Got a leaky driver side yoke seal on a 65k mile 81
I bought but haven't driven yet, been rebuilding.

The yoke on the leaky side has side play of .012"
per a dial indicator. The other side doesn't leak
or even seep, and has about .005" side play.

The (excessive?) side play seems to be the cause
of the leak.

I've got a factory service manual, but I can't find
any tolerances for that in there.

Anybody know any tolerance range for side play
in the yokes?

Is it likely the yoke is worn, or is it possible there
are other problems inside the diff?

Thanks!

 

I have looked for specs about diff yoke side play but have not found any info. The only info I have found is a yoke is worn out if the chamfer on the end of the yoke spline is gone. Thats got to be .030 or probably more. I don't think .012 is excessive, you may just have a bad seal.

 

 

I don't think it is excessive. Mine is in the .2xx range on one side, that's excessive.

 

I had the same problem but a lot worse. I had 0.035" on one side (with reco yokes) and 0.015" on the right side.

This is VERY noticeable. I can make the yoke CLUNK with my hand on the bench. With 350HP pushing the rear end I am sure that it would be both noisy and cause additional wear.

I guess 0.012" is OK but does it pass the clunk test? The regular GM books don't give a tolerance.

The "Chevy Hi Perfromance Manual" says less then 0.005".

From what I understand there are six ways to achieve this (and combinations of these) that I know of. In any case you need to pull the rear end and take of the rear cover to inpect and if needed remove the yokes to solve the problem. If the seal is blown then they are cheap but the diff needs to be pulled. Mine also blew and I think the reason was the in-out thrust of the yoke was stressing it. the in-out can also act as a pump action to let oil out (as mine did).

1. Properly set up clutch pack - with spacers etc. Do a search on GTR1199 and he tells in detail how he did his. His paper is in the corvettefaq.com website. I think this is the optimum solution BUT not within the capabilities of an average weekend mechanic.

2. Machine a wider slot in the yoke and add a second circlip like NorvalWilheim did. This is a cheap and VERY effective solution but does involve machining the yoke. If you have access to a machine shop then this is a great fix. You will need to measure yoke end play, the hardness of your yokes and then get the machining done so the new slot width and two circlips will remove the end play

3. Add a shim between the circlip and the clutch pack. This has to be hardened steel and can be difficult to fabriacte it will look like a wire ring because it will be so thin. You need to measure the play on each side and machine acustom shim (ring) for each side. ie if left yoke end play is 0.035" then machine a 0.032"-0.033" shim. the right may be different so you need to measure both. Again this relies on access to a machine shop.

4. Replace the centre pin for the posi. This is the pin that holds the yokes out. They are available from GM. This will probably (depending on wear) give you about 0.0013"-0.005" reduction of yoke end play, Probably to both side as it should have worn at the same rate over the years unless you always turned one way on a racetrack!. Mine had 100K miles and had about .003" of wear.

5. Get exact length yokes. Hard to do as there is no real quality control on vett yokes. A lot of peopl say that .025"-0.040" is acceptable. The only way to really check is to stick the yoke in the rear end and put a dial indicator on it and see the play, or alternatively stick feeler gauges between the end of the yoke tip and the centre pin. This option is desirable but hard to achieve.

6. Weld the tip of the yoke to make them longer. All I can say is YUCK! This could work but three things scare me. First the metal properties of the yoke will change with the heat of welding. Second you need to get the end machined after the weld to make it a nice smooth machined surface (it rubs on the centre pin). And third you need the weld to be hard enough(but not too hard) that it won't wear away and leave junk in your rear end OR wear the centre pin (Don't ask me how I know!)

I went with option 3 and 4. I was unfortunate enough to experience option 5 hence my change to new yokes and option 3/4. My logic is this. I am too chicken to do option 1. I had my rear end profesisonally rebuilt and the pos, ring, pinion etc are in great shape. I should have my new shims next week. This will remove the play without voiding any warranty on the yokes (just bought rebuilt ones). I am going to buy a new pin (option 4) and put it up for a few years. If I get the play down to .002" now then when it increases in a few years due to the yoke ends wearing then I will replace the centre pin and get it back under 0.005".

Thats my 0.02. Good luck.


Credit to the gurus before me GTR1999, Norval, and the other guys who have battled with this "QUIRK" of owning a vette.

 

Stingy, thanks for the kind words, although I wouldn't call myself a guru by any means.

Max, .012" is not enough to cause the seal damage and isn't excessive. I drove my 69 years ago with worn out yokes,.125" or better play and could feel the rear suspension shift under load at 65-70 mph. MY 72 had .040-.050" endplay and it ran fine. You have a bad seal which will require removing the rear end to replace them. Check to see if :
1- the pinion seal is leaking
2- side yokes are leaking
3- if the yoke hit the housing and ground into it.
4- the housing is damaged in any way.
I use NAPA side yoke seals,they are in stock and work well. I had some seals that were in the rebuild kits and the OD was too big. the seal would distort when installing. Is it possible someone changed the seals in the recent past?

Let me know if I can help, I'll be off line most of today working on a couple of vettes. I'll check back later.
Good luck
Gary

 

I don't believe there's a spec on yoke end play. In Corvette Fever, Feb/04, in Q&A section, it states that 1/16" end play is generally considered to be max allowable. Repair if over 1/16".

 

I really appreciate all the input, believe me!

Trouble is, the yoke play in question is not
end play (in & out) but rather side play,
"up and down".

I'm pretty much settled on making myself a
6 link (all kinds of parts reasonable in
McMaster Carr www.mcmaster.com and you
can buy from them over the net) so I'm not
going to be concerned with end play, anyway.

I'm just hoping I don't have to disassemble
the rearend for some reason. I am going
to take the cover off and clean it out,
check it for wear particles, and install
fresh lube (have the whole rear end out
now, ended up having to rebuild the whole
rear suspension, then I discovered the
body mounts are also bad, and I've got
rusty floorpans, and the area around the
#2 body mounts, the bottom of the door
pillars, is also about rusted away. Am
"discussing" this right now with the scam
artist I bought the car from who assured me
it was in good shape with only a couple
minor specific exceptions. Being new to Vette's
I didn't know what to look for, but sure am
learning fast - things I really didn't want
to know :-((( )

Anyway, going to do whatever is necessary
as long as I've got the thing pretty much
torn all the way down.

BTW - (81 car) the spacers above and below the
stock composite spring are bad and I can't
find anything anywhere. Any ideas?
Spring is fine, just need the spacers (hard
rectangular blocks).

Thanks much!