Something in the rear-end area of my '79 is howling, a resonance that starts at about 2800 to 3000 RPM, but not always. It's a bit tough to troubleshoot or narrow it down on my own. What are the likely suspects, and how can I check them with the car up on jack stands?
My guesses... any of the u-joints or spindle assemblies; wheel bearings; e-brake assembly (the rear cable is missing), something inside the differential. Anything else?

I don't know the repair/mod history of this car, I haven't had it very long and I've focused my attention on other areas until now.

..Todd

 

Did this just start occurring?

You mentioned RPM range but not MPH. What speeds does it manifest at?

Automatic or Manual transmission?

 

Automatic (TH350). I have only driven the car a few times since I've had it, and it's not driveable currently, I have the steering system semi-disassembled, and am rebuilding the column (so no steering column in the car atm). With that in mind, here's my answers: It was happening when I bought the car in Nov. '22. The previous owner mentioned it but didn't say how long it was doing that. From memory, it seemed to remain howling at any speed once it started, until I took my foot off the gas. Sorry, that's all I know currently.

 

I am sure Gary or GTR1999 will chime in here. Most likely howling is a result of a bearing going south. It could be the rear spindle bearings, differential bearings or internal differential bearings. If you are lucky, it is one or more U joints. Do you have a history on the car? Try to isolate the spindle bearings by removing the half shafts and check for play in the bearing by holding the rotor or wheel at the 3 and 9 position and again at 12 and 6 position. There should minimal to no play. The wheels should spin freely and smoothly. Next, inspect the U joints for rust. They should move and not bind. Also check to see if the yokes move in and out of the differential without too much endplay. If you put the car on jack stands, make sure the half shafts are horizontal and do not bind. I would not run the car while it is on jack stands. Doing so will result in damage. Good luck. Jerry

 

Good information thanks. No, I have no repair or mod history of the car. There doesn't seem to be any [obvious/visible] aftermarket parts outside of the engine bay, other than the long lowering bolts in the rear. My general plan was to check and replace bearings and bushings as necessary in the rear half of the car, and revert those lowering bolts. Just wanted to prioritize any likely howling suspects.

 

Is removing the wheels and tires sufficient to accomplish that? I guess I'll find out.

 

no
trailarm must be raised

 

If the noise changes when you let off the gas, my understanding is that is ring and pinion problem.

 

My impression, and it can be completely off base. It is based on 45 years around these cars and all the people I have met that were drivers, sellers, flippes, and conmen.

Usually, with a story like this, a new owner, happy to have a vette, buys someone else's problem or someone's scam. I hope that is not the case for you but man I have seen that happening since 1977 and today with inflated prices it's only worse.

If you get a whine driving and it sound like the rear of the car, it can be the diff or rear bearings in the TA. Usually, laying on the gas and letting up you hear the noise it can be pinion bearings or bad gear setup. Can also be new Richmond gears. If you can pull on a wheel stud and feel it move in/out that is not good. If you see the 1/2 shaft moving into the diff and out, that is not good. Buying a lot of common parts today, is not good as well.

Don't run the car in the air without the 1/2 shaft parallel, you will break a u-joint or the posi case in the diff and possibly get injured in the process.

Post some pictures of the IRS or directly contact me with questions. But if the car is new and it's been passed around, messed with, and sold, expect to get deep into it fast. Changing out rear bearing in the diff or TA is not hard- as long as you know what you're doing and have good tools. Exchanging everything back there for common exchange units may not result in what you want, and you won't know it until it's too late. Trust me on this. I posted a lot of threads and pictures the past 20 years, many of them are still up, do a search and not just here.

You need to address and build the car to your planned usage. Many sellers promote common basic rebuild, money is the influence behind most. The less expensive the work is the better, right? no, cheap is cheap no matter how it's packaged. If you are going to do the work, learn a lot before spending any money. Building an IRS for a 300hp car that is never driven is a lot different than building an IRS for a 800hp that is abused every time the key is turned. Know what you want and plan it out.

Good luck to you.

 

Well, there isn't really much of a story here. The previous owner was a tinkerer and fixed up a bunch of things. But he bought an old Porsche to work on and wanted the Corvette off his lift. I walked away from the deal originally and told the guy I didn't want to insult him with a low-ball offer but it would cost too much to fix at his asking price. He got in touch later and asked for a low-ball offer. So it's mine now and the price was fine even given the issues - even if I have to pay a shop to fix some things. I'm almost retired now but still bringing a decent salary for while yet so I can afford it. I had a 79 C3 back in the 80's, so this is kinda fun.

 

I have an 80 and a lot of my howling from the rear of my car was the body mounts fell apart. I thought for sure it was something in the driveline.

 

KEEP WORKING, I just spent $1550.00 on a new fuel system, tank, pump, sending unit, fuel line, regulator, old style hot air choke assembly, carb rebuilt by Lars = gets expensive real fast.

these days I'm sure trailing arms & rear end stuff isn't cheap either

 

If it was me, and you can afford the coin, this is what I'd do. Buy a Ridetech coil-over rear suspension and install it while Gary is rebuilding your diff. Will it be cheap - NO, but it will be the last time you have to worry with it.