I've searched through the archives and found several threads addressing this, but I'm left with a few unanswered questions.

My car ('79 L-82 Auto) was parked in 1982, and sat in a garage until early 2001. I know the car's history as my dad bought it new and I am the second owner. The car has just under 45,000 miles.

So, I've decided to replace a few bushings and basically give the rear end a good once over.

Here's the situation: With the suspension in tact and wheels on the ground, the car has a toe-out condition intermittently. Sometimes it looks just right, sometimes the toe is out noticably on both sides.

With everything assembeled and up on jackstands, if I grab a wheel at 12 & 6, I don't notice any endplay. With the spring and strut rods off, I can move the side yokes about .25". There is a noticable "clunk" or detent at the outward end of sideplay, which makes me think the circlips are still in tact. At the inward, the dust sheilds on the yokes look very close to the hosing, but I see no sign of contact between the housing & shields (no bare shiny metal).

It does not have any noticable endplay at the wheel bearings. Just at the differential.

My thoughts at this point are to pull the diff and take it to a local drivetrain shop to have it cleaned up and at the very least have the pinion and yoke seals replaced.

In my research, I've read that there are a lot of junk side yokes (non-hardened) on the market and I need to buy yokes from VanSteel to get quality parts (hardened).

Have I given enough info to absolutely confirm that I need new side yokes? Or, is this endplay normal due to having struts and the leaf spring un-attached?

Another thing to keep in mind is that upon visual inspection, my outward strut rod bushings were in much better condition than I assumed they would be. I haven't pulled the strut rods because I still need to dismount the exhaust and dismount the leaf spring from the diff. I bought adjustable strut rods from Willcox and will be installing them when I button everything back up.

I'm trying to keep from overspending on the car... it won't be raced or autocrossed. I just want to be able to drive the car and not have second thoughts about taking it on a 100 mile trip somewhere.

Pretty excited about the whole project... the trailing arms are in great shape... no signs of rust and they look pretty nice when cleaned up.

I'm also thinking about sending the halfshafts to VanSteel for a refurbish job with new U-joints.

 

Yes, you absolutely need to do something about the yoke movements.

Just to clear something up about the absence of movement with the spring tension. If you attempt to check frt ball joints with the suspension loaded (spring tension on the ball joints) you won't get any movements out of worn out ball joints either. The correct method of checking suspension components is to remove the load that is taking up the slop.

Leaving a quarter inch of slop in the rear suspension component that maintains camber means there is no point in aligning it because where ever it's set is not where it's staying.

Toe change is not usually visually evident from yoke or camber change. Look carefully at the trailing arm bushings as well.

Steve g

 

I'm sure this will turn into another battle royale so I'll say my piece and shut up.

Worn yokes will affect camber and not really toe-in. Best check your alignment to see which problem(s) you really have.

The contentious bit is about the yoke end play. Some believe that NO play is acceptable and will lead to all sorts of handling difficulties even under normal street driving. Others believe that it makes little or no difference and knowingly operate their cars with no clips in place or with huge amounts of end play. Many owners (like yourself) have operated their cars for years with lots of end play and never noticed a difference while driving.

After 20+ years of seeing and learning, I fall into the latter camp.

Enjoy the discussion.

 

Yes, Mike is absolutely right. Just as there are people that drive with worn out ball joints until they finally separate and don't think there was anything wrong with the handling of their car there are people who will drive their cars with rear camber constantly in flux and feel there is no need for improvement in the handling of their cars.

The issue is, what is acceptable to you. Would you drive your car with worn out upper ball joints allowing the top of your front tire to move in and out 1/4"? The Youtube video taken from under a moving car clearly illustrates camber change in driving conditions that would be found on normal street driving. This is absolutely no different from the camber change you would experience with worn out upper ball joints in the front end. The no clip camp sees only the point in the video where under an extreme maneuver the yoke with a missing clip comes out so far the wheel "over centres" and flops completely out. My interest is in all the movement between times it does this.

My position comes from the training I received in attaining an Interprovincial (now known as Red Seal) Journeyman's ticket in the mid 70's with real world alignment experience and having owned my first corvette in 1974.

Steve g

 

To absolutely confirm it...No. However the yoke ends wearing is the most likely cause.
Worn clutch plates in the posi assembly can also cause slop in the side yokes, but its not likely to cause as much looseness as you say you have.
Still, I would open the differential up before I ordered parts.

 

I'm in a similar situation...looking for quality side yokes. After speaking with Gary R. as some of you may know him, he comes recommended by a ton of people as one of the best for rear end rebuilds. He uses Tom's 30 spline which he sends out to get hardened before installation. Tom's also has the stock 17 spline but I think Gary uses Lone Start rebuilt GM yokes for 17 spline installations. The Lone Star yokes are what a lot of other vendors sell as well and a very careful inspection is needed before installation.

You will get a lot of different opinions, success stories and horror stories with the different yokes/brands. I am taking the easy way out and I will most likely let Gary do the job as I will have the entire rear end looked over and rebuilt.

 

For fun, I watched the famous YouTube video again and noticed that the poster (a member here) has modified the comments section :

"The Severe Camber change causing failure of the C-Clip inside the diff, shearig the splines at 1:22 and at 1:42
At the NJ BMW Autocross
For people in the Forums, the Average G load on the turns was 1.02G while peaking at 1.05G, the overall run G's were at 0.96G"


Not too many C3s are capable of inducing that level of Gs, nor is it likely to happen in normal driving.

 

I'm now 90% sure I'm pulling the diff and taking it to a local drivetrain shop to have it cleaned up, seals replaced, and posi clutches replaced if needed.

If I open it up and see the signs of worn yokes, my other thought is to also order known good quality yokes to take to the shop with the diff.

 

If the yokes are as worn as it sounds like they are it should be easy to tell. The ends will probably be worn down to the snap ring.
But if they look OK and you want to check them, the distance from the snap ring outer face to the end of the yoke should be .187" +/- .010".

 

Those refer to the points at which the wheel over centres and flops right out with the tire squeeling. Go back and watch the stability of the wheel and the constant camber change at the points in between.

I watched that video with pen in hand intending to mark down the time points it was moving outside of the two catastrophic failures. I gave it up because it would be a shorter list to mark the times camber wasn't changing. The wheel is constantly moving. And you will note that the entire video is not rounding a hard corner at over 1 g and the quick oscillation of the wheel is not only at minor corners, but is actually more in tune with the loading/unloading of the suspension. This is what the average driver will experience which results in less than optimum handling and creates the clunk as it moves back and forth.

Steve g

 

I just got done pulling my differential apart,yokes had slight movement and this is what i found.




The centershaft is shot not sure about yokes,need more input if i should replace or not?

 

Yokes look shot too. Measure from the snap ring groove to the end of the yoke. New ones are 0.187". The hardening is only a few thousandths thick, so once it is through the hardened bit it will wear much faster.

 

I've looked online at new ones and the amount after the snap ring doesn't look that much thicker. But the new ones claim to have hardened inserts in them?
Car has 80 thou on it and i'll probely only put 500 a year on it if i'm lucky.
Is there somplace i can send mine to have the inserts put in them?

 

If the diff in your '79 is original it may have the snowflake clutches; if so, the general consensus is that you should replace them. The serrated clutches (and later the carbon fiber ones) were meant to prevent the diff from hammering, but the snowflakes have a tendency to break. There are differing opinions about the carbon clutch packs; I used solid steels when I did mine and it's been fine.

 

Check with bairs.com

 

I suggest a cheap dial indicator from Harbor Freight. I thought it looked like I had 1/8" end play and it ended up being .019" which is within safe operating condition.

There was a time where the ends were not properly hardened and the yokes wore out quickly.

I am with Mike regarding the alignment but if there is indeed a 1/4" play there is the risk of a failure that could render your rear end a boat anchor.

Bill

 

1978-1979 yokes were improperly hardened. This is a documented issue from GM. When the sideyoke and cross shaft wear the play causes the end of the yoke to hammer the cross shaft when it loads and unloads causing further wear, metal shavings in the rear end, and will oblong the hole in the posi case causing you to need an oversized crosshaft or resulting in a broken posi case. The shaving circulate through the differential causing wear to the gearsets and wiping out the bearings. When the wear at the sideyoke hits a certain point the dustshields on the sideyoke start cutting the outer case down like a lathe making the case unuseable for a rebuild. In my opinion anyone that says that running long term with worn sideyokes and missing clips is not a problem has no concept of basic engineering. A rebuild kit and new yokes is way cheaper than replacing the complete differential and having zero core value to your unit. This is especially important with an NCRS type car where you want to keep your original, matching numbers differential.

 

Excessive wear at the machined surface of the cross shaft as well as the ends. Need a complete rebuild and yokes. All that metal shavings has been circulating through your gears and bearings. Check Muskeegon Brakes for yokes.

 

Gary R. is currently rebuilding my diff. I had about .25" endplay on one side, and about 3/16" on the other. His report was 1 yoke worn completely to the clip, the other very near. Posi was ok.
If you've got that kind of endplay, I wouldn't drive it hard, and would start looking for rebuilders.

 

My 79 L48 auto lost it's yokes @ 35,000 mi. I worked for GM in the tool room and ran them thru our inspection dept. They were RC 20. I argued with GM and lost. The metal in the lube ruined the ring and pinion. I did not chg. the R&P at that time and lived with the howl but now after 32 years and an additional 10,000 miles it's in the shop for a $2,000.00
repair. The posi let go from the previous damage. The replacemint yokes show no wear but the orig. factory ones were warn to the point that the snap ring fell off the pass. side and no sign of a ring groove was remaining.