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Effects of wrong pinion angle?

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Old 10-22-2006, 10:55 AM   #1
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Default Effects of wrong pinion angle?

So i took my car to the track and I'm experiencing serious problems. I have all the mods listed below and i ran slower than same model cars with 3 boltons.

I talked to a guy at the track with the same car as me. He had no bolt ons only suspension mods, 3.73, and slicks on 17icnh rims and he was running 12.7s. He asked me if my car was lowered and I said yes. He said that was my problem. He lost et when he lowered his until he got the adj. ta and set the pinion angle.

I have an adjustable torque arm but i never set the pinion angle. I have removed the driveshaft twice. Once to install the tq arm and once to remove the tranny.

My question is can my angle be so off that i lose massive et. I was running street tires at the track and i had massive wheel spin off the line. The car doesnt seem to grip well. Also when driving on highways the rear feels real loose on large turns. Can my pinion angle be so off that I get no traction off the line and lose about a second on my et? Also what are the effects of havin a large positive angle vs. a large negative angle?
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Old 10-22-2006, 12:03 PM   #2
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Pinion angle will always be a hotly debated topic. But I don't think that is your problem. You need LCA relocation brackets. When I lowered my car I had the same problem, added relocation brackets and had my traction back. I used BMR bolt-on brackets and installed them on the lower hole. Running a real street radial at the track is useless, you need to switch to DR's at the track. What was your 60-ft?
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Old 10-22-2006, 12:37 PM   #3
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i already have LCAs w/ relocation brackets. they are on the lowest setting for maximum grip. i was cutting 2.1 60 ft times whihc is horrible. i really think my pinion angle is way off so that all the energy is pushing forcing the differential up instead of down to put the power towards the ground.
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Old 10-22-2006, 12:47 PM   #4
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Have you tried a stickier tire?
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Old 10-22-2006, 01:02 PM   #5
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Default Sorry, but...

Quote:
Originally Posted by C_Rules
i already have LCAs w/ relocation brackets. they are on the lowest setting for maximum grip. i was cutting 2.1 60 ft times whihc is horrible. i really think my pinion angle is way off so that all the energy is pushing forcing the differential up instead of down to put the power towards the ground.
That's just not the case. Excessive angle will do 3 things:
1. Cause driveline vibration.
2. Break u-joints if angle is really excessive.
3. Could cause a slight lose in RW power, as the power required to work the joint[s] is higher than it would be w/ a correct angle.
The angle does not change the direction the "force" is going.
Pinion angle is not considered a tuning tool.

Suggest you set the angle to approx 3* down, and try some runs. Use a real tire when you do this, as a street tire is not consistent enough to make good comparisons with.

Now that the car is lowered, I'd suggest checking torque arm clearance w/ the tunnel, and making sure the rearend is centered.
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Old 10-22-2006, 01:17 PM   #6
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okay i'll check those things out. all i know is something is seriously wrong. i'm supposed to be running in or very near to the 12s with all these mods and im doing 13.77 @ best. something is definitely wrong. i was running that before i installed the tranny and converter.
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Old 10-22-2006, 03:58 PM   #7
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how much et can a stickier tire make up for? i know im about a full second off.
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Old 10-22-2006, 05:40 PM   #8
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Quote:
Originally Posted by C_Rules
how much et can a stickier tire make up for? i know im about a full second off.

A sticky tire can make a world of difference. Gator's 99ta on here is SLAMMED and he pulls 1.5s if not 1.4 60's by now. He also swears by the MT Drag radials.
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Old 10-22-2006, 08:21 PM   #9
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Quote:
Originally Posted by KCFormula
A sticky tire can make a world of difference. Gator's 99ta on here is SLAMMED and he pulls 1.5s if not 1.4 60's by now. He also swears by the MT Drag radials.

i wonder how quick gator's car was before he put on the radials. because im out some drastic et.
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Old 10-23-2006, 08:46 PM   #10
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your pinion angle should be roughly the same angle as your tranny output shaft to keep the angles that your u joints deflect equal and opposite. For instance, if your tranny/crank shaft points up (moving towards the front of the car), then your pinion angle should also be pointing up at around the same angle.
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Old 10-24-2006, 06:15 AM   #11
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now after i set the angle to the correct degree will there be a noticeable difference? I have all the suspension mods yet I get no traction. I know thats due to not running a radial, but when i adjust the angle will the grip be better or will I spin the tires even worse?
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Old 10-24-2006, 08:40 AM   #12
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I don't think your traction problem is pinion angle related. The main effects of a mal-adjusted pinion angle would be drivetrain vibration issues.
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Old 10-24-2006, 09:08 AM   #13
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Default Making comparos..

like this is of very doubious value. [Kinda like using RWHP to select parts, make comparisons w/ other cars.]
"I talked to a guy at the track with the same car as me. He had no bolt ons only suspension mods, 3.73, and slicks on 17icnh rims and he was running 12.7s."
1. His car is not the same as yours.
2.You have changed converter, and have a gear set that's not conducive to producing good et's.
3. Your tires are no way close to the other cars setup.
My suggestions:
Concentrate on what you need to do w/ your car.
A. Set the pinion angle to approx 3*.
B. Get a set of tires.
C. Do some testing.
D. Look at a datalog, and see where the new converter is taking you. Also, look at the tune you have.
E. Video the car, leaving. Pay attention to tires and how the chassis is reacting.

Back under my rock.....
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Old 10-24-2006, 09:26 AM   #14
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People seem to not distinguish between pinion angle, driveline
angle and torque arm angle. All three come together at the
pinion but that's all. They have different meanings and effects.

Driveline angle is about the vibration aspects, minimizing it and
in fact nulling it at max load is the way for your U-joints and
trans / diff seals & bearings / bushings to survive, and have a
minimum vibration. Driveline angle is the sum of trans-shaft
and shaft-pinion angles (one negative and one positive, you
want zero but under load / deflection so wisdom is -1 for hard
rubbers and -2 for stuck rubbers as measured unloaded).

Torque arm angle, relative to body, intersecting with the LCA
angle is what points to the instant center of the car. Instant
center defines the suspension reaction and weight transfer.
Changing it for higher and further back, transfers more weight
to the rear wheels under acceleration. But lowering changes
the LCA angle to push it down and forward. Relocating the
lower LCA mount point, lower by the same as you dropped
the car, would put you back to about stock in this regard. But
you also lowered the absolute center of mass and this you don't
get back. Changing the torque arm angle also manipulates the
fore/aft instant center position. Dropping the nose point brings
the instant center back toward the rear. But you don't want to
jack the driveline angle doing this so you need the adjustable's
degree of freedom perhaps. The nose point is fixed with the stock
mount, can be adjusted or is adjusted for you in the relocating
trans crossmembers from BMR, UMI, Yank. In my opinion these
are the "right" way to set bite with a long arm, you also have
the short-arm TAs that mount to the floor pan separately. The
shorter the arm, the more extreme the torque reaction (good for
launch, but watch the brake hop).

Tires are the #1 traction deal. Until you have good ones you
don't know what suspension work you need (though some things
are pretty universal, like relocation brackets for lowered cars).
There's no use trying to tune suspension around a greasy donut.

Now, great tires on a suspension that wheel-hops is a good way
to break driveline pieces. So once you find that, don't stay in it.
But if your suspension is quiet and the tires just smear, tires are
the (first) problem.
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Old 10-24-2006, 09:28 AM   #15
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I don't thnk one should state a certain pinion angle, as that will be relative to the surface in which the car is parked. I know when my car is in the garage, my crank/tranny angle is approximately 4.5* (pointing up as looking to the front of the car). I have my pinion angle set at approximately the same angle (also pointing up) as required for no vibration issues for an overall driveline angle of around 0*. I set my pinion angles relative to my tranny/crank.....
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Old 11-12-2006, 02:24 PM   #16
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so i had my pinion angle set to about -1. its a little hard to get a perfect angle with a non digital angle finder since one degree is so small. well after adjusting it i can say there is a noticeable difference. the back of the car feels more planted to the floor under acceleration. before the adjustment the car was at around +1. just figured id give u guys an update.
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Old 11-12-2006, 03:59 PM   #17
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Maybe my .02 isn't worth much here but it looks like some mods that might help on those ET's is some 3.73's and turn those KYB's down to the softest setting. The lowering springs are stiff and could be holding you back as far as weight transfer to the rear wheels. If you can knock a .5 second off your 60', you might lose a full second at the end. Other power robbers could be your exhaust. A chambered muffler and shorty headers can pose restrictions.
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Old 11-12-2006, 08:41 PM   #18
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Quote:
Originally Posted by JR HAWK 9
I don't thnk one should state a certain pinion angle, as that will be relative to the surface in which the car is parked. I know when my car is in the garage, my crank/tranny angle is approximately 4.5* (pointing up as looking to the front of the car). I have my pinion angle set at approximately the same angle (also pointing up) as required for no vibration issues for an overall driveline angle of around 0*. I set my pinion angles relative to my tranny/crank.....
So are you saying you have your rear yoke 4.5* postive? I'm having a blonde momment never heard of setting it like this.

Last edited by SILVERZZ28; 11-13-2006 at 01:35 PM.
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Old 11-13-2006, 06:23 AM   #19
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Exclamation Pinion angle is...

Quote:
Originally Posted by JR HAWK 9
I don't thnk one should state a certain pinion angle, as that will be relative to the surface in which the car is parked. I know when my car is in the garage, my crank/tranny angle is approximately 4.5* (pointing up as looking to the front of the car). I have my pinion angle set at approximately the same angle (also pointing up) as required for no vibration issues for an overall driveline angle of around 0*. I set my pinion angles relative to my tranny/crank.....
Not measured as a reference to the floor. It is measured as the difference in the driveshaft C/L, and the C/L of the pinion gear.
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Old 11-14-2006, 10:36 PM   #20
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TTT Hawk
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