Add-a-Leaf Helper Springs... Questions!

[dunedog]

Frank,DL didn't really do a lift.
She installed an extra leaf in her spring kit. Kind of like overload springs for a weary rearend (like that DL )
There was no body lift or longer shackle installed.The pinion doesn't change although the tailshaft end of the driveshaft might a hair.

[dumb lady]

Thanks dunedog.
Yep, after a few years, that old rear end sure drops like a dufflebag!

Hi Stewart, & thanks for the post.
BTW, I spent more time in New England than I did in NY. But close enough.
And thanks so much for the email! I'm sorry I'm a little behind (pun intended!)
I'll respond tonight.

[LiftedAWDAstro]

The shackle lift does change the pinion angle.

[st4s]

Frank,DL didn't really do a lift.
She installed an extra leaf in her spring kit. Kind of like overload springs for a weary rearend (like that DL )
There was no body lift or longer shackle installed.The pinion doesn't change although the tailshaft end of the driveshaft might a hair.

Pictures suggest that there is a kind of lift taking place by adding a leaf thereby stiffening suspension.
The body rear seems higher than before and as tran is linked to subframe which is linked to body front I don't actually understand why there should be no change in pinion angle as opposed to installing other shackles ?!

Did I get something wrong?

-Frank-

[dunedog]

The axle sits on the spring pack the same and swings as a radius from the rear of the tranny.
A spring flattens when you put a load over it,taking and distributing the weight.
The arch of the helper spring is in keeping with the OEM springs.As has been stated ,these springs fatigue and flatten over time losing their strength. So nothing has changed from the origional vehicle set up.
When you add a longer shackle at one end of the spring pac and start messing with hanger placement.it causes the axle to pitch differently. When the driveshaft and rear are no longer inline (as straight line of sight) you get problems.
There is a window of (help) a few degrees or so that the driveshaft to rear can be out of line and not be a problem.

[dumb lady]

Thanks for explaining that Mr dunedog. I actually think I understand. (Where's that dunce smiley at?)

[mdmead]

I don't actually understand why there should be no change in pinion angle as opposed to installing other shackles ?!

Did I get something wrong?

-Frank-

No, you didn't. And yesterday I actually (briefly) posted that you were wrong, but decided I needed to do some research to make sure I had my ducks in a row. And I didn't.... (I then deleted my response.)

We always talk about pinion angle and off-road guys know that keeping the pinion and transmission output angles in a stock relation (typically parallel) is the best course of action. I guess over the years I figured pinion angle was actually a measurement in relation to the ground or compared to the transmission output. Well, after reading up on it last night, the pinion angle is the angle between the driveshaft and the pinion. So yes, installing an add-a-leaf or level block DOES change the pinion angle. (I'm assuming this was your point.)

But, it seems the pinion angle is only one concern, and from an off-road point of view is secondary to keeping the transmission output and pinion input on the same parallel plane. The bottom line is that keeping the u-joints in sync is important to reduce/eliminate vibration and you can add some to u-joint angularity without any issues rising. (The longer the rear driveshaft, the more room to play you have.)

So thanks Frank for making me look this up. I learned something new! (Or maybe re-learned something I'd forgotten.....)

[st4s]

(I'm assuming this was your point.)

Right.

Thanks for that contribution. Very helpful indeed.

So if one was to use longer shackles (not due to technical conviction but because sending leaf springs to Europe IS expensive and exceeding their value by far) where do the shims which will help maintain the pinion and transmission output in parallel go then? Between the axle and the leaf spring?

[Rockwerx]

Yes, the shims go between the springs and the axle. You could also use a lift block which are usually tapered (to correct pinion angle) to give you some more lift.

[LiftedAWDAstro]

We always talk about pinion angle and off-road guys know that keeping the pinion and transmission output angles in a stock relation (typically parallel) is the best course of action. I guess over the years I figured pinion angle was actually a measurement in relation to the ground or compared to the transmission output. Well, after reading up on it last night, the pinion angle is the angle between the driveshaft and the pinion. So yes, installing an add-a-leaf or level block DOES change the pinion angle. (I'm assuming this was your point.)

Actually Matt, When talking pinion angle, we are not concerned much with the angle between the pinion and the drive shaft. We are mostly concerned with keeping the transmission or transfer case output angle and pinion angle the same +/- 0.5 degrees. Yes, you can have too much of an angle between the pinion and drive shaft but you need to be around 20 degrees to have any issues. but you MUST have the slip yoke and the pinion yoke within 0.5 degree to eliminate vibrations.

[mdmead]

Actually Matt, When talking pinion angle, we are not concerned much with the angle between the pinion and the drive shaft. We are mostly concerned with keeping the transmission or transfer case output angle and pinion angle the same +/- 0.5 degrees. Yes, you can have too much of an angle between the pinion and drive shaft but you need to be around 20 degrees to have any issues. but you MUST have the slip yoke and the pinion yoke within 0.5 degree to eliminate vibrations.

I thought that is what I was saying Dean! Sort of...

Remember, the comment was that the pinion angle would change regardless of the type of rear lift (shackle or leaf/block.)

You are where I was last night. The key is "pinion angle" is a specific measurement between the pinion and driveshaft, nothing more. Here's a pic showing a 7 degree pinion angle:

http://www.2quicknovas.com/pinionangle.jpg

The term has nothing to do with what we are concerned with, that is the parallel relationship between the transmission output and pinion input. So what we are really trying to say is the angle of the pinion input (not "pinion angle") needs to remain in the stock relationship (basically parallel when under load) to the transmission output.

As you say... and I thought I did too... is that the pinion angle itself is secondary and can change without major concern of vibration.

[dumb lady]

OMG, I'm sooooo confused now! Just please, someone tell me that my drive-shaft won't fall out!!!

[st4s]

Yes, the shims go between the springs and the axle. You could also use a lift block which are usually tapered (to correct pinion angle) to give you some more lift.

Would lift blocks be allowed/available for composite springs?

[Rockwerx]

Yes, the shims go between the springs and the axle. You could also use a lift block which are usually tapered (to correct pinion angle) to give you some more lift.

Would lift blocks be allowed/available for composite springs?

I don't believe that you should use a lift block with the composite leaf springs. You can order some steel replacement springs from NAPA and have them recurved and add an extra leaf or two. The recurved replacement springs that some companies sell will loose their arch in a short period of time...especially if you are hard on them...ie trailer towing, extra cargo weight, off-road 4 wheeling, hotrodding, ect. The best way to lift these vans is to get custom springs made up. This way you get the extra lift you want, weight capability, and have your axle centered perfect in the wheel well.

OMG, I'm sooooo confused now! Just please, someone tell me that my drive-shaft won't fall out!!!

Don't worry Christine, your driveshaft won't fall out.

[dumb lady]

Thanks, Stewart! That does indeed make me feel a whole lot better.