Question On 73-87 Brake Conversion

[Ole Blue 68]

I picked up a 75 front end this weekend for converting my 68 over to disc and I was wondering which way to go about it. I could bolt in the whole subframe or I could just use the spindles and change out the ball joints and tie rods.

Whose done this switch and which route did you go?

I read somewhere that if you bolt in the whole subframe, it'll cause your wheels to stick out about an inch wider than the rears. Anybody else hear that?

[Bus Ted Knuckle]

I'd do the whole crossmember.

If you go to swapping spindles, you might have trouble tracking down the right ball joints, the right tie rod ends etc.

To swap the whole crossmember is like an eight bolt deal, you will have to drill one hole on each side, IIRC. You do that by mounting the new crossmember with the holes that already do exist, and them drill the couple that do not line up. But it is an easy enough switch.

And no, as far as I know the track width (width of the wheels) is the same.

EDIT by me:

P.S. I HAVE done the swap too

[stepn67]

There was a thread recently, where it was said that both control arms (from the 75) will bolt right up to your 68 cross member. Just use the tie rods, drag link, etc from the 75.

[jbboater]

I did the whole crossmember. It was no where near as difficult as I thought it would be. If the track is wider I can't tell. I put an 84 into a 68. Good luck.

[Ole Blue 68]

Thanks all for the responses. Jbboater, it's good to hear from someone who did the swap. Originally, I was leaning towards just swapping in the spindles, etc. but the more I think about it, and hearing from you all, I might just try and do the crossmember.

[68C15]

the upper arms will NOT interchange. where they mount to the brackets is different. but you can get the later ball joints and put them in the older arms. direct fit.
the simple way would be to swap the whole shebang. including the tie rods and all.

[bad_turbo]

good info

[Bob Moore]

Old Blue - the crossmember swap is the way to go. You can clean and replace anything that needs it easier as a unit.

The drawback to doing a crossmember swap is the motor mounts bolt to the crossmember. The bolts are accessible from below the the cross but you must support the motor(oil pan/sump area) until you get the new cross in place.

There are 3 bolts vertically per side - cross to frame. These 3 line up perfectly. There are 4 bolts horizontally per side - frame to cross cast upright. Two of the 4 fit without a problem. The 2 that fit go into fixed nuts on the uprights. The other 2 nedd the holes massaged a little. These are the 2 that have loose nuts. Sometimes these are left undone. With the engine towers and engine in place it may be difficult to drill the holes. I wonder if they could be marked and then drilled from the outside.

The other area is the brake hoses from caliper to hard line. The early trucks run to the rear of the cross with a welded tab to connect the hard line. The newer style goes to the front edge of the upper control arm.

[Ole Blue 68]

More good info!!!

Originally Posted by Bob Moore

The drawback to doing a crossmember swap is the motor mounts bolt to the crossmember. The bolts are accessible from below the the cross but you must support the motor(oil pan/sump area) until you get the new cross in place.

Thanks for the heads up Bob, I was thinking about that too and figured I could use this as an opportunity to upgrade to polyurethane motor mounts.

[Tman]

I also did this swap on a 68 frame with the crossmember from a 75. Like Bob said this is very easy to do. I did mine with the engine out and used a die grinder to elongate one hole per side and drilled the other two. IIRC the holes that are off are the upper holes above the control arms, and should be able to drill from the outside. For the brake lines I used all the hardware from the donor truck, hardlines, splitter block, and rubber lines. There are holes in the frame for all of this stuff, including where the hardlines go through the frame to attach to the rubber. I think I also had to drill holes for the bottom holes in the engine frame mounts in the forward position. Very straight-forward swap in all it took me 3 hr. start to finish, including removing it from the donor. Go for it!!!!

[Ole Blue 68]

Anybody got the part # for the correct energy suspension motor mounts?