Bringing this back up I was asked about it on another forum- that I no longer post pictures on. Can one of you make it a sticky so it doesn't get lost.
Thanks

 

Will do :thumbsup:

Great reference material!!

 

I have about .25" of end play :surprised :surprised

 

I smell trouble. Did you check it with the halfshafts removed?

 

Chris, that is a lot of end play you got there. Since it is out of the car, I would open it up and check what is going on...but that is me. If you decide you are not going to do anything with it, then it only cost you RTV, a gasket and a little time.

I had less end play than that when I inspected my differential and it turned out one of the yokes was slightly mushroomed. Both were significantly less than the approximately .187 from the snap ring to the top that is normal for new. Of course, I ran into a cracked case......

You might want to start a new thread on this..........Edit, just saw the new thread.

 

Here something to check with rebuilt yokes, and I'll post this on the rebuild post as well.

I had some come in that were rebuild poorly and the splines didn't line up. Now most of the time this doesn't happen but if you're like me and buy parts to use in a year or more then look at them when you get them.

Here is the end of the yoke. You can see he tip is not aligned and this would not fit in the side gear unless it was hammered in. Maybe some do that as well:surprised

 

Here something to check with rebuilt yokes, and I'll post this on the rebuild post as well.

I had some come in that were rebuild poorly and the splines didn't line up. Now most of the time this doesn't happen but if you're like me and buy parts to use in a year or more then look at them when you get them.

Here is the end of the yoke. You can see the tip is not aligned and this would not fit in the side gear unless it was hammered in. Maybe some do that as well:surprised

Tips...TIPS?!! Where are my tips?!:huh:
Oh! There they are...still inside the differential!?:WTF

Just pulled my '78 rear end down for cleaning and 6-Link design & fab, and it seams that both of my yolk spindles are broken. It appears (from the pic you posted above) that the rod joining the main shaft of the yolk and the tip has snapped, leaving the tips inside the differential, still sitting in the splines, while allowing me to pull the yolks out of the diff. with no tools at! I don't know if these were rebuilt or not, also didn't know that the tip was a seperate piece.

So it looks like a the very least new spindles are in order, and I'm also in the middle of fabricating a 6-Link (the reason I pulled the rear end in the first place.)

With the 6-Link, I'm planning on floating the spindles, (no snap ring), but how much of the spindle gets shaved for this set up?

Have you heard of the tips snapping like this? I had the rear end rebuilt shortly after I got the car in the early 90's, so I don't know if this is a result of poor workmanship, cheap parts or just what happens to a daily driver over a period of 10 -12 years, (stopped driving it in 2002 when I moved to las Vegas from California.)

 

Gary, Have you ever seen a new yoke or a rebuilt yoke that after installation still has to much clearance. If you have what is the fix for this, or is there a fix.

Mine will probably come back out this winter just for a check and see how it all looks. I have about 2K miles on it since rebuild but it has been a hard 2K.

 

Gary, Have you ever seen a new yoke or a rebuilt yoke that after installation still has to much clearance. If you have what is the fix for this, or is there a fix.

Shim the clutch pack

 

The kids correct. If the posi is a stock spring setup then you may have too much play in the posi. How much yoke endplay do you have, .030-.040"?

With a tuned posi then I usually I have to face grind the yokes to set the endplay between .005-.010".

 

I really don't remember what the end play was. I am pretty sure I was at about .010 but I will check it all out this winter when it is on the bench/stand.

If you are already tight by tuning the posi and the clutch pack is shimmed to get the right preload is it possible to still have to much clearance? You just can't gp throwing more shims in the clutch pack. It does not sound like you have run into this and I'm not saying I do have this but just curious.

 

Gordon,
With regards to tuning the posi, you tune it to set up the spiders not the yokes. I have had new yokes come in that were loose but they were out of range. I can't say spec because I never found a published spec for yoke face to snap ring but I use .187 +/- .005" I had some come in .170-.175 and returned them. You are correct on shimming the spiders, you can only go so far until they bind and then you have to back off .005 or grind to size like I do. With yokes in the .182- .190 range with a tuned posi they usually fall in the .000-.003 endplay range. That is why I have to grind them. Again, no spec but I like to set them at .005-.010"

 

I was really just curious on this subject as I know you have done a lot of them. It really does not apply to my setup as I removed the snap rings all together due to the 6 link setup I have in mine. I'll get in touch with you this winter if I have or show any signs of strange happenings inside the diff. Thanks again.

 

Ok Gordon you know where I am. How much do you think the yokes float with the 6 link?

 

Really not much at all. I moved the trailing arms full swing without the spring attached and did not see much movement at all. I can put an indicator on it this winter before removing and check it out. That was kind of the design behind the 6 link to limit the movement. As we all know it will move under stress also.

 

would it be correct to say..

that if my side yolks have excessive endplay, while driving, the yolks would beat back n fourth untill eventually the half shaft would grind into the rear?

 

that if my side yolks have excessive endplay, while driving, the yolks would beat back n fourth untill eventually the half shaft would grind into the rear?

Yes, espcially on the 75-79's. If let go long enough they will grind the housing boss down until they hit the yoke seal by then it may be too late to save the housing.

 

Hard to say as driving style and maintenance play a big part as does the way it's rebuilt.

Example. I took my son's 75 and built it. The posi case was hit by the pinion when I opened it up. In most cases it would have been replaced but since this was a car I was going to see all the time I wanted to test it. Plus I knew the kid was going to beat it to death.

Under "normal" driving conditions I expected it to go 100,000 miles but my son's normal driving stlye was full throttle, 200' burnouts through all 4 gears. The rear tires lasted 8k miles from new to bald. The posi cracked about 8-9k miles into this routine.The ring gear and caps were rock solid, the cross shaft just could handle the abuse and the weakened case finally let go.

So again I really couldn't say, everyone is different. The one I did in my 72 is fine and I expect it to go many thousands of miles with the correct oil in it.
In fact I don't expect to ever put that kind of mileage on the car anymore. 1-2k miles a year is all I do now.

Some rebuilds I've seen have a lot of yoke endplay in them as the posi's were left sloppy and in stock form. I would not expect those to last as long in comparision to a tuned unit. Also the ratio of stock unit to tuned units out there is very high. Not too many have the tuned posi's unless the car owner,Tom's, Mike or I did them. I don't know who else puts that kind of labor time into them?

 

thanks for your time, you've been a big help... one more question please. How much endplay should I accept before I go back to the place that put a rear in my car for $2500, and tell them they goofed? I put 1k to 1.5k miles on it since it was done in aug, 07.

 

Hard for me to comment on another job as I don't know how it was done. I can guess, and that would be it was a stock setup. All the diff I do I have to grindthe yokes faces to set the endplay to between .005-.010" max. With a stock posi setup .030 is about what you will see. As Mike said they can be all over the place and I've had some new and rebuilt yoke come in that were not machines correctly and were way off. In your case I would ask the guys who did the job how they did it and what the spec's were on it.

 

If it was set up right with good parts about .020 max. and that's being generous. Absolute worst case with a lot of hard miles .050. If you have more then that something wasn't set up right or is wearing out very fast.
Mike

 

Gary,
How do you feel about button welds on tips of the side yokes and ground down on side yokes that are too short and the person doesn't want to spend the cash t fix it correctly?

 

Ryan,
I have not done that but have heard of guys doing it. If the weld is hard and neatly done then it would work. The spline portion doesn't matter on the end of the yoke. Me, I prefer to replace the yoke and fit them but again it has worked in the past.

What I have not seen is a good fix for the housing once the yke grinds it down into the seal, anyone know of one?

 

That's my next project as soon as I get caught up on other work.
Mike

 

The only thing I can think of is to setup the housing in a mill and bore the side and install a steel sleeve. Not sure of the wall thickness in that area and the radius. It might be less costly finding a used diff, that's what I've done.
The one in my 75 was ground pretty good but I was able to reuse it with no leaks. I was watching it to see but that's the one Kevin took care of for me:thud:

 

differential

help ive got nearly an 1/8 of an inch play in the yolks where do i go from here,great site lads

 

I'm sure Gary will chime in but it looks like you will be pulling the rear and pulling the cover off to see what is worn. You might get lucky and find the snap ring off but more likely you will find the axle stubs worn over.

 

What year is the diff? The later C3's (75-79) had bad side yokes,they were not hardened. .125" is an indication of several possible areas.
1- worn yoke
2- posi setup
3-cross shaft wear in the case
4 some vendor's rebuild:laughing: Yes, some people have been told .100 is normal- it is not.

 

63-79 differential inspection

differential is 1971,when i bought the car some years ago after driving the car approx 400 miles home the diff started to groan on lock when reversing,oil was low,topped it up with gm oil and additive didnt give any problems since just the excessive play in the yolks

 

The only way to tell what's going on is to open it up for a look. Could be any/all of what I listed above.:thumbsup:

 

I'm doing a 72 diff now and the yokes are original. I reconditioned them and here's a cool tool my buddy had. Checking the original yoke hardness. Still good. I have been able to reuse many original yokes from the 60's - 73. The later yokes are not as good and softer.

 

it's been a while since I had my materials lab in school where we did hardness testing. Are you going off a Rockwell scale? Is this one of the tools that puts the dimple in the surface? What's your acceptable hardness range?

 

yes rockwell scale, about 60. This unit is a Wilson portable hardness tester. I wasn't sure how close it was but checked it against a 12 bolt axle I had hardened and it was right on.

 

Question for us n00bs

Gary,
I have a 79 and had to move her from my garage to another garage for storage. She drove very well and I didnt hear any whining coming from the diff apart from a little when in reverse. To be honest, Im not sure if it was diff or trans noise.

Anyway, what is the procedure for testing endplay/movement etc with diff still in the car or is it something that can only really be checked with the unit removed?

I will be doing a body off but would like to drive it a little first just to get some idea of what I need to do with regards the engine, trans and diff.

Thanks in advance.

 

You can check them in the car to a degree. Remove the 1/2 shafts and mount an indicator against the yoke to check the endplay. However endplay is usually a combination of yoke wear,posi setup and posi cross shaft play. Replacing the yokes alone in most cases is not enough. A lot of rebuilders are sloppy and don't get the clutches setup as they should be, so you really have to get the unit apart to get an accurate check.