Kaldar142

i have a question about the adjustable LCAs, and the pinion angle...

i still dont have mine properly adjusted, but my LCA's are all the way tightened and i know this is not right but i dont know where im sopposed to put it at, im tired of waiting on shops and half the time cant even do it (or say they dont know what im talking about, they say i need to go to a performance shop)

so what tools do i need to do the alignment?

CrazyAl

You need a way to lift up the car so you can work on it: jack and jackstands, or ramps, ora lift.

You need some wrenches to do the adjusting, some loctite to make sure the adjustments stay where you put them, and finally you need an angle measuring tool.

Here is a picture of what one looks like:
http://www.bmrfabrication.com/Universal.htm(Second product on the page).

You can get this from many different race car shops or a good hardware store. Sears sells them for $10, so that's a good choice.

Kaldar142

ok cool, do you have a write up or could you best describe to me how you would go about measuring the angle, like where is it sopposed to be?

Timmay!!!

Your pinion angle should be 2-3 degrees. You measure it at the pinion yoke andaft driveshaft flange. The difference of the two angles should be 2-3 degrees. I wish I knew how to post a drawing for you to see how to take the measurement. Did your LCAs not come with instructions?

CrazyAl

OK, here is the pinion angle setting procedure for an OEM 2-pc driveshaft. (This is NOT correct for a solid 1-pc aftermarket driveshaft)

First, lift up the car so that you can work under it. Be sure you use safe lifting procedures. Youmust have the rear suspension loaded--in other words, you need to have the tires on ramps or the rear axle tube on stands so the weight of the car is compressing the rear suspension.

It is best if the car is as level as you can get it, so if possible lift up the front to the same height as the rear. You're not going to be working on the front end, so it doesn't matter if the front suspension is loaded or not.

You are now ready to take measurements. I attached a rough sketch that shows where you are doing the measuring.

Now, use the angle gage to measure the angle of the driveshaft right next to the rear end. It doesn't really matter what this number is, just measure it and write it down. Take the measurement at the place labeled "1" on the sketch.

Move the angle gage over and measure the angle of the pinion itself. The actual pinion shaft isinside the rear end housing, so you have to take the measurement on the piniondrive flange. This isthe place makred "2" on the sketch. Make sure you are holding the gagefirmly on the wider part of the flange.Don't allow the gage to lean across the little step machined on it. (See the note on the sketch) Write this number down too.

You are interested in the difference between these two numbers. So, take the angle of the driveshaft and subtract the angle of the pinion from it.

The correct measurement will be about 3 to1.5 degrees difference, with the pinion being closer to horizontal than the driveshaft is. In other words, 0 degrees would have the measurements the same: The driveshaft and the pinion would be perfectly in line. You want the pinion to be angled down lower by about3 to 1.5 degrees. (Technically, this is called a negative angle, as in "-3 degree pinion angle", but wether or not the actual measurement is negative depends on how your angle gage is calibrated, so that is not always reliable)

If your measurement is not correct, then you need to adjust it. To do that, loosen the locknuts on your LCAs and then turn the center adjusters. Lengthening the LCAs will bring the nose of the pinion down, which will give you a larger angle difference. Be sure you have both LCAs set the same. You can either count turns and repeat the same change on both sides, or you can use a tape measure to measure the LCA lengths and keep them the same that way.

Once you've adjusted them a bit, check the angle again. Repeat adjusting and checking until the angle is where you want it. Once you've got it set, put a few drops of loctite on the adjusting nuts and tighten them down. Lower the car and go for a test drive.


How do you know what the proper angle is? Well, some of this is trial and error. You might have to reset it if things aren't to your liking. However, the general rule is that the more aftermarket parts you have in your rear suspension, the less the angle difference needs to be. 3.0-2.5 degrees is about right for a street car with relatively minor suspension mods. If you have a lot of aftermarket parts in the rear end (combo type UCA and LCAs+ more) then you could try 2.0 degrees instead. A full race setup might be 1.5 or even 1.0 degrees, though this would be an extreme situation: no rubber or polyanywhere in the rear suspension, reenforced frame, etc.

What is the theory behind this? Well, when you accelerate hard the whole axle assembly rotates a bit. Newton said every action has an equal and opposite reaction. Well, when the engine turns the wheels, a reaction torque is applied to the axle. On a race car with a SOLID suspension nothing much happens, but on a street car the rubber/poly bushings flex a bit and the axle housingrotates a little. You are setting it up so that when you get on the gas hard, and the axle twists a bit, THEN the driveshaft and the pinion are in perfect alignment.

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fairlane292

CrazyAl: this is helpful as usual. I will be doing this soon. let me ask you though about this that you said:
Level on the car is kinda arbitrary as you know, where do you put the level, ya know. Here's the thing... wouldn't it be best if the front is loaded as well, meaning the car sits as it will on the road. (If I was the size of a three year old kid I wouldn't raise the car to do the measurments). So with both front and rear loaded seems best over the level car approach, I mean where talkin 2-3 degrees here. I'm thinking I will raise about 6" all loaded and do the measuring. ...sound good?

Kaldar142

so i measure at the two places labeled 1 and 2?

CrazyAl

Well, the only thing that REALLY matters is that the rear suspension is loaded when you make the measurements. The front suspension doesn't affect the pinion angle at all.

Having the car level makes it easier to visualize the whole process, but it is not critical to the procedure. If you really want to be perfect, then, yes load the front suspension too, and to be sure the car is level, measure from the ground to each wheel. When the car is level, the measurement front and rear will be the same. You're right--there is no good spot to put an acutal level!

Kaldar, yes, you put the measuring gage at the places I labeled 1 and 2. You'll see it clearly when you get under the car. I'll go back and edit the original post to make it a little more clear.

06GT4RAD

Al would it be possible for you to post this info for a lowered car that runs a one piece driveshaft?

Richard

CrazyAl

Ok, here is the pinion angle procedure for a ONE PIECE DRIVESHAFT. This procedure is not correct for the OEM 2-pc shaft. This works for lowered cars or for stock-height cars, but this is for 1-pc shafts only.

Jack up both the front and the rear of the car so you can get under both the transmission area of the car and the rear-end area. The rear suspension must be loaded. This means the rear tires must be sitting on ramps, or the rear axle tube must be supported by a lift or jackstands. The front end can be lifted however you like.

It is good if you can get the car level, but it is not required.

Get under the car and removeyour 1-pc driveshaft. (or if you are installing the driveshaft for the first time, you can do thisafter you've got the OEM one out, and before you put the new one in).

Get your angle finder and measure the angle ofthe transmission output flange. Write this number down. Refer to the sketch for taking this measurement.

Move over to the rear end of the car and measure the angle of the pinion flange. Write this number down. Note that this can be tricky if you have a "triangle" shaped angle gage. If you flip the triangle over, you are nowmeasuringangles from a different referance point--don't do that,it will mess up your results. Use a carpenter's square as shown in my sketch, sothe angle gage is held in the same orientation as it was for the trans flange. If you have a "square" type of gage then just use the side of the square opposite the one you used for the trans flange.

Now adjust the LCAs so that the two angles are the same. Keep adjusting and checking until the angle at the pinion (#2) matches what you recorded for the transmission flange.

At this point the two flanges are paralell. If you are running a full racing suspensionthen you're done here, skip to putting the driveshaft back in.

On a typical car with minor mods, you now need to add a little negative angle. Adjust the LCAs so that they lengthen (if you are using an adjustable UCA, then shorten it instead), making the nose rear end housing dip down alittle bit. Go about 2 degrees beyond the trans flange measurement. Again, this is called a negative angle but depending on how your angle gage is marked, it might not actually be a negative number by your measurements. The same thing I wrote above applies here. If you have a fully aftermarket rear end, you could run about 1 to 1.5 degrees. If you are running a common street setup with one set of control arms only, then 2 degrees or so is more appropriate.

Once your angle is set where you want it, loctite your jam nuts and torque them down. Re-install your driveshaft, and go for a test drive.


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