Converting from leafs to coils

[JJ Deuce]

I want to change over the leaf spring rear suspension on my GMC to the trailing arm setup from the Chevy. I figure it'll reduce wheel hop, and I plan on running a torquey big block in it.

I'm still new to these trucks, but it looks to be a simple conversion. Anyone have any tips, or a source for an off-the-shelf kit?

Thanks in advance.

[SCOTI]

You'll need all the coil spring suspension related parts & it's basic R&R from one to the other.

[smbrouss70]

I am wanting to do this to my 4x4 blazer frame also. From what I know you will probably have to fab up some type of bracket to hold the top of the coil spring. If you look at the pic below you'll notice that a coil spring frame bends outward to hold the coil, whereas a leaf spring frame is just straight right there.

[SCOTI]

Originally Posted by smbrouss70

I am wanting to do this to my 4x4 blazer frame also. From what I know you will probably have to fab up some type of bracket to hold the top of the coil spring. If you look at the pic below you'll notice that a coil spring frame bends outward to hold the coil, whereas a leaf spring frame is just straight right there.

2wd trucks use the same frame, just different brackets. The frame rails in that pic are the same on both sides. That pic also demonstrates that both types of bracketry can be bolted to these frames.

[smbrouss70]

That is a 2wd coil frame, that Early Classic set up in their showroom to show off their suspension pieces for both coil and leaf frames. I can take a pic of the back of my 4wd blazer frame tomorrow when the sun is up to show how the frame rails are straight on the leaf frames.

[SCOTI]

Originally Posted by smbrouss70

That is a 2wd coil frame, that Early Classic set up in their showroom to show off their suspension pieces for both coil and leaf frames. I can take a pic of the back of my 4wd blazer frame tomorrow when the sun is up to show how the frame rails are straight on the leaf frames.

Your frame might be straight because it's a 4wd frame, which is different than a 2wd frame. 2wd frames are the same frame, regardless of which suspension type they were fitted with. That's why ECE was able to bolt both suspension types to the same 2wd frame.

I guess the million dollar question for JJ Deuce is: Do you have a 2wd or 4wd?

[smbrouss70]

I had a 68 2wd GMC with leaf rear for a parts truck, and I can't be 100% sure but I want to say that the frame rails were indeed straight. Maybe JJ can look under his truck and maybe take a pic to let us know for sure.

[SCOTI]

Originally Posted by smbrouss70

I had a 68 2wd GMC with leaf rear for a parts truck, and I can't be 100% sure but I want to say that the frame rails were indeed straight. Maybe JJ can look under his truck and maybe take a pic to let us know for sure.

First, I'll admit I haven't actually swapped the parts yet, but . . ...... I have a leaf frame in my driveway & they have the same 'kick-outs' over the rear end housing because the frames are the same. I purchased this 'leaf' frame to replace my current 'coil' frame on my RestRod. All I'll be doing is swapping my coil related bracketry over to the leaf frame. I took measurements before buying the frame to make sure they were indeed similar.

Coil equipped trucks have a different crossmember where the coils mount specifically for locating the upper end of the coil & shocks, + reinforce the frame in that area. They also have a bracket for the panhard bar. Leaf frames have a crossmember & are reinforced @ the frame where the front hangers mount as well as having different style shock mounts.

Think about it. Even though it was a long time ago, it wouldn't have been very cost effective to use different frames when building the 2 different suspension types.

I would take some pics but the frame currently has a swb steel floor sitting on it. I don't think pics from the bottom side would show the similarities.

[Longstep70]

Good subject - I'd like to do this same swap.
How are the anchor brackets for the trailing arms and the extra X-member for the coils attached to the frame? Are they bolted, riveted or welded?
I see the holes on the front X-member for the trailing arm mounts on my leaf frame. Presumably if I got hold of the parts from a coil frame i could bolt everyhting on it?

[SCOTI]

Originally Posted by Longstep70

Good subject - I'd like to do this same swap.
How are the anchor brackets for the trailing arms and the extra X-member for the coils attached to the frame? Are they bolted, riveted or welded?
I see the holes on the front X-member for the trailing arm mounts on my leaf frame. ?

They are rivited.

Presumably if I got hold of the parts from a coil frame i could bolt everyhting on it?

Yes.

[chevy72blu]

Just so you know... Coil springs arent the best idea if your looking to eliminate wheel-hop when you launch.

Nothing beats a set of leaves and some quality trac-bars when it comes to hooking it up.

[SCOTI]

Originally Posted by chevy72blu

Just so you know... Coil springs arent the best idea if your looking to eliminate wheel-hop when you launch.

Nothing beats a set of leaves and some quality trac-bars when it comes to hooking it up.

I've seen many leaf spring vehicles encounter hopping from spring 'wrap-up'. I think each has benefits depending on specific vehicle applications. One thing that's common, which ever set-up is utilized needs to be tuned properly for best results.

[69 longhorn]

Originally Posted by chevy72blu

Just so you know... Coil springs arent the best idea if your looking to eliminate wheel-hop when you launch.

Nothing beats a set of leaves and some quality trac-bars when it comes to hooking it up.

I have learned to live with leaf springs, & tightly clamped slapper bars.....cant say its the best setup, but it dont work too shab! For an "all out effort" on leafs, I would run housing floaters, & a fairly long ladder link bar crazyL

[JJ Deuce]

sorry it's taken me so long to get back to the thread. It's a 2wd SWB stepper. I just looked under the frame, and it is flared out over the axle like the Early Classics picture.

I'm planning to drop the truck 5-6", and I don't believe I'll have room for traction bars. Plus, I can run a wider tire with the coils, and it looks cleaner. I plan on driving this truck hard, but I'm real picky about how things look, too.

[el curioso]

I made this conversion a couple of months ago the parts that were needed are as follow correct me if im missing some thing.:
2 trailing arms,
2 u-bolts and hardware,
2 coil springs,
4 coil retaining plates,
4 nuts and bolts for retaining the coils,
12 grade 8 bolts to retain the trailing arms to the center crossmember,
2 spring perches or an axle that came from a truck with oem coils (which I opted to do) cuz u got a bargain,
2 lower shock mounting harware( early classic sells a kit that includes panhard bar and shock hardware which I would highly reccomend do to the amount of drop that you looking into)
The last thing that I think im missing is the track bar mounting bracket.
Just my $.02

[gringoloco]

Bringin' back an oldie here...

Originally Posted by elcurioso

I made this conversion a couple of months ago the parts that were needed are as follow correct me if im missing some thing.:
2 trailing arms,
2 u-bolts and hardware,
2 coil springs,
4 coil retaining plates,
4 nuts and bolts for retaining the coils,
12 grade 8 bolts to retain the trailing arms to the center crossmember,
2 spring perches or an axle that came from a truck with oem coils (which I opted to do) cuz u got a bargain,
2 lower shock mounting harware( early classic sells a kit that includes panhard bar and shock hardware which I would highly reccomend do to the amount of drop that you looking into)
The last thing that I think im missing is the track bar mounting bracket.
Just my $.02

Contemplating the same, I believe mine was an original trailing arm that some PO converted to leaves for who knows what reason

The truck has the trailing arm brackets on the cross member and the panhard bar bracket on the frame (both riveted, all of the leaf brackets are bolted on.) I will crawl under and see where the crossmember is in the morning. Hopefully there is one in the rear position.

Question is: I don't see it on elcurioso's list; is there some sort of upper mounting plate for the coils or do they just bolt to the frame directly? a spring perch of some sort?

Thanks in advance,
Chris

[el curioso]

Check out picture 2, 3, 4, and 5 they illustrate exactly where the coil would mount if it wasn't an air bag

The LINK

You can also get a glimps at the two extra crossmembers that came with a coil frame one for the shock perches and spring reinforcement; and one for the panhard bar reinforcement.

[67Fleet]

Since this was dug up, and it hasn't been mentioned before, another alternative to your solution to wheel-hop would be to 4-link it and go with a coil-over setup. That would be ideal if you're planning on running a lot of HP. Not the cheapest way, but worth the money IMO.

[gringoloco]

Thanks alot again elcurioso. Crawled under the truck, wadayaknow- spring perches and crossmembers are there. Also found a clutch pedal that some previous clown sawed off while I was under the dash today. Now to find that rust free fleet bed...

[ozzyracing]

Keep the leafs or go coil over. I would not pay the money to change it to the original coil setup. There is a ton you can do to your current leafs to get great traction with a BB.

[ozzyracing]

Also, what size of wheels are you planning on running. my 15x10's fit great all aorund.

[68LSS1]

With very little work you can get a coil spring set up to stick pretty good at the track.