Frame shortening

[mechanicalman]

I have given this a LOT of thought. I have a 72 LWB Cheyenne C10 Super. I already have a short bed, not installed. My frame has been re-straightened and it measures out "X" method. It has trailing arm rear suspension. I'd like some opinions on my frame shortening method, positive or negative.

I plan on sliding the suspension cross-member forward 12". This leaves 23" of straight frame behind the member, take 12" straight cut out of the center of that area and that leaves me with 11" I can box in with the CPP frame stiffeners. I can drill some holes to bolt the stiffener channels inside the rails (or clamp) to help align when I weld the outside of the frame rail, then flip them the other way to box it in later after welding the inside and grinding welds flush. I could fish plate before boxing the stiffener plates, using the metal from the section I cut out to fashion those.

At this point the welded part of the frame is only stressed for towing and the weight of the bed and load. If you cut/weld in FRONT of the cross member, then you have accel/decel/bed and load/and towing all stressing on that area. I will use really good bolts to re-install the suspension cross-member and make sure they are big enough to fit snugly into the holes to prevent walking and re-use the lower frame straps to reinforce the lower frame with 4 bolts on each side. Maybe tack weld it in a some spots?

Before I make my cut (to minimize frame drift), I slide the suspension cross-member out of the way and measure 2 new REAR holes EXACTLY 12" forward off the original REAR 2 holes on the bottom of the frame. Using the rear holes, bolt the cross member in and drill through the front two holes through the lower frame rail using an angle drill downward, then drill from the bottom upward through the upper rail. Bolt the 2 front upper to rail, then remove the lower rear bolts and drill through the rear upper frame rail and install those bolts. Install the two lower bolts each side with the stiffener strap that came off the bottom, drill the extra outboard holes through it through bottom of frame and bolt it in. Now it fits right having only made the critical 12" measurement off the rear two holes. THAT is your critical measurement that puts the wheels where they need to be.

I believe I can easily do all this with the cab still on, I can slide the cross-member under the cab when installing my new cab/core support mounts, leaving the rear cab mount brackets where they are.

Some people like to weld up cross and X braces in case the frame wants to twist or jump around after the cut, making alignment difficult. My long frame has been bent and re-straightened so I'm sure I will have to do that.

Please critique this method if you feel it needs it, I can only benefit from that (the reason for the post). Feel free to ask any specific questions about this method. Here's a link to the frame stiffeners I want to use.

http://www.classicperform.com/Store/...ck/6372RFS.htm

[hugger6933]

I have two trucks that are undergoing long to short transformations. I own a body shop and have since 1987. Now, with those two statements being made I will tell you that neither one of the trucks will be cut down in the frame there will be frame replacement and I have already gotten the frames for both projects. It was not a matter of can I do it or am I comfortable doing it or anything along those lines, it just seemed to me that for the time difference involved I could do better working elsewhere on the truck if I am getting to work on the truck. I have no problem if someone does it right and makes a plan takes there time and checks it all out so they are sure it is right. Good luck Jim

[cdowns]

i've seen quite a few frames that have been hacked and wacked to shorten and have ended up as good for the junkyard and at the very least a terrible lookin driving unsafe menace on the road

[Lee H]

Sounds like you have this well thought out. Lots of folks doing this and lessons learned is a great way to get the best possible results. If I were to build or buy a shortened truck I would want fish plates. I say cut that baby up. Good luck with your project. Lee.

[jjzepplin]

I would personally just look for a frame. Easily had and pretty cheap. I paid 175 for mine and that was delivered as a roller with 73 up front suspension and good wheels. Sold the rear end and trailing arms for 200.
Just keep looking!

[67 chevelle]

Nothing wrong with cutting and welding a frame IF DONE CORRECTLY . Stacy David on the greaz show did one the right way , step cut under the bed . I have one going now on a 67 c10 . I have seen hack jobs also , just don't do that . Its a fairly strait forward modification , cutting a bedside on the other hand is a nite mare , luckily you have a bed .

[mechanicalman]

I saw Stacy David's frame shortening, and it looked good, but it was under the cab in front of the cross-member; he also had all the shop equipment to easily lift the cab off. He said it was stronger than the original frame, with the fish plate and flat box plate in place, and I believe that for sure.

Mine will be cut and fish plated under the front part of the bed with the box plate ends bordering just behind the suspension cross-member and under front of the bed. Not enough room for a "Z" cut, however, in an area under much less stress behind the suspension cross member rather than in front of the suspension cross-member. With a similar fish plate and the frame stiffening channels (as opposed to flat box plate) to box it, I believe mine will be almost as strong as David's and not under as much stress.

Big difference between stress in front of or behind the suspension cross member, IMO.

I'm from Arizona and short bed trailing arm frames out here start at 800$ and up. I really like the bolt on rear frame rail kits from nolimit engineering but I'm not going to lower it very much and don't want to raise the bed floor.

I've considered 73-86 and going leaf or installing a cross-member. That frame is longer by 1.5" and not sure it's the way to go or if the cross-member will fit the thicker gauge frame and if the axle would clear the frame rail with it 1.5" forward compared the the 73-86.

[mechanicalman]

I just love those frame stiffener channels.

[bs46488]

I'm going to cut and fishplate mine under the cab with a Z cut. There are some good tech tips on here on how to chop with and without removing the cab.

There is a guy out here in SoCal selling a SWB frame for $1200 that has been powdercoated. And a SWB bed that needs body work (and then of course paint) for $1400.

[Oldtruckfanatic]

I have done a few of these both ways. One thing I liked about moving the trailing arm crosmember forward is that I could adjust for the weird rear wheel too far forward in the opening thing the fleetsides have. Remove your 12" but take a few measurements and a good look at your wheel position. I have found that moving the crossmember 11" centers the wheel in the opening and cutting 12" allows for the correct bed to cab gap.

[Oldtruckfanatic]

I do have to redrill the upper spring mounting hole and alter the track bar a little when i do it this way but my trucks are always really low.

[mechanicalman]

Thanks Oldtruckfanatic. That's the kind of info I was looking for.

[mechanicalman]

Oldtruckfanatic: I am using a step-side bed. Have you ever experienced having wheel centering problems using a step-side bed?

I was thinking about modifying the track bar anyway. I will have an extra track bar left-over, I was thinking about cutting one end off each bar, threading them and putting an adjuster sleeve between them. Want to use stock upper bracket and make a bracket for the rear of the driver's side trailing arm. Thoughts? I was wanting to lower 1-1.5" and thought it would be easy to make an extended lowering block for that side.

[Oldtruckfanatic]

On the steps the wheels are too far back by about an inch move it 13 and cut 12. If you're unsure cut the rivets and slide it and clamp it do your cutting and set the bed on and bolt it and adjust the wheel centerline before you drill and bolt the x member

[Oldtruckfanatic]

And I know that safety is a major concern but done correctly there's nothing wrong with seaming a frame. I was the head fabricator and foreman at a local rod shop for 10 years. All the 55-57 Chevy car California frames were welded together at the front clip and another place. Guys have been doing Camaro clips etc. since before I was born and quite a few of the late model trucks and cab and chassis setups are welded together including this 03 silverado 2500hd about 8" forward of the rear axle.

[mechanicalman]

Excellent info, Oldtruckfanatic. Thanks again.

[mechanicalman]

Actually I like the way the later model chevy truck frames go together with the slip joint and the weld; innovative IMO. One of the reasons I like the CPP frame stiffener channels. Did I mention that yet? LOL

[Oldtruckfanatic]

I'm doing a 72 like that now we cut the frame section off and slit the corners I'm working on stepping the sides now and I will step the upper and lower flanges and then tig weld the slits at the corners. Hopefully it will slide inside the other frame section and I will weld it back together. I got the idea while putting a gooseneck hitch in a guys 08 silverado.

[Fitz]

Early classic Enterprises did a very good tech article on this with pictures.

http://www.earlyclassic.com/tech.asp...20no!-shortbed

[mechanicalman]

Thanks for the link, Fitz. I think I'm at least going to raise the cab if I want enough frame rail exposed to weld the top and to use the frame stiffener channels to align/reinforce it properly. I think I'm going to have to move the rear cab mount brackets as well.

See there I'm learning! LOL

[the ideaman]

We shortened the frame on my '67 using the frame stiffeners from Early Classic Enterprises. Once the bed is off, it only took about 12 hours with cleaning, measuring and welding. We lifted the back of the cab off the back mounts and tilted it forward a couple inches to get at the frame. I wouldn't hesitate to do it again.

[Turbo1dr]

This is the method I'd do if I were to shorten my frame. There are several videos showing all the steps but this one is about cutting the frame below the cab. Watch all the video's and you will see how easy it really is.

LMC Truck: Shortbed Conversion [S7 Ep. 3-3] -...

[the ideaman]

Originally Posted by mechanicalman

Actually I like the way the later model chevy truck frames go together with the slip joint and the weld; innovative IMO. One of the reasons I like the CPP frame stiffener channels. Did I mention that yet? LOL

The ECE ones also fit inside the frame tightly. They can be used as frame "guides" once welded into the rear half of the frame and hold it in place for final welding.

[mechanicalman]

I think I scored a 68 SWB frame, supposed to be delivered tomorrow LOL

Probably for the best. 1500$ with nice a/c cab and fair front clip, no bed, engine, trans, bumpers, or steering gear and busted windshield. Figure I can sell some parts and come out sweet.

[mechanicalman]

Originally Posted by the ideaman

The ECE ones also fit inside the frame tightly. They can be used as frame "guides" once welded into the rear half of the frame and hold it in place for final welding.

The "Bee's Knees" LOL

Next thing someone will come out with a box to go completely around both frame stubs; it could become a "bolt in" affair LOL