottom. Can see the pinholes in the cheap metal seam on the bottom front end of it. Brake fluid everywhere - I originally thought it was from bleeding the MC.

Upon receiving the new FJ80 MC a day after it was promised (that would be today, thanks FedEd), on it goes. Super careful seating of the hard lines in the the MC inlet ports; cleaned everything very thoroughly first. Bled all the lines extensively (might as well flush system since this has gotten silly), but the pedal still goes to the floor. It can almost hold pressure but there is a barely-detectable loss of pressure if the pedal's held. Wife bailed and I've no bleeder kit. More bleeding should do it....

The calipers are off an '85 Eldorado, I believe, per Sky Manufacturing's recommend.
http://www.sky-manufacturing.com/new/detaproduct.php?id=128
They have no spring kit or clips with them, and so the outer disc brake pad moves around a bit more than it should. Perhaps it will seat itself after initial use.
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Old 11-05-2010, 10:50 PM
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I fixedded it
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Old 11-08-2010, 09:05 PM
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Re. rear disc swap on the '84

Deathcougar, I did fixeded it. Bled the proportioning valve, completing the system flush, bled my little heart out and then, despite the pedal still being too soft, took her out for a spin. Three pedal pumps and she's stopping great. I take her to a local shop with the best brake tools in town. They say she's as bled as bled can be, which made me feel better.
This particular shop thinks that the left rear bearing was not pressed in too exactingly - it's out of round, they say, and so there's a vertical motion, not a wobbily-wheel lateral motion. I sensed it and was able to see it just barely at speed, with a few 32' ladders on board, and then on the way home, too. This bad pressing-in could be prohibiting the caliper piston from working as it should, I'm told. That doesn't add up to me... But what do I know.
The shop where they pressed in the bearings says that could be the case. Nobody's perfect. All I have to do is tear that left axle out again and bring it to them to make it right.
There is a test one can do to measure the pressure being put on the rotor by the caliper piston and pad. Same tool measures the pressure drawing the piston back into its home in the caliper. What this tool is called, I will find out tomorrow when I find a place to measure whether or not each caliper's working properly.
At least she's drivable - it snowed today.
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