Pinion Angle Questions (confused)
 

We are trying to set pinion angle on my dads 1986 Trans Am,it has the Spohn adjustable Torque arm,and crossmember,and Energy Suspension tranny mount. We are getting confused about the pinion angle setting. We read to set it about -2*. And then we read in magazines,that you need to keep that angle at the transmission and driveshaft the same as the angle at the pinion and driveshaft (equal but opposite),Example: If I have -2* at the pinion,then I need +2* at the transmission,wouldn't this become a 0* pinion angle? It looks like to me that they could never be "equal but opposite",or else the pinion angle would always be 0*,is this right? I have also noticed alot of articles on the web for pinion angle setting,only talks about setting the pinion angle at the rearend,it mentions nothing about the angle at the transmission. So what should we do?

Thanks, Brian

Re: Pinion Angle Questions (confused)
 

Yes, you want the angles equal BUT opposite just as you have read. Pinion angle is also known as u joint operating angle (UJOA). Yes, if you have -2 at the trans you theoretically want +2 at the rear. BUT you need to know the angle of the drive shaft to know what the u joint operating angles are at both ends. This is what allows you to figure out the angles. Equal but opposite should give you even (but opposite) UJOA's helping keep vibration out of the driveline. Sometimes this cannot be done such as in my case as my car is lowered. I had to compromise. I would start be setting the rear equal but opposite the trans, install the driveshaft and record all of these readings. Get some numbers and I can help you out some more.

Most any article or instruction I have seen for setting pinion angle on our cars only relates to the rear angle. Yes you can set it as most of them suggest and be correct, but if it isn't equal but opposite your front angle (I have yet to see any aftermarket manufacturer mention the front!) you will more than likely have vibrations you will constantly chase.

I also will include this link: http://www.iedls.com/IEDL_PTS_LGL_091008_Secure.pdf

I learned all about this trying to set my angles up just last month with the help of the owner of IEDLS. He was more than helpful. Post back with your findings and I can help you out.

Re: Pinion Angle Questions (confused)
 

Thanks onebad82z for the reply,we got some measurements last night,and we measured the transmission angle off the harmonic balancer,(i read that people do it this way),because Crankshaft and outputshaft should be perfect in line anyway.

Here is the reading we got:

outputshaft of Transmission pointing down 1*
Driveshaft is at a 1.5* down toward the pinion
Pinion is pointing down 1*

This is how we set it up last night,thinking it was right,but now that I get thinking about it,we think the Pinion was supposed to point up 1*,not down 1*, to be equal but opposite of transmission angle,because the transmission was pointing down 1*,so there for the pinion is supposed to point up 1*, (to be equal and opposite),correct?

If this is correct,all we should have to do is adjust the pinion to were it is 1* up,and that would make it (equal but opposite),in other words it would be at "0" angle,and then after you get that,I read on here that you just add your 1-2* negative(down) pinion angle,so that "under load" it is equal and opposite again,is this correct?

Thanks

Re: Pinion Angle Questions (confused)
 

You will basically never want a positive pinion angle. I have run as much as -6 w/o any vibration problems.

Magazines are great toilet reading. Sh*t to read while you sh*t. Adjust the pinion off of the driveshaft angle and forget about the transmission. Unless something is WAY off with the trans angle, you will not have any issues.

I many years of drag racing I have never seen some one set the pinion angle off of the transmission. I have also rarely seen an OE angle other than 0(in-line with the driveshaft), which we all know it would not be possible to be at that angle at the trans in a stock application of any sort.

Re: Pinion Angle Questions (confused)
 

Yes the balancer will give the same angle as the output shaft in the trans. To start yes, if the trans is -1 you would want to start at +1 at the yoke.

I see the front angle as .5 degree

The rear angle is 2.5 (again also known as pinion angle)

I would set the rear yoke angle to +1. You will see the drive shaft angle change some. Hard to say what definite amount. On my car changing yoke angle 2.5 degrees changed my drive shaft angle by 2. I assume yours will vary. In theory this 2 degree change may net you a drive shaft angle of 0 or so degrees. Then you will be at 1 degree Front UJOA, and a rear of 1 degree. Equal but opposite. It will take some adjusting and it will become clear, it did for me anyway. I wouldn't get hung up on setting the rear angle to a set -2 to -3 degrees yet. Myself get them as close to equal (but opposite) as you can and see how it rides. Adjust from there. Is this a street car, drag car, mixed use? Street only shoot for equal but opposite since you don't want to vibrate the u joints out of it. Drag, start at EBO then adjust to what the car likes in the 60ft. Mix use, again go for EBO... maybe dial in 1 degree at the rear. Try to keep the angles within 1/2 degree one another if it will see any substantial street use.

I don't worry to much about pinion angle on these cars. With all this poly suspension bushings and after market parts I find it hard to believe there is enough flex to need -3 degrees pinion angle so when under power the drive shaft will be in line with the pinion. I can understand it on leaf spring cars..but. Can't see there torque arms flexing that much. I have no data to back this up, but look at the parts.. could you see it flex that much?

Another great link on this topic: http://www.jeepfan.com/tech/tech_driveangles.htm

Post back with what you find.

Re: Pinion Angle Questions (confused)
 

This is true, some amount of negative is best at the rear. Just don't think a ton is needed with our suspension design (stock location).

Yeah, most any magazine makes for good office time material. I am not suggesting to set the rear angle off the trans, just use that angle as a start. And also to figure out the front UJOA. At that point adjust the rear as needed to give an equal angle off the drive shaft. Front and rear.

Better to know the trans angle than to assume and chase a vibration that may be caused by it.

I had to fight with a -3 degree trans angle and a drive shaft that runs uphill to the rear. That sucks. Gregg @ IEDLS was a great help in getting my car set up with this hurdle.

Re: Pinion Angle Questions (confused)
 

I'll agree with your reasoning for setting the starting pinion angle in relation to the trans angle.

As for wanting/needing negative pinion angle; pinion angle plays a big role in how hard you hit the tires during launch. The lower/shorter the IC is, the more negative angle you will need to get the desired effect at a given power level. - Going from -2 to -6 ended up netting me over a tenth in 60ft. That said, a shorter tq arm and/or a raised mounting height at the front would have negated the need for the excessive pinion angle.

From a tuning aspect, you work with what you have.

Re: Pinion Angle Questions (confused)
 

Thanks for the replys everybody, we reset the pinion so it had +1* ,so it would be " opposite but equal" of the trans angle,and then adjusted the pinion down 2* from there,and we are going to try it like that,and see what happens. This is 100% street car,although not driven daily. The instructions from Spohn Performance says to place the angle finder on the bottom plate of the torque arm and take the reading,but we found that the angle at the torque arm plate was different by 3*-4* than measuring right of the pinion,so since they are wanting to find pinion angle,we have been measuring off the pinion. I don't understand that,since Spohn says it is at the same angle as the pinion,but it isn't on my car. My rearend is a Moser ford 9".

Re: Pinion Angle Questions (confused)
 

there's you answer right there....

Re: Pinion Angle Questions (confused)
 

what, the Moser rearend? if so why? thanks shagwell

Re: Pinion Angle Questions (confused)
 

also,we was running the "preload" shim that comes with the Energy Suspension tranny mount,but we took it out this time,before we set all the angles. Most people on here say not to run it,including Steve Spohn himself.

Re: Pinion Angle Questions (confused)
 

Did you ever get this setup to work?. I am having some vibration problems after installing the Spohn tourqe arm. Your mention of setting the angle off of the pinon itself sounds good. Mine is way off, we followed the install manual, which may be the problem. You might also check the height of the replacement poly trans mount, mine was quite a bit higher than stock. I have also heard of worn motor mounts changing the angle at the trans, but mine worked great till I changed the torque arm.

Re: Pinion Angle Questions (confused)
 

We have driven the car a couple times so far,and there seems to be no vibration at all,but we also removed the mount "pre load" shim that energy suspension provided with the mount before we set the angle. All seems good so far,it will probably get better traction now also,because when we first set pinion angle,after installing all the spohn stuff,we had it set way positive compared to what it is now,but we still did not have any bad vibrations,just thought we would recheck it,and sure enough we had it wrong,this time we are pretty sure it is right. I'll let you know more on how it turns out,been really busy latley.

Re: Pinion Angle Questions (confused)
 

onebad82z, I was wondering if you would share with me, as I am somewhat dumbfounded, what you come up with for a setting of the pinion. I have a similar problem like you. My trans is a -2* with the driveshaft running up to the pinion. I have the trans as high as i can get it without hitting the tunnel. Any help would be much appreciated.

Re: Pinion Angle Questions (confused)
 

Nice link to the Inland Emprire Driveline info! Thanks

Re: Pinion Angle Questions (confused)
 

i know this is a little old, but i could certainly use the help. i have been chasing a vibration in my car or over a year now, and i think it has to do with the pinion angle. i dont have a drive on lift or 4 jackstands, so i jacked the rear of the car up yesterday and the angle on the balancer was up 1 degree. the angle on the bottom of the spohn torque arm i have was 7 degrees up. i adjusted the pinion angle to about 1 degree down. i drove it today and it seems to accelerate a little better but i still hve the vibration, only it starts about 78 or 80 mph now instead of 75 mph like before the adjustment. any suggestions? i would appreciae any input

thanks

Re: Pinion Angle Questions (confused)
 

What all have you done chasing this vibration? Where do you feel it most from? (seat of the pants, or thru the steering?)

Re: Pinion Angle Questions (confused)
 

- i have had new u joints installed and had the driveshaft balanced
- changed axles
- put stock tires back on to eliminate the spacers needed for the 4th gen rims
- had tires balanced multiple times
- replaced front rotors (thought studs were bent)
- removed shim from poly tranny mount (suggested by spohn)
i think thats all i have done


i feel it most through my back, almost like one of those vibrating chairs everyone loves. it makes the seats shake, dash shake, console shakes a bit. i will be unable to get online for a few days but any suggestions would be greatly appreciated