Clunking Rear Axle

[bigcoconut]

The patient is a 92 Chevy regular cab, step-side with a 350 engine. The rear axle is making a clunk-pinging sound when I take off and after I stop and sit for a couple of seconds at a stop light. Also, I hear the same sound when I accelerate in a right hand turn. I've not noticed it when turning left, but that may be because it is normally a more gradual rate of turn.

I've replaced the U-Joints, both of them, and the transmission mount with no change. The axle has new oil seals at the wheels and it is full. My dad had this work done about 2 years ago. Now, my dad drives a little like Grandma and the truck has never been overloaded or towed anything but U-Haul trailer. I now own it and of course inherited this problem. My dad said it has been making this noise for some time now, were talking years.

Looking for some axle expertise...

[MT-2500]

Pull the cover off the back and have a look in there.
Check spider gears and pin and for loose bearings or ring gear or ring gear condition.

Here is a link with some repair info.
http://www.differentials.com/install.html

[bigcoconut]

I've checked on the price for a full bearing kit for the pumpkin, it isn't too bad. What kind of job am I looking at? Can I do this in my garage?

Ah haa, just read the website you posted. Looks do-able as long as I re-assemble just as dis-assembled.

[MT-2500]

Originally Posted by bigcoconut

I've checked on the price for a full bearing kit for the pumpkin, it isn't too bad. What kind of job am I looking at? Can I do this in my garage?

Ah haa, just read the website you posted. Looks do-able as long as I re-assemble just as dis-assembled.

First thing have a look and find the problem.
May or not be the bearings.
I posted the web site for a trouble shooting the problem procedure.
Ther parts may be OK but I would go local parts if possiable.
If a bearing kit or bearings is needed your local parts place can take care of that end.
MT

[bigcoconut]

OK, this took me awhile. I Had to wait for a weekened without family in town. I pulled the cover and found that the Pinion Shaft is loose. All of the gears looked good, normal wear, except the small spider gears on the Pinion Shaft itself. When I rotated the tires back and forth while watching the spider gears there was movement, more than I would expect, on the smaller gears the pinion Shaft goes through. These gears would move laterally (not in line with shaft) and make the same sound I hear on the road.

I pulled the Pinion Shaft out and there are wear marks on the ends, grooves worn into the metal. I was looking for bearing problems but the oil looked OK with only a little "metallic" sheen. I ran a magnet around the drain pan and picked up only a couple of very small slivers of metal. The Pinion input coupling is tight, no oil leak and no axial play. Now, the small spider gears that ride on the shaft have what appear to be very small chips at the ends. The defects appear smooth, almost like washed river rocks but definite very small chips missing in the tooth edge.

I called the auto parts store and the Pinion Shaft isn't a normal wear item, so I figure there must be another underlying problem that would cause the shaft to be loose in the differential.

This is my daily driver so I put everything back together with fresh 80W-90 oil, tomorrow got to go to work. What would be my next step? At this time I'm figuring that the shaft wouldn't fail on me and lock up the differential so I'm going to leave it as is unless someone says something different.

[MT-2500]

May be this link will help.
http://www.differentials.com/install.html

Are you saying the pinon shaft and pinion bearings are lose?

Or you saying the pider gears and spider pin is lose?

[bigcoconut]

The Pinion Shaft I'm talking about slides through the differential, through the smaller two of the spider gears. There are four "spider" gears in the differential, the two larger ones are splined to the left and right drive axles. The Pinion shaft is loose in the diff allowing the smaller gears to have some backlash on take-off and quick stops.

The Chevy manual is calling this piece a "Pinion Shaft", but it is not attached to the "Pinion" gear at the front of the Diff where the transmission power comes from. This "Pinion Shaft" is attached directly through the differential housing that is bolted to the Ring Gear. This is a picture of the shaft I am talking about along with the four spider gears.

[MT-2500]

If the pin/shaft is lose in the case the case is worn.
And will need replaced to fix it right.
Lot of work.
If just the pin worn where the spider gears turn on it or the spider gears worns or chipped bad. usually caused by a lot of wheel slippage in mud and snow and or burn outs.
They can be replaced fairly easy if the little bolt/pin that holds the shaft in does not break when removing it.
Also for clunking noise make sure drive line u joints and engine mts. are good.
MT

[bigcoconut]

The pin/shaft is definitely loose in the case. With the holding screw in place and torqued, you can push on it and it will wiggle moving the gears with it. The wear marks on the pin/shaft appear to be from the holes in the case.

BTW, I've had this truck for almost a year, before that it was my dads. Trust me no wheel slippage in its history.

Is this something I should be able to find in a junkyard? I'm a garage mechanic, working on my cars is a hobby of mine, I love it, but I know my limitations in knowledge and the correct tools. Is this something best left to the professional or can an experienced amateur get this done?

[MT-2500]

You might check some of the bone yards.
But a lot of the used ones will be worn some or a lot.
Check the web page I posted for a price on new one.
MT