2002 ZR2. New OE springs from General Spring. Rear height increased by 3 inches and now the truck sits mostly level. I now have a new sensation of a shudder (for lack of a better description) when I first pull away from a stop. It kinda reminds me of the shudder we used to get on old manual shift cars when the pilot bushing got worn out. It's probably just coincidence but could changing the springs/ride height amplify this shudder if it was tranny or torque converter? Never noticed it before, but tend to listen/feel harder after a repair.

 

Sounds like just a drive line u-joint angle shutter. Threw the angle off with the added height.

Most new springs WILL settle after driving for a while, normally just an inch or so, but it will probably stay higher than it was before the spring swap obviously if your old springs were worn out and sagging.

 

My thinking here was to get back to factory ride height. If it is indeed a u-joint angle shutter, is that something to worry about? I would think the if the angle was off enough to cause a shutter then something might give out. I haven't brought the front up yet, but I don't think that would change the u-joint angle anyway......would it?

 

You should not feel the u-joint turning.

Get "Clinometer" for your Android phone. Zero on level floor underneath your Blazer. Don't jack up your vehicle for or between any of this.

Measure driveshaft angle and state the measured angle, relative to floor (i.e. rear is down -3.1°). Disconnect driveshaft and place phone across u-joint saddles that have been turned so they are vertical. Measure pinion angle and state measured direction, relative to floor (ie front is up 1.6%). Find a flat surface on the engine that is parallel to the crankshaft - for example the valve cover sealing surface on a cylinder head. Holding the phone on the surface, measure the engine tilt and state measured direction, relative to floor (i.e rear is down 1.8%). It is important to not tilt the phone to the side when doing these measurements and make sure you are measuring vertical angles.

Pinion angle should be approximately equal to engine tilt, relative to the driveshaft (but in opposite direction). They cancel each other's jerky rotational motion out, and this is what makes operation smooth. Both should be within a couple of degrees of the driveshaft angle to avoid spinning the little bearings too fast and too much. Usually takes quite a bit of difference to feel anything. Maybe you have a u-joint going out? Good luck!

If significantly different, could be that the axle mounts on the new springs at a different angle than before. In that case, the new springs would not be made right. But you can use pinion angle adjustment shims to correct for as much as ±6°.....

 

Definitely has a bad rear U-joint (squeak-squeak-squeak) heard it in the drive thru yesterday, will have the shaft re jointed and balanced and try again.

 

Getting my driveshaft back today, will see if that corrects things. Found a driveshaft place that said they don't use heat to melt out the plastic injection on the front joint. Being a welder for over 40 years I know what heating metal does to it's integrity so I wasn't interested in having the front joint burned out like you see on Youtube.

 

Has your ride height dropped in the rear yet with the new springs?

I am ready to order the same springs for my 01 ZR2 Blazer and really dont want a 3" lift in the rear.

Any other issues with your purchase?

Thanks in advance

 

Ride height hasn't changed yet and am going to have to tweak the torsion bars a bit to level it out. On a different note The u-joint replace took care of the shutter.

 

Rear height increased by 3 inches and now the truck sits mostly level.

 

Got it, so basically the 3 inch lift brought it up to where it should be. Wasn't sure if the new springs jacked the rear up beyond factory level since he had a U joint issue.