Need help adjusting my pinion angle

[Gabe]

Hope you guys can make some sense out of this for me

BMR adjustable UCA, I'm finally adjusting it.

This it what the adjusting area currently looks like:

All the angle finder pics were taken from under the passenger side of the car looking toward the middle

This is the angle finder under the factory 2-piece driveshaft, it's on the rear section of the shaft, at the front of it:

Angle finder under the pinion yoke:

And under the flat section under the pumpkin:

Car's lowered about 1.25" on Steeda Sport springs.

All of the above pics were after I adjusted the arm to lengthen it quite a bit. When I started, it was almost as short as it can be.

So, should I call it a day and stop here or do I need to keep adjusting?
And if I need to keep adjusting, what should I do next?

Sorry for my newb-style post, but BMR's instructions kinda sucked ....

 

[swflastang05]

Hope you guys can make some sense out of this for me

BMR adjustable UCA, I'm finally adjusting it.

This it what the adjusting area currently looks like:

All the angle finder pics were taken from under the passenger side of the car looking toward the middle

This is the angle finder under the factory 2-piece driveshaft, it's on the rear section of the shaft, at the front of it:

Angle finder under the pinion yoke:

And under the flat section under the pumpkin:

Car's lowered about 1.25" on Steeda Sport springs.

All of the above pics were after I adjusted the arm to lengthen it quite a bit. When I started, it was almost as short as it can be.

So, should I call it a day and stop here or do I need to keep adjusting?
And if I need to keep adjusting, what should I do next?

Sorry for my newb-style post, but BMR's instructions kinda sucked ....

You need to confirm if those readings are positive or negative, it's hard to tell in the pics but to me it looks like the top pic (DS) is reading -1 and the yoke pic is reading +1.5, which would leave you with +.5 pinion angle which a no-go. You would want to tighten the UCA (make it shorter) until you're around -2 degrees total (or whatever negative number you're shooting for).

 

[Gabe]

You need to confirm if those readings are positive or negative, it's hard to tell in the pics but to me it looks like the top pic (DS) is reading -1 and the yoke pic is reading +1.5, which would leave you with +.5 pinion angle which a no-go. You would want to tighten the UCA (make it shorter) until you're around -2 degrees total (or whatever negative number you're shooting for).

The pointer in all three pictures is to the right of the zero, toward the front of the car.
So I think they're all positive ...

I'm shooting for -2 to -3 as I keep reading that's recommended as a great starting point

 

[skwerl]

The first angle pic of the driveshaft doesn't matter, you can discard that one. What matters is the difference between the transmission output shaft and the pinion input shaft. As the rear axle moves up and down on the suspension, the driveshaft angle will change but the transmission and pinion angles will remain constant in relation to each other.

As far as I can tell the rear end is angled slightly higher than the transmission so that is bad. Under hard acceleration the rear end will torque upward slightly making the rear end and transmission angles even further apart. I believe you need to aim the rear end lower.

 

[Gabe]

The first angle pic of the driveshaft doesn't matter, you can discard that one. What matters is the difference between the transmission output shaft and the pinion input shaft. As the rear axle moves up and down on the suspension, the driveshaft angle will change but the transmission and pinion angles will remain constant in relation to each other.

As far as I can tell the rear end is angled slightly higher than the transmission so that is bad. Under hard acceleration the rear end will torque upward slightly making the rear end and transmission angles even further apart. I believe you need to aim the rear end lower.

Thanks Brian. Everywhere I read it says to measure at the back of the transmission and under the pinion coupler at the front of the rear diff.
BMR's instructions don't mention the transmission at all, in there it says to check under the pinion coupler and the driveshaft angle for the rear half of the shaft (factory 2-piece).
And that's confusing, since everywhere else the driveshaft isn't really mentioned, but the trans is.
What also confused me and caused me to have huge brain farts was the way they wrote to subtract one number from the other ... why they couldn't describe it as a degree difference, I don't know.
Cuz doing proper subtraction when you have 2 negative numbers like -1 - -2 would become -1 + 2 which is 1, but some people can also understand -1 - -2 as being -3

So if I measure at the back of the trans and at the front of the rear diff (under the round coupler that the driveshaft connects to, the coupler that I've been calling the pinion coupler, hope I was calling it right).
What difference in degrees should I be aiming for?
Should they both be at the same number?

 

[skwerl]

Where I wrote 'transmission', I was referring to the transmission output shaft. The pinion input shaft should be aimed slightly lower than the transmission output shaft.

 

[oldVOR]

The difference in pinion nose down angle all depends on your suspension setup since the various bushing materials flex differently.
Rubber bushings - between 2-3° pinion nose down
Poly bushings - between 1-1.5° pinion nose down
Rod-end/Heim - between .5-.75° pinion nose down

The end game is to obtain a pinion angle that never goes nose up in relation to the transmission output shaft under the best traction conditions with WOT. The tighter the suspension the closer to a zero angle reference your initial settings.

 

[Gabe]

The difference in pinion nose down angle all depends on your suspension setup since the various bushing materials flex differently.
Rubber bushings - between 2-3° pinion nose down
Poly bushings - between 1-1.5° pinion nose down
Rod-end/Heim - between .5-.75° pinion nose down

The end game is to obtain a pinion angle that never goes nose up in relation to the transmission output shaft under the best traction conditions with WOT. The tighter the suspension the closer to a zero angle reference your initial settings.

Yup, I now realize that, and I feel like a link to this video should be included in the instructions to set the angle, haha
It's a Lightning rear-end under cruise and acceleration ... and it totally brings home the point as to why you'd want the rear-end to point down a bit while static, especially in relation to the driveshaft in front of it:

Where I wrote 'transmission', I was referring to the transmission output shaft. The pinion input shaft should be aimed slightly lower than the transmission output shaft.

I got that, but am wondering if BMR's instructions are mentioning only to measure the angle of the rear half of the driveshaft and the angle of the rear pinion yoke, because the 2-piece driveshaft effectively cancels out any angle difference coming from the trans?
Since the 2-piece D/S is solidly mounted in the middle, the angle of the front half really doesn't matter since it only affects the relation it has with the transmission.
Which means the only part I need to worry about (at least until I do another 1-piece D/S) is the angle difference between the rear driveshaft half and the rear diff.

Which means that BMR's instructions now make a bit more sense, at least as to why they never mention the trans at all:

 

[Gabe]

Went back under the car and shortened the UCA a bit.
I'm now showing 1 degree at the back of the rear driveshaft half:

And -1.5 degrees at the pinion yoke:

So does that mean that the pinion yoke is 2.5 degrees negative compared to the driveshaft, and I should stop adjusting now?


.

 

[46addict]

If you have poly LCA bushings and aftermarket springs/shocks or some combination of those, I would aim for -1.5 to -2 but that's just me.

On the stock 2 piece shaft, pinion angle is not as critical than a car with a 1 piece shaft because the stock CV joint is supposed to correct for minor deviations. But don't quote me on that.

 

[swflastang05]

That looks good to me, assuming the measurements were taken with the suspension loaded.

 

[Gabe]

Thanks guys for trying to help.
Just got off the phone with Kelly at BMR and his recommendation was to get the angle under the rear pinion yoke to read zero and ignore the rest.
This being as I'm using a factory driveshaft and the car is sitting level. I have the car sitting on wood supports in my garage, same amount of supports under each tire, so it's level and suspension is loaded.
His reasoning for the zero was that the engine/transmission sits tilted down 2-3 degrees from the factory and having the rear pinion at zero when static will allow it to tilt up to just about make a parallel line with the line coming from the engine/trans.
So the angle under the pinion is now zero and the locking nuts are right.
Can't drive the car yet since it's crappy out, but hopefully I'll get to take it out soon.

And as she's currently sitting:

 

[mpm_1]

Gabe was this a you just wanted to check kind of thing or were you reacting to something that made you suspicion pinion angle ?

 

[Gabe]

Gabe was this a you just wanted to check kind of thing or were you reacting to something that made you suspicion pinion angle ?

The car's had a high-speed driveline vibration pretty much the whole time I've had it.
It got worse with the 1-piece DSS driveshaft in there, and I finally got the adjustable UCA to see if it would cure it.
The DSS is now gone, my factory d/s developed a loud click in the rear half, and I'm now using another factory d/s that I'm borrowing from a friend, since he's not using it on his '12 Roush (he's got a DSS on there, lol)

 

[BMR Tech]

Take it for a spin when you can and let's see if bringing that pinion back to where it should be with a 2-pc DS cures the issue.

Whatever the result may be, you know we are here for ya boss.

 

[Gabe]

Take it for a spin when you can and let's see if bringing that pinion back to where it should be with a 2-pc DS cures the issue.

Whatever the result may be, you know we are here for ya boss.

Thanks Kelly, and thank you for your help earlier.
I'll update as soon as I get to drive it

 

[Poonishr]

Pinion angle follow up

Did zero work? I know this post has been buried for a while but it's relevant to my situation. My 2piece stock DS is showing -4 at rear portion. My pinion flange is showing +4. I don't want to touch it until I figure out the math. Because I'm figuring a -4-4=-8, or 4--4=8 either way is bad. A minus minus is a positive or has common core jacked us up? Which way do I adjust UCA?

 

[Gabe]

Did zero work? I know this post has been buried for a while but it's relevant to my situation. My 2piece stock DS is showing -4 at rear portion. My pinion flange is showing +4. I don't want to touch it until I figure out the math. Because I'm figuring a -4-4=-8, or 4--4=8 either way is bad. A minus minus is a positive or has common core jacked us up? Which way do I adjust UCA?

I always have to Google shit whenever driveline angle comes up.
You might be best off calling Kelly at BMR and chewing his ear off a bit. Didn't take long for him to talk some sense into me, but since I did it it's all become jibberish again.
My car still has driveline vibration at about 100, it always has and until I can start replacing more parts, I think it always will.
There's a chance it's caused by the loose tolerances in my manual transmission, and I certainly can't afford to fix that these days.

 

[Pentalab]

Will one of those small digital readout torpedo levels fit in there ? Mine is aprx 6" long and includes both bubbles and the digital readout. Cool part is when the level is inverted, like placed on the ceiling, the entire display also inverts, so u can still read it.

It also indicates in .1 degree increments..and will beep when at 0-45-90 degrees. It also has several heavy duty magnets built into the flange, so it sticks like glue. If 6" is still too long, it could be cut down in a band saw easy enough, so its only 1-3" in length. The digital display also includes a depicted angle, so u know asap, which side of zero etc, you are on. Cheap at any tool store, sears or your favorite big box store.

The story I got with my DSS DS was, the pinion angle was not as critical as most other brands of one piece DS... like shaftmasters. The DSS uses a replaceable CV joint at the back end. The DSS is also balanced to 9400 rpm. On the local dyno, there was no DS vibration with the DSS installed, and also using a BMR adjustable UCA + mating BMR UCA mount on my 2010...and that's wound up to 150 mph in 4th gear ( 1:1 tranny ratio..and a 3.31 rear gear + 27" tall rear tires).

 

[Poonishr]

I set the pinion flange to zero and the drive shaft is at -4. It's drivable but feels sluggish, but no vibration at least under 60. Haven't been on hwy yet. Little clunky sounds appeared though but I'm gonna pretend they are just nvh acquired from having all poly bushings. Thanks for responses, I did this mod during a few days off work and panicked thinking I need to get this fixed before work tomorrow.