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03-03-2008, 06:33 AM | #1 |
Questionable
Join Date: Mar 2005
Location: Atlanta
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Crossmember/frame differences (a rant)
Ok, so, I jsut want to have a little "Mythbusters" session about frames and crossmembers.
There are two major differences that make a '73-87 front crossmember (possible 71-72 as well) NOT a "direct bolt on" to a '68-'68 frame. Back story: I picked up an entire '73-'87 front clip and rear end recently to swap into my '68 from another board member/friend. I got a killer price from him, and it's in great shape, so I can't complain now that i'm finding I can't easily use it. I want all of you to learn from my experience. I cannot even BEGIN to tell you how many different times I read all over this forum that this would be a direct bolt-on swap, that the '73-87 front crossmember would fit like a champ in my frame with nothing more than "warbling" out one or two holes a bit. THIS IS ABSOLUTELY NOT TRUE. I'm here to set the record straight after spending 5 hours today taking off brake lines, unbolting parts, cleaning up suspension and brakes, pulling off wheels, and finally swapping to my mid-70's crossmember. Here's the problem: 1) The framerail on '73-87 trucks is 6" tall at mid-crossmember. The framerail on 67068 trucks is 5.5" tall at mid-crossmember. This matters to me because I'm using the ECE GenIII engine mounts for my LS1 swap, and they incorporate the '73-87 stands, so while they are a perfect bolt-in for the '73-87 frame+crossmember, they require drilling with the 67/68 frame using a 73-87 crossmember. 2) There are four bolts that hold the crossmember to the frame on the side. They use a completely different pattern in 67/68, so when you go to bolt that 73-87 crossmember to your frame, two of the four holes line up perfectly, one hole needs to be "warbled" out to make it work, and you will need to completely drill a new hole for the fourth bolt. Be aware. The other pair of three holes on the bottom of the framerail seem to work like a champ. On a positive note, the access holes for the press-in studs for the upper control arm are perfectly accessible . Anyway, that is all for my complaining for now. I just wanted to share my experience with others so you can learn from my mistakes. I know some guys would be like, "Dude...just modify it!" But you know what? I already modified my old one and it was working. I swapped to 73-87 so my ECE GenIII mounts would fit like a champ...I dunno about you, but I don't want to do work I've already done, and swiss-cheese my frame in the process
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If I've got anything up for grabs, it'll be here: 7-hole gauge cluster for a 67-72 p/u FREE (link) I can't check the forum daily. If I don't reply to you within 24 hours, drop me a PM! I'm (hopefully) still alive and will reply faster to a PM. Last edited by shifty; 03-03-2008 at 06:34 AM. |
03-03-2008, 06:38 AM | #2 |
BlahBlahBlah
Join Date: Feb 2002
Location: Wa.
Posts: 19,943
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Re: Crossmember/frame differences (a rant)
Ive never done this, but I have read several times that one hole needed elongated and one hole needed to be drilled.
Must be more than a pain in the tukas to do than it sounds. |
03-03-2008, 06:54 AM | #3 |
Questionable
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Re: Crossmember/frame differences (a rant)
It's not really a pain at all. I'm sure it's actually fairly easy.
This is my beef: My reason for upgrading to 73-87 front crossmember were simple: - beefier U-bolts for the lower control arm - already have the proper bolt pattern drilled for my ECE GenIII mounts, direct bolt-up - the upper control arm bushings are rubber vs. metal that mine have stock - the arms are a little bit beefier - My original '68 crossmember was already drilled and fitted for my GenIII mounts Now, I still walked away with $150 in parts, so I'm not upset by any means, nor did I "lose" money in this case (I can bounce back). I am going with ART tubular ams b/c I'm bagging the truck. This negates the ruber vs. stell bushing situation, and they're just as beefy. The framerails are different n my '68, so I'm swapping drilling the crossmember for drilling the framerail. It's a lose-lose situation IMHO. I dunno, just sucks. I don't mind, but I want to make sure others know that this isn't a direct swap, because I'd read it was one too many time. I'm kicking myself afterthis. I should have listened to board member uncle all this time. Tim, if you are reading this, please slap me next time you talk to me or see me. Oh - but hey - can someone with a 71 and 72 truck measure the height of the framerail at mid-crossmember mount and tell me if it's also 5.5"? Or is it 6"? I'm curious, myself. Want to make sure I don't misinform anyone in the future when talking about the ECE GenIII mounts.
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If I've got anything up for grabs, it'll be here: 7-hole gauge cluster for a 67-72 p/u FREE (link) I can't check the forum daily. If I don't reply to you within 24 hours, drop me a PM! I'm (hopefully) still alive and will reply faster to a PM. Last edited by shifty; 03-03-2008 at 06:54 AM. |
03-03-2008, 12:55 PM | #4 |
1972 Chevrolet SWB
Join Date: Jan 2008
Location: FT Smith AR
Posts: 512
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Re: Crossmember/frame differences (a rant)
Hey shifty,Im up and can go measure for you if youd like right now,I have a 72 and it wouldnt take 5 minutes for your answer.
I added this picture so you could point to the area needed.
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My New thread with pics (not my build thread yet.) http://67-72chevytrucks.com/vboard/s...46#post2573646 1972 Chevrolet 1/2 ton short wide bed,68 frt clip Project. 1980 Camaro Inherited when father passed,68K Miles 2003 Ford Mach1 FUN as Hell!! 2002 Dodge Ram 5-8 slam Rolling BillBoard (Gone not forgot) 2004 Dodge Ram HEMI 10" lifted on 37's and 2wd. Last edited by slammed1; 03-03-2008 at 12:57 PM. |
03-03-2008, 06:10 PM | #5 |
67-72 parts collector,…
Join Date: Nov 2002
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Re: Crossmember/frame differences (a rant)
Shifty,... that's why I like leaving the original crossmember and changing everything from the a-arms out. Then use all the 73-up steering linkage. Seems easier to me. You still have to deal with the "hard" brake lines. Thanks for the input from someone who has done it. What was the exact year of the donor truck?
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03-03-2008, 10:06 PM | #6 |
Hittin E-Z Street on Mud Tires
Join Date: Nov 2004
Location: Greenville, SC
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Re: Crossmember/frame differences (a rant)
71/72 cross members are NOT any different than the 67/68's. I took a complete suspension from a '71 and bolted it into my '67. Direct bolt in. No hole drilling or wallering required.
What is different between 67-69 and 71/72 (that I can think of)? Most of the differences have to do with the disk spindles vs drum spindles: On the lower control arms, the bump stops for steering are different. You can use 67-69 A arms with 71/72 spindles, but you have to grind the tit down on the spindle. Outer tie rod ends are different. On the cross member itself (I'm a little fuzzy on this one) but I think the location of where the steel line/rubber hose meet are different. Is it truely 73-87 suspensions that can be used? I though I'd read a few times that the ones around 80 or so and newer won't work?
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Jesse James 1967 C10 SWB Stepside: 350/700R4/3.73 1965 Ford Mustang: 289/T5-5spd/3.25 Trac-Loc 1968 Pontiac Firebird: Project Fire Chicken! 2015 Silverado Double Cab 5.3L Z71 2001 Jeep Wrangler Sport 4.0L 5spd 2020 Chevrolet Equinox Premium 2.0L Turbo 2011 Mustang V6 ~ Wife's ride American Born, Country by the Grace of God 1967 CST Shop Truck Rebuild! My 1967 C-10 Build Thread My Vintage Air A/C Install Project "On a Dime" Trying my hand at Home Renovation! 1965 Mustang Modifications! Last edited by 67ChevyRedneck; 03-03-2008 at 10:07 PM. |
03-03-2008, 11:45 PM | #7 | |||
Questionable
Join Date: Mar 2005
Location: Atlanta
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Re: Crossmember/frame differences (a rant)
Quote:
The main differences I see between the '77-'78 crossmember and the '68 crossmember is this: - '77 has larger holes for the lower control arm u-bolts. - '77 has a 1/4" reinforcement plate riveted to it around those larger holes. - '77 crossmember has wider flange area where the u-bolts pass thru on each side. - '77 bolt hole pattern is different for the four side bolts. The '77 is nearly a perfect 4-square pattern, the '68 is not even close to a square pattern. Quote:
Quote:
Things I can tell you: * '77 control arms look damn near identical in diameter and whatnot. * The cross shafts look identical as well, and the upper arms appear to direct-swap (interchangeable). * The lower control arm U-bolts are relatively different in diameter and width BUT the lower control arms have the same diameter shaft, so you can theoretically use your '68 crossmember and u-bolts and directly bolt a '73-87 LCA to it. * 73-87 u-bolts DO NOT fit into a '68 crossmember for two reasons, possibly just one reason: The holes in your '68 are smaller diameter. I personally believe it would be a perfect fit if you just opened up the holes on the '68 crossmember, BUT you wouldn't have the advantage of the beefier reinforcement plate. So - seems like a catch-22...you either upgrade to the larger stronger u-bolts and possibly weaken your crossmember, or you use weaker u-bolts and maintain the original structural strength of your crossmember. I've still got a lot of work to do today. If I have any epiphanies or find any other quirks, I'll post on it. I guess my big interest is the framerail height at the crossmember of a 71-72 pickup. I have someone checking that out for me.
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If I've got anything up for grabs, it'll be here: 7-hole gauge cluster for a 67-72 p/u FREE (link) I can't check the forum daily. If I don't reply to you within 24 hours, drop me a PM! I'm (hopefully) still alive and will reply faster to a PM. |
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03-03-2008, 11:48 PM | #8 |
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Re: Crossmember/frame differences (a rant)
PS - crappy picture of the u-bolt size diff'ce.
I did not measure them from center-to-center on the posts to check for width, but ... I probably will do that when I head back down to get a couple more hours work in.
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If I've got anything up for grabs, it'll be here: 7-hole gauge cluster for a 67-72 p/u FREE (link) I can't check the forum daily. If I don't reply to you within 24 hours, drop me a PM! I'm (hopefully) still alive and will reply faster to a PM. Last edited by shifty; 03-03-2008 at 11:49 PM. |
03-04-2008, 02:11 AM | #9 |
Registered User
Join Date: Mar 2005
Location: Alberta
Posts: 316
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Re: Crossmember/frame differences (a rant)
What diameter are the new ubolts? The ones I used when rebuilding my front suspension were larger than original because the original are either hard to locate or not being made. I believe the ones I have are 9/16 but its been more than a year since I had to drill out the mounts
Just so I'm clear, you wanted to change the front clip so you could avoid using two holes on the crossmember you'd already drilled? I read your list above but to be honest those seem more like justifications |
03-04-2008, 02:38 AM | #10 | |
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Re: Crossmember/frame differences (a rant)
Quote:
The larger u-bolts fit once the holes are drilled to the larger size. The reinforcement plate can be swapped into place as well (shave to fit). Once done, the arrangement is equally strong = no catch-22. As I've stated previously, I don't understand why one would go through the extra effort to use the later crossmember if the swap is just to swap in disc brakes. If there's a specific reason it makes sense (LS motor mount conversion, powder-coating, original c.member is damaged). Otherwise, all the parts will swap over (I've done more than one disc swap on pre-71's).
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67SWB-B.B.RetroRod 64SWB-Recycle 89CCDually-Driver/Tow Truck 99CCSWB Driver All Fleetsides @rattlecankustoms in IG Building a small, high rpm engine with the perfect bore, stroke and rod ratio is very impressive. It's like a highly skilled Morrocan sword fighter with a Damascus Steel Scimitar..... Cubic inches is like Indiana Jones with a cheap pistol. Last edited by SCOTI; 03-04-2008 at 02:47 AM. |
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03-04-2008, 05:51 AM | #11 | |
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Join Date: Mar 2005
Location: Atlanta
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Re: Crossmember/frame differences (a rant)
Quote:
Oh - and I just realized that I should probably tell you - this thread isn't aimed at you or 'gringoloco' or any of the guys on the suspension forum that have been helping me out. I actually should have paid attn to what you guys were saying, but went off and read a bunch of threads around here about crossmembers instead. You guys were basically spot-on with everything.
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If I've got anything up for grabs, it'll be here: 7-hole gauge cluster for a 67-72 p/u FREE (link) I can't check the forum daily. If I don't reply to you within 24 hours, drop me a PM! I'm (hopefully) still alive and will reply faster to a PM. Last edited by shifty; 03-04-2008 at 05:52 AM. |
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03-04-2008, 06:19 AM | #12 | |
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Re: Crossmember/frame differences (a rant)
Quote:
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67SWB-B.B.RetroRod 64SWB-Recycle 89CCDually-Driver/Tow Truck 99CCSWB Driver All Fleetsides @rattlecankustoms in IG Building a small, high rpm engine with the perfect bore, stroke and rod ratio is very impressive. It's like a highly skilled Morrocan sword fighter with a Damascus Steel Scimitar..... Cubic inches is like Indiana Jones with a cheap pistol. |
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03-04-2008, 06:38 AM | #13 |
1972 Chevrolet SWB
Join Date: Jan 2008
Location: FT Smith AR
Posts: 512
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Re: Crossmember/frame differences (a rant)
Shifty,my truck is a 72 and in the area you wanted a measurement I got between 5 1/4" and 5 1/2" height as best I could measure.This was as best I could get which was from the bottom of the frame rail to the top of the frame rail in the center of the crossmember where you wanted. If you need any other measurements I can easily go get more in certain areas.
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My New thread with pics (not my build thread yet.) http://67-72chevytrucks.com/vboard/s...46#post2573646 1972 Chevrolet 1/2 ton short wide bed,68 frt clip Project. 1980 Camaro Inherited when father passed,68K Miles 2003 Ford Mach1 FUN as Hell!! 2002 Dodge Ram 5-8 slam Rolling BillBoard (Gone not forgot) 2004 Dodge Ram HEMI 10" lifted on 37's and 2wd. |
03-04-2008, 08:16 AM | #14 |
The Older Generation
Join Date: Aug 2006
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Re: Crossmember/frame differences (a rant)
Shifty,
Maybe I'm not understanding your post but I have replied in most of the following threads (with pictures) about the differences in the frame holes. The last link mentions the difference in frame height. http://67-72chevytrucks.com/vboard/s...ember+enlarged http://67-72chevytrucks.com/vboard/s...ssmember+holes http://67-72chevytrucks.com/vboard/s...ssmember+holes http://67-72chevytrucks.com/vboard/s...ssmember+holes http://67-72chevytrucks.com/vboard/s...ssmember+holes http://67-72chevytrucks.com/vboard/s...ssmember+holes LockDoc
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Leon Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles (My Dually Pickup Project Thread) http://67-72chevytrucks.com/vboard/s...d.php?t=829820 - Last edited by LockDoc; 03-04-2008 at 08:20 AM. |
03-04-2008, 09:46 AM | #15 |
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Re: Crossmember/frame differences (a rant)
Another point for confusion. There are 2 different height frames in the 73 up trucks. I parted out 3 different 73-78 trucks and used parts on my 70C10. The truck that I used the front crossmember from was a 74gmc C10 454 truck. Crossmember bolted right in. But that frame was something like 3/4" taller then either of the 2 3/4 ton trucks I parted out at the same time. One of the 3/4 tons was a 73, the other was a 78 crewcab. Both frames were shorter then the 74 454 trucks. I do wish I'd moved the motor mounts forward though. I left them in the same position that it came out of the 74.. and the 454 fits pretty tight when that far back.
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70 C10 long fleet, 355/200 4r, 6 lug disc conversion, 3" drop 70 gmc changed to 67/8 chevy, 454 with voodoo cam, th400, all 74 running gear.. in progress |
03-04-2008, 10:30 AM | #16 |
Questionable
Join Date: Mar 2005
Location: Atlanta
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Re: Crossmember/frame differences (a rant)
Well, for prosperity, here are some pics of '68 control arms and '77 control arms, for comparison. They're basically the same. Just thought I'd post em here for the future.
1st pic is '68 arms, second is '77 arms.
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If I've got anything up for grabs, it'll be here: 7-hole gauge cluster for a 67-72 p/u FREE (link) I can't check the forum daily. If I don't reply to you within 24 hours, drop me a PM! I'm (hopefully) still alive and will reply faster to a PM. Last edited by shifty; 03-04-2008 at 10:31 AM. |
03-04-2008, 10:59 AM | #17 | |
Bloo
Join Date: Feb 2001
Location: Barren County Kentucky
Posts: 6,285
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Re: Crossmember/frame differences (a rant)
i put a 76 crossmember in my 69, 3 of the 4 bolts that go sideways lined up dead even.. the lower front bolt had to be elongated though. i did have to make all new brake lines, but i used a 76 prop valve which has 2 outlets for the front lines instead of one. my reasoning behind doing the whole crossmember was because i dont have a coil spring compressor and i absolutly HATE compressing coil springs
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ASE Master Certified-GM Trained-Mechanic 1968 Chevy C30 157" WB Wrecker 1969 Chevy CST/10 SWB 1971 Chevy Custom/10 (first truck) 350, NV3500 5 speed 1971 Chevy K20 Custom Camper 4x4 350 TBI, SM465/NP205 1974 Chevy Custom Deluxe/10 1979 Chevy Custom Deluxe K10 farm truck beater 1989 Chevy K2500 Quote:
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03-04-2008, 11:21 AM | #18 | |
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Re: Crossmember/frame differences (a rant)
Quote:
Why would we have two drastically different experiences? Were there more than one type of frame for halfton trucks, or is the 3/4 ton truck setup with diff't bolt holes for the crossmember or something?\ it looks like all of the brake provisions are the same between my '77 and '68 crossmember and shouldn't cause any problems. Although, there are no tabs for the hard-to-soft line on the '77 as there were on my '68.
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If I've got anything up for grabs, it'll be here: 7-hole gauge cluster for a 67-72 p/u FREE (link) I can't check the forum daily. If I don't reply to you within 24 hours, drop me a PM! I'm (hopefully) still alive and will reply faster to a PM. |
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03-04-2008, 12:32 PM | #19 | |
Bloo
Join Date: Feb 2001
Location: Barren County Kentucky
Posts: 6,285
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Re: Crossmember/frame differences (a rant)
im just as confused as you are, lol. mine came from a plain jane bonanza-10 light duty half ton. here are some pics i took back in october
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ASE Master Certified-GM Trained-Mechanic 1968 Chevy C30 157" WB Wrecker 1969 Chevy CST/10 SWB 1971 Chevy Custom/10 (first truck) 350, NV3500 5 speed 1971 Chevy K20 Custom Camper 4x4 350 TBI, SM465/NP205 1974 Chevy Custom Deluxe/10 1979 Chevy Custom Deluxe K10 farm truck beater 1989 Chevy K2500 Quote:
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03-04-2008, 12:35 PM | #20 | |
Bloo
Join Date: Feb 2001
Location: Barren County Kentucky
Posts: 6,285
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Re: Crossmember/frame differences (a rant)
pic of the 69 M/C, and the two victims
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ASE Master Certified-GM Trained-Mechanic 1968 Chevy C30 157" WB Wrecker 1969 Chevy CST/10 SWB 1971 Chevy Custom/10 (first truck) 350, NV3500 5 speed 1971 Chevy K20 Custom Camper 4x4 350 TBI, SM465/NP205 1974 Chevy Custom Deluxe/10 1979 Chevy Custom Deluxe K10 farm truck beater 1989 Chevy K2500 Quote:
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03-04-2008, 07:17 PM | #21 |
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Re: Crossmember/frame differences (a rant)
I used the post-73 prop valve & hard lines on my 68. The prop valve is installed in the same location as a post-73 truck vs. up @ the master cyl like on a pre-73 truck.
It required slight spacing where it mounted on the splash pan up front, but everything worked.
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67SWB-B.B.RetroRod 64SWB-Recycle 89CCDually-Driver/Tow Truck 99CCSWB Driver All Fleetsides @rattlecankustoms in IG Building a small, high rpm engine with the perfect bore, stroke and rod ratio is very impressive. It's like a highly skilled Morrocan sword fighter with a Damascus Steel Scimitar..... Cubic inches is like Indiana Jones with a cheap pistol. Last edited by SCOTI; 03-04-2008 at 07:18 PM. |
03-04-2008, 10:08 PM | #22 |
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Location: Oakdale, Ca
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Re: Crossmember/frame differences (a rant)
On factory disc brake trucks the hard brake lines ran on the front of the crossmember. The junction block where the hard lines meet the soft lines was also on the front of the crossmember. On pre 71 crossmembers, the hard lines and junction blocks are on the rear of the crossmember.
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03-04-2008, 10:15 PM | #23 |
Questionable
Join Date: Mar 2005
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Re: Crossmember/frame differences (a rant)
Sounds like I need to order brake lines for a '68 when I pick those up down the road, just to stick with what is supposed to be there.
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If I've got anything up for grabs, it'll be here: 7-hole gauge cluster for a 67-72 p/u FREE (link) I can't check the forum daily. If I don't reply to you within 24 hours, drop me a PM! I'm (hopefully) still alive and will reply faster to a PM. |
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