Need Help Getting Her On The Ground (Suspension Noob)

[lolife99]

Originally Posted by 2500HD

If you use a 6 inch sping the track arm will hit the frame before the axle move into the notch area.

I have never heard this.
I've installed 4 sets of 6 inch rear springs with no issue.
My 69 has 6" rear springs with a 1.5" block.
All static.
Care to explain this,... in relationship to a static drop?

[lolife99]

Originally Posted by cericd

Hey Keith, thanks for the Q&A breakdown. Have you seen the same thing as 2500HD in regards to trying to use 6" drop springs with a c-notch?

Nope.
I install 6" springs with no c-notch.
Any lower,... I install a notch.
Nate's truck has no notch.

[cericd]

Yeah I saw that Nate's truck doesn't have a notch. Neither does Original-71 (Hector) here in Houston and he's got a 4"/6" drop. I just see a lot of guys saying they wish they had put one in. I guess I'm just trying to do it right the first time.

[2500HD]

My 70 has 6 inch spings and no notch and i do not have any issues other than bottoming out every now and then.

below are the pictures when i was bagging my 67. The pictures below have no sping installed, I just wanted to see the how everything was going to work if the axle actually moved into the notch area. As you can see, the track arm is hitting the notch/frame before the axle touched the bump stop. The only remedy i found was to use 2 inch blocks to create space between the track arm and the axle. I do not have picturess with the 2 inch block installed but it was (from the bottom up) trailing arm, track arm bracket, 2 inch block then axle.

I did see this problem with another forum member and his solution was to notch for the track arm as well. I do not recall who it was.

[CC69Rat]

Chris -- First let me say, man I'm sorry it has been a while. I have not really posted that much in the last couple of weeks. Just stuff with the wife, house projects, etc. Just a lot going on.

I'd like to add another thing for you to consider that I don't recall being mentioned (maybe I missed it) When you drop the truck, you will want to think about your shocks. It all depends on how you drop it.

Front - If I use a 1" drop spring for example. The truck sits 1" lower (in theory) because the distance between the a-arms is 1" less. (the spring is shorter) therefore it's like an elephant sitting on the hood. The suspension is compressed from the shock's perspective. If I use dropped spindles and say the factory springs.. the height of the truck changes because the center line of the wheel hub mounting point moves up. It has nothing to do with the height of the spring. So, the shock doesn't change nor does the alignment etc.

So here's where the combination of a dropped spindle and a dropped spring can help with front end geometry and ride as well as alignment issues and premature tire wear.

In this example, a 3" dropped spring compared to a 1" dropped spring and 2" dropped spindle. You'd think, what's the difference right? Yes, the spring/spindle option is going to be more expensive but the end result will be much nicer in many different ways. a 3" dropped spring with factory spindles will make the truck more difficult to align later on. (not impossible, just more difficult) The ECE kit will use a 2" dropped spring and 2.5" spindle. = 4.5" up front. In reality your truck will only think it has been dropped 2". Get 2" drop shocks .. I think they come with the kit (?) and you're all set. Just make sure you get 63-70 kit. The 71-72 balljoints are different.

This brings up a new point. While you have all this apart, I'd throw in some new Moog (brand) balljoints. The originals will be a royal pain to get out, but new ones will tighten up your steering control, that sloppy feeling in the steering wheel and just overall make you have more of a driver's feel. IF you're dropping this kind of coin on your suspension take the time to replace them. It's really difficult to install spindles and NOT damage them too. You'll want to factor in about another $100 for new upper and lower balljoints. Stick with Moog too..

When you install this kit, plan on your front tires being toed in once you let it off the jack for the first time. (the front edge of both tires will be turned pointing in. L side turning right. R side turning left.) This is easily adjustable. When you get to this point let me know or call me and I'll explain.

I agree with the guys about a CNotch. I would use Nate's stuff throughout. In fact, I have an extra upper shock bar. Pay the shipping and it's yours. (in my build, the bar that goes across the top) IF you use Nate's upper / lower shock bars and track bar / brackets you won't need to worry about the track bar hitting the frame as pictured. I just got mine the other day, I'll post a picture of them, or lolife99 might have a picture somewhere.

Rear springs / blocks. Different people do it different ways. 6" spring, 5" spring + 1" block, 4" spring and 2" block etc. Having the shorter spring just takes away from travel overall. The 4" dropped spring is longer than the 6" obviously so it saves that amount the truck could actually move if it had to rather than the spring bottoming out. Makes sense, I wish I would have done that but I wanted a 7" rear drop. (45 series tires) I kinda wish mine was 5" spring, 2" block.

The trailing arm flip mod is kinda cool. It's just a LOT of work. While you have the trailing arms out of it putting in new bushings .. .. there will be 6 rivets in those brackets. A good grinder, or an air hammer and chisel is even better. (Plasma?) and knock them out. Turn the brackets over and just mount the arms back in the holes with some good grade 8 bolts.

Gringo said this takes away about .75" of your rear drop. BUT it also corrects about 3* of your rear pinion angle issues. So your truck will only think it has been dropped about 3" in the rear. Not really enough to even cause pinion angle issues. .. you'll be good. Good trade off IMO. just get 1" more drop blocks

Up front you also mentioned the LCAs being close to the ground. If you're running 15" wheels you want to pay close attention to the overall height of your tires.

Ex: 235/60/15 235 = width of the tires in mm. There are 25.4mm in one inch.

So, 235/25.4 = 9.25 in wide.

The next number is the aspect ratio. Take your width and multiply by this number. In this case, .. 9.25196*.60 = 5.55 in. this is the height of the sidewall of the tire. from the bottom of the wheel to the ground.

You have a bottom and a top sidewall + the rim size. = 5.55*2+15 = 26.10 in. This is the overall height of your tire.

The reason I went into detail is because if you get the front tires too small to accomodate the drop, and to be able to turn then the height of your tires will ultimately determine how low your LCA will be to the ground. You have to think from the center line of the wheel to the bottom of your tire. Tire diameter overall / 2 =13.05 with a 26.10 in tall tire. Make sense?

Now, take the 255/40/20 most people run. = roughly 28.04 in tall. So it will lift the front of the truck a little bit as compared to the 235/60/15 at 26.10 in tall. .. just gives you a little more clearance. Or 255/45/20 right Keith? (kidding ..) just another reason I did 45 series.

$3,000 you'd be good. You could do the same kit I put on my GMC for that.

Stock trailing arms - blasted and painted with Chassis black - $60
New bushings - $25
Hotchkis front and rear springs, McGaughys front spindles, drop, big brakes (bought it all from Summit all at the same time) $1869 - This takes care of the 5 lug up front and 4 wheel discs so yours might not be this much. BUT, I recommend this kit if you're interested
Balljoints $100 upper and lower Moog
Moser axles - $350, new bearings and seals
CPP booster - $200 (bought it new off the parts board)
Hotchkis anti-squat - $75 (bought off the parts board, new)
Donation to Nate - ~$600 (some stuff I bought off the board) includes new shocks, shock bars, brackets, CNotch.
Wilwood prop valve $75
Wilwood MC $300

Im around $3500. .. So, $2-3k is do-able. Dig into it man!

(sorry for the novel, just trying to help)

[CC69Rat]

Here's that picture of the PB upper / lower shock bars, track bar, etc.

[Calvin D.]

CC69Rat

I read your post twice and it confirmed what I learned and was thinking, mainly with the front end but what if you your truck have leaf springs, you are limited to a few options to drop your truck with out changing to trailing arm set up, flip kit, shackles, hangers, or maybe lowering leaf springs and if your gonna spend the money for lowering leaf then considering a trailing arm swap aint to far from that ref the cost. I have a budget for the rear drop is no more than 1500 and I would like to get the most bang for my buck. I want to do a 4.5/6 or maybe a 7'' rear drop on my truck is a 69 GMC SWB stepside.

[69gmcc10]

Calvin,

You seem to be on the same page I was when I started my GMC build, leafs what to do? I got rid of leafs and never looked back. I am not trying to sway you any direction, just let you know where I was, where I am and how I got here.

When i first got my truck the only direction I knew I wanted to go on my truck was down and I didnt even know how far I wanted to go with that. There were options with leafs (shackles, hangers, flip kits and a combination of all or some of them), they can and will get you lower, but the more I read and learned about these trucks the more I realized how unique the truck arm suspension is and how well it worked.

From an all around driving stand point the trailing arms transfer traction to the ground better (no axle wrap), have less lateral deflection (panhard Bar), have a more smooth predictable ride than leafs and are more easily adjusted. From a lowering stand point trailing arms seem easier, more adjustable and more entertaining. If you want to go 2" or less throw some blocks and u-bolts at it for $100 and a few hours, if you want to go lower throw some springs at it , if you want to lay frame add some bags and a notch, it all works with a truck arm suspension. You cant "bolt on" a set of bags to a leaf spring set up and expect it to sit lower, not without extensive fabrication.

For me swapping to the trailing arm set up made allot of sense, it handles better and it will accommodate my changing taste in the future (lower). Currently I only have 2" blocks under the truck and when I want to go lower all I need to do is swap in a set of lowering springs or bags with just 4 bolts. I think of the trailing arms like a leatherman tool, it has a blade on it just like any other knife, but if you need or want something other than a knife, it can do that too.

Good luck with your decision! Either suspension will get you where you want to go, you just need to decide how you want to travel.

[CC69Rat]

Calvin if I were you I would look for a 71-72 parts truck. Get the trailing arm setup, rear end housing, brake booster whatever you wanted from the disc front setup etc. SWB roller and just get what you needed off of it. (?). Just an idea. Sell the rest for scrap or part it out. Might even make a little money.
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[69gmcc10]

I got lucky and found a 72 parts truck without an engine or trans that had my disc breaks on it, no trailing arms on the truck (that would have been convenient!), and I also found the trailing arms, mounts springs and shock cross member even if I crush the shell of the parts truck I will be money ahead. There are good deals to be had in old trucks behind someones house or here on the forum, sometimes you just gotta ask.

[Calvin D.]

I do have a 72 lonely truck that I can use for parts not sure if the trailing arms will fit a short bed truckI planned on using all the parts that I can off to 72 parts truck it's just that the trailing arms on a truck maybe too long.
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[69gmcc10]

All trailing arms are the same length. The difference is where the cross member is mounted in the truck, LWB-behind the cab, SWB-under the cab. you have everything you need to convert right now. here is a picture for reference of cross member locations, lwb on the top swb on the bottom.

[Calvin D.]

well I went out and checked the 72 long bed truck that I have for parts and just my luck it has leaf springs on it also I really can't complain though because it has a lot of other good parts on it the previous owner add a cowl induction hood on it And a 402 big bloc, tilt steering so now I'm back to deciding my direction on dropping the rear,
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[Calvin D.]

Oh and it also has a 10 bolt Dana 60 rear end which I may sell
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[Coursey]

Originally Posted by 2500HD

My 70 has 6 inch spings and no notch and i do not have any issues other than bottoming out every now and then.

below are the pictures when i was bagging my 67. The pictures below have no sping installed, I just wanted to see the how everything was going to work if the axle actually moved into the notch area. As you can see, the track arm is hitting the notch/frame before the axle touched the bump stop. The only remedy i found was to use 2 inch blocks to create space between the track arm and the axle. I do not have picturess with the 2 inch block installed but it was (from the bottom up) trailing arm, track arm bracket, 2 inch block then axle.

I did see this problem with another forum member and his solution was to notch for the track arm as well. I do not recall who it was.

Will the CPP track bar have this issue? I think it mounts lower down on the trailing arm.