Details aroung mini-truck to FJ40 disc brakes convert

Details around mini-truck to FJ40 disc brakes convert

First off... I promise I read the FAQ's and did many searches in the forum before posting this.

I am not asking which disc brake conversion is the best as I have already aquired a complete mini-truck front end.

Some details about my FJ-40 that may or may not matter: 95% off road use with the other 5% on road use being slow speed forest service roads. Spring over, shackle reversal. 36X12.50X15 tires with front and rear locker. Chevy power steering.

There are 2 main goals that I need to accomplish and I am hoping this forums obvious expertise can help me dodge the "gotchas" and do my conversion correctly the first time around.

Goal #1 - replace drums with discs
Goal #2 - replace broken birf with new one

Here is where I need the help:

The mini-truck front end that I have is really rusty. The rotors and calipers are borderline useable. Ideally I use these parts as cores to get new ones. What new ones do I get? Exactly what year of rotors and calipers should I go after?

Are the mini-truck birfs really that much stronger than the FJ-40 birfs? How much better are aftermarket birfs compared to mini-truck birfs? I would rather spend a little more money now and get a good set of stronger birfs than have to replace another broken birf in the future. However... I've seen birf kits around $500-700 and that is just insane IMO. So: what are my birf options that don't require me to sell a kidney to afford? - Don't miss-understand... I am sure those higher priced birfs are worth their weight in gold... I just cannot afford them.

I know that I will have to change steering arms (drag link, tie rods, etc.) and there is not enough room between my springs and frame for a hi-steer set-up... and I don't have enough time to do lots of trial and error, so who makes a really tough set-up that will work with my Chevy pitman arm as well as the mini-truck set-up that I am converting to?

How critical is getting the shims perfect when aligning the knuckle housing with the axle? I don't have the tools described in some of the posts. There were discussions about creating your own tool but I never found details on how to create said tool.

81-90 fj60 rotors,
86-88 4runner calipers(ifs)
allpro offroad has cryoed birfs for $99
someone has suggested a chevy starter bushing to use for the steering. going to try that one sometime next week when I do my swap, or get 81-84 landcruiser top arms, and your old steering is supposed to fit.
all I know at the moment

Read and enjoy.

With the exception of the Birf strength issue, all your questions have been answered in these links.

Regarding which rotors you need, be carefull on blanket statements. The rotors you need depend on the vintage and design of the minitruck stuff you are using. I used a 79 and could not find rotors anywhere but the dealer at $100 each. Autozone's computer said all take the same which is WRONG. IIRC, if you are using a 79 & 80 minitruck then you will need 76-78 FJ40 vented rotors. You can identify these as the studs only go through the hub, not the rotor and hub. The two also bolt together with (2) 8 or 10mm bolts. 81-85 minitrucks use longer studs that go through the rotor and hub, sandwiching the two together. These rotors are from the 79-82 FJ40 and can be bought anywhere for as little as $10/ea from Rockauto.com.

I have been told 60-series stuff can be used but have no personal experience. Others can chime in and I believe it is addressed in one or more of the links I supplied.


https://forum.ih8mud.com/showthread.php?t=47734
https://forum.ih8mud.com/showthread.php?t=51163
https://forum.ih8mud.com/showthread.php?t=51858
https://forum.ih8mud.com/showthread.php?t=51271
https://forum.ih8mud.com/showthread.php?t=53129
https://forum.ih8mud.com/showthread.php?t=79569
https://forum.ih8mud.com/showthread.php?t=79941

dgangle said:

if you are using a 79 & 80 minitruck then you will need 76-78 FJ40 vented rotors. You can identify these as the studs only go through the hub, not the rotor and hub. The two also bolt together with (2) 8 or 10mm bolts.

Click to expand...

The style hub and rotor combo that you are talking about here uses six (6) 10mm diameter fasteners to secure the rotor to the hub, not two (2). The 1981 and later 40/60/62 style hub uses two bolts, in conjunction with the six wheel studs.





On the calipers....I would get 88-91 V6 4Runner calipers....as they have four 40mm pistons instead of two 40mm and two 24mm like the 4cyl 4runner and Land Cruiser calipers....



On the birfs...

Yes the stock disc brake birfs are stronger than the drum brake units. If you are going to be running larger tires/locker up front and beating on this thing, you probably will want to just get the 30 spline Longfield kit, as if you do not do it now, you will be doing it later....or just get used to being broken and fixing your junk all the time.


I do not know anyone that has used all-pro's birfs and had anything good to say about them.

4WheelingPlus.com said:

How critical is getting the shims perfect when aligning the knuckle housing with the axle? I don't have the tools described in some of the posts. There were discussions about creating your own tool but I never found details on how to create said tool.

Click to expand...

When you take the minitruck front apart, keep the shims that were on the top of the knuckle with the steering arm and knuckle for that side, and do the same with the bottom shims on the trunion bearing cap, and transfer them over to the axle housing that you are using to convert to disc brakes...

The upper set of shims adjusts the pre-load on the knuckle bearings....

The lower shims adjust the height that the knuckle housing is in relation to the centerline of the axle housing/seal area...if this is not "close", it will create an oil leaking mess on the knuckle from gear oil leaking past the inner axle seal.


Good luck!


-Steve

Lots of great info. Thanks!

I would love to run the Longfield 30 birf's... but the cost is making me look for alternatives.

For the record... I ran the stock drum birf's for 10+ years with front locker and 33" Super Swampers. I beat the living crud out of my Cruiser and never had one issue with the birf's until I was trying to back up a small hill to get in position for a group picture. I could have made it in 2WD but I didn't think about taking it of 4WD until POP!!! I'm guessing I must have weakened it over time and it just let go in that situation. It was very comical since I had just finished a tough rock climb with no problems and when I was backing up for a picture it breaks.

If I run the Longfield birf's will the shim suggestions that you mentioned still work or will the new axles change things?

If the shims are not perfect... is the worse case just a leaky diff or can it cause undue bind on the axles/birfs as well?

Sorry for the elementary questions. I just want to make sure I have a full mental picture before I start tearing everything apart and ordering new birfs and rotors and calipers.

If the shims aren't right, gear lube will leak into the birf and wash away the grease. Then the lube will eventually find it's way out and make spin art on your tires. If you let it go long enough you'll actually manage to wear out the birfs.

As for the breakage, I'm going to guess you were probably turning at the same time. Reverse uphill and turning is the worst possible scenario for a birfield to be in.

If you've only broken one drum brake birf in 10 years, I doubt you'll need to upgrade the stock minitruck birfields any time soon.

The reason you'd want the FJ60 rotors for that axle is because they're vented, versus the mini truck's stock non-vented rotors. The FJ60 rotors can also be had for $25.

POSER WROTE: "When you take the minitruck front apart, keep the shims that were on the top of the knuckle with the steering arm and knuckle for that side, and do the same with the bottom shims on the trunion bearing cap, and transfer them over to the axle housing that you are using to convert to disc brakes...

The upper set of shims adjusts the pre-load on the knuckle bearings....

The lower shims adjust the height that the knuckle housing is in relation to the centerline of the axle housing/seal area...if this is not "close", it will create an oil leaking mess on the knuckle from gear oil leaking past the inner axle seal."

------------------------------------------------------------------------------------------------


So, poser, you are saying that basically you need to keep the same shims from the donor minitruck axle and transfer them over to the LC axle exactly how they are sitting on the minitruck axle, top and bottom of the minitruck axle knuckle? Wondering about this as I will be doing an FJ55 setup soon. Good thread.

Noah

Advent said:

As for the breakage, I'm going to guess you were probably turning at the same time. Reverse uphill and turning is the worst possible scenario for a birfield to be in.

Click to expand...

YUP.

Turning hard left and popped the left birf.

Since I will be using the mini-truck steering arms now... what tie rods do I need to get? In other words: What are the best tie-rods to get for my set-up. I do not want to run a chevy starter shim as one thread was suggesting??? I didn't really read it so I may have mis-understood. I would like to get a tough (easy to find) set-up so that I know I will be able to get spares if needed.

Does anyone sell/make a complete tie-rod and drag link kit that will fit the mini-truck steering arms as well as be able to accept the chevy tie-rod where it goes into the steering box? I can tap it like we did the stock FJ link.

4WheelingPlus.com said:

If I run the Longfield birf's will the shim suggestions that you mentioned still work or will the new axles change things?

If the shims are not perfect... is the worse case just a leaky diff or can it cause undue bind on the axles/birfs as well?

Click to expand...

The axle shafts(Longs or otherwise) have nothing to do with the shims....the shims are again, for setting the knuckle relationship to the center line of the front axle housing, and the knuckle bearing pre-load, bottom and top respectivly..

4WheelingPlus.com said:

For the record... I ran the stock drum birf's for 10+ years with front locker and 33" Super Swampers. I beat the living crud out of my Cruiser and never had one issue with the birf's until I was trying to back up a small hill

Click to expand...

I twisted an outer stub off a drum brake axle, open with 31's...

I then broke my third and last fing disc brake birf on the starter motor...

I then in '98/99 I built a Dana 60 front and rear, and have not looked back.

There has been some remarkable progress in the strength of Land Cruiser front axles/fing birfs since 1998...but if I had it to do over agian, I would build another Dana 60 in a heartbeat.


Good luck!


-Steve

Poser said:

The style hub and rotor combo that you are talking about here uses six (6) 10mm diameter fasteners to secure the rotor to the hub, not two (2). The 1981 and later 40/60/62 style hub uses two bolts, in conjunction with the six wheel studs.

On the calipers....I would get 88-91 V6 4Runner calipers....as they have four 40mm pistons instead of two 40mm and two 24mm like the 4cyl 4runner and Land Cruiser calipers....

Click to expand...

I stand corrected. It has been a while since I did mine. Going from memory...which is not so good sometimes. I second the V6 minitruck calipers. If you want to go even bigger use the same vintage 4 skinner V6 calipers...they are bigger yet.

dgangle said:

I second the V6 minitruck calipers. If you want to go even bigger use the same vintage 4 skinner V6 calipers...they are bigger yet.

Click to expand...

V6 pickup and V6 4runner of the 88-91 era use identical calipers....

1973Guppie said:

POSER WROTE: "When you take the minitruck front apart, keep the shims that were on the top of the knuckle with the steering arm and knuckle for that side, and do the same with the bottom shims on the trunion bearing cap, and transfer them over to the axle housing that you are using to convert to disc brakes...

The upper set of shims adjusts the pre-load on the knuckle bearings....

The lower shims adjust the height that the knuckle housing is in relation to the centerline of the axle housing/seal area...if this is not "close", it will create an oil leaking mess on the knuckle from gear oil leaking past the inner axle seal."

------------------------------------------------------------------------------------------------


So, poser, you are saying that basically you need to keep the same shims from the donor minitruck axle and transfer them over to the LC axle exactly how they are sitting on the minitruck axle, top and bottom of the minitruck axle knuckle? Wondering about this as I will be doing an FJ55 setup soon. Good thread.

Noah

Click to expand...

Yes.


You want to keep the shims for the knuckles from the donor axle in the same location that they were removed, and put back on that knuckle in the same locations, on the new axle housing. The only shims that may end up needing to be adjusted would be the ones under the steering arm when you install new knuckle bearings, in the event you do not get proper preload with the new bearings WITH THE SEAL AND WIPER ASSEMBLIES REMOVED/NOT INSTALLED.


Good luck!


-Steve

Well... after reading all the notes about mini truck front ends, it looks like the one I got is an older 79-80 model. I'm not exactly sure.

I posted some pics of the front end here:
http://www.4wheelingplus.com/Toy-Straight-Axle/index.htm

If it is the older one... is it worth using the parts from it as apposed to just buying the better versions outright from somewhere?

It will all work just fine...


Take a picture of the hub and rotor assembly from strait-on....

It looks like you have the earlier hub and rotor assembly.....or answer this...


Between the wheel studs on the flange that the wheel seats on, are there six bolts that you can see the end of, or only two???


Six= early
Two= later


You can get vented Land Cruiser rotors for either....Some folks have found the earlier rotors to be more money, but I will take a look and see what I can get them for...seems to me it was not a pile of cash last time I picked up a pair.

Poser said:

Between the wheel studs on the flange that the wheel seats on, are there six bolts that you can see the end of, or only two???

Six= early
Two= later

Click to expand...

SIX studs on mine

I am thinking that these 1979-80 vintage rotors and calipers are just fine! I'm guessing that everyone desires the newer vented rotors and larger caliper pistons for the obvious benefits of cooler brakes and more stopping power. I've never really had brakes on this FJ40 and as such I have become very good at driving it knowing that if something goes wrong and I need to stop... brakes are NOT an option. These are going on a strictly off road FJ40 that rarely sees more than 25 MPH unless its strapped to my trailer being towed.

In other words: Whatever this disc brake set-up offers in stopping power has to be magnitudes better than what I currently have.

Question: It was said earlier in this thread as well as others that the disc birfs are better than the drum birfs, BUT are the newer (1981+) birfs any better than the 1979-80 birfs?

Next question: Are there better steering arms out there than what is on my donor axle? Does someone make an aftermarket (not high steer) arm that will fit these knuckles? I REALLY want the toughest steering arms and tie rod ends that I can get for these knuckles.

The 1979-80 birfs will be the same as later...


Toughest stock arm?

Get 1989 FJ-62 steering arms....they are the thickest/strongest stock steering arm.

I think I have enough info to get started now.

Thank you to everyone that has helped me figure this out! Special THANKS to Poser!