4700 lpx build
 

I am considering turning our international 4700 lpx into a small toterhome. maybe something like a 14' box with the bunk over the cab for a bed. the question is... do we stretch the frame ourselves or leave it to a company that stretches frames on a regular basis? we are a welding and fab shop so im confident that we could do it but i wonder if something like that is best left to someone that does it on a regular basis. next question is... is it a problem to build the framework out of aluminum tubing? i look at NRC Mod's stuff and they use steel tubing in their builds and renegade uses wood from what ive been told. im thinking aluminum on ours for weight since its a smaller truck to begin with. thoughts?

Extending a frame is not the hardest thing to do, but if you question your capability then I would suggest you farm the work out. Far as aluminum for framework of the box, there are lots of them made that way!

Yes what Tom said. Not only the frame to consider. The driveline angles are important to get right when you move the drive axle back.

I don't think I question our capability with it perse. I mean in my opinion were more than capable. It's more of a thing where we don't do it everyday like a truck shop would so they'd do it in 3 days and we would take 6 is more what I was driving at. We build dragster chassis and have our line of race wheels. So it's all welding and fab. Just a matter of application is all. The driveline angle deal is something I haven't had to deal with. All the cars we've built only have one driveshaft or none in the case of a dragster. So is there a rule of thumb for driveshaft length? We always use our local driveshaft builder here in Indy so he should be a good one to ask on that stuff. I hope? Another thought id do we section the frame in the middle (like so many I've seen done) or do we extend the rails at the back and then move the suspension and axle housing back accordingly? What about adding air ride. There is no air system on the truck now but obviously it would be more comfy to drive with air ride seats and air ride suspension. Should we look at adding that? Our current trailer weighs in around 20k# so it's not crazy heavy but certainly not a lightweight by any means.

I guess it would be up to you if you want to section a piece of frame in the middle or extend what you have. Since you desire air suspension I would look for a cut off that has the air springs on it rather than try to remove your springs and bolt the air ride on. You should be able to find out about the pinion angle from your driveshaft supplier. The worst of that would be getting the right wedges. As far as I know the only rule of thumb for the length of the drive shaft is it needs to fit the wheel base. I have seen some so long that there were three carrier bearings on them.

FWIW, I have four carrier bearings in mine, and six U-joints in main driveshaft from trans to fwd differential. Then another two U-joints and single driveshaft connecting the rear-most diff.

I think an air-ride frame section, spliced onto the rear of your existing rails, would be the easiest way to lengthen and get air ride at the same time. Then just remove your springs and diffs, and fab the appropriate crossmembers and carrier bearing supports to connect up the now farther back differentials.

I'm with mntom and 38chevy. If you are thinking about air ride, no way I'd consider all the hassle of swapping and modifying all the components and/or relocate the axle position on the rails. Think drilling dozens of 5/8" holes sideways on heat treated frame rails. Just find a truck in the junkyard with air ride that is good from the cab back, and buy the entire rear frame section. Have them cut it as far forward as possible. Then cut yours farther back. Roll your back half out of the way, and roll the new one in. One splice and you accomplish both the air ride and frame stretch in one relatively uncomplicated project.

As to the driveshaft, you definitely want the advice of a competent truck driveshaft shop. The length of each shaft, and angle of every u-joint/carrier bearing is important. When I was thinking about a frame stretch I drove the truck down to my favorite driveshaft shop and got their opinion and an estimate on building my new shafts. I modified my planned wheelbase a bit to make it easier to build the shafts. They told me 54" max length for each shaft, and all carrier bearings would have to have the height adjusted to get all the angles right, not just add one more shaft on the end with no other changes. The plan was just to drop the truck off there after the stretch and let them put everything in place.

yeah. i spoke to our driveshaft shop (that we use to build all of the driveshafts we use in the race cars we build) and they offered to come over and take the measurements and so on and tell us where and how to put the carrier bearings in too. so, the more time that goes on... i think we may tackle this project ourselves. its not the work that scared me. but the knowledge or lack thereof. now after talking to several people that really sound like they know what theyre talking about theres no doubt we can do this project. the biggest help so far has been the chrome shop mafia guys out of missouri. i sent them a message on fb yesterday and man they sent me back a reeeeeaaaalllly long message step by step how they do it. very very helpful. that is a group of people i will definitely be buying from when i need to. as a side note... do i really need to put air ride on the truck? right now there is no air system so i would have to add that to it. which again is something that can be done. just a question of is it needed or not? our truck rides a little rough now as its only 150" wb with heavy springs on the rear. but when we would haul engines back and forth to cummins (2500# each) and put 2 of them on there it rode like my suburban. so, between the weight of the toter install and our gooseneck trailer (20,000#) does it really need air ride? im not trying to wear you guys out with all of my newb questions. so i hope this doesnt grow tiresome with you guys. trust me... if/when we pull the trigger on this project there will be plenty of pics for the build section. thanks!

No, you don't NEED air ride. You could even get by with the old Hendrickson "hockey puck" suspension, but if you had two trucks to compare the difference in ride quality....... For an air system since you don't have air brakes you probably could put an electric air compressor and a small air tank on that would handle the bags just fine.

An electric compressor and tank would definitely be adequate. I run dual compressors on my truck "just in case", but a good compressor is only about $150 so not a big deal to mount two. If you don't want to fool with all the self leveling controls and what not all you need it a pair of air paddle switches and a gauge in the cab. I don't know what you are towing, but mdt/hdt steel sprung trucks are pretty hard on the trailer frame if you are putting any kind of miles on there. Unless you have a premium trailer designed for a big truck, your average budget race trailer is only designed for a dually. If you don't go with air ride you will want an air hitch. I run a trailer saver air fifth wheel, and there is a gooseneck ball conversion available for it. Also the farther back you put the hitch the more it magnifies the bumps to the trailer. check out bmzero's build thread in the hdt section. He fabbed his own air hitch (incredible piece of engineering) and there is a link to a video where you can see how much the hitch moves and soaks up the bumps.

I am like the rest, i got the ability but not the knowledge, and why tackle all that when you can focus on the other things that are ahead of you in your build. What ever you do good luck with it!

Sam