63-79 Differential Yoke inspection

14798 Views 41 Replies 12 Participants Last post by Metalkid, Jul 12, 2010

gtr1999

Discussion Starter · Jun 10, 2007

8

I see and get a lot of questions on wore yokes in an otherwise good differential. Guys find a lot of endplay~over .050" and want to repalce the yokes,seals,and bearings. If the yokes are worn a lot then all the metal grinding dust is in the oil, bearings, gears,ect- I would rebuild the unit in most cases and that is outlined in the "sticky" post.
This is for you guys who are not comfortable tearing down the diff, whether this is from lack of tools, work room or just don't want to do it.
First you have to see if the yokes will tap out. I use a long brass rod to drive them out but one in a while they are mushroomed pretty good and you're not going to drive them out. In that case you have to grind the ends and remove them. Try to use something to catch the chips. The seals will pry out but unless you have a 3 jaw slide hammer that will grab the bearings I would leave them in. They last a long time and as long as they feel ok leave them alone. Don't expect the new yokes to take up endplay to the point I fit them, probably not going to happed with a stock posi setup.

Here is a good one to look at. I had to grind this one out,but I was rebuilding the whole thing.

Here are the 90* snap ring pliers I use. These were given to me in 1977 when I was a kid rebuilding Bridgeport Mills. I haven't seen one like this in years. The ones Sears have aren't bad but most I see are junk.

Ground end

I always fit my jobs here I'm grinding a new yoke to fit the endplay to .005"

Done

Here you have the seal tool you can make from any junk screw driver you find for a $1 at the flea market.

Have Fun, I'd still rebuild it if it were mine, but you're the boss.

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gtr1999

Discussion Starter · #2 · Jun 14, 2007

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

matchframe

· #3 · Jun 14, 2007

gtr1999 said:
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!!

yellow73sb

· #4 · Aug 11, 2007

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

SmokinBBC

· #5 · Aug 11, 2007

yellow73sb said:
I have about .25" of end play :surprised :surprised

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

yellow73sb

· #6 · Aug 11, 2007

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

Yeah. I have the whole diff out.

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SmokinBBC

· #7 · Aug 11, 2007

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.

gtr1999

Discussion Starter · #8 · Nov 16, 2007

2

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

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Gordonm

· #9 · Nov 16, 2007

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.

yellow73sb

· #10 · Nov 16, 2007

Gordonm said:
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

gtr1999

Discussion Starter · #11 · Nov 16, 2007

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".

Gordonm

· #12 · Nov 16, 2007

gtr1999 said:
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.

gtr1999

Discussion Starter · #13 · Nov 16, 2007

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"

Gordonm

· #14 · Nov 16, 2007

gtr1999 said:
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.

gtr1999

Discussion Starter · #15 · Nov 16, 2007

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

Gordonm

· #16 · Nov 16, 2007

gtr1999 said:
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.

silvershark

· #17 · Nov 28, 2007

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?

gtr1999

Discussion Starter · #18 · Nov 28, 2007

silvershark said:
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.

silvershark

· #19 · Nov 28, 2007

gtr1999 said:
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.

under normal driving conditions, how many miles would you expect to get from a rear that was built right?

gtr1999

Discussion Starter · #20 · Nov 28, 2007

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?

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