CAMS69

69 corvette, on jack stands. Drive shaft gone.
How far should I be able to turn the pinion before it "engages" the half shaft yokes? I can turn mine approximately 1/8 to 3/16 inch before it " engages"
Is this normal? If not what's wrong?
Alan71. Yours seems to be apart like mine. Can you gently turn your pinion and gauge when the half shafts turn?

DUB

I would be more concerned about the backlash of the pinion to ring gear.

Then it would be how much end play do your side yokes have. If you side yokes can move in and out more than the thickness of a paper matchstick. The beginning of the end is occurring.

Then I would check the clutches in the diff....but without the driveshaft installed. It can not be done. But if everything is connected and in gear...if your wheel turns when you go and tighten the lug nut with a torque wrench set at 40 lbs/ft. and the wheel turns...the clutches are shot also. Which is common if your side yokes have excessive in and out play.

For what it is worth...if the diff gets rebuilt I strive for the side yoke in and out play to be at or very close to .08".

DUB

72LS1Vette

You could PM Mike (Tracdogg2) - check the spelling - for information. He is known as the best Corvette differential builder in your part of the country. The other best guy is in Connecticut but he is no longer on this forum.



Rick B.

Solid LT1

1/8-3/16 as in 12 to 20 degrees of rotation. TOO MUCH! 1/8-3/16 of an inch of travel at outer part of yoke probably OK in low HP Vette.

Peterbuilt

There is another "best guy" and he is in Charlotte, NC.
See post #2.

CAMS69

Outer part if yoke. The diff worked for the hour I drove the car around the yard before starting a frame off.
I've replaced the pinion seal , yoked seals , rear seal and fluid. The diff will not be used for probably two years so when I noticed this I wasn't sure if it was normal.

DUB

Replacing the pinion seal is something that should not have been done....while the diff was in the car. I WILL NOT do a pinion seal while the diff is in the car...PERIOD. The torque on the nut for the pinion is specific to getting the setting of the ring and pinion gear wear pattern and and backlash etc. There is a "crush collar" along with shims for this setting. If by some chance you either did not tighten the nut enough or went to far...it can alter the depth of the pinion just enough to create problems in the future. A few thousandths +/- is a big deal in some areas of your car. And this is one of them.

I can not tell you how many diffs I have seen come into my shop after someone replaced the pinion seal...only to either have teeth break off the ring gear..or the pinion seal leak again or teeth break off the pinion itself. And it can not be a coincidence that the diff was fine for years and years and then all of a sudden after the work was done...a few moths later...BANG...something breaks....on most of what I have seen.

Once again...how much play do your side yokes have when you push them in and pull them out til they stop??? Just curious.

DUB

CAMS69

Thanks for the reply DUB
The diff was off the car. I'm doing a frame off
And the car is going back together. Both yokes are .030
I was just curios when I could rotate the pinion slightly
Probably 1/32 to 1/16 inch travel at the diameter of the pinion threads.
I just don't know if this is how it was or if something was wrong before.
I only drive the car in my yard for minutes before I started the frame off.
I marked the pinion nut and tried to get it back. I guess if you could turn the pinion and notice if there is any and I mean any lag. It's so slight but I'm not sure it should be there. Thanks for your help!!
Easier yet. If you hold one yoke still with one hand and frag the pinion with the other can you turn the pinion ever soooo slightly?
And I mean thousandths?

CAMS69

DUB
I found this statement on another site. This sums up what I'm feeling. Absolutely no movement up / down or in / out on my pinion. I just feel / see the slight rotational slack. Can you verify?

First: grab hold of the pinion yoke and try to move it up and down and in and out. If you have any play at all you have bad pinion bearings. A little slack when turning it back and forth is normal.

Solid LT1

if I had never helped one of my good friends replace the pinion yoke seal on his SS350 Camaro, I wouldn't know how to build differentials today

I remember well the test drive, about 3 miles away from his house, first time he actually banged off a shift on the Muncie, then total carnage and rear wheel lock-up! The pinion had not been preloaded properly, we hadn't replaced the crush sleeve and it proceeded to climb its way into the Positraction differential case. Waited for a hour in the cold for tow truck, got the SS back to his house and the thrash began because he had to head back to college in 3 days and this was Sunday evening, we had been under the Camaro all weekend long, now it was a thrash with friendly advice from the auto mechanic we had both worked for. Ripped the rear end out of the Camaro, took down to the shop, ordered all parts we though might be needed and started to read the GM service manual. The Posi case was cleaned up, it was determined the pinion gear was still servicable, and away we thrashed. Used a pinion yoke holding tool made from the Camaros fastory jack and some scrap steel welded with a stick welder. That quickie job was still going strong 5 years and many drag strip passes later when the Camaro was sold.......Hope the poster knows about crush sleeves and pinion pre load.........

Solid LT1

Trully the only correct way to determine the shape of your differential is to remove back cove and start measuring clearances, starting with gear back lash using a dial indicator (should be between 0.006"-0.012".) Good differential work is costly, there are many vendors selling poorly refurbished C2/3 differential assemblies. Don't know what your end plans are for your Vette but, if you plan on keeping it for a while, your best bet is to have differential rebuilt for long term comfort and reliability (nothing like tooling down the road with a differential whining away...)

DUB

What "Solid LT1" wrote can happen. Due to the pinion nut being such a precise setting...anytime you mess with it you are "pulling the pin of a potential hand grenade".

I know many mechanics who replace pinion seals..and swear by it...but I seriously doubt that they would ever admit they had a car come back with the result that happened to "Solid LT1". An EGO kinda thing that occurs with many mechanics when one is looking at what the other is doing and shaking their head in dis-agreement on what is being done. I usually end up walking away with the thought that here is another mechanic ruining the profession and making US all look like we do not know how to repair things correctly.

IN MY OPINION:
I do not like the end play of your side yokes at .030". I strive to get at or around .008".

You can look up what the backlash specs are for your diff and see if that matches what you are feeling. BUT...as mentioned before...when you start to mess with the nut for the pinion...your can change the way it wears in with the ring gear. And now...it can be "ridiing" on teh ring gear differently...and can cause wear to the pinion or the rring gear itself.

When I open up a diff...I look at and inspect the ring gear because it can often let me know how it was wearing and if the ring and pinion are going to be used again. Hard to describe what I look and feel for.

If you have not replaced the side yokes...it may more than likely be required. Also...if you do replace the side yokes...or had replaced them with new ones...and you did not replace the pinion shaft....the side yokes can get damaged right off the bat due to the surface of the pinion shaft that the side yokes press against has been damaged due to age from the original side yokes. The long special bolt that holds the pinion shaft may also need to be replaced due to they can have a small crack( or bend where it will crack off) in the end and it it breaks...there is another "hand grenade scenario".

Also...checking the value of your clutches can still be done with a torque wrench and a home made set-up to hold the pinion while allowing you to try to turn the side yoke with the torque wrench. IF you plan on doing anything on the diff and assume that the clutches are good...and not knowing for sure.....is also pointless.

You diff is an area that is very specific and precise. It is taking all the power from your driveline and getting it to the ground. It is one of the major links if the chain...SO...if you have a great strong engine...an awesome transmission...very good strong solid U-joints with NO grease fitting in them....bitchin' tires and wheels...and a "questionable diff". A chain is only as strong as its weakest link...and if one of those links is a "zip-tie"...it does not take a rocket scientist to figure where the potential problem will occur.

I do not know how much more clear it can be explained. BUT...The choice is yours...and I do not have a "crystal ball" nor the "magic wand". So..I can not state that it is good or bad...but if you were standing at my shop and stated that you removed the pinion nut....WELL...I think you know how I would handle this.

DUB

CAMS69

DUB
I appreciate everything you are saying, thanks for the advice.