View Full Version : 1970 FJ40 4-wheel disk brake conversion

06-26-2010, 10:58 AM
Hi guys, as some of you know, I recently purchased a 1970 FJ40. I am in the middle of installing the Saginaw power steering, all is going well. Wile I have the front end pulled apart, I am considering going with 4-wheel disk breaks. I have found the conversion kits, one online with everything less the booster (which I will need to find locally) for aprox. $1350.00 delivered. I wanted to get some opinions, in general, is it worth moving away from the drum setup? I have 33's on it now and will be looking to move up in tire size in the future. It also has ARB's front and rear. Thanks in advance for your thoughts!!

06-26-2010, 12:22 PM
need to know more about the kit to be able to tell you if it's any good. is it jtoutfitters? if so, search mud, they don't have a great rep. is it using oem parts? drums are great for stopping...a lot more pad to surface ratio, but they require a lot of maintenance to keep them that way. that's why discs are great.

will you be getting the better birfs/knuckle housings? what hubs are included? if it is oem, is it land cruiser, or mini truck? do they mention that to get the larger birfs in, you have to grind on your axle housing?

all those questions concern the front end only. the rear end will be a chevy conversion with floating calipers. are the rear rotors included? they need to be, otherwise, you have to have chevy rotors machined to fit the cruiser hubs.

fwiw, i have most to swap the front to discs with the larger birfs/aisan hubs/large pattern knuckles that i'm selling. you'd definitely want to get new rotors and you'd need a proportioning valve.

06-26-2010, 02:20 PM
Hi Ige, thanks for the reply, yes it is the JTO packages so I will check out Mudd and see what is up.. I know that these kits do not replace the birf's.
I am not afraid of rebuilding the drum brakes and existing system, so long story/short the drums would be just fine for larger tires as well?? I will PM you so we can discuss what you have and what else I will need to do the disk conversion... Thanks again! I will talk to you soon...

06-26-2010, 06:18 PM
Here are some pics of the Man-A-Fre kit that I installed. Very good quality. Two things,
1. You will have to remove the restrictor (small white plastic piece) from the master cyl to rear brakes
2. You will need to install a variable pressure regulator to the rear brakes or you will lock them before the fronts.

You will REALLY like having the disc brakes. Makes all the difference. Terry

See this link about proportioning valves - http://forum.ih8mud.com/40-55-series-tech/82821-popular-demand-proportioning-valve-install-without-brake-line-flaring.html

06-27-2010, 09:55 AM
Terry, thanks for the info and the pic's!! Those look really nice!!


Air Randy
06-27-2010, 10:00 AM

Properly operating disc brakes are head and shoulders better than properly operating drum brakes. As Ige already said, just the ease of maintenance and finding replacement parts makes it worth while before you even begin to discuss improved braking performance, no fade when wet, reduced fade when hot, etc.

You also need to go to the large pattern knuckles and get rid of the coarse spline axles and birfields in the process or you will for sure be breaking those if you run larger tires and a locker. I would get all of that stuff from Ige as she knows what is good and what isn't.

If you plan on wheeling this rig hard, now would be a good time to think of other upgrades. TrailGear sells a six bolt knuckle, or you can use a Marlin Crawler 4 bolt high steer arm and do the 5th bolt conversion it. This will help prevent another common breakage point running big tires. Marlin is also now selling 25mm trunnion bearing kits which is supposed to greatly reduce the chances of breaking that part. Thats what I installed into the Gecko along with the 5th bolt conversion, so far so good running 39's.

You may also want to go to the Toyota 1 ton master cylinder as it is larger bore and moves more fluid, almost mandatory if you decide to do disc brakes in the rear too. If you do, you will probably need to shorten the actuating rod 1/4" or your brakes will randomly lock up. If you keep your stock MC you will need to remove the 6 psi check valve from the front line, otherwise the disc's will drag. Ideally you want to install an aftermarket 2 psi residual valve to keep the pads slightly touching the rotor. This keeps crud from getting on the rotor and reduces the gap so you have less pedal travel before the brakes engage.

FWIW, I've bought lots of stuff from JTO and it's always been good quality stuff. I've done several returns and credits and I've always gotten good support from them, never an issue.

As far as buying the turn key kits, whether from JTO or somewhere else, they make the job a little less stressful since you get everything you need. On the other hand, you're paying a premium for what are mostly off the shelf Toyota (front)and chevy (rear) parts you can get any where. There is usually 1 custom bracket (which they sell separately) and then you have 1 small bump to grind off of the caliper for clearance. If you source the other stuff yourself you can save quite a bit.

Dr. Schlegs
06-27-2010, 10:17 AM
To echo Randy, trim the plunger when you convert to an 80 Master Cylinder. I know from personal experience the rear discs will lock up and than you have to drop to 4 Low to get it home. :o

06-27-2010, 10:22 AM
the pic terry posted is what 99.9% of the rear disc brake kits are, but looking at jto's website, it looks like they just modified it to fit the front.

issues are...
you still have your smaller bell and course spline birfs which are fine for stock, but weaker and more troublesome when you go larger.

you still have small pattern knuckles...see above.

you still have the long hub, which is more likely to get into rocks

you have chevy calipers/rotors...if you need to replace the rotor, you have to have a chevy rotor machined because the hub is too small.

if you break on the trail, i highly doubt anyone will have spare parts to fix ya.

if you go oem, it will cost about the same for a mix of used/new parts. the pics below show what i've got, which includes the shorter stouter fine spline birfs, short style aisan hubs, wider pattern knuckles. if toyota did it, this is how they would...oh, wait, this is how they did ;)

in addition you would need a knuckle rebuild kit, two rotors, brake pads, two caliper rebuild kits, two birf c clips, one lug stud (broken, although a good time to replace all), and 2 spindle nut kits (keeping them for my pig). you'd also need to check mud to see what they're doing to make the tie rod ends fit since the taper is a bit larger.

jto kit is $549. i'm looking to get $300 for all the stuff i've got and i priced the rest through marlin and napa and came up with another $225. so pricewise, you're about the same, but you've put stronger stuff underneath, your front end is now completely rebuilt, and it's not a gerry rigged setup to get you brakes. now, you see i've left out brake proportioning valve. you are talking about doing 4wheel discs, in which case you can run without one. i did it for years and i had to lock up the brakes on my soa40 on more than one occasion driving it on the road. if you only do the fronts, you will need one.

06-27-2010, 10:51 AM
Thanks All!! I am trying to digest all of this.. I did a little checking to try and help with my own confusion. I have ARB lockers front and rear in the 40 now, I have not pulled anything to look but going to ARB's website and looking at the 40series Land Cruiser application guide, it looks like the only ARB lockers available are all 30 spline. If this is the case, Ige, would I be better going with this knuckle http://www.trail-gear.com/images/130052-1-k-800.jpg and possibly this axel and berf http://www.trail-gear.com/birfields along with your setup for disk break conversion? Just trying to look at all options for the different components...

Thanks for all the great advise!!

06-27-2010, 12:46 PM
Sorry, I missed the part about doing all the brakes. I made the assumption this was for rears only, which is what my note is about. T

06-27-2010, 01:52 PM
OK, so after researching let me know what I am missing and what you think..

Trail Gear
30 Spline Birfield/Axle Kit 549.00
Fully Loaded Six Shooter Knuckle Kit 299.00
Rock Assault™ Trunnion Bearing Eliminator Kit 199.00
Birfield Snap Rings 6.00


LandCruiser Power Disc Brake Booster Conversion Unit 250.00

JT Outfitters
Booster adaptor plate 60.00

TOTAL $1923.00 so far W/O shipping

Still need:
Late model 40 series or 60 series, Spindle (30 spline) and Hubs, Calipers, Rotors, pads and miscellaneous materials.

Any thoughts?

Air Randy
06-27-2010, 03:33 PM
ok, So After Researching Let Me Know What I Am Missing And What You Think..

Trail Gear
30 Spline Birfield/axle Kit 549.00
I Like Tg But For $80 More I Would Get A Full Longfield Set

Fully Loaded Six Shooter Knuckle Kit 299.00
I Have These On My 40, If You Want To Use Ige's Large Pattern Knuckles And Add The 5th Bolt That Works Good Too

Rock Assault™ Trunnion Bearing Eliminator Kit 199.00
I Have No Experience With These But It Looks Strong, Basically Gives You A King Pin Setup, Or You Can Do The Marlin Crawler 25mm Trunnion Bearing Kit, Also Very Strong

Jt Outfitters
Booster Adaptor Plate 60.00

Total $1923.00 So Far W/o Shipping

Still Need:
Late Model 40 Series Or 60 Series, Spindle (30 Spline) And Hubs, Calipers,you Should Be Able To Get All Of This And The Power Brake Booster From Yoda Jim's, I Would Also Check To See If He Has A Complete Late Model Disc Brake Front End. You Can Usually Get Those For $350-$400

My Comments Above In Caps

06-27-2010, 03:39 PM
Thanks Randy, much appreciated. What is the difference between a birfield ans a longfield? I'm learning...

Dr. Schlegs
06-27-2010, 04:07 PM
I would suggest getting the 80 master and trim the plunger unless you need a new booster. I picked up a used 80 master and reservoir from yoda yard for $25.00. The bolt pattern is the same on 40's-80's. If money is not an issue go wild, but I remember when I was married I was on a budget :rant:. That little thing that looks like a measuring cup from JTO I don't have.

06-27-2010, 04:19 PM
Thanks Keven! Yes I will need a booster as my 40 is early 1970 with no booster on it at all. The thing from JTO is what will set the booster off the firewall so it will fit otherwise, I would have to mod the firewall...

Thanks again for the input!

Air Randy
06-27-2010, 05:20 PM
Thanks Randy, much appreciated. What is the difference between a birfield ans a longfield? I'm learning...

Same thing except Longfields are made by Bobby Long, if you get his 30 spline superset (inner axle, birfield) and his chromoly hub gears everything is guaranteed for life against breakage.

The TG stuff may be pretty good but for $80 this is one time where I say spring for the name brand stuff.

06-28-2010, 07:37 PM
TSM also makes rear disc brake conversion kits...supposed to be pretty good :dunno:

06-28-2010, 08:05 PM
Thanks Keven! Yes I will need a booster as my 40 is early 1970 with no booster on it at all. The thing from JTO is what will set the booster off the firewall so it will fit otherwise, I would have to mod the firewall...

Thanks again for the input!

FYI...You'll need to trim the upright reinforcement bar on the firewall to make the booster fit with proper clearance and a reinforcement plate for the booster to the firewall (available from JTO or just make your own from 3/16" plate). I converted this past winter and it's been the best upgrade I've done to my '69-40!

BTW, I have a complete stock front axle from a '76 with factory discs and 4 bolt knuckle arms if you want to go that way. You don't have to take the 3rd members if you want to use yours. LMK if you're interested and I'll shoot you a price.

06-28-2010, 09:51 PM
Thanks Matt and Dave!


06-28-2010, 09:56 PM
Randy, Thanks I checked them out and they do look great!! The MAF's also have a lifetime warranty but I like the fact that the Longfield's are made here and they have a GREAT rep...

Same thing except Longfields are made by Bobby Long, if you get his 30 spline superset (inner axle, birfield) and his chromoly hub gears everything is guaranteed for life against breakage.

The TG stuff may be pretty good but for $80 this is one time where I say spring for the name brand stuff.

Shark Bait
06-29-2010, 12:06 AM
I've got a complete set of dual circuit brake lines for an FJ40 for this conversion if you'd like them. LMK. :D

06-29-2010, 08:36 AM
Chris, I did not even think about the lines yet :o . Am I well advised to replace all the lines? This being said, if i am replacing the lines, should I replace them with new line? I have never replaced lines before, do I have to remove the tub? Again, with silly questions... :confused: