Clicking when I let off the gas
 

Something I've been noticing more recently is when I let off the gas in my manual 1985, I get a clicking sound. It's fairly high pitched and is describe it roughly as marbles in a tin can. I also get it when accelerating hard sometimes, or at low speeds (like in a parking lot I notice it). It goes away if I press the clutch in (and thus getting rid of the engine braking torque from the wheels).

I thought it was the wheel bearing, so I replaced that. I'm still getting the clicking. It's definitely coming from the rear of the car. I'd say driver's side but I replaced that bearing.

I also just replaced u joints in the main shaft. The half shaft joints have no play in them and seem fine-plus this noise doesn't sound like u joints.

Of course now I'm thinking differential. I can't think of what else it would be. Anyone have any thoughts?

Thanks!

My first thought was right hand half-shaft U-joint, per history with my '88.

Have you checked play in the drive-shaft U-joints?

I replaced the main drive shaft u joints. The half shafts seem solid so I didn't change them.

Is there excessive play where the drive shaft enters the rear of the tranny?

Nope

All my U-joints were tight like you describe. However, mine weren't making any noise like yours. But, since I was already going through the whole drivetrain I decided that I'd replace them anyway as they had 90K miles on them. Everyone of them were in bad shape and headed for failure. You are lucky, yours are talking to you before they fail. Tightness of the joint does not indicate a good bearing.

Ok you're right. They're not expensive or that hard, I should just do them for peace of mind.

Is it possible to remove the rear cover for the differential while it is still on the car, to inspect? I'd feel a lot better if I could take a look in there.

I think that would be quite a trick since the cover is what holds the whole differential in the car.

Yeah, I did some reading and realized that's a stupid idea.

I've been doing a lot of reading and the more I read, the more convinced it is the U-joints. It's more a 'ping' than a click sound, and every anecdote I can find on the internet of a pinging from the rear end ended up being u joints.

Only other thing I'm wondering-since I did the main driveshaft U-joints already, is there a chance I screwed them up? Nothing SEEMS wrong with them, they moved smoothly and in general the car drives much better than it did before. This sound didn't start at that time, but it's gotten worse recently. I actually think fixing one weak link made another worse, but wanted to make sure I didn't possibly screw the others up.

Got under the car again today. I'm now able to move the half shaft by hand. I replaced the wheel hub which apparently made the u joints deteriorate more quickly. That's what happens when you replace a weak link-the next weakest link breaks.

I'll be getting new u joints and putting them in soon. Hopefully that's the end of the drive train issues.

Do you really have to remove all the suspension to remove the half shaft? It looks like you could work it out of there if you just remove the u joint straps. I'm a fan of not removing things that don't need to be removed for a job.

No! IIRC, I've been able to pull my halfshafts by just removing the camber rod and shock mounts at the knuckle. Maybe not even the shock mount. You really just need enough outward movement to clear the yoke coming out of the diff. Once you have that end of the halfshaft out and below the diff, you can pull the splined end out of the wheel bearing.

Hello again BFENTY!

My rear half shaft joints were all nice and tight on the outside when I tested mine by hand from underneath and like Randy said above "they were falling apart inside". While out looking/shopping for parts at Corvettes@Carlisle I found a spare set of half shafts for both of my Corvettes and they were a GREAT deal so I bought 2 sets.

I had the Posi rebuilt in my C3 and they raised the rear end causing the half shaft U-joints to wear out very quickly. I ended up going thru all four u-joints in the half shafts in less than 6 months. My rear end is designed for the Big block so it has caps instead of the wire clips. After fixing the rear end and getting it down where it belonged I got on the throttle a bit too hard one day and I lost the left outer joint in a large BANG and sent pieces of u-joint all over two lanes of the road I was on. This is a very bad feeling to be stuck with a broken half shaft, fortunately I had new joints installed in the used half shafts I had purchased so I got my wife to bring one of them to me and I replaced it on the curb.

Use a quality SPICER brand u-joint when you replace the originals. If your car makes significantly more power than it did out of the factory then the stronger U-joints might suit your car better. I have gone to the harder to break non-grease-able type u-joints on my big block C3 and the standard Spicer's for the C4. Having a spare half shafts ready for action is not a bad idea, I sandblasted the used half shafts and powder coated them prior to installing the new u-joints. Then you put the shaft in a vacuum bag and seal it without any air until I need one ensures a lack of corrosion.

Half shaft U-joints can make a lot of strange noises while they are failing. We raised the car into the air on a lift and had somebody start it and put in gear and the racket was clearly coming out of the u-joints. I did the same to my C4 and the joints were silent. You might try this test on a lift or jack stands but you need to put the car into gear while the wheels are off the ground. Be Very Careful doing anything like this please!! I had lots of hands available when we did it at the Corvette shop. That idiot charged me $400 to tell me that I had a problem, no solutions available from him.

It wasn't until I spoke to the owner of Vette Brakes and Products and he told me that the correct bolt length is supposed to be 8" or 10" and I had 5" bolts installed by a Chevrolet dealer and that started the hole chain of events related to my rear half shafts. The bolts I am referring to are the ones that go into the holes at the ends of the rear spring on a C3.

The C4 half shafts are tight but not too hard to remove. I have a lot of Gleim jointed aftermarket performance suspension parts back there and they come apart easily. It is a good time to replace any loose bushings you find while you are in there. I rebuilt the rear of my 1988 many years ago when I detected a bit of movement back there. After using (Noisy) Polyurethane bushings on my C3 I chose rubber for the C4, even then they were a bear to install in some places. Lube all the bushings you see while you are in there! If you hear the noise coming from the differential that might be another whole issue. I would drain the oil out of the differential and then fill it with the proper type and weight of fluid.

The reason I had my posi rebuilt was it was clicking going around corners, they make a lot noise going around tight turns when the posi-traction parts are chattering. Sometimes a bottle of the Posi additive will quiet them down but not in my case.

Good Luck with your half shaft removal! As always I wish you the very best in getting your Corvette back on the highway soon!

Chris

I had that clicking in my 92. It was the bearings in the half shaft as others described. It is a pretty easy fix.

Thanks man, I really appreciate the support.

I have a sand blaster, I'd thought about blasting the shafts while they're out but I was worried that I'd screw up their balance if I did that. Sounds like that's not a big deal though. I'll probably throw some caliper paint on them too if I do blast them, just to make them look nice. No money for powder coating right now lol.

Hello again Bfenty!

Many years ago at Corvettes@Carlisle I went to the Eastwood tent and got a great deal on one of their $100 Powder Coating guns. I came home and bought a used household oven for $30 removed the burners and made it part of my powder coating station. On top of the oven is a box in which I spray the powder onto the part. and then I cook it in the oven below for 20-30 minutes at 400 degrees F. The plastic particles are not good to breath nor is the smell from the parts curing so I put the station next to my garage door.

Any part comes off either of my two Corvettes and I sandblast them and either spray them with Eastwood Epoxy Black which is really durable or just powder coat them. Sand blasting is most of the job, the final coat is just there to protect. Once you set up a powder coating station like mine you will find all kinds of stuff to powder coat. I have even powder coated aquarium light hoods shiny chrome and it does not corrode any more on a salt water tank. Powder coating is very nice to play with. Eastwood makes some really nice paints and powders that look like aluminum, chrome or even S.S. or other colors found on our Corvettes. By the way, I doubt you could upset the balance by cleaning it with a sand blaster. I do it after I removed the U-joint so I can clean the shaft down so there is no paint left. Cover the important holes while you paint the part, with powder coating you would plug the holes with silicone tape or plugs to keep from getting painted or powder coated. It is very easy to powder coat things, you have to have them cleaned and dry before it will stick.

CASWELL.com is another site that has some neat tools. I have been plating parts in Bright Nickel in my garage for about 15 years or more. First I sandblast, then clean and off to my Copper tank to build up a nice layer and then I go to the bright nickel which looks like Chrome with a blueish tint to it. Nickel has smaller pores and is way more resistant to rust or corrosion. Several of the convertible parts have been plated on my 1968 C3 and I can't tell. (I am Color-Blind) so it all looks good to me!!

I love to collect nice tools, the problem is I have less room for my Corvettes. I have a (2 car) "wood-shop" garage and a (2 car) "Car" garage, the wood shop is attached to the house and the car garage is a detached garage out in back of my house. Now if I convince my wife that garages are not "storage buildings" life would get better. My electronics shop is in the attached garage off to one side. Electronics stuff needs to stay clean so it is out of the way of normal traffic. I have too many hobbies. Corvette are a "Lifestyle" right not a hobby? I will be dreaming (and fixing) Corvettes until my last breath.

Have a great day and I hope all is well for you and your family!

Chris