Hi,

Another problem found yesterday. I had the car in my service shop on the lift and accidentally one mechanic found that when pushing in the top of the wheel, the side yoke moves in and out of the diff. I think on the driver's side it's slightly more than half an inch, on the other side it's a bit less.

I've been browsing other topics here and on other forums. Ofcourse everybody say what and how to replace, but nobody has said much about how dangerous it is to drive like this. I read one guy saying to wait until winter if possible (I wonder - is it possible?) and another one said he drove 4-5 years with a playing yoke until he replaced them.

I haven't planned on spending such amounts of money right now but I want to know if it's ok to drive the Vette as it is.

I have heard some sort of screeching or metal-to-metal noise coming from the rear when making a tighter left turn and accelerating from halt. It only sometimes comes when starting from a stop, not when driving around, and only on a stronger left turn. I don't know if this noise is related to this or it could be also brakes or something.

Thanks for all the help!

 

The drivers side you said moves 1/2"--that means the snap ring has fallen off the shaft. If that snap ring finds its way in between the ring gear and pinion gear it can lock up the rear wheels-- thats probably the worst case scenario. With that kind of movement I would be hesitant to drive the car but on the other hand I've seen people drive the car for years after finding this much movement with no problems. Its your call.

 

I would get it fixed. I found out I had the same problem when I started to replace my trailing arms. Driver's side had about 1" of play in it. I got it fixed immediately.

 

I see. So what do you think does the fixing involve? Just the clamps or new yokes?

Done by a professional, is it a long/hard job to get into the differential?

 

The diff has to be removed from the car because the cover is also the mount.
IMO 1/2" play is huge. The camber is changing as you going around curves. I'd fix it now. It will probably need new yokes and a new differential pin. you can price the parts easily enough, but IDK how many shop hours you'll get charged.

 

Maybe this thread give you an idea of what direction you should go.PM Gary (GTR1999)he will give you info.
http://forums.corvetteforum.com/c3-t...e-w-paper.html

 

Okay... Firstly I appreciate all the information and it seems like I need to go the fixing route. Perhaps it's still okay to drive it around since I have driven it a lot already without any further issues rising. I guess I should just stay away from longer road trips. What do you think?

Meanwhile, is there any chance you could estimate what parts I'd need to order? I guess I'll have to place the order from Willcox and since the parts need to be shipped to the other side of the world, it's better to have all of it ready. Both side yokes and the diff. pin - got it; but any other not remarkably expensive items which MIGHT be shot and should be replaced while the diff is off?

Thanks.

 

I will offer a very different opinion, do what you like with it.

There's thousands if not tens of thousands of C2/C3 Corvettes running around for years with worn diffs just like yours. In most cases the owners have no idea that the side yokes have lost their circlips and the side yokes are 'loose'. You yourself were none the wiser until your car got inspected- nothing in the handling prompted you to start looking, just like the other thousands that are also 'in the dark'. I know of several owners who deliberately left the circlips off during the last rebuild. They report no negative effect on handling whatsoever.

If the engineering calculations are done properly, the only time a side yolk is completely unloaded is either when the car is off the ground or has slid sideways into a curb striking the lower part of the tire and wheel. While driving in a straight line there is approx. 300 lbs of force pushing the yoke inwards. While cornering this number changes by a only a minor degree, contrary to popular thinking. At no point does it reach zero or achieve a negative value.

The small circlips chosen by GM to retain the yokes are not a load bearing part of the rear suspension system. If they had been, something more substantial than a stamped steel circlip would have been used, and GM would have incorporated a method of controlling and adjusting yoke end play precisely, much as is done on the front and rear wheel bearings.

With all that in mind, I would continue driving the car as-is. I would also plan to eventually overhaul the entire diff and not just swap the yokes. Once the unit is opened up, you are likely to find many components that need attention up to and including the ring and pinion gears. Consider buying an exchange unit and returning yours as a core.

 

speedbird, the rear wheels are mounted by three links on each side. One is the control arm that the wheel spindle is in, another is the strut rod, and the third is the wheel drive shaft.
The wheel drive shafts and the strut rods work together to control camber through the arc the wheel travels through. If the wheel drive shaft is allowed to move in and out of the differential the way yours does, it can't control the camber of the wheel.
BTW, on solid axle Chevys, that "little" c clip is the only thing that holds the axle and wheel in the car, and therefore are a critical load bearing component. They are hardened steel about 3/16" thick and are held inside a recess machined into the diff. These are not superfluous little do-dads as some of the mis-informed among us seem to think.
IMO continuing to drive it is ill advised.

 

I'd get it fixed as soon as is convenient for you. You not only have metal floating around in the diff. but the side yokes are mushroomed and sooner or later they'll start wearing into the housing. That is what happened to me and I was told it was not rebuildable. I was lucky and found a different rear on Ebay for around $300 with a better ratio and very little side yoke play. That may be something for you to consider.

 

Interesting ideas and I sure don't plan on getting into anyones post. You can see how I do them in the link DW put up.

One thing I would recommend you check, with the amount of endplay you report,is to see if the yokes are hitting the housing. This is important to check because if left with slop the yoke will grind the 1/8 boss off the housing and start on the seal, then you may loose the whole deal. No one will give you a dime for it as a core either.

Your problem is a very common one with these cars. How it is corrected,if it is,depends on the mechanic/owner. With that much wear in the yokes chances are the bearings gears and posi case need attention. It can add up real fast,from a basic $600 master kit job to Thousands for a 1000 hp deal.

Your location may limit you for help as well. There are few here who do custom work on these let alone overseas.

I recommend you look at all your options and make the best decision for your use.

My 69 yokes were so bad years ago, I felt the rear end sway in curves at 65 mph on the highway.

Good luck, do your homework.

 

The snap ring on C3 Corvettes is approx. 1/16" thick, one third of what is used on solid axle Chevies.


Try to keep the name-calling to yourself, btw.

 

If the side yoke moves in and out 1/2" the differential needs a total rebuild. The end of the yoke is more than likely worn down past the c clip. All the metal from the yoke and the pieces of c clip have been floating oround in the differential for a long time. This eats up the bearings, spider gears, ring and pinion and the pin that goes thru the posi case. As Gary said the the side yoke may well have eaten into the side of the housing. Might be able to rebuild it, might need to start from scratch. Hard to tell how much damage there is until you remove it and open it up. In any case I would do it now. With a 1/2" of play it is real bad. The only way I could see possibly leaving the c clips out is if you had an upper strut rod similar to the dragvette setup. These cars do not come with that originally so as stated earlier the only thing maintaining your camber is the lower strut rod and halfshaft and to some degree the trailing arm front pivot bolt and shims and your halfshaft isn't holding anything. This is a common problem on these cars, more so on the 78 79 cars because of improperly hardened original sideyokes. The screaching, metal to metal noise you are hearing on left turns is probably the drivers side yoke grinding into the housing and in my opinion is a good sign that this needs to be addressed now. Because of this and obvious safety issues, I don't agree that it is good advice telling you to go ahead and drive it like that because there are a lot of them like that.

 

Are you sure the 1/2" is at the shaft or is it at the top of tire.If the 1/2" is at the top of the tire it may not be that bad at the shaft.

 

Hi

At 5 mm ( 0,200 " ) play means the joke is worn down so much that the circlip falls off.

1/2 " ( 0,500 " ) is a hell of a lot more. Nearly not possible !

If it realy is 1/2 " , there must be lots more worn down than only the joke.

Rgds. Günther

 

Things are getting interesting

I'm going to find out today how much play it really is.

Can somebody please just explain to me how it is "impossible" or "very bad" to have it move so much. As far as I understand, the only thing preventing the yoke move is the c-clip. The main reason for keeping the yoke position as strict as possible is to maintain correct camber setting. Am I wrong?

Now if the c-clip is gone, the weight of the car is still sitting on the wheels when driving and although changing by an x-amount when going through curves, it won't change as much as one can see when having the car up on the lift. Now - what is the extremely bad thing that the sliding yoke causes?

I'm just trying to get myself a bit more educated on this and make the right decision before starting to throw out money. And I will need to throw quite a bit of money into it, that's for sure

I used to have a Jeep and I have many friends in that community. I just talked about my Corvette issue with one of the guys and he said that with Jeeps it's usual that shafts slide in and out of the diff by half an inch or more. Sometimes it's even designed like this and even if not, it's not really considered too much of a problem. I know this car is far from a Jeep, in fact perhaps it's like comparing apples and oranges, but anyway...

Thanks for everything, guys!

 

Speedbird you surely have received a lot of opinions and very good information,not to take anything away from anyone's posts but I feel if you reread Mike and Garys posts you can make your decision once you go back and determine the actual amount of wear.When your mechanic moves the wheel watch the yoke as it moves out of the differential and see if it stops abruptly with a thunk, if it does the snap ring is most likely still intact. Look at the side of the diff case just behind the thjn metal flange on the yoke and see if you see shiny metal. Also look at the side of the diff at the point where the u bolts hold the yoke and see if the end of the u bolts are eating into the diff case (if you have u bolts).
The screeching you speak of on turns can be the yoke eating the side of the diff but I would lean more towards that noise being something more like a broken parking brake spring rubbing the inside of the rotor.

Moving on to a question I have for both Mike and Gary. Mike and Gary are engineers so I hope to learn something here.
Mike said "At no point does it reach zero or achieve a negative value". Engineering wise and having been under these cars a few times that sounds exactly the way it should have been engineered but Gary said " My 69 yokes were so bad years ago, I felt the rear end sway in curves at 65 mph on the highway". These 2 statements "SEEM" to contradict one another or do they ? I to have felt that rear end movement at highway speeds and have always thought it was possible for the worn yoke to move out of the diff. Thinking about it more after reading Mikes post this movement if possible seems as if it would only allow the top of the tire to move outward causing the camber to go pos but the tire that is on the pavement remains at the same place only rolling slightly over the face of the tire. Could this cause that noticeable shift of the rear of the car ?

As far as the yoke moving out of the diff it seems after reading Mikes post that that would be nearly impossible from an engineering standpoint unless the car did hit a curb as described. Mike just so I can try to wrap my brain around this do you think if you would crank the camber cam as far as it would go to pos camber would it be easier to unload the yoke and get it to come off the pin ?
(I do have a car here that has worn yokes I guess I could rig up a bolt slightly off the thin metal flange on the yoke and go out and whip the car around a bit and come back and look for a shiny spot where the bolt had rubbed the flange.)
As I said before I have felt this side movement of the rear of the car at highway speeds but have never come back and changed only one variable - the yokes - and then went back out to see if that changed the condition. It seems that many other things were also worn out and were replaced before re road testing.

 

If the yoke moves a 1/2" you either
1. have worn the yoke down past the c clip or
2. the c clip is just broken and has fallen off.
#1 is most likely. Either situation has large amounts of metal fragments and chunks of the c clip floating around in the differential mixed into the rear end fluid and flowing into the bearings, spiders and ring and pinion. The extremely bad thing this causes is for your differential to become junk and unrebuildable. It will also cause a lot of additional stress on your strut rod bushings and front trailing arm bushings that they really wern't designed to take causing further wear and play issues. If it is not too late you can get by with a basic rear end rebuild. At a certain point it becomes a much bigger issue turning into a rear end replacement and total rear suspension rebuild. Been there, It is not cheap. Either way you know for a fact there is a major problem. You also know it needs to be fixed and you should know that driving it as is it will only get worse and lead to more expensive repairs once you do them and could lead to catastrophic failure. A large chunk of c clip running through where the ring and pinion mesh is not a good thing.

 

This is my third attempt to respond; we are having power outages here with repair work going on locally after a major wind storm.

The quick answer to your question is that positive or negative camber is not quite the defining point. To actually 'go negative' on yoke loading would require first that you bring the pivot point of the tire (let's say the center of the tread) inwards so that it is vertically inline with the outer u-joint of the half shaft. At this point any side load on the tire would cause the yoke load to go above and below the zero point.

It is not possible to adjust stock suspension to achieve such a condition.

I knew full well that my orignal post above flies in the face of conventional wisdom but was offered as a counter point to the sky-is-falling crowd.

 

I for one am glad you did,I always wondered if it could unload short of a shot into a curb. Thanks