Rear discs on HJ61 - questions

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N

NeverClean

Joined
May 8, 2009
Threads
12
Messages
77
Location
Brisbane, Australia
Hi everyone, I had a no brakes situation on the weekend :eek: which means that I am looking at replacing all of the existing standard braking components, or looking at upgrading the brake system on the HJ61.

I plan to upgrade the fronts with the 4runner calipers and slotted rotors, and use the early FJ80 master cylinder.

I have looked through 'mud at all the disc brake conversions that I could find, but it doesn't look like anyone has installed the rear discs out of a late model hzj75 (or Hj75 or FJ75) into a 60 series - is there a reason for this?

The reason that I'm looking at this conversion is that it seems that I can get rear discs wit an e-brake using all Toyota parts and a minimum of custom mods.

I have found the following information, can any of you confirm or correct the following:

  1. The hzj75 spindle (FF axles) and disc hub is the same length and uses the same bearings as the drum brake version, and the drum brake version is the same as the components on the 60.
  2. The differential flange bolt pattern is the same on both the hzj75 and the 60 series.
  3. The e-brake cable arrangement on the hzj75 rear diff for both the disc brake version and the drum brake version is the same.
Modification laws here are pretty strict and if I can put a conversion together without custom components it is way easier to get it approved. It also means that I can easily get replacement parts.

Any other comments or information would be appreciated also.

Hopefully this will work and I can post up the conversion as I go.
 
In the US, we don't have any 75 series trucks, but we do have 80 series trucks. If you take a J80/J81 full floating axle and put it under your 61, then you will have rear disks and a functional e-brake with all Toyota parts. That's what I did for my truck.

If the J75 full floating axle is similar / identical to the J80 full floating axle, then yes, it should work just fine.
 
swap in entire axle...
 
I have a disk brake conversion using chevy s-10 rear pads and calipers. It has been a pain ever since as I've put off hooking up the e brake. If I had to do it all over again I'd stick with stock drum brakes in the rear and make sure they were properly adjusted and working well.

I do not believe that I gain that much stopping force from rear disks. I am not trying to dissuade you. Make sure whichever route you end up going it thought through real well.
 
Randy88FJ62 said:
I do not believe that I gain that much stopping force from rear disks. .
Click to expand...

My real motivation when I did that was just maintenance and cleaning .. since we do have lot's of rain and mud down here .. drums were royal PITA .. disc are much more simple ..

E-Brake it's another story tho ..
 
Thanks for the responses.

Like I said in the original post, the transport department here is a real PITA - if I swapped in an 80 axle (which I agree is a good way to go) it would require welding of the housing for spring perches - to get this approved I would have to have the welds x-rayed and certified by an approved engineer - $$$$$$.

In regards to drums versus discs, for highway driving I don't really care either way, the 60 drums aren't too bad. EXCEPT I use the 60 off road frequently in mud and sand and it seems that within 6 months the internal components have disintegrated because I didn't completely strip them down and wash everything each time I have taken it off road. I know better and should have stripped them down, but it is a real pain.

I want the discs because they are easier to inspect and clean.

Does anyone know if the 80 series backing plate can be bolted onto the 60 diff?
 
I saw something about this....did the earlier 7Xs series drums cross over to FF 6Xs series rears? Maybe the 80 series forum, maybe the 70s...I think 70 series forum....someone wanted to put disks on their rear and wanted to use later same series stuff to do it...I wanna say the 80 backing plate does not bolt up...there is a set of plates that can be welded to the ends of a semi floating axle that allows for front spindles, hubs, rotors and calipers to use, still doesn't address the be brake tho:hhmm:
 
looks like it might be a flat NO...buuuut with a good welder, a guy could cut off the spindle/backing plate mounts and swap em over without anybody knowing, no? there is a sleeve that the spindle inboard end slips into on the housing proper, about 7-8mm slice thru the housing at the spindles weld joint-just behind the weld joint that is- and around the housing, and the spindle end can be driven out of the housing. if you make your cuts nice and tight to the weld, you'll still have about 20mm of the stub end to locate it into the other axle housing, pack the bearings and load the hubs and bolt the axle shafts to em and drop the diff in and send the axleshaft/ stub hubs assemblies home. set the brake caliper angles and burn em in. some paint, and it'll look like factory;) MIGHT have to have a tiny bit of machine work done to match the inside outside of the receiver and socket ends...you could say it was a saudi cruiser option....
 
Thanks Lambcrusher - it does look like a big fat no. :bang:

Looks like I have to come up with something else to fix the problem. An axle swap might be the way I have to go - I can feel the money pouring out of my pockets as I write this, damn it!

I'll keep searching and post any other ideas. Does anyone else have some ideas they have been considering that aren't already on mud? I'd be keen to hear what they are because I have to do something to get the truck back on the road - and I don't want to buy all new standard parts to have them fail again after driving through some salt and sand.
 
I have been looking through the threads I listed above and it has occurred to me that it might be possible to index the backing plate by about 15deg drill new holes to fit the 60’s diff bolt pattern and use a spacer (ie the centres out of the 60 drum backing plates) so that the 75 backing plates can be bolted up hard against the flange. See sketches below.
Sketch_zps14c5f316.gif


I note in the posts by Beanz (https://forum.ih8mud.com/70-series-tech/81157-80-rear-disk-brakes-70-ff.html) that the spindle in the disc brake rears are longer and it appears to be only in the section closest to the flange and looks to be about 3/8” or 10mm longer than the drum spindle. Does anyone know how much clearance there is between the e-brake components and the hub flange in the 70 series? If there is enough space, maybe my plan can still work.

The top sketch requires some explanation. What I am trying to do is compare the layout of the disc rear and drum rear. You need to look at it as if each side of the centreline is a section of the brake arrangement – the red being disc brake components and the blue being the original components. If anyone can fill in any of the Ø? Values or the X values it would be much appreciated. Also, please note the # items – these represent the most likely areas of interference (from what I can see). If anyone knows if these areas do clash please let me know. The interference areas are:
#1: between moved seal (including bolts) and hub;
#2: between wheel studs and drum brake components;
#3: between drum brake components and moved seal;
#4: between bolts and e-brake penetration through backing plate.

The dimensions that are included have been drawn from brake component specifications. If anyone is able to provide any of the above information I hope this will aggregate some of the information from the threads listed above for easy reference.

Thanks.
 
Last edited:
I have continued to look at the HZJ75 brake swap and have found the following after a rushed trip to a local scrap yard. I thought others might find the information helpful if looking at either the rear brake components of a 'J80 or a 'J6x LC.

In the drawing below are the APPROXIMATE dimensions from the two vehicles - the blue component is the diff flange from a HJ61 while the red component is a plate showing the bolt holes in the caliper tabs and the backing plate for mounting to the diff flange. I'll upload the photos that I took today also.

Does anyone have the OD of the inner bearing face on the HJ60 spindle (forgot to get this)?

layoutCopy_zps126ed504.jpg
 
The rest of the HDJ80 photos:












 
Now for the HJ60 photos:













 
Further to what Lambcrusher said above, and what Beanz has posted on the threads listed toward the beginning of this thread, it looks like the e-brake/handbrake components will hit the j75 hub flange due to lack of space as the spindle is shorter on the J6x.

However, the J80 hub should fit directly onto the J6x spindle and provides an extra 35mm of space between the backing plate and the flange.

I had a look at the clearance between the internal rib of the brake shoes, the upper brace, the e-brake/handbrake adjustment ring and the hub. Because the hub does not taper, it should clear by more than 6mm or 1/4" at the closest spot, regardless of how far the brake components are placed over the top of it. So, I don't think this is going to be a deal killer. It just means that I have to use the early 80 disc rotors that are 312mm in diameter, 18mm thick and have the 103mm high hat (as opposed to the 68mm hat on the 75 series rotor which is 35mm shorter). It also appears that all of the J80 hubs are the same from 1990-99.

If you have a look at the measurements in the photos above you can see that on the J6x the end of the spindle to the outside surface of the diff flange is approximately 135mm, whereas on the J80 the distance is approximately 168mm, which is 33mm longer. So, from the diff flange I get an offset of 35mm from the rotor (on the basis that the disc sits in the same place within the caliper) and the hub flange sits out 33mm. I think this means that I need to use a 2mm spacer between the hub flange and the disc hat so that the rotor doesn't foul on the caliper - but we'll see. ;)

Finally, it looks as though the J80 (90-92) and J75 (90-99) backing plates are the same and are what I need to use with the above components.

If anyone can see any issues with my plan please let me know.

Cheers :beer:
 
someones been doin their homework;) keep going....:popcorn: you might get us all somewhere...
 
Just a few more photos from a HJ61:
Inside of backing plate to outside of hub flange:
s_P5250070_zps1fb55005.jpg


Hub flange thickness:
s_P5250071_zps6bf93c36.jpg


As you can see from the last photo there is almost no room behind the flange on the HJ61, so the extra clearance that the J80 hub provides will be critical to fit the drum brake components.
 
I came across a truck with two calipers mounted behind each of the rear wheels today - it looked like one was a mechanical e-brake/handbrake. There was no brand on it though, so I am wondering if these are generally available and can be used more successfully than the combined hydro/mechanical calipers?

I have had a look on 'mud but it doesn't look like anyone has tried this. I have found the following Wilwood products (the ones I saw look like the second product), does anyone know if any of these have sufficient clamping force to use as a ebrake/handbrake on cruisers:
1. http://www.wilwood.com/calipers/CaliperList.aspx?subname=MC4 Mechanical
MC4_Mechanical-lg.jpg


2. http://www.wilwood.com/calipers/CaliperList.aspx?subname=Billet Spot Caliper
Billet_Spot_Caliper-lg.jpg


3. http://www.wilwood.com/calipers/CaliperList.aspx?subname=Mech Spot
Mech_Spot_Caliper-lg.jpg
 
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