Build Trailer from 1985 GMC S-15 Frame

Reply

  #1  
Old 02-18-10, 10:56 AM
H
Member
Thread Starter
Join Date: Feb 2010
Posts: 3
Received 0 Votes on 0 Posts
Build Trailer from 1985 GMC S-15 Frame

I'm having trouble finding a forum anywhere dedicated to this kind of thing, but this seems like a good place to ask...

I have a 1985 GMC S-15 (better known to many as a Chevy S-10 or GMC Sonoma) here which is no longer street-legal and not worth fixing. What I am planning to do is strip the truck down, leaving only the frame, rear bumper, rear axle/diff/springs/tires, and use the frame to build a specialized flatbed trailer.

I am hoping someone has done something like this and can give me some tips, or at least warn me of some caveats. I primarily have concerns about the weight capacity of the single axle (albeit the truck originally weighed 3,000lb with a 1,700lb payload, so it should hold 2,500lb easily enough!), and the stability of what will be a relatively high deck. The frame is primarily 4" C-channel steel (3/16" or 1/4" thick), going up to 5" on the lower part. If I keep the solid rear bumper mounts and cut the frame just ahead of the driver's door, I will have nearly a 12' section of frame with the rear axle being 4' from the rear (creating a nice 60/40 weight split). (see hand-drawn with measurements and GM's schematic)

First off, to get any decent width, I have to build the deck over the tires. This is more or less required anyway, as the top of the frame at the rear is level to the top of the tires. I presume I would need to leave at least 5" clearance over the tire, which puts the top of my deck at 32" off the ground, which seems a little high to me. The really unusual bit for a trailer, obviously, is the 1' drop and the narrow wheelbase (62" wide). I have three plans in mind, still weighing the pros and cons of each:

- Option 1 is to build a solid flatdeck 32" off the ground, with sheet metal toolboxes underneath (built on the low section of the frame). The flatdeck would be built from 1 1/2" x 1/8" angle steel, and plain ol' 2x lumber.

- Option 2 is to build a dual-level flatdeck. Upper section 6' long, lower section 5' long. The lower section would likely be built with drop-down doors. The front of the trailer (partially on the tongue) would have a steel toolbox built, with a ledge at a height equal to the rear deck, allowing a 6' panels made from 2x to be dropped over the low section (creating one long 12' deck). I like this option, as it creates a 20" deep lower section with sides where I can easily throw garbage and such when on the job, and not worry about it blowing away on the road. Also a place to put smaller things (tools, nails, etc) when hauling long lumber on top.

- Option 3 is to build either Option 1 or Option 2, but make the rear portion of the deck hinged at the rear and latched down as a dumping deck. This would require building removable walls and a removable rear door (something I might have done anyway for use as a general utility trailer), and adding a mount underneath inside the frame for a ram of some kind (or a 4' jack-all until I can afford a ram!).

Excluding the toolboxes (which I would probably add later to save money now, or temporarily build from plywood other than structural bits), option 1 is the cheapest at about $450 in material, including 1 1/2" angle, lumber, 4" tube steel for building the tongue, the hitch, and assorted other bits (safety chain, marker lights, etc). Option 2 comes in at about $600, and option 3 adds about $200 (excluding the ram). All of these are much cheaper than $2,000 for a single-axle, 12' x 7' flatbed with no walls or toolboxes!

Other planned little bits:
- I plan to leave the diff and U-bolt in place to keep the oil inside, rather than trying to strip the gears out. It's just easier, and I'm lazy. I am also considering leaving the rear brakes in place so that I can hook up a handle to the E-brake cable and engage it from the front. Reason for this is I will often be handling the trailer alone, and on even slight slopes it can be difficult to get the trailer in position then rush to get blocks under the wheels. I figure it should be safe to leave them in, so long as I remove the shoes to prevent anything strange happening. (Unless the brake shoes are also what engage the e-brake? can't remember...)

- I will be re-using the S-15's taillights as well as some other detail bits, just to add a touch of cool. I would also like to mount the old headlights under the front corners of the trailer (facing backwards) to provide me with some surround-floodlight at night while reversing (as I often am working at night). However, the standard 4-pin trailer connector does not include wiring for reverse lights - any suggestions?

- I might need to replace the aging springs. A 1,200lb load of 14' 2x10's in the back of the old pickup would drop the rear bumper about 8" (albeit about 80% of that weight was behind the rear axle). If I hit the Pick-N-Pull, how can I evaluate replacement springs? I know there are trucks there that have not been loaded and abused nearly as much as mine.

- If the 32" high deck over the narrow 62" wheelbase creates a substantial stability risk, what are my options? Best I can think of is to mount the existing axle lower with smaller tires (current tires are 25" high), or get a proper trailer axle with really small tires. Either would let me drop the deck to 26" high. But by the time I hit that expense, I might as well not be using the truck frame, I won't save anything...

Well, that's all. Does anyone have any suggestions for me?
 
Sponsored Links
  #2  
Old 02-18-10, 06:09 PM
hopkinsr2's Avatar
Member
Join Date: Feb 2005
Location: canada
Posts: 1,563
Received 0 Votes on 0 Posts
What is your time worth?? I know I wouldn't build a trailer as I could make more working than I would save building a trailer.. What is the law in you'r area regarding brakes on the trailer?? Also you have to be sure the tunge & frame are square to prevent "dogtracking" on the road.. Also regular "P" series tires on the S-10 won't hold as much weight as a trailer tire.. There's lots of other stuff,, but think of the time thing,,, I could build a trailer that I don't know if it would pass a MTO safety or I could buy one & work that week & still be money ahead.. Just Thoughts... Roger
 
  #3  
Old 02-18-10, 08:28 PM
Speedwrench's Avatar
Member
Join Date: Apr 2008
Location: Oklahoma
Posts: 1,698
Received 0 Votes on 0 Posts
the build is easy, other than getting the tongue straight, that is the hard part, however light weight trailers around here are only around $1200 for 3000lb limits, In my opinium my time is worth more than that, the brake shoes will be needed to activate the parking brake. to use the lights on the front you will need either a 6 pin or a 7 pin rv plug, I set all of my trailers up with the rv plug from the git go because they are much better quality than the 4 pin plugs, never use stakeon wire connectors, they are corrosion magnets, best is soldered connections with glue insert heat shrink tubing to water proof the connections, no easy way to test springs with out a vehicle to preload them. you could lay them down and stretch a straight edge over and measure the drop at center and compare to a new spring but what is your time worth to pick thru a bunch of used parts?

Murphy was an optimist
 
  #4  
Old 02-19-10, 12:03 AM
H
Member
Thread Starter
Join Date: Feb 2010
Posts: 3
Received 0 Votes on 0 Posts
Work is slow right now, so time is not really an issue. Gives me incentive to finally get the garage cleaned out. And laws here allow me to build a trailer with a legal weight limit of 2,500lb, and register it with no inspection as long as I promise it's safe and has appropriate equipment (safety chain, taillights, etc).

Bear in mind the prices I mentioned above are Canadian... a decent 12x7' trailer runs about $2,000 or more new, so building some capable for around $500 is a great deal for me, especially when selling parts of the truck is going to pay for the parts to build it.

My local steel costs are $18 per 20' length for the 1 1/2" x 1/8" angle, around $100 per 20' length for 2x4" x 1/4" tube (to make the tongue). Maybe less if I can find suitable scraps in the yard.

My total costs to build a trailer from scratch would be close to $1,000, money I don't have. Trying to do the best I can with what I have.
 
  #5  
Old 02-19-10, 07:09 AM
M
Member
Join Date: May 2006
Location: Iowa!!!!!
Posts: 4,156
Received 12 Votes on 12 Posts
Some things you can do...

If you have the clearance, under sling the springs on the axle. This will drop the load about 5 or 6 inches.

Add a leaf or two to the stack to stiffen the load sway.

When you build the tongue/hitch, set the frame up on stands with the wheels off. Then, with two equal length wires (to avoid stretch), hook one end of each to a front wheel stud and form a triangle to the point you want the hitch. This will make sure it pulls straight.

*** If you decide to put the springs under the axle, post back and I'll give some instructions on that stuff.
 
  #6  
Old 02-20-10, 11:17 AM
Speedwrench's Avatar
Member
Join Date: Apr 2008
Location: Oklahoma
Posts: 1,698
Received 0 Votes on 0 Posts
for the tongue, most of the ones i have seen built from old Pu beds just notched the frame and angled it in then welded the hitch onto that, just be careful to center the hitch within the frame, I prefer the bulldog hitches they seem to be the strongest and reasonable price, try not to make the tongue less than 4 ft long longer is better for towing and backing helps with sway and preventing jackknifing. what kind of lights are on the tow vehicle? integrated stop/turn or separate, that will also affect the type of connection you use for hooking up your trailer lights; my 2001 Sonoma has the springs above the axles, since you will not be powering the differential you probably can just get by with cutting the spring hanger and inverting it under the axle and welding it into place the differential angle is not going to be as critical on that set up. my Sonoma has the integrated tail lights that means you could get by with a 4 pin plug if you want, depending on the tow vehicle.

just a thought but can you trade for a 3/4 tn Pu that in not in running shape. the differential and frame would make a much more stable trailer? or would the weight be to much for the project?

what part of shall not be infringed do we not understand?
 
  #7  
Old 02-20-10, 07:46 PM
H
Member
Thread Starter
Join Date: Feb 2010
Posts: 3
Received 0 Votes on 0 Posts
Cutting/notching frame will not work. This is not a pickup bed trailer; it is a flatdeck built on a pickup frame. I am using every straight part of the frame, right up to the former front wheels. If you look at the GM Schematic linked in the first post, you will see what I mean. I am using right up to the bracket mount by the number 3 (where 4 points, I think). It is possible I might be able to use more ahead of that and notch it in (especially since it rises back up to a good hitch height), but it's a pretty funky area with all the engine/shock/steering arm mounts. Have to take it apart before I can say.

Trading might be possible, but I don't think a 1/2 or 3/4 ton frame would be good for my purposes - they sit even higher, albeit some have nice straight frames rather than the big drop mine has, would allow for installing small wheels and beinging the whole thing down... have to look into it.

The new truck is a 2010 Ranger SuperCab V6 with a 5,700lb rated tow capacity and a class III hitch with a 4-pin connector. The only real problem for any true towing is the vehicle's weight, which is only 3,600lb (dry) vs 5,000+ for 1/2-ton trucks like the F-150 or Sierra. But then again, I guess that's not THAT light... heavier than the old 2,900lb S-15 which towed trailers this size without too much problem.


Anyway, I think I've gathered up enough information to figure things out and kludge it together. Of course, more tips and solutions are always welcome! I will post my progress here as I get started on it.
 
Reply
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description: