86 C10 Trailing Arm Conversion
 

Just want to show a project that I am starting and see if anyone has input and interest. I've read many articles about how great the trailing arm suspension is in the 67-72s and how it has been used in Nascar, etc. I saw the hotrods to hell site and their project truck and read about all the cars that they have built using the trailing arm setups. It seems like trailing arms can be setup to take on road courses, drift, and drag. So naturally, I was interested. CPP recently came out with a kit to install trailing arms in a 73-87 but at $2000 i would assume it is out of the average person's price range. Through the parts for sale section here I got a great deal on some rust free 70 trailing arms and a crossmember and am going to make it happen on a budget. Where there is a will there is a way.

Re: 86 C10 Trailing Arm Conversion
 

Here are some pictures of my initial mockup just to see if things would fit and if it would be possible.

Re: 86 C10 Trailing Arm Conversion
 

Here are a few...

Re: 86 C10 Trailing Arm Conversion
 

and lastly... there seems to be plenty of frame clearance

Re: 86 C10 Trailing Arm Conversion
 

I am a beginner with the whole custom fabrication thing... If anybody could help me figure out how to truly mock everything up and locate the crossmember front to back on the fame that would be appreciated. Also, I am switching to a 69 axle that is setup for leaf springs. I am curious how to locate the trailing arm perches and center the axle. My plan was to leave the leaf springs in until the last steps so that I could use them to locate everything. I believe the perches on both the 69 and my 86 axle are in the same place so I was just going to unbolt the old axle and put the new one in and locate the crossmember based on that. Sorry if any of this is unclear. Thanks for any help or contributions.

Re: 86 C10 Trailing Arm Conversion
 

If it were me, I'd start like this . . ....

Remove the rear leaf hangers & shocks to allow rotating the current rear housing up until it touches the frame rails. Using a square, scribe a line in front of & behind the housing tubes. Find the center of these two lines & you have your rear axle center-line (C/L).

Use a 36" piece of 3"OD pipe as your mock-up axle housing. With the 'new' rear axle centered on the C/L reference marks in a fixed position (ratchet straps, tack welds, etc; you just don't want it shifting), install the truck arms & crossmember. The pipe allows mounting the truck arms & tightening them enough w/the u-bolts to get a pretty decent feel for spacial requirements while allowing the assembly to rotate as needed (rotate it up to the bottom of the frame rail like in your pic). Use jack stands or blocks of wood as needed to keep things @ the required height.

Once you know approximately where the c.member needs to go, put a piece of angle/steel (butted up against the c.member) to scribe reference marks on the top & bottom of the frame rails (each side). Remove the truck arms & wedge the c.member into place between the rails. Using the angle/steel (again butted up against the c.member), align the c.member back up to the reference marks previously scribed. This will get you close enough that you can use a large carpenters square to square the c.member w/the frame rails. You can either make templates to figure out where to drill holes or weld the c.member in.

The Panhard bar brackets should be fairly easy. Use an aftermarket long bar (Super Track bar). This puts the pass side bracket on the pass side truck arm vs. attached to the housing. The drivers side mount would be attached to the bottom (or inside) of the driver side rail (whichever helps the level of the PHB better).

There will be a little more work to get the springs (bags??) in the right place & you'll need to make an upper shock mount that not only locates the top portion of the shocks, but should also reinforce the frame for additional spring support.

(Can you tell I've ran this scenario through my knoggin once or twice :lol: )

Re: 86 C10 Trailing Arm Conversion
 

Try finding a rear housing that's ready for truck arms. While this can be done several different ways, 12-bolt 67-69 truck rears aren't commanding premium dollars in used, non-posi condition. Become a supporting member ($25/yr subcription) & post a want-to-buy ad in the 67-72 classifieds. I bet you'd get a few hits from fellow members in your area.

Re: 86 C10 Trailing Arm Conversion
 

Thanks SCOTI for your response. I believe that the crossmember has to go under the frame rails. This is the way they did it at hot rods to hell. I was going to modify the ends of crossmember and make some brackets out of 1/4 steel to attach to the ends of the crossmember and the outside of the frame rails. As for shocks I am torn between air and coil overs all the way around. I want the truck to be more like a pro-touring vehicle while still being able to hit the drag strip once in a while. I am wondering what you would recommend.

Re: 86 C10 Trailing Arm Conversion
 

Here are a few pictures of the truck from the hot rods to hell shop. I talked to the owner of the shop and he was very helpful and gave me some good advice. He builds his own arms but they are the exact dimensions of the factory arms. He makes his own crossmember and panhard. He also uses coil springs with screw jacks instead of regular coil-overs. He says they offer more adjustment and handle better.

Re: 86 C10 Trailing Arm Conversion
 

here they are...

Re: 86 C10 Trailing Arm Conversion
 

Nice work. I am doing this conversion this winter, along with my C4 DM. I have been planning on this conversion for sometime now. I plan on making my own crossmember from steel tube. I plan on running dbl adjustable coilovers.
Since you got it started it will now be a bit less work for me.

Re: 86 C10 Trailing Arm Conversion
 

For coilovers I was looking at these for ease of installment plus the spring rate is right for the angle of installation etc. or so I hope. I have to do more research later on.

Re: 86 C10 Trailing Arm Conversion
 

Re: 86 C10 Trailing Arm Conversion
 

Some good points. Here is how it was runnning through my head. I would set the ride height then tack a peice of tubing on my axle then either tack it to the frame or secure it to the frame some way. Then I would remove the leaf springs and bolt the trailing arms to the housing (I already have new perches). I would then fab up my crossmember with adjustable mounting brackets for the arms. I haven't thought about the side to side placement of the trailing arms yet. I doubt I will shift it from the "stock" position. Haven't thought about whether or not I can gain anything from having them wider on the axle or not. I plan on running the super track bar as well, which I already bought.

Re: 86 C10 Trailing Arm Conversion
 

As you can tell I am really a newbie at this. I've have built engines and done engine trans swaps and some paint work etc. but nothing like this. My axle is a 69 with a 3.73 posi so I would really like to use it. It has the leaf perches on it which I need to remove. After removing them, how do i figure out where the trailing arm perches need to go.

Re: 86 C10 Trailing Arm Conversion
 

How low are you planning to run your truck? I am assuming you want it low because you mention Pro-Touring. With the crossmember mounted under the rails your not going to be able to run as low as you would with it mounted between the rails.

The truck you pictured that HRH built is a C/20. I'm not sure what the reason was for the T/A conversion but I will guess they have no intentions of running low.

Re: 86 C10 Trailing Arm Conversion
 

I assumed 'under the framerails' meant between the upper & lower rail, but under the lip of the rail. JW76, can you clarify?

I'm familiar w/the HTH set-up. I like it but think the price is too much considering the dimension between the frame rails of 67-87's is basically the same width thus allowing a stock or aftermarket truck arm c.member to bolt in. Their PHB set-up is nice but it requires welding. If you have that ability.... fabbing your own PHB brackets so that the bar is level @ ride height shouldn't be an issue. Ditto on the CPP kit.

Re: 86 C10 Trailing Arm Conversion
 

Mark your axle centerline then I would do as Scoti said and unbolt the rear spring. Then find your desired ride height. Get your pinion angle set. Then loosely fasten the arms and perches to the rear, next put the crossmember in based on where the front of trailing arms place the crossmember. Once you get the crossmember in and the trailing arms bolted to it you should have your location set for the perches. Of course it sounds good in theory but it may not work in real life.
Anyone see anything wrong with my process?

Re: 86 C10 Trailing Arm Conversion
 

Maybe I shouldn't have said pro-touring. My intentions aren't 100% pro touring perhaps. I do not want it extremely low with 18/20 inch rims with a mini tub. I am shooting for a slightly lowered aggressive stance, with a stock body, very good handling with some adjustability, but street-ability and reliability are paramount. I do not want it super low because as we all know east coast roads are a nightmare. I contemplated a 4 link or ladder bars but decided they wouldn't behave how I wanted and would be a little too radical for street use. In the summer the truck is pretty much my daily-driver as weather permits. In addition I like the idea of going retro with the truck. It will eventually be powered by a carbed LS, its has old school corvette rally wheels, it has a th400 out of a 70 malibu wagon, etc. and the old truck arms are just the icing on the cake. Here are pictures of where am I now

Re: 86 C10 Trailing Arm Conversion
 

I would like to lower the truck so that there is about a 2-2.5 inch gap between the top of the tires and the wheel arch.

Re: 86 C10 Trailing Arm Conversion
 

Right now the gap between the top of the tire and the bottom of the wheel arch is a little over 4 inches in the back and around 3 in the front. My rationale for the crossmember being under the frame (as in the picture before) is that 1. it gives me extra clearance for the trailing arms so that when the shocks compress the arms have plenty of room to move upward without hitting the frame rails and 2. it allows me to run the driveshaft through the hole in the crossmember with just a little bit of widening to allow for driveshaft movement. With the truck at my desired height this allows plenty of ground clearance. My headers, exhaust, and the center of the differential are a few inches lower than the crossmember will be.

Re: 86 C10 Trailing Arm Conversion
 

If this doesn't make sense I am open to any input/suggesstions.

Re: 86 C10 Trailing Arm Conversion
 

I'm doing the trailing arm swap into my 67 Chevy II, so I've contemplated this for quite some time.

In this situation, I'd get the trailing arm crossmember between the frame rails. As far as suspension travel, there are guys using the stock crossmember , and dang near laying frame.

So, with that, get the x-member where it belongs. There is a kit from CPP I think, for adapting a non-trailing arm axle. Otherwise, you'll have cut the axle mounts off of a trailing arm axle, so that the axle has a flat surface to mount to the trailing arms.

Just my two cents. As far as the panhard, I don't have experience with that yet, so I won't even try...haha.

And as a side note - isn't putting an aftermarket truck arm suspension under a pre-72 pickup kinda redundant? Unless it has leaf springs...I dunno. If it ain't broke...

-Sam.

Re: 86 C10 Trailing Arm Conversion
 

I thought I understood your intentions when you mentioned "Pro-touring". My reason for bringing that up as mentioned was to clarify your objective.

As samwise68 mentions there are lots of trucks running some version of the T/A crossmember that are really low. I may be wrong here, but I feel running it below the frame is going to be a prohibitive choice.

If you look at what many of the 67-72 guys have done, you will note that they have modded (or replaced) the crossmember to address driveshaft and exhaust clearance issues.

Beyond that, I think its a cool project.

Re: 86 C10 Trailing Arm Conversion
 

The crossmember needs to go between the frame rails. To place it under is going to compromise the geometry rendering the effectiveness of the swap pointless. The desired ride height can then be established w/proper spring selection.