Rear Disc Brake Conversion

1911

chupacabra
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Parker County, Texas
Hi. I have a 1977 FJ40 with 78 power steering. I’m converting the rear drums to disks but have no idea of what kit to use or what else I need to do.
If you can help guide me through the process I’d be grateful.
Also, fronts are discs but I want to redo them too. Should I replace or rebuild the calipers and where to get them and new discs. Thanks.
Paul

Paul,

As has been mentioned, there are several kits to do this, or you can assemble the pieces to do it yourself. At the time (13 years ago?) I used a kit from Man-A-Fre. As has been mentioned, you can get kits from several places. All of the kits use chevy Monte Carlo calipers. @Poser makes good brackets also, if you want to just buy the monte carlo calipers seperately. There are threads on this conversion in the 40 FAQ and/or here in the forum. If you can't find them, let me know. It's pretty much a bolt-up procedure. As long as you're taking off the drum brakes and related parts, now would be a good time to replace the rear axle seals, and your wheel bearings for that matter if there is any doubt at all as to their condition.

The stock front calipers are adequate, and if they're in decent condition there's nothing wrong with just putting new pads on and running them. A reasonably common upgrade is to replace the stock calipers with dual-piston 4Runner calipers. I haven't done this yet but would like to. There are threads on that here also.

The stock master cylinder will work with the rear disc conversion, and I ran mine that way for years, but found it a huge improvement after I replaced my stock master with a non-ABS FZJ80 master cylinder. If you do that, you will probably have to bend and probably do some cutting and flaring of your brake lines to fit. You will also want to run a proportioning valve for the rear brakes in either case.

As you can see, the rear disc conversion, while fairly simple in itself, can quickly take you down a long rabbit hole if you're not careful! Don't let all this overwhelm you; just giving you some options to think about depending on your budget and desire to work on your Cruiser.

Lee
 

1911

chupacabra
Joined
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Messages
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Location
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Check the FAQ section for this common mod. You'll find listings of parts and part numbers. Poser sells full kits. Well worth doing. The only thing I did extra was replacing the bleeder screw in the GM metric calipers with Speedi Bleeder to ease my one man bleed process. While the stock toyota bleeder screw in the front stock discs has very fine thread to ease the bleeding process because air will not slip past the tight/fine threads while loosened only a 1/4 turn, the GM caliper bleed screws are coarse thread and allow air to easily pass through, making bleeding a PIA. The Speedi Bleeders stopped that. I use the Phoenix system to bleed, and their catch bottle has a nice one way valve on it to stop backflow. You can make up your own cheaper version with a Dorman one way valve from a parts store, a bottle, and tubing.

I have the Phoenix system bleeder and like it too.

If you wrap multiple turns of teflon tape on any bleed screws, it will stop air from leaking through the threads, just FYI. As I remember, Phoenix even instructs you to do that.
 
Joined
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Messages
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Los Alamos New Mexico
Paul,

As has been mentioned, there are several kits to do this, or you can assemble the pieces to do it yourself. At the time (13 years ago?) I used a kit from Man-A-Fre. As has been mentioned, you can get kits from several places. All of the kits use chevy Monte Carlo calipers. @Poser makes good brackets also, if you want to just buy the monte carlo calipers seperately. There are threads on this conversion in the 40 FAQ and/or here in the forum. If you can't find them, let me know. It's pretty much a bolt-up procedure. As long as you're taking off the drum brakes and related parts, now would be a good time to replace the rear axle seals, and your wheel bearings for that matter if there is any doubt at all as to their condition.

The stock front calipers are adequate, and if they're in decent condition there's nothing wrong with just putting new pads on and running them. A reasonably common upgrade is to replace the stock calipers with dual-piston 4Runner calipers. I haven't done this yet but would like to. There are threads on that here also.

The stock master cylinder will work with the rear disc conversion, and I ran mine that way for years, but found it a huge improvement after I replaced my stock master with a non-ABS FZJ80 master cylinder. If you do that, you will probably have to bend and probably do some cutting and flaring of your brake lines to fit. You will also want to run a proportioning valve for the rear brakes in either case.

As you can see, the rear disc conversion, while fairly simple in itself, can quickly take you down a long rabbit hole if you're not careful! Don't let all this overwhelm you; just giving you some options to think about depending on your budget and desire to work on your Cruiser.

Lee
Wow. That’s great info. I’ve checked out the TSM website and it looks good. I also like the idea of dual piston 4-Runner calipers on the front. I will try to find the discussions in this forum. But wouldn’t object if you led me to them.
I think I have a semi float rear axel and not a full float. I don’t know the difference but I know it’s stock.
I heard that my parking brake hooks to the transmission and not the rear wheels. But I can’t verify this info.
I also have OEM power steering installed from a 78 FJ40. I’ll have to check out to see what room I have for the master cylinder and proportioning valve you mentioned.
I would be very happy to finally put this brake job behind me and get on to other things.
The engine (Chevy 305) hasn’t run since 2007. I have no idea what shape it’s in. I’m hoping to put a new 350 crate engine in, but still haven’t decided.
The Cruiser had little rust. Some concern along the top above the windshield and along the front underside of the hood. But nothing that can’t be dealt with.
Thanks for your help. I hope to keep this channel open as I progress. You sound like a great resource of information and experience.
Paul
 

1911

chupacabra
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I also like the idea of dual piston 4-Runner calipers on the front. I will try to find the discussions in this forum. But wouldn’t object if you led me to them.

Here's a start; don't worry much about the discussion on spacers in this thread, not needed: 4-piston 4runner calipers - https://forum.ih8mud.com/threads/4-piston-4runner-calipers.521704/


Here's a more complete thread doing this mod on a 60-series, but there won't be much difference from your '78: 4Runner Calipers, T100 MC, Rotors and Backing Plate Eliminator install - https://forum.ih8mud.com/threads/4runner-calipers-t100-mc-rotors-and-backing-plate-eliminator-install.281660/
 

1911

chupacabra
Joined
Aug 11, 2006
Messages
6,680
Location
Parker County, Texas
I think I have a semi float rear axel and not a full float. I don’t know the difference but I know it’s stock.
I heard that my parking brake hooks to the transmission and not the rear wheels. But I can’t verify this info.
I also have OEM power steering installed from a 78 FJ40. I’ll have to check out to see what room I have for the master cylinder and proportioning valve you mentioned.
I would be very happy to finally put this brake job behind me and get on to other things.

If your Cruiser is a U.S.-market Cruiser (i.e., not an import from South America or Australia, etc.) then your rear axle is semi-floating. The foreign market full-floaters have a long hub that sticks out very obviously; the semi-floats don't stick out at all, they're practically flush.

A stock '78 Cruiser will positively have the parking brake on the end of the transfer case. This means you can easily convert the rear brakes to disc, and not worry about losing your hand brake. The parking brake didn't go to the rear axle until 1981 if I remember correctly.

The non-ABS FZJ80 master cylinder is shorter than the stock master in my 1980 (12/79 build). The City Racer vacuum booster was quite a bit shorter than my stock one, but still works as well or better. So, you could gain some under-the-hood real estate by switching to this booster and master combo.
 
Joined
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Messages
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Location
Los Alamos New Mexico
Here's a start; don't worry much about the discussion on spacers in this thread, not needed: 4-piston 4runner calipers - https://forum.ih8mud.com/threads/4-piston-4runner-calipers.521704/


Here's a more complete thread doing this mod on a 60-series, but there won't be much difference from your '78: 4Runner Calipers, T100 MC, Rotors and Backing Plate Eliminator install - https://forum.ih8mud.com/threads/4runner-calipers-t100-mc-rotors-and-backing-plate-eliminator-install.281660/
Thanks. (Do I refer to you as 1911 or Chupacabra?).
Anyway, I have read the threads and still confused about what exact parts to get. There was so much discussion that I couldn’t tell what the final parts list was. I replied to the main comment, asking for clarification but it’s an old thread. I’ll see if he responds.
I need to organize this on paper. Identify the parts, part numbers, where I can purchase them and note any peculiar tasks like stud replacement, grinding, spacers, ss lines needed etc.
Thank you so much for your help.
BTW, my Cruiser has aluminum rims that my sister gave me. I don’t know what brand but I know they were expensive. I guess I’ll have to check for information interference when I get the parts.
I’m simultaneously trying to identify the parts and sources to convert rear drums to discs.
I’m a physicist. Auto mechanics is a bit out of my talent range so I’m having the work done by my mechanic here in town. I will order the parts and drop ship them to his garage. So I want to make sure he has everything he needs and that I understand the process.
 

DSRTRDR

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Hi @Pmanhart,

converting the rear to disk brakes isn't really rocket science (and I am saying this as a molecular geneticist :lol:):

get the Poser bracket and the Monte Carlo calipers - and then you need to install, in-line to the rear brake line coming off the master cylinder, a proportioning valve that limits the rear brake force - proportioning valves can be sourced from any of the speedshops, like Summit or Jegs, or somesuch - mm diameter on the fittings may need some adapters, depending on which valve set-up you go with By popular demand: proportioning valve install without brake line flaring - https://forum.ih8mud.com/threads/by-popular-demand-proportioning-valve-install-without-brake-line-flaring.82821/

and when it comes to bleeding the brake system, nothing beats the two-person system :cheers:
 
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