FJ40 HydroBoost Brake Upgrade (Relatively Cheaply 🤣) (1 Viewer)

[Rock40]

Never enough projects.

I’ve been running vacuum assist brakes (2nd Gen Toyota mini truck booster) and a T100 master cylinder for 22 years. It’s time to do better and I have my doubts that the T100 master cylinder is capable of taking full advantage of the 2 piston front and rear Wilwood D52 calipers.

And I’m going to do this without hacking the firewall up or modifying the factory FJ40 pedals. The same procedure could be used for any FJ40 that already has vacuum assisted brakes

I’ll spare you the gratuitous pic of a vacuum assisted unit mounted in an FJ40 but here it is next to the hydroboost

$10 junkyard hydroboost from an ‘06 GM van with a 4.8 LS. I’ve already removed the large threaded nut which holds the mounting plate and hydroboost to the firewall. The nut is a BUGGER to get off

The hydroboost plate is keyed off center to keep the unit flat and level when mounted. Going to use the keys, not the GM plate

This is “one” of the firewall plates behind the Toyota booster. It’s a perfect template since that’s the bolt pattern that needs to be matched to the FJ40 firewall

 

[Rock40]

At rest, the Toyota pushrod from the booster to the pedal was about 5.25” and the hydroboost is about 7”

Need to shorten the hydroboost rod appropriately and then thread it M10x1.25 for the Toyota clevis

Overall stroke on the hydroboost is roughly 1.1” which matches the Wilwood 1.12 bore master I have for it. According to Wilwood these are considered “short stroke” components

The GM rod is quite close to the correct diameter to tap the M10 threads onto it. I just had to taper the shaft a bit at the end to get the die onto it

 

[Rock40]

Firewall plate mount. I used the plasma to cut the center ring out, sanded it down to a 2.5” OD. Threw the GM plate out at this point

Found a scrap piece of 3/16” steel. Used the Toyota plate from above as a template to drill the mounting holes. 2.5” hole saw cut the plate next

I had centering lines to keep the alignment right between the hydroboost and firewall. Everything is tacked in place here

 

[Rock40]

Plate is done. Welded in all the mounting studs, verified it fit in the firewall, shot it with Steel-It

Wilwood master and the hydroboost. Wilwood supplied the small aluminum “pill” which fits up inside the master cylinder. I needed to shorten the pill by about .125” as it was a tad long. It would have prevented the master from fully returning.

Pill is shortened and installed in its bore

 

[Rock40]

And it’s in, fits DARN good. Waiting on some fittings to make high pressure lines and a stainless bung to weld into my reservoir for the low pressure return. Have about 6 hours into this which frankly is lightning fast with how my projects normally go

 

[Rock40]

Going the exact same “cut nothing up route” with the clutch master. After the LS swap, I’ve never been able to get the clutch to quite fully release. I believe there is just not quite enough fluid movement between the 3/4” bore FJ40 master and 13/16” bore FJ40 slave.

Picked up a 7/8” bore Wilwood master. The pedal will be heavier but it’ll certainly push enough fluid

Grabbed a scrap piece of .25” cold roll plate, cut a 1.5” hole in it. Mocked up a junk (soon to go in the trash) FJ40 master. Clamped it to within an inch of its life, drilled centering marks for the mounting holes

The Wilwood master uses vertical mounting bolts, fortunately I can use the lower hole on the FJ40 pattern. Top Wilwood hole was drilled and tapped for a 5/16-18 stud

Done with the plasma and it’s sanded

 

[Rock40]

Adapting the FJ40 clevis to the Wilwood master is far more straightforward compared to the hydroboost.

Undo the FJ40 wave clip, pull the pushrod and discard everything else

Remove the Wiwood circlip and swap the Toyota rod on, using all the Wilwood parts and circlip. The rounded portion of the pushrods is nearly identical.

DUN. It was harder to install the Wilwood boot And the welded nut on my clevis was an attempt to get just a bit more throw out if the slave to release the clutch. Didn’t work

 

[Rock40]

It’s in. Need some metric studs for the firewall but you get the idea. The Wilwood boot just fit through the factory FJ40 firewall hole

 

[Ditcherman]

Thanks for the write up.
Did you use the GM hydroboost unit after weeks of research, or because it’s what was at the junkyard, or something in between?

This looks like a great solution. I have a brake booster fitting in on my project but am prepared to do something like this if it’s not enough.

 

[Rock40]

I guess this was a long time coming but I didn’t research it, I just figured there had to be a way to do it without hacking the firewall up. And my 1 ton trucks have fantastic brakes with hydroboost. So there was that, coupled with the FJ40 clutch master not being able to release the clutch and the fact I couldn’t get the Wilwood clutch master to fit next to the vacuum booster. All of that pushed me towards the hydroboost I guess.

 

[Rock40]

Little bit of a brake upgrade on the front Dynatrac D60…

1/4” NPT stainless bung for the low pressure return…

I rigged up a booty fab back purge with argon while welding it, kept it REALLY clean

 

[cruisermatt]

Nice work, maybe I should post the firewall plates I already make and sell for $25 on my website, probably would have save you some time
I actually manufacture the clutch master adapters already too

 

[Rock40]

Hahaha! Man I just don’t look around for stuff enough before I fab it, oh well.

Looking at that pic tho, that hydroboost bracket wouldn’t have worked with the unit I got out of the junkyard anyway. The anti-rotation tabs on mine were offset quite a bit, odd.

 

[Rock40]

Update: the brakes are FANTASTIC. Best brakes I’ve ever had on the 40 in 25 years. Need to bed the Wilwood pads in a bit more then just run them.

There is most certainly much higher line pressures. I have a mechanical in-line hydraulic parking brake which worked fine before. Now I can’t even rotate it with the rear brakes under pressure. Oh well

 

[GLTHFJ60]

Hydraulic parking brake shouldn't be an issue with higher line pressure, because it's not changing the pressure, just rotating the ball valve inside it (in my mind anyway). Is it free when you're off the brakes?

 

[Rock40]

That was my thinking too. It’s free off the brakes but impossible to turn with pressure on it. Could be getting old too, it’s been on there a long time, might be time to swap it out

 

[Ditcherman]

That was my thinking too. It’s free off the brakes but impossible to turn with pressure on it. Could be getting old too, it’s been on there a long time, might be time to swap it out

TWSS.
Old and hard to turn. On.

 

[Rock40]

TWSS.
Old and hard to turn. On.

Ha! Walked right into that one