Well i dont know if this will help as i only did a 2" rear drop with belltech shackles.

Anyway i used a angle finder and compared the differnce at the pinion center line to the drive shaft (2 deg), then at the trans output shaft centerline to driveshaft (3 deg). After the 2" drop this went from 2 to 3 deg pinon and 3 to 4 trans.

I was first going to remove the factory shims, turned out to be a pain to try and remove as they would not seperate from the leaf so i decided to just turn them 180 and recheck.

Now the differnce is 1 deg for both the pinion and the trans output to driveshaft angles. Which i belive is perfect for the angle portion. So i guess the moral of the story is that just the 2" drop put me over u joint agle spec (1 to 3 deg diff) then more than likely you are quite a bit over.

 

Hmm, I did the Belltech 2" shackles on mine and didn't need to flip or remove the shim. No problems here

Steve

 

Wouldn't axle wrap be another problem with the already positive angle?

 

what is axle wrap?

 

Oh fer crying out loud.... Go get a cheap angle finder and measure the angle of the tranny. Then measure the angle of the pinion and get back to us.

BTW: Don't get on it hard til you get this straightened out.

Rich

 

The best $5.99 you'll ever spend...

Angle Finder

 

Correct pinion angle is to keep your U-joint from binding under power or deceleration. Pinion angle can not affect "hook" whatsoever.

The housing of the differential tries to walk "up" on the ring gear causing positive pinion angle. Negative pinion angle is what's required to make your pinion angle as close to "zero" as possible when under full throttle.

In the end, pinion angle is a longevity thing, not a "hook" thing.
Many people misunderstand this, and it appears the advertiser who said that the pinion angle gives you better hook is one of them.

 

Greg, I have to disagree. Pinion angle DEFINITELY has a major affect on traction. If it is allowed to go positive on launch, the rear end twists up, and then it is whipped back down with a spring action that immediately unloads the tires. You'd be surprised at how many people have no idea that improper pinion angle is causing them major traction issues. I used to be one of them. My truck used to immediately blow the tires off on launch no matter what I did or tried. After talking to a few suspension gurus, I was told to check the pinion angle and found it to be only -1, which told me it was going positive on launch. Adding in some -3 shims put me at -4, and now the truck pulls the wheels.

As for the actual procedure, I don't know what this one guy is doing, but you definitely don't measure it at the trans (I'm also curious where these "stock shims" are you can flip around). You need to measure the different between the driveshaft and the rear u-joint. You want it to be around -3 for a street driven truck.

 

The Watson Guide to Happy Pinion Angles

 

Well Sal, I'll defer to your better judgement on Lightning specific issues. I also spoke to a major chassis builder in my area about this, and he basically told me what I had mentioned in my post, but the discussion revolved around cars, as opposed to trucks.

 

I would think in a car like a Mustang with a 4 link style suspension, that it would probably not be critical like you say. Since you have 4 control arms, there is only adjustment, not deflection, other than bushing movement. But on our trucks, there is nothing to limit the twisting of the axle. Think about the force of that huge *** leaf spring whipping that rear end back down .

 

When measuring the pinion angle do you subtract the u joint angle from the driveshaft angle? Also when you asked about the stock shims, are you referring to the ones that only came on the 03-04s?


Chris

 

What about (non-slapper) traction bars. With Metcos, my pumpkin, for all practical purposes, cannot move at all.

 

Makes sense. You're right, the Mustangs have the adjustable control arms, so that the pinion angle can easily be adjusted with them. Hearing that these trucks are so particular, it makes me think twice about doing any lowering.

If I leave it stock height, will that give it the best response/characteristics for hooking at the track?

 

It moves under load, trust me.