I have been experiencing vibrations and noises from the rear of the car after a long drive and especially when I'm making very slow turns. I figured it was the rear diff getting hot and the oil in it being very old (possibly original from 79?) so after searching through and reading a few posts out here, I thought that was the problem and brought it to the shop today for a rear diff oil change. The service dept just called and said while it's there, I should replace the left and right yolks which are severely worn.

My questions:
Is this a needed replacement common for a car with 90K?
Should it cost ~$1,000 for parts and labor?
Is it worth doing sooner than later or can I put it off for a while - what's the risk?
I'm NOT a mechanic by any definition so any other advice or comments would be greatly appreciated! Thanks in advance!
-Kevin

 

Read GT1999's posts. There is lots on this subject. If it was mine, I would not be doing just the yokes. Go through the entire diff while you are at it....otherwise you will be back in there soon. But short answere....yes this is typical. Also...make sure you are at a shop that will take the time to set it up well including new bearings and quality seals.

When done...you will also need an alignment. Have you noticed the top of your rear wheels leaning inboard? That is another sign of worn yokes.

Oh.. your other question. Yes do it now. They will start eating into the diff case which means you will likely be looking for a complete new unit. I am sure there are safety issues here too.

 

Yes these are common wear parts. $1000 is about right IF they rebuild the diff as well. $1000 to remove the diff, slap in some side yokes and button it back up is way to much. Make sure you get side yokes with hardened ends so they won't wear away nearly as fast. Depending on how bad they are, and your other suspension component, I would do these right away. The hardened side yokes are $90 each.

 

Thanks for the info. I told them to hold off for today. I need it buttoned up for a parade on Wednesday and the parts were going to be a 2 day wait. I actually received an offer to buy my car for a pretty good price at a cruise-in last Friday so I'm not eager to dump a grand into my car if I'm going to sell it next week and not see any of that money in the purchase price.

 

Do I need rear end Yokes, or just a fluid change?

When you tear down the rear end of your car (1963-1979), the first think you should look at is the rear end yokes. The driver side yoke is the least likely to wear out. Yes this is common for a yoke to be bad, but the passenger side (drive side) is more common!

To inspect the yokes, take off the snap ring and pull the yoke out of the side of the rear end. If no snap ring is present, then after you remove the yoke inspect it for the snap ring groove. If there is no groove present (seen picture with snap ring installed) then the yoke is for sure defective or bad!

The best way to tell if a yoke is bad is to look at the tip. On a new yoke, there is a fluted edge about 1/8". (See picture). If this is gone then yes the yoke needs to be replaced. Failure to replace a bad yoke will result in the yoke shield wearing on the part of the rear end housing that holds the side yoke seal.

It is not un-common for the passenger side yoke to be worn, but for the driver side to be worn out is un-common! (Usually driver side failure is a direct cause from not changing the fluid in your rear end).

Many cars have positive traction rear ends. Do not confuse "duck waddle" while going around a turn with a bad yoke! Noise (popping sounds) heard on slow turns may be the lube in the rear end and the posi clutches sticking. The positive traction rear end units require the lube to be changed about every thirty to forty thousand miles. To do this you need 2.5 quarts of lube and 1 can of positive traction additive.

When you feel what we call duck waddle when turning, this means the clutch's are sticking in the posi unit and the wheels are in direct drive of equal proportion. Something has to give and thus you create what we term duck waddle. If you are feeling duck waddle then an additive and lube change may solve (and will quite often) this problem. You might need two cans of additive and you might also need to change the fluid after a few hundred miles to free up the clutches in the rear end.

Van Steel is correct too! If the car is torn apart, and the yokes are bad then go with the harden tip rear yokes. If the yokes are bad you might want to consider doing the entire rear end too! The metal off the worn yoke had to go somewhere, and in most case's it will end up in the oil which will eat the bearings up! The carrier, side yoke, front pinion or rear pinion bearings may be shot from the metal in the lube.

Establish what the cause is before spending the money.


Willcox Inc.

See link for picture:

http://willcoxcorvette.com/product_i...ducts_id=24512