Crossmember identification and brake line selection
 

So I'm getting ready to order hard lines for my 70 brake system and have a few questions. The front end was fitted with 73+ front end parts when I purchased it but what I haven't been able to figure out is if they swapped those onto the stock 70 crossmember or if they swapped the crossmember out as well. I'm assuming which crossmember it has will dictate whether I get 70 or 73 front lines? I've attached a few pictures of the front end before disassembly. Also to muddy the waters even more my rear axle is out of a 66 donor, for hard lines on the rear I'm assuming I'll use 66 lines and then a 70 intermediate line to connect the front and rear? I appreciate any help y'all can give!

Re: Crossmember identification and brake line selection
 

I have a 67 and my brake lines ran on the rear of the crossmember and connected on the rear of the A-arms. At some point chevy moved them to connect on the front of the A-arms (maybe someone can chime in with the year they made the change). But with your lines being on the rear of the crossmember and rear of the lower A-arms; I would lean towards it being an original 70 crossmember with the 73 A-arms being added.

Re: Crossmember identification and brake line selection
 

Thanks for the reply. If that's the case I'm assuming getting a set of the 67-70 power disc conversion lines would be the way to go and then I'd connect them to 73 soft lines coming out of the calipers? Being such a mix of years has made this more confusing than I'd hoped for (or maybe I'm overthinking it).

Re: Crossmember identification and brake line selection
 

If the connection is on the front of the 73 A-arms, then the 71-72 pre-bent lines may work better since they attach on the rear of the crossmember and then loop over to the front for the connection. Someone with better knowledge should be along in a bit with more detailed info.

Re: Crossmember identification and brake line selection
 

They are on the front of the a arms so maybe that is the way to go. Here's a picture of the drivers side cleaned up where you can see that bracket on the upper a arm.

Re: Crossmember identification and brake line selection
 

Since you already have the 73+ upper control arms with the attachment point for the 73+ flexible hoses, it would make sense to go that route. Sticking with the original rear-routed 70 routing with disc brakes is a big compromise due to the way the hose gets scrunched and stretched when turning. I had mine rear-routed and the hoses were rubbing on my rims. Some have made it work, so it isn't impossible, but it is far from ideal. There's a reason GM moved the line routing to the front when they went to disc brakes. I ended up switching to 71-72 front routing on my truck. It was a bit of a pain to add hose attachment brackets to the front of the crossmember. I think 73+ would be easier since the hoses run through the frame rail. It would require bending some custom lines though, whereas pre-bent 71-72 kits are available.

Re: Crossmember identification and brake line selection
 

Here is mine (1967) with original crossmember and original A-arms but I used the 71-72 brake lines. I'll end up needing to attach a bracket to hold the line where the flex hose connects to the rigid.

Re: Crossmember identification and brake line selection
 

Thanks for all the replies guys! So a 71-72 front kit would match everything I've got if I'm understanding correctly?

Re: Crossmember identification and brake line selection
 

You would need to add brackets to the front of your crossmember if you were to go with a 71-72 kit. Here's a write-up I did on my conversion:

https://67-72chevytrucks.com/vboard/...d.php?t=823192

Re: Crossmember identification and brake line selection
 

Thanks for the link the only thing I see different is I've already purchased calipers for the 73+ front end. Was that a mistake? I was hoping to find a set of lines that would fit as is but that sounds like it may not be possible.

Re: Crossmember identification and brake line selection
 

I believe the calipers for 71-72 are the same as 73+. I did a quick search on oreillyauto.com for 71 and 73 calipers, and they both came up with the same part number (18-4035).

Re: Crossmember identification and brake line selection
 

Well that's good news. So what is the benefit of going with the 71-72 lines over the 73+ ones? I apologize for my ignorance on all this, learning as I go on some of this stuff.

Re: Crossmember identification and brake line selection
 

The benefit I see of going with 71-72 is that you can buy a pre-bent hard line kit. The downside is that you have to install brackets on the front of the crossmember.

The benefit of 73+ is that the flexible hose attaches directly to the frame rail (you'd have to drill and shape a hole for it). The downside is that you'd have to make custom hard lines since there are no pre-bent hard line kits that accommodate 73+ flexible hose routing location with a combination valve mounted to the master cylinder. The 73+ trucks had their combination valves mounted to the crossmember that's in front of the engine.

Re: Crossmember identification and brake line selection
 

This video shows how the 73+ flexible hoses are routed (not my video).

https://www.youtube.com/watch?v=uZxOUGGNklk

Re: Crossmember identification and brake line selection
 

Thanks for the detailed explanation! Makes sense, sounds like the 71-72 lines are the way to go as far as ease of installation.

Re: Crossmember identification and brake line selection
 

Selecting and mounting 71-72 brackets is the hard part. The brackets I used were a real pain. I spent many hours modifying them for my application. If you can find some better brackets out there, maybe you could save yourself some headache.

Re: Crossmember identification and brake line selection
 

I think I'm getting my heard wrapped around it all. So if redoing the entire brake system like I'm doing what would the issue be with running an entire 73+ setup with the combo valve on the crossmember? Then I could use the 73+ prebent hard lines as well as the "correct" soft lines for my a arms and all that is needed is the frame hole provision if I'm understanding correctly.

Re: Crossmember identification and brake line selection
 

That might work, although there may be enough subtle differences between the 67-72 chassis/cab and 73+ that would make pre-bent 73+ lines not fit your truck.

Re: Crossmember identification and brake line selection
 

Did they mount the A arms onto the stock 70 cross-member or if they swapped the cross-member out as well

I agree it's the 70 cross-member still installed. Missing the front bracket for the lines. inlinetube.com sells the bracket. I could only find this one and it's out of stock. Inserting the image as an example of what I think you need.

If you haven't painted your front cross-member you can just cut the tabs off the back and weld them in the proper position in the front for little or no cost.
My cross-member was powder coated before I figured this out so I cut the brackets off and welded a tab onto them and then bolted them on like the one from Inline Tube would be if you purchased them new. I converted my 70 to the 72 style brake lines. I had lowered spindles and went through three sets of rubber lines before I found a set that worked for my application. The ones that worked were 1972 3/4T lines. They were longer and worked perfectly.
Cheers

Re: Crossmember identification and brake line selection
 

>>and then a 70 intermediate line to connect the front and rear?<<

I'm not sure about your '66 rear lines, but the '67 and up past '73 has a coupler on the pass side frame rail (Green arrow). No intermediate line.
All '73 and newer brake lines, Combo Valve, flex lines and MC, simply bolt in place. The hole in the frame rail (Red arrow) is already there where the hard line connects to the flex line. The hole in the upper A-arm (Red arrow) is already there for the flex line mid-clamp. The cross member under the radiator had one hole in the correct location for the Combo Valve so I just used one bolt.

On my '67, if I need anything for the hydraulic system forward of the COUPLER (Green arrow), I can go to any parts store and ask for parts for a 1976 GMC. Calipers, Disc. flex line, MC, Comb valve. Everything is '76

mccolum007
>>I was hoping to find a set of lines that would fit as is but that sounds like it may not be possible.<<
>>Being such a mix of years has made this more confusing than I'd hoped for (or maybe I'm overthinking it).<<

Re: Crossmember identification and brake line selection
 

For the rear, on my 70, the flex line runs from just above the passenger side rear spring to the tab on the axle.

On 71, they moved the flex line behind the axle to a tab bolted to the diff cover.

If you plan on running dual exhaust over the axle, you'll want to consider moving this line. I did my brakes first, then the exhaust, and ended up having to remove the shock so I could move the line to the other side of it so the brake line wouldn't hit the exhaust, but now it rubs against the shock.

Here's a good pic of the later style routing:
http://67-72chevytrucks.com/vboard/s...64&postcount=7

Re: Crossmember identification and brake line selection
 

That's great news if the 73+ hard lines will work with the 67-72 trucks. If not the bracket Accelo posted along with the 71-72 setup may be the way to go. I do like the idea of having all my front suspension, and braking system be a factory 73+ setup, would be alot easier to remember and find parts for when maintenance/replacement parts become an issue.