Rear end geometry 67-72 questions

[VA72C10]

This is on my 70 C10 longbed with RE-7 bags. Entire frame is on jack stands right now. Hope to have the rear on the ground on tires tomorrow night. Waiting on front end suspension parts (2 1/2" drop spindles, RE-7's, and upper and lower plates on stock control arms.

Worked on centering my rear end today in the truck. Fought with it for a while before realizing the rear is off-center by 1". The 72 5 lug is the same as the 69 6 lug...offset by 1" This ends up making the yoke off center as well as making the U-bolt under the notch on one side and against it on the other. I guess this is unavoidable...but wanted to make sure by some wild stretch that I didn't have two rears that are wrong for the truck

I have centered the brakes now so the wheels will each be the same distance from the frame by adjusting my ECE super trac bar. So I guess the 2 piece driveshaft will make up the difference?

Also, I thought about flipping the trailing arm mounts, but that looks to pull them further forward into the notch even though it corrects the angle...
Is my best bet just spacing the mounts? I really don't want to move the crossmember and have to deal with moving the carrier bearing mount as I already set that upside down to get the correct angle. Will this be a good fix to the wheel too far forward in the rear wheelwell issue? My plan is to mock up the bed, get an exact measurement to what I need to center it and then shim out the mounts. Any other ideas?

Right now the driver's side U-bolt binds against the notch and won't allow me to drop it to the bumpstops (in the notch). I can shift the rear to clear the U-bolt and get it down to the bumpstop but then the wheels won't be equidistant from the frame. What am I missing?

[VA72C10]

Pictures are in my build thread...I will be posting more shortly...

[VA72C10]

Here's a picture of the rear in the notch



and the interference of the U-bolt with the front edge of the notch

[VA72C10]

It is resting on the notch...I can adjust the rear out of center and get it to tuck up and hit the bumpstops...but that obviously won't work. You can see in the first picture how the rear sits to the very front of the notch. I'm thinking an inch or more to space out the trailing arms to make the rear centered but like I mentioned, want to mock up the bed first to be sure.

[Twisted78SS]

I thought I have read that extreme drops might require or at least it's advisable to move the cross member back 1 inch. Have you heard of that as well?

[VA72C10]

That's what I'm figuring I'll have to do, but wonder how that affects the carrier bearing...so I wonder if just adding spacers behind or making new mounts for the trailing arms is a better solution...

[SCOTI]

What was your procedure for determining where your notches needed to be?

[VA72C10]

Originally Posted by SCOTI

What was your procedure for determining where your notches needed to be?

When mocking up, We re-set the rear on the arms, without the springs and moved it all the way up till it hit the frame, then allowed a little for the blocks (but didn't have them at the time) It ended up lining up the hole in the notches with the factory spring bolt hole so we felt that would work well. Obviously it would have been better to wait for the blocks, but in reality, once I shim out the trailing arms and center the rear back in the rear wheel wells, it should be dead center in the notches....If I had put the notches where they would need to be for the rear to be centered now, it would be too far forward once I space out the trailing arm mounts and get the tires where I want them at ride height.

[Twisted78SS]

Good question,

Not to hijack, but...
I have read this thread a few times, http://67-72chevytrucks.com/vboard/s...d.php?t=195566 and have been planning on using it as a guide. Any advice if it is still a valid way to go?

Also,

If I do place the cross member back an inch, and run the 5 inch lowering spring for a static drop, do you think my wheels will be centered?

[SCOTI]

Originally Posted by Twisted78SS

Good question,

Not to hijack, but...
I have read this thread a few times, http://67-72chevytrucks.com/vboard/s...d.php?t=195566 and have been planning on using it as a guide. Any advice if it is still a valid way to go?

Also,

If I do place the cross member back an inch, and run the 5 inch lowering spring for a static drop, do you think my wheels will be centered?

I don't know that I would go thru the trouble w/only a 5" drop (you didn't mention blocks). You can also shift the bed forward.

[Twisted78SS]

Your right, I forgot to mention I am planning 2 inch blocks as well..

[SCOTI]

Originally Posted by Twisted78SS

Your right, I forgot to mention I am planning 2 inch blocks as well..

Judge for yourself. Bags + 1.5" blocks (~8" drop) . . ....
http://www.67-72chevytrucks.com/vboa...26&postcount=4

[VA72C10]

Originally Posted by Twisted78SS

Good question,

Not to hijack, but...
I have read this thread a few times, http://67-72chevytrucks.com/vboard/s...d.php?t=195566 and have been planning on using it as a guide. Any advice if it is still a valid way to go?

Also,

If I do place the cross member back an inch, and run the 5 inch lowering spring for a static drop, do you think my wheels will be centered?

That is exactly how we did my notch...except no bolts...welded the thing entirely including filling the bolt holes...Once I move it back the inch or so to original spec it will be perfectly centered at ride height. If you don't plan on moving the crossmember or mounts, then you would need to move the notch itself back an inch or so...just mock up the trailing arms, blocks, and springs and then you could get that centerline.

But the more I think on this, I'm glad we centered the notch in the factory location which keeps it centered in the wheel well....Now, once I fix the trailing arm mounts, I will end up with a rear, c-notch, and wheels all centered perfectly in the rear wheel tubs without having to move the bed.

[VA72C10]

Here is what I am trying to avoid...this is a BEAUTIFUL truck but personally I don't like how far forward the rear tire is....



This truck was bagged with blocks from what I remember and spindles and bags in the front.

[Twisted78SS]

Sounds like a plan.. I'll keep watching as you are farther along than mine.. It sounds just about the same as what I did on my Blazer project, but it was a conversion from 4x4 to 2wd with trailing arms.

Best of luck with the build..

[PBFAB.COM]

Originally Posted by VA72C10

Here is what I am trying to avoid...this is a BEAUTIFUL truck but personally I don't like how far forward the rear tire is....



This truck was bagged with blocks from what I remember and spindles and bags in the front.

I wonder if that truck was a LWB to SWB conversion (and they didn't measure quite right?), as it looks to be even further forward than it should be with the factory arms/bags/blocks.

[SCOTI]

Originally Posted by VA72C10

That is exactly how we did my notch...except no bolts...welded the thing entirely including filling the bolt holes...Once I move it back the inch or so to original spec it will be perfectly centered at ride height. If you don't plan on moving the crossmember or mounts, then you would need to move the notch itself back an inch or so...just mock up the trailing arms, blocks, and springs and then you could get that centerline.

But the more I think on this, I'm glad we centered the notch in the factory location which keeps it centered in the wheel well....Now, once I fix the trailing arm mounts, I will end up with a rear, c-notch, and wheels all centered perfectly in the rear wheel tubs without having to move the bed.

Keep in mind, when you move the arm, you change the location of the spring & shock mounting C/L.

And, on my 68.... the notches were installed centered w/the axle bottomed against the frame. I used that frame when I started playing around w/stretching the wheel-base @ the extreme drop & it wasn't quite 1" to center the housing in the notch (@ 1", the housing was close to interfering w/the opposite side of the c-notch). Measure closely.

[VA72C10]

Originally Posted by SCOTI

Keep in mind, when you move the arm, you change the location of the spring & shock mounting C/L.

And, on my 68.... the notches were installed centered w/the axle bottomed against the frame. I used that frame when I started playing around w/stretching the wheel-base @ the extreme drop & it wasn't quite 1" to center the housing in the notch (@ 1", the housing was close to interfering w/the opposite side of the c-notch). Measure closely.

I figure i'll use some scrap wood as you mentioned or scrap 1/4" plate I have and stack it...that will let me fine tune things.

[VA72C10]

Does anyone have an answer about the rear and how it's off center by an inch? Is there a reason for that? I've never read it on here and I've searched and not come up with anything...

[Twisted78SS]

I have never noticed that, I am surprised nobody has chimed in yet.

[VA72C10]

Originally Posted by VA72C10

Does anyone have an answer about the rear and how it's off center by an inch? Is there a reason for that? I've never read it on here and I've searched and not come up with anything...

???

[VA72C10]

ttt

[SCOTI]

Originally Posted by VA72C10

Does anyone have an answer about the rear and how it's off center by an inch? Is there a reason for that? I've never read it on here and I've searched and not come up with anything... ???

Off center 1" L to R or F to R?

[VA72C10]

Originally Posted by SCOTI

Off center 1" L to R or F to R?

Left to right...the pumpkin/yoke are 1" to I believe it's the passenger side. So that puts the U-bolts in different locations in relation to the frame...one is under the C-notch and one is just outside the notch.

[SCOTI]

Originally Posted by VA72C10

Left to right...the pumpkin/yoke are 1" to I believe it's the passenger side. So that puts the U-bolts in different locations in relation to the frame...one is under the C-notch and one is just outside the notch.

It's not uncommon for there to be some tension on the rear suspension system when it's set up to be centered. That 'tension' will want to pull one way or the other... whichever offers the least resistance.

Measure it out so you know the center. Use a tie-down strap to hold it in place while adjusting the PHB to length. It should be fairly close & will be just a matter of adjusting the PHB to 'true' center (full weight on the suspension w/vehicle @ ride height).

This is where the 'adjustable' feature of the Super Track Bars kits SUCK. As soon as you pull the bar to re-adjst the C/L, the whole freakin thing wants to shift one way or the other & you have to struggle w/re-aligning everything again. Unless..... you use a true double adjustable PHB. Then you can establish the baseline centerline & tweak L or R w/o removing the bar.