It’s finally differential service time (71 LS5 with 4-speed). I’ve been putting it off because of the hassle of putting the car on jack stands, but with winter storage looming and some weird noises coming from the rear-end, it’s overdue. I’m getting a “Click, click” noise very time I pull away from a stop and the noise from the rear-end at speed has change from a drone to a harsher tone. Also, last time out while driving on a twisty road, I felt a thump from the rear-end on a couple of swiping left hand turns. I was rolling through the lefthanders and as the radius of the curve tightened, I felt the thump and the rear-end seemed to loosen-up, momentarily being a little more free to swing out and track a little more right. A right turn, a swallow left, another right, and a tighter left and thump, does it again…at which point I slowed down and drove home cautiously. I’m hoping the noise and the thumping sensation is from the clutch plates binding in the differential and new gear oil and a couple bottles of GM additive will take care of it. While I’m servicing the differential I figure I would inspect the rear-end and suspension. However, I won’t know a good universal joint from a bad one, and was hoping you guys would give me some advice on what to look for. The trailing arms were rebuild about 2 years ago and the spring is a composite mono leaf unit, but I don’t know the age of the other rear-end and suspension components.

Thanks

pat

 

One quick inspection is to floor jack on the pumkin and let the wheel hang down. If your yokes come out of the housing more than .100 it's time to pull the pumpkin out.

To inspect U-joints it's best to just remove the half shaft. But you can just grab the half shaft and twist it back and forth. The needles ware out inside the u-joint end caps and you would see some slop between the center section and the caps.

Oil and posi lub is a waste of money. My original pumkin was wasted in under 50K miles with a small block. The ends of the yokes ware away adding metal to the oil and it snowballs into eating everything up.

 

[QUOTE=gkull;1575895116]One quick inspection is to floor jack on the pumkin and let the wheel hang down. If your yokes come out of the housing more than .100 it's time to pull the pumpkin out.

I have her on jack stands with the trailing arms hanging down. How do I tell if the yokes are pulling out...is there a point of reference to measure from?

 

Here is what I found so far. Notice some moistness where the wheel contacts the rotor. Thought a caliper was leaking but wasn’t. Pulled the rotor and found grease between the parking brake shoes and the hub (see photo). A ring of grease was deposited around the inside of rotor. What’s causing this, bad grease seal…trailing arm bearings bad? What’s the fix?

 

Yoke slop. With the wheels off the ground lift the passenger side a-arm and see if the yoke goes back into the pumpkin. It should not slide in and out.

You have rebuild trailing arms. It is very easy to over grease and or set the wrong bearing preload. Just wipe off as much grease as you can and use brake clean to clean it all out. Bearing preload can be determined with the tire on and grab the top and bottom any yanking it back and forth you should not have slop and you should be able to spin the tire with the caliper removed. When you spin it it should make a few rotations before coming to a stop

 

In addition to what gkull said above, a visual reference for the worn ujoints could also be the presence of a red(ish) colored dust covering the ujoint. This reflects the metal to metal wear from the absence of grease that would normally lube and cool the friction contact of the bearings, bearing cap and joint lug.

The clicking you mentioned could also be from a bad ujoint. I experienced this same sound (along with a minor vibration) under acceleration on my Vette. Replaced all joints and sound/vibration went away. Good luck!

Terry

 

Bearing preload can be determined with the tire on and grab the top and bottom any yanking it back and forth you should not have slop and you should be able to spin the tire with the caliper removed. When you spin it it should make a few rotations before coming to a stop[/QUOTE]

Do the half shafts have to be disconnected before I do this?