Quick background: I'm building a MKIV base kit using Gordon's Wilwood brakes for 15" Halibrands and the new IRS setup. 15" wheels for street, 18" for track, but I'm still relegated to brakes that fit the smaller 15 inchers. This option unfortunately doesn't allow for many parking brake options since the often used spot caliper doesn't fit inside the rim according to Gordon. He offered a line lock-style hydraulic parking brake and I think is still working on some other option. I didn't like the hydraulic idea for a number of reasons that I won't get into here.

I decided to take a page from my Jeep/offroad history and go with a driveshaft mounted disk setup. This is often used for either parking brakes and/or regular brakes on Unimog and other portal-style axles used in offroading where mounting standard disks is simply not an option.

First was getting all of the right yokes for the T56Magnum and Super 8.8 rear diff, both with 1350 style u-joints(WAY overkill). I documented that challenge in a different post but in summary if you have a T56M and new IRS and want 1350 ujoints, the Spicer part numbers you want are:
3-2-119(Super 8.8 pinion flange yoke)
3-3-5961X(31 spline T56M slip yoke)
5-1350X(1350 series non-greasable ujoints)



Next was finding a suitable disk. I'm heavy into the snowmobile world and between my brother and I came up with a late model 1/4" thick heat treated disk off a sled. It was drilled(unnecessary for my application), slightly too large of a diameter, and had large 1" mounting flanges on each side. I faced one side on a mill(the opposite side of what's in the pic below), then drilled the mounting holes for the pinion adapter on the same mill. Next I bolted the flange adapter and rotor together then chucked it in a lathe and turned down the rotor on the other side, cleaned up the braking surface, and brought the overall diameter in 1.5" so it fit between the tunnel tubes. In the pic you can see I milled the same flanges into the face of the rotor that the pinion adapter and yoke flange have. One side is raised on the horizontal plane, the other side is sunken. This centers the parts perfectly(.002" tolerances) and allows for only radial load and not vertical load. It turned out perfect.



I needed all of this to measure properly for a driveshaft. With the monstrous T56M, my engine placement, and the extra width of the 1/4" brake rotor, I needed a driveshaft 4" center of ujoint to center of ujoint. Went to a local driveshaft shop that specializes in heavy truck and equipment and he shrugged and said "sure, I can make it that small but can you use one 3.5" instead?" There is plenty of travel in the T56 slip yoke and sticking out another .5" wasn't going to matter so I said "sure". He handed me the center of a huge CV joint that was 3.5" center to center and said $35. It is WAY stronger than any short-tubed welded driveshaft, no need to properly phase it, and works perfectly. BOOM! There's about $200 in savings from a custom shaft.



Here it is all assembled. I still need to set all of my final angles but the flange faces are all already within 1*. The diff is offset to the passenger side more than my engine/tranny(damn that T56 is big...), but using all the same principles as long as all angles are equal and opposite it doesn't need to be lined up. In fact, ujoints need at least .5* of offset/angle or you get brinelling which is when the roller bearings don't actually roll inside the ujoint caps.



Bonus points for anyone that can see what's wrong in this picture.

I still need to build the bracket that holds the mechanical caliper on the rotor(caliper in first pic). It was a $26 Amazon item from a go-cart shop but during intense inspection, it is LITERALLY the exact same aluminum casting and design that Wilwood sells for $95 except theirs is powder coated and has what I can only assume is a $69 Wilwood sticker on it. Along with the caliper bracket, I plan to pic up a Pontiac Fiero parking brake lever and mount it on the floor to the left of the driver's seat, tucked away and somewhat hidden. The Fiero lever is unique in that once you pull it up to engage, you can push the handle back down(still engaged though) to get it out of the way.

In the end, I think the solution will work out very well. It's a mechanical setup instead of hydraulic which is what I wanted and plenty strong enough for a parking brake. Only time will tell just how good the brake and CV joint "driveshaft" truly work though. I'll need to get the car moving on it's own and rack up some miles before I claim any kind of real victory.

-TJ