Cross member interference with PS conversion
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Posting Guru
Joined: Feb 2002
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From: seattle us
Cross member interference with PS conversion
I am putting a '78 F250 4x4 PS unit into my '71 F250 4x4 and have read all the conversion articles, but never saw this issue addressed. The '78 had the 460 motor in it, the '71 a 390. The cross member from the '78 is about 4" further back than the '71. So the '71 crossmember interferes with the correct placement of the box. So, question is, what to do?
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Joined: May 2003
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From: california
I guess I have that to look forward to as well. I haven't actually taken mine apart yet to fit the 78 steering box. I've been busy and haven't looked into that Superlift adjustable drag link. I've seen a 69 F250 highboy truck that has had a "c" cut out of the cross member to clear the ps box. He welded a plate over the cut out to box it in. It looked very nice and sturdy. I don't know which ps box he used.
Elder User
Joined: May 2003
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From: california
Sounds like you have more of a headstart than me. I have to plan this around work. I wouldn't even consider moving the whole cross member. I haven't looked into that, but sounds like opening up a can of worms. Notching it and welding a plate to cross member would be my option.
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From: seattle us
Yeah, well, I was looking at it and it doesn't look that bad. The other option is to use the '78 cross member, which is beefier. Right now I'm still planning. If I get into cross member moving, then it might be mid summer before I dive into this. I personally don't like the idea of making the cross member smaller, but it's probably 6 of one, half dozen of the other. I'm still looking for other ideas from other people that have gone through this before.
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From: seattle us
Well, in taking a closer look and making further measurements, notching the cross member may be the way to go afterall. When I first looked at it, it appeared I was going to need to take a bigger chunk out of the cross member than I felt comfortable doing. I looked at it again, and it may not be as bad. I haven't had the time to really dig into this and take things apart, which is what I really need to do to be sure.
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Joined: Sep 2003
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From: Portland, OR
You should not have to touch the crossmember. I have a 2wd box on my truck and it's very close to the 78-79 4x4 box. I've also seen several 4x4 boxes installed on the 67-72's and they work fine with no cutting on the crossmember. I think you're trying to put the box too far back. The box should be about 3/4" from the radiator when properly installed.
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Joined: Feb 2002
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From: seattle us
Thanks Averagef250. Yeah, I was trying to get it as close to the rad. as possible. So that surprises me that you did not have to cut the cross member. That doesn't seem possible with mine. Did your go on a Highboy? One thing that might make that possible I guess is that the '78 4x4 box bolts to the frame, but the actual box sits on top of the frame. Whereas the '71 4x4 box sits down inside the frame. Like I said in my last post, I think I just need to get in there and start playing with it.
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