New suspension problem (pinion angle)

[v8astregt]

So of course, a couple weeks ago, I tore my left upper rear control arm mount completely off. This tweaked the mount some, and I was not able to hammer it completely flat again since it was such a weird shape. So I did the best I could and welded it on. With it all put back together, the axle sit a little further back in the wheelwell... kind of expected that to happen, so right before the races I was gonna adjust my upper control arm in a little, to compensate for the tweaked mount. So I take it apart, and adjust it till the rearend is close to center (not quite enough still), and here's what happened.


Yeah, that's ugly, and yes there is quite a vibration. Plus, the wheel is still a little too far back for my tastes, don't want to rub when I launch hard again.



On the rearend... it's an S10 unit, I had the brackets transferred over best as I could. There was no scientific process to getting them clocked dead on, so they might be off by a few degrees.

So I know there are adjustable LCA's, but those are for fine tuning... I don't want to buy them to fix a larger error such as this. So I'm thinking this... welding the holes on the rearend brackets closed... and drilling and reinforcing a new mounting point about 1/2" or 1" back... that should work, shouldn't it?

[cosvega76]

Josh,

Didn't you get the Spohn adjustable upper control arms? That angle looks pretty severe, but try adjusting them to see how close you can get before making any changes to the brackets. It will take some trial and error since they are curved. Try one side first and see if it will get you where you need to be.

I have corrected my pinion angle with the adjustable upper arms I made, but they are straight so I could adjust them in place.

Chuck

[spyder_xlch]

Josh, I'd think you may have tweaked more than just the left UCA mount. When the mount tore loose you may have bent other brackets or even the control arms. Even if a bracket or arm on the right side is tweaked just a little bit it could make a big difference on the left side.

[Fasterthansome]

Is it just the picture or is that pinion headed toward the camera?? It looks from pic like the pinion is not just down but also angled toward the camera.

[BillPappy]

Sometime I think I would like lose my torque arm. But then I see something like this. Im glad
I got it.

[73astregt]

josh i think you need to remeasure your car looks like you bent more that that upper mount. adjusting the upper arms isnt going to help you theres more going on there you need to get that pinion angle right or you are in trouble. id be looking at the lower arms and mounts as i remember you saying the axle was pushed over to one side about 2 inches wasnt it! measure your chassis and see what you come up with. get in touch with ray(peterpan) he hadspecs for measureing the frames in these cars not shure if it was just for the early cars or if they were the same for all the hatchbacks he would probably email you a set if you ask nicely lol!

[spyder_xlch]

Roger (SunbirdMan) sent me some good files with frame specs. They were for the 2nd gen cars so the upper control arms specs wouldn't be in them.

[v8astregt]

cosvega- they aren't the Spohn adjustable uppers... I got these off ebay before Spohn was even in the picture. But yes I do have them, and the reason the pinion angle is so screwed up is because I shortened them up by a lot... the pinion has about always been flat with the ground.


I checked everything very well... the right bracket was starting to come off... welds were cracked, but nothing was bent yet. I'm going to attribute this to the fact that my upper left bracket was severely tweaked... it was such an odd shape, I couldn't get it 100% back to how it was, so I got it "close" assuming I could get it closer by adjusting the upper links. I guess it was bend a little more than I thought.

Fasterthansome- no, the pinion is not pointing to the right of the car... the axle is even from side to side, no twisting action going on there.

Actually, the axle moved more than 2"!!! Look at this following pic. This is the car, strapped down on the trailer... so it's loaded down a little bit. But look closely... you can see on the pinion, and the seatbelt mount where they made contact with each other!


I really doubt I bend any other brackets. Since that one bracket was practically torn off, it should have absorbed any other energy in the suspension. That, and the twisting of the bushings.

I think I should just be able to redrill the lower holes, and be okay. I remember my pinion angle was always barely acceptable... but bending this bracket just pushed it over the edge.

[heinz057]

are the brackets on the rear bent at all?

[v8astregt]

Nope, the brackets are fine on the rearend. I had them welded on by a fabrication guy at the time, and they are solid, and never gonna come apart. But yes, they are straight.

[heinz057]

can you get the rear in the correct position with the bad side upper arm not conected,and then measure to see how bad it is,to see what can be done .maybe a different lenth arm will solve the problem

[gt350fme]

Man that pinon angle does looks extreme, couldn't be right.

[chevyart]

the last post says your pinion angle cant be right. guess what, it could be right if the rear of your motor was pointing up instead of down, and thats why I think you should look at a long, easy to understand article i posted over a year ago in reference to colins predicament with his pinion angle. Its in the trans and driveline forum, dated dec 20 06 and titled by colin-oh boy i need help. get your rear end back in place, in the right place side to side and square to the centerline of the whole car (each wheel must be the exact same distance from the center of the same side front wheel spindle and when this is done then worry about the pinion angle. If your rear is not in straight your car will take a wicked hike right or left when you take offall 4 wheels should be paralell, but could have a wider track in front or in rear. If you dont understand my article, then give me a shout and I will write it over in an even easier form to understand chevy art PS get all your control arm connection points beefed up

[v8astregt]

I have a good basic understanding about pinion angles. I know that the angles coming out of the rear should be the same, but opposite of the trans. About 5-7* I think? But it is much more extreme going into the rear, there is no way it can be right. Plus, there is the new vibration I have going down the road at about 3k rpm.

[spyder_xlch]

I know definatly for sure that the upper control arms have to be longer than they are and the lowers have to be shortened to get the pinion angled up more. Or as you said Josh, move the holes. I presonally would measure all the mounting points to be sure something isn't tweaked. When that mount tore loose it was like taking a big pry bar and pulling back on it. Something moved. You might not see it with the naked eye but a tape measure will tell you. It might not be tweaked enough to matter but I would bet something is tweaked alittle.