Register now to get rid of these ads!

Frame shortening

Discussion in 'The Hokey Ass Message Board' started by Stephen67, Mar 18, 2010.

  1. Stephen67
    Joined: Jun 24, 2009
    Posts: 73


    I'm getting close to shortening the frame on my 1956 Ford F-600.

    I'm pretty sure I have it all worked out but I'd like to run it by those who have done it to avoid a stupid mistake.

    I was going to move the axle up, cut off the rivets and use bolts, but I've decided that it will be a lot easier to cut the frame. I had thought I would have to add more length to the end of the frame for the bed (the back wheels are close to the end) but after measuring it shouldn't be a problem, and shortening still strikes me as easier.

    I plan on doing the cut the same way as 53ChopTop did on his Chevy:

    With the plate in the back as well.

    Any tips on keeping that all straight? Best places to measure from?


    I have a 2 part driveshaft, one goes straight and out from the cab, then it connects and the second driveshaft goes down. Cutting the length out of the straight across one should allow me to keep everything straight as far as the rear axle goes, there would be no change to the angles. It's going to end up pretty short though, about 4" of tube, ha, and I'll have to bolt on the support piece under the cab which probably won't be fun.

    Any tips on figuring out exactly how long that is going to need to be?

    Brake line:

    This one dawned on me today after I took off the old air-brake tank that covered it up. I'm thinking the best way to go about it is to disconnect it at the end, and after I shorten it, cut the excess length and re-attach.


    Any tips on how to do this without getting air in the line?

    Anything I'm missing or anything that worked well for you? Ideas?

  2. daliant
    Joined: Nov 25, 2009
    Posts: 684


    I would cut the rivits and move the spring hangers insted of cutting the frame to move the rear. Get a bed first before you move the rear around.
  3. Hackerbilt
    Joined: Aug 13, 2001
    Posts: 6,247


    Love those old trucks!!!

    Move the brackets and keep the frame intact.
    You'll be WAY better off to do it that way.

    Your idea on the driveshaft will work, but if your new(?) transmission has a slip yoke you can make a single piece shaft.
    If it doesn't, then you can use what you have in the back and shorten the front as you say, or you could spend extra dollars and get a slip yoke shaft built, like a 4x4 uses.

    Shortening your driveshaft can be done at home but you need guidance or such things so it might be better for you to get it done professionally. Don't want no vibrations!!!

    The brakes will need bleeding, but your gonna replace all the old flex lines and go thru the wheel cylinders etc for safety anyway...right? ;)
  4. Stephen67
    Joined: Jun 24, 2009
    Posts: 73


    Whats the benifit from moving the springs over cutting the frame? (Honestly asking, I can't think of a way to say that that might not sound snotty)

    To do the springs I'll also have to do the spring stop and bumper for it. Works out to be like 48 rivets to cut off, 48 holes to drill, 48 grade 8 bolts. Just seems like it would be easier and easier to keep straight to take it out of the frame. But of course maybe there is something I am missing, I was planning to do it that way till earlier today.

    I "should" have enough past the wheels too that I shouldn't have to add any extra space to go past the bed.

    I don't know if it will make a difference, but the frame does get thinner towards the wheels. The angle is such I believe the axle could be moved forward without changing the angle of the driveshaft, but it would also raise the back end a couple inches. Not a big problem, but if I plan on keeping the springs when I swap out the axles later, it could effect things.

    Its not the easiest to see in the picture, but it's dark now, lol:
    (it starts to raise about 2' from the cab, the 3 drilled holes point it it)

    (the angle of the wheels is caused by the lens, they're not angled in person, lol)

    That flat bed is off now, was a 4,000# steel bed with a 5,000# broken compressor on it. Granite the scrap probably could have paid for the whole truck, but I was without means of getting it all home.

    I'm awaiting my bed till I do anything, I wanted to put it on the frame and find out exactly what I needed to do. The whole build is custom, it be such a 'pound-your-head-in-the-wall' mistake if the wheel base was off an inch or two either direction. I'm putting a step-side bed on (or as the puriest would scream at me a flare-side, but for some reason when I hear flareside I think the flat sided ones with no fenders... everyone thinks the same with step-side).

    I should note that the current axles and powertrain I won't be keeping in the long run. The thing turns, goes forward, and stops like a ship. Very not daily driver friendly. It's my business truck and I'll need it all year, so I'm making it a 4x4, staying as low as I can but keeping large tires. The current ones need replacing anyways, but right now they'll let me fab everything exactly how I will need for the 4x4 wheels. Right now I just want to keep it drivable enough to load onto a truck when I move. The shorten driveshaft would never see speeds over 30mph even if I drove it in the mean time, I don't think you could pay me to drive it any faster until I really fixed it up well.

    Also, should it make a difference with the brakes, not sure why it would but who knows; they where once converted to air-breaks, then converted back. It use to hall that 9,000# on the back, but I don't know when they went back to the regular brakes. To be honest I have no idea what condition they are in, I can't tell if the pads are just horrible or if something in the line is causing them to suck. The break pedal only kicks in at the last inch...
    Last edited: Mar 18, 2010

  5. 333 Half Evil
    Joined: Oct 16, 2006
    Posts: 1,440

    333 Half Evil

    I've done them both ways, cutting frames to shorten them, and moving the spring hangers, stops, etc. Personally I like moving the mounts and leaving the frame rails intact. Once you get a hang of removing the rivets, that is easy to do. The only real work is drilling the holes, and that really isn't all that bad with a good drill and a high quality drill bit set. It is a lot easier to line up the axle and drill a couple holes to hold it in place, then you just finish drilling and put in the bolts.
    Cutting the frame isn't that hard, neither is welding, but making those cuts straight/true is a little tougher and keeping everything lined up and getting it tacked in place can be tricky unless you have a fairly good bit of experience. Same goes with quality welds. I do not know what your welding experience is, but if it is limited then you would be better off having someone else welding it for you to make sure the welds are going to be strong/safe enough to hold. What are you going to use to cut the frame with? If you torch it, depending on your torching ability, you might have some grinding to do to clean off the slag from cutting. You also should grind the paint/rust off so you have decent/clean metal to weld.
    I guess a lot of it boils down to how clean do you want the finished product to look, what experience you have, and the tools involved for both ways? By moving the mounts, you will have a cleaner/factory look, with welding it will be obvious that the frame has been cut/spliced. Do you have the experience/ability to cut/weld the frame so it looks good and is safe? Do you have a welder, torch/plasma cutter, etc to do the frame work? My personal preference/choice would be moving the spring hangers, mounts, stops etc.
  6. Stephen67
    Joined: Jun 24, 2009
    Posts: 73


    I'm a blacksmith so I'm set up for it. I'd use a large angle grinder over a torch, torches are messy for this kind of work.

    I may just move the springs forward, tomorrow I'll take a rivet out on something I'm going to have to move anyways and I'll see if it's going to be a pain for me or not. Any suggestions on removing them without damaging everything else? (no air chisel at this time).

    It will raise the back a little, but I don't think it will effect the driveshaft angle and it's a long slope change and how they're already connected. Might not even be an issue, might even work better since I'm planning on making it a 4x4 and doing so would raise the front anyways.
  7. 333 Half Evil
    Joined: Oct 16, 2006
    Posts: 1,440

    333 Half Evil

    The easiest way I've found for removing the rivets is this:
    Grind a smal fat on the tip,(makes it easier to start drill)
    drill a 3/16-1/4 hole through rivet,
    chisel the head off,
    drive out rivet(usually they fall out once the head is chiseled off).

    Depending on how big or small(diameter) the rivets are, the heads normally snap right off with ease once the holes is drilled thorugh. Most all of them I've done I have always used a 1/4" drill bit. If the point on the head is actually kinda flat, it is easy to just use a prick punch for a start spot for drilling, but some rivet heads have a point. It is easier to just hit it quick with a grinder to put a small flat on to start drilling in. Once you do it, it really isn't that hard at all. I just did all the rear spring mounts on an OT chevy 1 ton truck to shorten it up, took me less than an hour to knock out all the rivets (38) on the spring mounts and bump stops etc.

    As for the drive shaft, I'd look into making it a one piece drive shaft. No need to have the carrier bearing in it once you shorten it up. There will be less of an angle on a one piece then there will be on the back half of the two piece. Just my opinion....
  8. 29nash
    Joined: Nov 6, 2008
    Posts: 4,544

    from colorado

    That's what I would do too.
  9. garagerods
    Joined: Dec 15, 2006
    Posts: 451

    from Omaha

    I didn't read everything but....

    I wouldn't do anything until you have the box, rear end, etc.. that you want to run....or you may be doing things over and over and over :)

    Good luck!
  10. Stephen67
    Joined: Jun 24, 2009
    Posts: 73


    Thanks for the advise.

    I finally found a box, I've been looking for months for what I wanted, I'm not shortening anything till it's on so I know exactly what needs to change.

    Granite I'll end up changing out the rear axle, but I'll also be running the same size tires. The parts I need aren't where I live (no where Wyoming) or around, so I'm waiting till I move on those, be easier then anyways. Problem is a 154" wheel base doesn't fit most car haulers, and I am in the mood to get something done, having the bed on it will give me lots to do, plenty of custom work needs to be done for it to look right on a 2 ton truck.
  11. Mr48chev
    Joined: Dec 28, 2007
    Posts: 28,360


    I agree that don't do anything until you figure out what box or bed your are going to use.

    No easy way out on the air/ brake lines if you want to do it right. You just need to do what makes it right there without cutting corners.

    That frame has a taper of several inches toward the back and if you slide the spring mounts up on the frame without cutting the frame it will raise the back of the truck several inches. I vote for shortening the frame.

    Here is a pattern that shows the cut and splice (it's on Chev pickups) the measurements won't be right for your truck but the concept is the same.
    You do have to reinforce the frame at the splice.

    The hop farmers shorten trucks about the same size as yours in a similar fashion around here to tow their hop trailers all the time.
  12. Stephen67
    Joined: Jun 24, 2009
    Posts: 73


    I asked this question on another site with some Ford truck fans. I've decieded to just move the axle, but something interesting about cutting the frame came up and in case this is read later by someone, it's good to know.

    It seems that a Z-cut can cause stress points, not allowing the frame to flex propperly, which can also be caused by having the fish plate being made of thicker steel than the frame. How Ford does it and some large truck techs is to cut it at an angle only, weld together and use a fishplate of the same steel (usually from the left over cut out piece), that was shapped like <==> with the corners ground to a 1" radious. Having too much steel for the fishplate or a z-cut apprently causes fractures at the end of them. Course this is all for large trucks where the frame needs to be able to flex a little.

    Here is a link to Ford's how-to on it, around the 12th page they show the angle cut:

    Just thought it was interesting.

    Though moving the axle will raise the back a little, it will work better with the future plan on putting in 4x4 axles, since the front straight axle raises up before the wheels, when a 4x4 axle is used it raises the front several inches and the back has to be raised to match.
    Last edited: Mar 19, 2010
  13. low budget
    Joined: Nov 15, 2006
    Posts: 5,564

    low budget
    from Central Ky

    After doing a search on this subject this morning to help justify my thoughts on moving the hangers instead of cutting the frame on a 55 chevy 3/4 ton to make a short bed, I found this thread and thought what the heck I will try it this way instead of cutting the frame etc. etc. like I did on a 3/4 56 ford a while back.

    A half a days work later and the hangers have been moved and bolted securely in place with grade 8 bolts and it looks pretty clean.

    Having it on jack stands,tires lightly touching the floor,I ground all the heads off the rivets one hanger at a time (4 per hanger)and then wacked the hanger itself downward pretty good with a large sledge hammer loosening the rivets enough to knock the side ones out with a center punch (pretty easily) then the hanger just came off the bottom ones.

    It has the slight hump over the rearend in a diffrent location than a actual short bed would be and I may hafta do a little modifcation to the underside of the bed to compensate for it but you wont see it after the bed is on and of course cut the driveshaft but all in all (so far) I think this is the better and easier way to do it.
    I will also need to cut a little off the back now but no big deal.

    ............oh and I didnt even need to cut the brake line to do it this way either,the rubber line reached;)
  14. krooser
    Joined: Jul 25, 2004
    Posts: 4,583


    That Ford info is a great resource.

    Back in the 70's we built several class 8 'glider kits' from old trucks and we had to shorten on lengthen to suit the application... we always use an angle cut and never had any problems. But it seems all manufacturers now recommend a straight cut with a fisplate andan insert. my F100 has been shortened and has a straight cut with a fishplate...
  15. low budget
    Joined: Nov 15, 2006
    Posts: 5,564

    low budget
    from Central Ky

    This is the old ford that I cut a while back and this is as pretty as it got while I had it.:D

    Attached Files:

    • 56.jpg
      File size:
      134.8 KB

Share This Page

Register now to get rid of these ads!


Copyright © 1995-2021 The Jalopy Journal: Steal our stuff, we'll kick your teeth in. Terms of Service. Privacy Policy.

Atomic Industry
Forum software by XenForo™ ©2010-2014 XenForo Ltd.