Is there a holy grail thread for shortening lwb to swb frame

[rs74]

I have read a few different post about shortening a lwb to swb frame. I think I have seen three different ways to cut the frame. Pretty much I would be cutting out 14" out of the middle right behind the cab. What I have seen differ is on the back of the frame. I have seen cut 3" and also seen cut 6". Which? Also what is the best design to cut the frame and splice back together. I have seen just making 45 degree angle cuts and splicing back that way.

I have also seen what I call the half nazi swatstika type. Then there is the swatstika type and then cut out a diamond shape within that and weld it back in place. Kind of hard to describe. Just looking for the best design or way to cut and splice back together. Also do I need to weld in a glove or inner support plates.

[jitteryguy]

http://67-72chevytrucks.com/vboard/s...highlight=ccsb

http://67-72chevytrucks.com/vboard/s...highlight=ccsb

http://67-72chevytrucks.com/vboard/s...highlight=ccsb

http://67-72chevytrucks.com/vboard/s...highlight=ccsb

http://67-72chevytrucks.com/vboard/s...highlight=ccsb

http://73-87.com/7387garage/chassis_...lwb_to_swb.htm

here are some I've saved over time, I think the second link is my favorite.

[jitteryguy]

I'm gonna do mine soon, the "S" cut is what I plan on do'n.

[rs74]

Originally Posted by jitteryguy

http://67-72chevytrucks.com/vboard/s...highlight=ccsb

http://67-72chevytrucks.com/vboard/s...highlight=ccsb

http://67-72chevytrucks.com/vboard/s...highlight=ccsb

http://67-72chevytrucks.com/vboard/s...highlight=ccsb

http://67-72chevytrucks.com/vboard/s...highlight=ccsb

http://73-87.com/7387garage/chassis_...lwb_to_swb.htm

here are some I've saved over time, I think the second link is my favorite.

Thanks but these are all the same link except for the last one.

[andrewmp6]

Try http://www.73-87chevytrucks.com/lwb_to_swb.htm

[b454rat]

14" between cab mount and bed mount, I think I cut off 5-6" behind, but that is easy, just a straight cut. I kinda eyeballed mine....I would do a Z cut....

[Tx Firefighter]

I just cut one this week. 14 inches out of the center and 5 inches off the back. I've done a fair number of frame splices and have always done it the straight way, full penetration welds, and a fish plate on the inside with small fish plates on the bottom webs of the framerails. There's a lot of people on here who will disagree with my methods, but a large percentage of them have never cut a frame in their life and just repeat what they've read on the internet, so take their advice with that in mind. I learned to do it this way from an old truck mechanic as we built dump trucks.

I fit them with about a 1/16 gap between the beveled edges, tack and measure to verify that you have it all straight and aligned, then weld it up. After adding the doubler plates to the inside, I plug weld through whatever holes happen to be there on the outside of the rails also. You can cut your fish plates out of the sections of rails you removed. Most of the time I stick weld them rather than use my MIG. That's just a personal preference though. Whatever you're most comfortable with.













Don't get too wrapped up in all the hysteria. It's not gonna break and send your careening into a bus full of nuns on their way to the orphanage, with a trailer full of puppies behind them. Worst case, you would see some cracking. Keep in mind, the bed adds a bit of a truss factor too since it's bolted in front of and behind your splices.

[jitteryguy]

Originally Posted by Tx Firefighter

I just cut one this week. 14 inches out of the center and 5 inches off the back. I've done a fair number of frame splices and have always done it the straight way, full penetration welds, and a fish plate on the inside with small fish plates on the bottom webs of the framerails. There's a lot of people on here who will disagree with my methods, but a large percentage of them have never cut a frame in their life and just repeat what they've read on the internet, so take their advice with that in mind. I learned to do it this way from an old truck mechanic as we built dump trucks.

I fit them with about a 1/16 gap between the beveled edges, tack and measure to verify that you have it all straight and aligned, then weld it up. After adding the doubler plates to the inside, I plug weld through whatever holes happen to be there on the outside of the rails also. You can cut your fish plates out of the sections of rails you removed. Most of the time I stick weld them rather than use my MIG. That's just a personal preference though. Whatever you're most comfortable with.



Don't get too wrapped up in all the hysteria. It's not gonna break and send your careening into a bus full of nuns on their way to the orphanage, with a trailer full of puppies behind them. Worst case, you would see some cracking. Keep in mind, the bed adds a bit of a truss factor too since it's bolted in front of and behind your splices.

your's look's good, what's your opinion on grind'n the weld's down on the out side ?

[Tx Firefighter]

Originally Posted by jitteryguy

your's look's good, what's your opinion on grind'n the weld's down on the out side ?

That's an age old debate. Too much grinding can lessen the strength of the finished product. I figured since its under the truck and out of sight I'd just leave them be.
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[Duster]

Originally Posted by Tx Firefighter

I just cut one this week. 14 inches out of the center and 5 inches off the back. I've done a fair number of frame splices and have always done it the straight way, full penetration welds, and a fish plate on the inside with small fish plates on the bottom webs of the framerails. There's a lot of people on here who will disagree with my methods, but a large percentage of them have never cut a frame in their life and just repeat what they've read on the internet, so take their advice with that in mind. I learned to do it this way from an old truck mechanic as we built dump trucks.

I fit them with about a 1/16 gap between the beveled edges, tack and measure to verify that you have it all straight and aligned, then weld it up. After adding the doubler plates to the inside, I plug weld through whatever holes happen to be there on the outside of the rails also. You can cut your fish plates out of the sections of rails you removed. Most of the time I stick weld them rather than use my MIG. That's just a personal preference though. Whatever you're most comfortable with.













Don't get too wrapped up in all the hysteria. It's not gonna break and send your careening into a bus full of nuns on their way to the orphanage, with a trailer full of puppies behind them. Worst case, you would see some cracking. Keep in mind, the bed adds a bit of a truss factor too since it's bolted in front of and behind your splices.

Nice welds.

[BigBlocksRule]

Easiest and bestest way is to find a short frame and swap your stuff onto it. Saw one locally a couple of weeks ago for $150.

[Tx Firefighter]

Easiest is an opinion. I can shorten a chassis much quicker than going to all the swapping hassle. Plus your frame VIN will still match your can VIN.
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[mrhino]

I agree with TX firefighter 100%. I researched and researched the "best way" and like you I came up with three different "best ways". I happen to live in the RV capitol of the world and I made it a point to look at many frames and chassis everything from class A's to big rigs extended for sleepers. Everyone I saw was straight cut and plated. If its good enough for them!

I straight cut mine. welded on a diamond plate on the inside of the frame. Then took the section I cut out, and made a outside support that I bolted on. bracing the side, top and bottom. Plus I made it where the fuel tank brackets bolt to either side of my splice. Im no engineer but Im confident It aint going anywhere.

[rs74]

I am thinking of doing this splice here. Do these measurements look right. To me it looks like you are actually moving it 20".

[mrhino]

14" out of the front. thats a fact! How far from the cab never really concerned me. I just made sure I stayed with in the front bed bolt holes, once you get the bed off it will be pretty easy to see where you should remove those 14" The rear is not the same for everybody. I was cutting a 1 ton and only need to take of about 4". If memory serves me correct i could have taken as much as 5.5 or as little as 3.5. I believe the 1/2 ton frames are different. Do you already have the bed? if so just measure your last bed bolt hole back and transfer that number to the frame rail. Its really simple and easy to over think it.

[mrhino]

to answer you question. no your drawing doesnt look right. the frame is shortened 20" total 14" in the front. Find where you want to remove those 14". draw a line down the middle of that. That would be 7" either side. then make your Zcut 7" both ways.

[BigBlocksRule]

Originally Posted by Tx Firefighter

Easiest is an opinion. I can shorten a chassis much quicker than going to all the swapping hassle. Plus your frame VIN will still match your can VIN.
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And if you ever decide to sell it, you'll be selling a welded frame truck. Many buyers will shy away including myself. I've never seen anyone check the VIN stamped on top of the frame. I have a gantry crane and cab/bed dolly at my shop, I can have the whole swap done in a day with a helper, maybe quicker. Plus it gives you a chance to do any suspension work with nothing in the way before you do the swap.

But, as you said, it's an opinion.

[rs74]

Frames, beds, cabs, they are too hard to come by around here. I just went up and bought one yesterday for an 86 and it was for a 73-79 and had the shock holes wallowed out and had a plate welded over one of the holes. At this point in time my best bet is to shorten the frame. Not my first choice as ideally I would like to have a 81-87 swb 4x4 factory frame. Too dang hard to come by in these parts.

[BigBlocksRule]

Originally Posted by rs74

Frames, beds, cabs, they are too hard to come by around here. I just went up and bought one yesterday for an 86 and it was for a 73-79 and had the shock holes wallowed out and had a plate welded over one of the holes. At this point in time my best bet is to shorten the frame. Not my first choice as ideally I would like to have a 81-87 swb 4x4 factory frame. Too dang hard to come by in these parts.

Yeah, those of us living in dry southern states tend to forget how quickly things get rusty in other parts of the country

[wraprail]

Originally Posted by BigBlocksRule

And if you ever decide to sell it, you'll be selling a welded frame truck. Many buyers will shy away including myself. I've never seen anyone check the VIN stamped on top of the frame. I have a gantry crane and cab/bed dolly at my shop, I can have the whole swap done in a day with a helper, maybe quicker. Plus it gives you a chance to do any suspension work with nothing in the way before you do the swap.

But, as you said, it's an opinion.

If you ever bring it to nevada DMV from another state they will dam sure check that VIN on the frame. They awalys check frame vin #.

As far as shorting the frame, I did mine last summer. Straight cut , retained saddle tank mounting holes same as rhino and txfirefighter. Used piece cut out as support plating. You will also have to move the rear crossmember forward. My 85 had 8 rivets holding it in. Cut the rivets and use 3/8 bolts. Crazy thing my 85 already had the 8 holes punched in the frame for the crossmember in the forward location. I just moved it forward and bolted in.
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[rs74]

Where are the numbers at? I thought they were on top of the frame.

I think I am going to go ahead and do the (S)? pattern. I am looking into a shop doing it or I am going to see if my painter will let me do it at his shop. I don't have a bed yet so I hope everything goes well.

[izzy_Britton]

Originally Posted by Tx Firefighter

Easiest is an opinion. I can shorten a chassis much quicker than going to all the swapping hassle. Plus your frame VIN will still match your can VIN.
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i know this is off topic, but i am getting ready to do a frame swap, WHERE is the vin located on the frame? i have never been able to find it on any of my trucks in the past. I have found numbers but none of them coordinate with the numbers in the vin.?

thanks in advance.

[meatwagon83]

i would definatley use a stick welder over mig while doing this, 1/8 7018

[Tx Firefighter]

Originally Posted by meatwagon83

i would definatley use a stick welder over mig while doing this, 1/8 7018

I've got a nice Miller 250 amp MIG machine, but this antique is often my go-to machine when it counts. I guess it's just a comfort level thing. A 250 amp mig with 035 wire is fully capable of jobs like this without any excuses, but I sleep better at night when I crack open a fresh box of rods and roll out my old Lincoln Tombstone


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[rs74]

Originally Posted by Tx Firefighter

I've got a nice Miller 250 amp MIG machine, but this antique is often my go-to machine when it counts. I guess it's just a comfort level thing. A 250 amp mig with 035 wire is fully capable of jobs like this without any excuses, but I sleep better at night when I crack open a fresh box of rods and roll out my old Lincoln Tombstone


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I use to have on just like that. Hardly ever used but when I did, it did the job well.