Trailing arm hitting differential

[77-4speed]

Hello all,

My 77 has been making a strange sound occassionally. It makes a sort of dragging sound when turning hard left. So I slid under the car and it seems as though the rear trailing arm is actually contacting the differential cover. There is a hemispherical scratch mark on the differential case on the passenger side where the trailing arm bolts "would" hit the differential in a hard turn.

I know I need to replace the bushings all around but I was wondering if you guys and gals think anything else needs to be done.

I have attached a pic to show what I'm talking about.

Also, the drivers side wheel well has a bump stop that is also pictured. The passenger side does not. Does anyone know the name of this part or where to find one? I have searched high and low to no avail.

Thanks,

Russ

P.s. the pic is not of my car, it is just for demonstration.

 

[Bob Chadwick]

Russ,

I'm no help on your question but am curious about your choice of bushings; are you going to use rubber, poly or graphite impregnated poly when you do the work? I'm looking at doing my front end in the next month or so and don't know which way to go.

As I understand things, rubber is a softer ride but doesn't last as long, poly is firmer and more durable but squeaks and impregnated poly doesn't squeak but maintains the firmer ride and durability of the poly.

Let me know if you have considered any other choices.

Bob

 

[Bullitt]

The trailing/control arm bumper stop can be found at Eckler's: Part #2039-$16.50ea., Corvette Central: Part #583007- $14.95 or Dr.Rebuild: Part #7504281- $14.30ea. Try giving Corvettes of Houston a call off of I-45 North, too.

--Bullitt

 

[77-4speed]

Thank you Bullit!! How do you make it seem so easy when I know it is so hard?

Actually Bob,

I hadn't heard of the impregnated bushings. I might have to look into that. I was originally planning on using the rubber bushings. My expedition squeaks because of some poly parts in the front wheels and I can't stand it. It sounds like a cheap toy! So I planned on using rubber and maintaining them. I have been told that properly maintained rubber bushings should last 15-20 yrs. Far longer than I'll probably have this car. Plus I'm not looking to go out autocrossing. I just want a comfortable cruising ride. I don't need it to handle like it's on rails.

Russ

 

[wolf_walker]

The poly will not squeak if properly and generously lubricated with the correct goo. I've done several old cars with them all around and never had a squeak yet. I do like the look of the poly-graphite bushings though, but I'd lube them too just to be sure.

The bolts you show in your picture don't actually move in relation to the rearend other than rotating round when the wheels move, try jacking the car up so as to keep weight on the suspension on that side and rotate the whell while looking under there. The bolts could just be too long and contacting, or maybe the heads are suposed to go toward the differential instead of the threads?
I can't remember off hand. I do remember mine were very very tight, and when rotating under full drop, no weight on the suspension, the caps of the joint would almost bind with the flange on the differential, but full drop dosent occur often and not for long when it does, so..

 

[Bullitt]

You're welcome. Have those differential yokes looked at, also. There's no telling what the extra side load from the interference has done to them. Better safe than sorry.

I don't know if the later years use the same set-up as my '71 (some years used u-bolts), but my bolt threads face the differential. The head of the bolts are visible from the outside, so to speak. Otherwise, it would be too complicated to just drop the half-shafts when changing the u-joints.

--Bullitt

 

[77-4speed]

wolf_walker,

The scratch marks are hemispherical on the differential case and are consistent with the bolts rotational travel when moving. I'm pretty sure that the threads do go toward the diff. because that is how it is on the drivers side, and the drivers side doesn't hit. Where have you seen the poly-graphite bushings? I have been looking at Vettebrakes and all they have are rubber or poly.

Bullit,

what are the differential yokes? I planned on taking the car in to a local Firestone to have the guys give me a list of what needs to be replaced: which bushings, shocks, etc. I would like to know what the differential yokes are so that I can explain that to them as well.

Thanks,

Russ

 

[Bob Chadwick]

http://www.vettebrakes.com/search_r...Search&iLevel=1&btnSearch.x=32&btnSearch.y=13

 

[77-4speed]

Holy Crp!! I didn't realize the poly bushings were that expensive! Geez, there's not that much more material or work in making poly bushings. I know, I'm a chemical engineer. That sounds like typical manufacture price fattening for the "latest and greatest".

Well, at $190 for the poly bushing kit, I'll probably stick with rubber for about 1/3 the cost.

 

[69MyWay]

You have bad side yokes on the diff. The C clips on the inside must have popped off, and the yoke has worn its way into the housing.

You need to park the car ASAP, pull the rear diff, and take to a shop.

If you are into shipping things, I have a local guy that can fix it up fast.

Otherwise, you could do this yourself as it won't really require any special tools. However, you will have to beat the ^$$##$ out of the side yoke, or use a slide hammer to jerk them out of the diff since they have been work up in there. You will find on the inside of the diff that they have mushroomed out making them not simply able to slip out when the clip has been pulled.

You can get new side yokes for like $100 each or so.

Good luck.


Chris

 

[77-4speed]

Chris,

Corvettes of Houston here said it would be about $600 in labor, about 8hrs to replace the side yoke.

I didn't realize this would be such an expensive repair. Does that price sound about right? I don't know if I can do something like this myself. The biggest job I've done is replace the radiator and the calipers.

Thanks,

Russ

 

[69MyWay]

Does $600 include pulling it and all? If so, not too bad of a price. Yanking the diff alone is a fairly involved job (mainly dangerous when you are doing in your own garage without a lift.

I have a buddy here that would be able to do this for $250 or less, but you would have to pull the diff and ship it to him. At that time, you could also change the gear ratio if desired, etc.

He may be able to do it for less than that if he can get a good price an a set of nice used side yokes.

 

[Bullitt]

There's Corvettes by Ray, another shop you could call. I can't remember where that's located though. He should in the yellow pages. If you honestly wanted to do at least the removal on your own of the differential carrier and the reinstallation, I could lend a hand. That way, you're just paying on the differential work. Let me know and maybe we could hatchet it out.

--Bullitt

 

[wolf_walker]

69MyWay seems to have covered it, I assumed you'd notice if your side yolks were worn enough to let the thing move THAT far in, glad you decided to ask, that's dangerous!


Poly's always been pricy compared to rubber, and it's not new by a long shot. You get what you pay for though I guess, I'm content with the cost usually.


There should be a C3 F.A.Q. post explaining to everyone that one may as well yank the suspension, brakes, stearing and rearend out and rebuild them if they have more than about 50K miles or so on there Vette. It's hard to hear, but that's what it comes down to, they just don't last in a stock configuration that I can see. It's hard to keep telling people they have to spend such and such thousand dollars to even make them safe and drivable.
But if they havent already been replaced, there either bad or heading that way rapidly more often than not.


I've been through this with several people locally, they either had or bought a "pretty" vette, but underneath it's falling apart and leaking everything, at barely 100K miles. Then they don't understand why everything's so expensive for them. ugh..

 

[77-4speed]

Chris,

$600 is only the labor cost for pulling and installing the new side yoke. It does not include the cost of the side yoke. Would I have to replace both yokes or just the bad one?

Bullitt,

I think I'm going to take it somewhere to have the side yoke looked at. Nothing against you Chris, but I'd like to make sure before I plop down the cash that I don't have If you think dropping the diff is something we could do, I would definitely be interested in trying to get together. I don't have a lift, only floor jacks.

If the side yoke needs to be replaced it'll probably be a little while before I can scrape together the money, depending on what it would cost.

Bullit, I'll PM you with my phone number.

Thanks guys,

Russ

 

[Bob Chadwick]

I hear what you are saying Wolf. Even if the car is in good shape, the previous owners stopped maintaining the little things, like the clock, tach, a/c, etc., and when you get the car it has 20 little things at $100 or more a pop, it adds up quick.

Bob

 

[77-4speed]

When I bought the car I had a "certified" mechanic check everything out. He basically said that the car might need new shocks and pointed out the obvious aftermarket stuff. He actually said that the underbody was in pretty good shape. The previous owner said that he put new shocks on the car about 2 yrs ago but did not replace the bushings at that time.

This is my first real project car aside from helping on my brothers 65 mustang, and it is by far more complex. I don't know what the side yokes look like but I can say that the passenger and drivers side trailing arm connections and both sides of the diff. don't look all that different. It doesn't look like one of the trailing arms is any more "inside" the diff than the other.

I guess it's a moot point as I'll soon take it to be looked at.

-Russ

 

[69MyWay]

No worries on my end. However, I have seen this EXACT problem before. I stumbled upon the solution because the rear diff I was working on needed to be rebuilt anyway.

When I took it to my buddy, he was the one that showed me the side yokes. I could not believe me eyes. I had not notice how they had mashed up into the diff housing and were putting pressure on the center member.

I hope this is not your problem, but other than the wrong length bolts as a possibility (which means it had to be scraping from the day one that the larger bolts were put in), there is no other explanation for the side yokes to have moved so inbound that it now rubs the housing.


Good luck, keep us posted.

 

[77-4speed]

Chris,

Just to clear it up, they only scrape on hard left turns. Also, the bump stop on the passenger side is missing. I don't know if it is possible for the bolts to scrape on full travel in stock configuration without the bump stop.

So, I'll have it looked at hopefully this weekend and keep you guys posted.

-Russ

 

[wolf_walker]

Just remember, it will all be worth it!!