putting 71-72 brakes on a 68?

[seekhunt]

I put the complete crossmember from a 76 1/2 ton onto my 67 1/2 ton. I used the master and proportioning valve from the 76. You need to increase the bore of the rear wheel brake cylinders to the 1 1/16 variety or your rear tires when braking will lock up too easy in the wet. The inner tie rod end is from an 89 3/4 ton. Have the machine shop knock about 1 1/4 inches of thread off (That'll leave you with about 5 inches to the good).
So that being said, now you have 5 bolt lugnut pattern up front and 6 bolts on the rear. So for the rear I used a 3 series diff housing from the mid 70's or 80's so I dont have to run around with 2 spare tires. Weld new spring purchases in new locations. Pete

[SCOTI]

Originally Posted by seekhunt

I put the complete crossmember from a 76 1/2 ton onto my 67 1/2 ton. I used the master and proportioning valve from the 76. You need to increase the bore of the rear wheel brake cylinders to the 1 1/16 variety or your rear tires when braking will lock up too easy in the wet. The inner tie rod end is from an 89 3/4 ton. Have the machine shop knock about 1 1/4 inches of thread off (That'll leave you with about 5 inches to the good).
So that being said, now you have 5 bolt lugnut pattern up front and 6 bolts on the rear. So for the rear I used a 3 series diff housing from the mid 70's or 80's so I dont have to run around with 2 spare tires. Weld new spring purchases in new locations. Pete

It's not an absolute on the rear brake cylinder size. Larger diameter wheel/tire combo's possibly won't see the same issue. I did the post-73 suspension/brake swap to my 68 (using the original 68 c.member) & did not have issues w/lock-up using 29" tall tires. I used a master cyl & power booster for a 71-72. All the brake lines were post-73 up to the OE union under the pass side of the cab. From that union back it was OE 68 lines/cylinders.

[seekhunt]

Thats a good point. Its totally dependent on your situation, and as with anything, do a lot of reading and research so you dont have to completely reinvent the wheel every time you come up with something you'd like to do. Us older guys have been through many projects, and its important to just take it all in, and then just do what you were going to do anyway!