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Old 03-03-2017, 02:54 PM   #1
chevy72blu
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'72 Leafs to trailing arm conversions

I have a '72 C20 cut down to a C10 and converted to 5 lug. The factory leafs were kept with the overloads and a few leafs removed to lower it about 2".

All of the leaf bushings are shot and instead of replacing them all I'm considering swapping over to trailing arms (or less likely a 4 link). My primary goal is ride quality, but I'd also like to make it hook up a bit better and lower it another 2" (4" of total drop).

My rear end is a '70-82 (63.5" wide) GM 12 bolt without a panhard bar mount. I want to keep my rear end.

Obviously the most cost effective thing would be to find a pair of stock trailing arms, brackets, and spring perches. I could then use something like the CPP super track bar in lieu of a PHB. I've found a few sets of '60-66 arms. Are these the same dimensionally as the 67-72?

Other than cutting off and re-welding the spring perches, and torching out the factory rivets, what other fab work is involved? I assume I'll need to install new shock mounts, also.

I'd love to spring for the CPP, No Limit, or Porterbilt kits but they are over my budget for the time being. Would the ECE kit and CPP track bar combo be a more affordable option?

I may just rebuild my leafs with drop shackles and add a set of caltracs, but I've never really liked the way leaf springs ride compared to a coil spring '72 BBC truck I owned years ago...

Any tips or pictures you can share would be helpful. Thanks
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Old 03-03-2017, 03:11 PM   #2
69gmcc10
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Re: '72 Leafs to trailing arm conversions

I think the '60-66 arms are the same, but I cant be 100% sure. I do know the lower spring mounts on that vintage are interchangeable with 67-72 and are sronger (double shear).

Read my thread: http://67-72chevytrucks.com/vboard/s...=501676&page=2. Starting at post #39 I did a coil conversion and it might have the info you are looking for.

It rides way better with the coils and with the trailing arm mount flipped it hooks up and puts the power to the ground real well!
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Old 03-03-2017, 03:39 PM   #3
chevy72blu
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Re: '72 Leafs to trailing arm conversions

Thanks, I'll take a look!

Are there any differences between C10 and C20 frames with reference to the trailing arm setup? I was under the impression that they are the same, but a guy on Craigslist is adamant that they are not.
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Old 03-03-2017, 03:58 PM   #4
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Re: '72 Leafs to trailing arm conversions

Quote:
Originally Posted by chevy72blu
Any tips or pictures you can share would be helpful. Thanks
Quote:
Obviously the most cost effective thing would be to find a pair of stock trailing arms, brackets, and spring perches. I could then use something like the CPP super track bar in lieu of a PHB. I've found a few sets of '60-66 arms. Are these the same dimensionally as the 67-72?
Yes they're the same. 3/4 ton arms are as well but they will have partial reinforcement plates on the top & bottom of the arms.

Quote:
Other than cutting off and re-welding the spring perches, and torching out the factory rivets, what other fab work is involved? I assume I'll need to install new shock mounts, also.
Leaf frames do not have the same upper shock x-member as a coil equipped truck so upper mounts will be required. An alternative is No Limit Engineering's rear shock relocation kit. It changes where the shocks mount & provides better geometry. Check into their Panhard bar kit as well & compare vs ECE or CPP's set-up.

Quote:
I may just rebuild my leafs with drop shackles and add a set of caltracs, but I've never really liked the way leaf springs ride compared to a coil spring '72 BBC truck I owned years ago...
Night & day difference of a swb 1/2 tons ride quality when comparing the leaf set-up vs coil in my opinion.

Quote:
Are there any differences between C10 and C20 frames with reference to the trailing arm setup? I was under the impression that they are the same, but a guy on Craigslist is adamant that they are not.
69-72 2wd & 4wd Blazer/Burb frames are shaped different.
63-72 1/2 ton & 3/4 ton frames are shaped similar but I believe the C20 frames are thicker/taller (73-87 C20's are vs C10's).
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Last edited by SCOTI; 03-03-2017 at 04:03 PM.
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Old 03-03-2017, 03:59 PM   #5
69gmcc10
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Re: '72 Leafs to trailing arm conversions

the c20 has the same dimensions, but uses a thicker steel for strength. There is also a reinforcement insert in the frame over the area of the axle and a reinforcement plate on the top of the trailing arms I have seen on some c20s. The upper shock crossmember I use in my conversion came from a c20, so from what I have done I personally don't see any conversion issues between the 2. Hopefully someone else can chime in with some info if they have info to the contrary.
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Old 03-03-2017, 04:13 PM   #6
chevy72blu
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Re: '72 Leafs to trailing arm conversions

Thanks for all the replies.

I especially enjoyed this quote in your build

Quote:
If you ever ask someone on this forum, “How difficult it is to convert from leafs to trailing arms?” and they reply “If you get the parts form a junk yard or from forum member it bolts right in.” don’t believe them!!!!!! - 69gmcc10
LOL

When you say "There were no existing holes for my cross member to bolt into", can you elaborate? My cross member has holes already predrilled for the trailing arm brackets to bolt to. I didnt think I needed to mess with the crossmember at all?
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Old 03-03-2017, 04:40 PM   #7
69gmcc10
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Re: '72 Leafs to trailing arm conversions

The holes in the crossmember that the trailing arm mounts mount to are already there and you can just bolt them up or drill 2 holes in the crossmsmber to flip the mount for a better traction.

Where the lack of holes to bolt the crossmember to was referring to the upper shock crossmember that is needed to mount the upper shocks, locate the upper spring retaining bolt, and strengthen that area of the rail. It is easy to locate the holes if you flip the crossmember upside down and backwards then center it on the oval reference hole on the side of the frame rail that locates the crossmsember and use the crossmember an a template for the hole locations on the top and bottom of the frame rails.
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