lowering and pinion angle shims...

[Brad]

You guys that have a 4/6 stance or thereabouts, what pinion angle shims are you using on your trailing arms? Where'd you get them? Did you have to modify them for our trucks?

[Brad]

...or 2/4 drop??? I don't have an angle finder and can't afford one for a one time use.

[crazy longhorn]

You can pick up a cheap magnet base angle finder at Lowe's or Sears in the tool department(about $12).......thats money well spent even if you any use it 1 time

[Alexis]

you need shims on a 4/6 drop never was told to put any from ECE, on thing i stuck between the diff and trailing arms was a bracket for the pan-hard bar and a plate to level it out on the other side.

[billogna]

I have 5" lowering springs (had) 3/4" shims in the rear and I asked this question a while back, and got no good answer, so I made my own shims. I don't know how accurate this method was, but traced the angle of the axle perch with a squared 2x6 against the frame rail, then let the trailing arms hang down 5" and remarked the board. I laid the board on the floor and extended the two lines until they met and, with a cheapie protractor, determined that there was a difference of 5.5 degrees.
I made my shims out of block aluminum with a hack saw, vixen file, and dotco, since I don't have access to a milling machine. I don't know how accurate I am right now, only time will tell, and I'm trying to find a shop that will look at it, but no one wants anything to do with lowered vehicles. I think I'll go look for one of those level tools mentioned above, and see how close I am to the tranny angle. I've heard that the pinion angle needs to match the trans, though I don't know if the pan is parallel to the output shaft, or where to measure the pinion angle to exact, either. Hope this rambling helps.

[Brad]

Thanks billogna, it appears we're in the same boat. Maybe I should pitch in for that angle device, lol. I was going to get, say, a 3 degree shim, but didn't want to find out I needed a 5 and spend more $$$ buying another pair. Also, I was always kinda confused as to exactly how to measure. I had access to one at one time, but never measured.
I think we both just want to be fairly accurate and reduce u-joint wear and vibration. Thanks for the pic and description! Let me know if you buy the device and get good measurements.

[CustomChevy]

hello,

fist you need a magnetic protractor, available at sear's for $10.

rear axle needs to be inclined at 3 degrees (to offset motor/tranny declination of 3 degrees.

as long as motor/tranny declination angle is canceled out by rear axle inclination, then you are good to go.

hope this helps.

[Brad]

Very cool, thanks!

[lofly'a]

before you ever change the pinion angle on any suspension you should know the angle of the driveline. with you angle finder, pull the driveshaft yoke if necessary, and get the determine the angle of the output end of the transmission. the pinion angle should be +/- 3 degrees of the driveline output shaft angle even if you must use shims under the trans mount to get them to that point. this is the rule that street rodders and monster trucks use, and you may have seen the wicked driveshaft angles that the truckers use. hope this helps

[SCOTI]

Brad have you already lowered your truck? When I spoke w/AirRide tech & asked this very question, they told me due to the length of the trailing arms, shims wouldn't be necessary. I figured he was full of it but decided to lower & put some miles on it to see whether there was any vibration or not. After 3yrs now w/a 5/7 drop I've had no vibrations or u-joint probs. I'm running 2600# dbl convoluted rears @ 30psi w/1.5" blocks. I've put several 4-5hr one way road trips to OKC, Ok. & Houston @ 60-70 mph w/no probs. My biggest concern has been the fact that my driveshaft is so close to the top of the hoop in the crossmember, it has on a couple of occasions made contact. Just wanted to share my experiences w/this subject. I was wondering what you decided to do about your shock dilemma? Instead of buying aftermarket relocating brackets, I just tweaked my stock brackets for FREE, minus my own personal time in labor & I use my wood bedfloor as my bumpstop.

[Brad]

Scoti, thanks for the advice. I haven't put any shims on yet. Haven't had time for much of anything with school coming down to the wire for the term. I should be getting the shock relocators from Big Orange and will put those on when I can. Seems my shocks are close to a 45 degree angle and I don't think they do much. I thought about trying to modify the original brackets and came up with a couple ways, but really don't have the time or welder to create something.

Eventually, I want to put in a C-notch, because right now with poor shock action, I'm hitting my bumpstops alot.

[Project1970]

That's the beauty of a nice long truck, you can do some fairly major suspension mods and the driveshaft lengh/angle won't be affected much. I've never shimmed my '70 after dropping it 2.5" front and 4" back (leaves), and I've put over 20,000 miles on it in the past few years.