Need advice.. Changing from leaf to trailing arms.

[funkytechmonkey]

My suspension from porterbuilt should be here tomorrow, so I am pretty excited about getting this truck back together. Now this is my first truck build and I truly have no clue what I am doing so any advice would be great. And please dont knock me for such a noob question.

Here are a few questions I have.

I would like to keep the rear end I have but change the gears. How are the trailing arms going to mount to the axel? How do I align the rear end?

I am doing a mild notch and want to make sure I cut and mount it in the right spot. The rearend is not going to be mounted up so are there measurement I can go off for the cuts? This may be a question for porterbuilt.

Since I am changing from leaf to trailing arms I have already removed the leaf mounts and crossmember. I have a bare frame. But I am curious about this crossmember. Does the leaf spring crossmember with the big red arror in the middle need to be removed?

[funkytechmonkey]

Perdy plezzz
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[SCOTI]

That looks just like the shock x-member for the coil applications too. It's been a while since I've seen a leaf frame, so I can't really tell by your pic if it's in the right place as is or not. Maybe post up some other pics from the top side??

For the rear end, you'll need the rear-end 'swap' axle pads. I know ECE (early classic enterprises) has them..... Not sure if any of our board supporting vendors carry them, so check them out first.

I would not do the notch until the rear end is in place. Too much possibility of being off enough to render the notch useless.

Also, from the angle of the pic, it looks like the frame is pretty straight after the front bed mounts (might just be the angle of the pic as viewed from the monitor). Was this a 4wd leaf frame or 2wd leaf frame?

[no moa]

Might be easier to just find a trailing arm frame? Then changing pads and stuff over.
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[bw4sale]

My frame is converted from leaf to ta. You don't have to remove that crossemember, but depending on how low you go you may have to notch it for driveshaft clearance.

I agree with Scoti. Wait till you at least get it all mocked up to do the rear notch. You don't want to get that wrong and have to redo it...trust me.

You can see here how mine is notched. It was this way when I got it.

[bw4sale]

Oh and to address you're centering question. You'll need to add a panhard bar to keep it centered.

[SCOTI]

bw4sale,

If that frame in your pic is the leaf frame you discussed changing, the x-member between the front leaf hangers does indeed look like the same x-member the T/A trucks use for their upper shock x-member. On the T/A trucks, it's moved further rearward between the coils location & the rear end.

[Normy71]

I feel your pain I'm doing the same as you
Leaf spring to trailing arms on air.
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[bw4sale]

Scoti,
That is the frame but the crossmember is actually a little different. There's a hump in the middle of it that isn't there on the t/a crossmember.

Here's another pic. Maybe you can see it better there.

[bw4sale]

Also, this is what I got for assuming that the notch that worked for the spring set up would work for the t/a. Never did figure out why it was different, but it was. I had to redo it once I got the t/a rear under there.

[SCOTI]

I remember the x-member 'lip' having the center higher than the outer mounting points but I don't think that would impact the shock mounting. Of course, it would prob be easier to just build a new shock x-member (similar to yours).

[crazy longhorn]

Yea, the leaf trucks had the crossmember right tween the front spring hangers. The coil trucks moved that crossmember back, & set it right above the coil springs. Now you can trim it, or cut it out completely....but if it were mine, I would locate & mount the coil crossmember, before I cut the front one out(helps keep an old frame 'square"). crazyL

[steinepstein]

I'm doing the same conversion. I'd keep but the front and rear crossmembers (where the leaf spring mounts are located), they will add additional strength to the frame.

You will have to figure out how to mount your shocks and that will depend on your ride height....you will have to weld in some new crossmembers.

Also, you need a panhard or watts linkage. I really don't like the original panhard design, it needs to be much lower and much longer....get one of the kits out there to solve this problem.

But, I agree with your decision, it is an improved design and smoother ride.

JE

[68 TT]

Are the frame rails themselves any different between the leaf and trailing arm trucks?

I'm switching from trailing arms to leaf on my 69 to complete the 4x4 conversion. Wish I could find somebody local going the other way around so I could get the correct spring hangers & cross members to do it with stock parts.

If a PO hadn't converted the front end of my frame to leaf already I could just swap frames with somebody wanting trailing arms.

I have a square body K5 blazer chassis and a 74 K10 chassis to cannibalize parts from so I'm not starting from scratch at least.

[bw4sale]

Mine only had slight differences that I could find. My leaf frame has raised areas (bumps) inbetween which the spring hangers were riveted. Not really sure they served any real purpose. My TA frame also had these extra pieces riveted in at the bend for support. The rust inbetween the two pieces is the main reason I decided to switch frames.

[funkytechmonkey]

Man I wish you were local too... I'd sell you my axel and leaf setup CHEAP!
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[no moa]

You guys that are doing this convertion would you be willing to sell the springs and frame bracketts? I'm keeping my leaf rear in my 1/2, as I'm going to tow with it. My brackets are pretty warn.
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[SCOTI]

Originally Posted by 68 TT

Are the frame rails themselves any different between the leaf and trailing arm trucks?

I'm switching from trailing arms to leaf on my 69 to complete the 4x4 conversion. Wish I could find somebody local going the other way around so I could get the correct spring hangers & cross members to do it with stock parts.

If a PO hadn't converted the front end of my frame to leaf already I could just swap frames with somebody wanting trailing arms.

I have a square body K5 blazer chassis and a 74 K10 chassis to cannibalize parts from so I'm not starting from scratch at least.

There are 'beads' in the frame rail (formed in the steel) to increase strength where the hanger attached to the frame. Basically the same otherwise (2wd leaf vs 2wd coil comparison). 4wd frames are different but the truck arms will still swap over on these as well.

[funkytechmonkey]

Originally Posted by no moa

You guys that are doing this convertion would you be willing to sell the springs and frame bracketts? I'm keeping my leaf rear in my 1/2, as I'm going to tow with it. My brackets are pretty warn.
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Sure I'll sell you mine. I have pretty much averting you need. Even a 5 lug rearend with the leaf mounts. Shipping will be a crazy amount but if you pay for it I'll ship it.
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