Heavy popping in left rear (U's? Half shafts?)

[Schrade]

I got a new sound in the drivetrain - a heavy 'clunking' in the left rear, as I roll up and down the driveway.

The speed shop that did the auto conversion had the wheels in the air, testing the speedo link. I said, "Isn't that bad for the U-joints?"

They said no. They spun it up to 50 - 55 on the speedo.

Car only has 32k on it here.

Thoughts? Opinions?

[mike100]

Its loose axle nuts. The best solution will be to pull out the 1/2 shafts and grease the hub splines. Seems to happen to most C4's at some point.

[Schrade]

Thank you Sir...

Any special tools / hardware necessary?

[scottfab]

You say up and down the driveway.
Does the noise happen going forward only ?
or backward only ?
or both?

[mike100]

he said driveway- usually while turning or maybe transitioning a grade change. It is the dry, rusty axle stub splines popping against the loosened axle nut. I think it is a 34 or 35mm nut. I took my rear tires off, but i know on some vettes you can pop the center cap off to acess the axle nut for a quick tightness check.

the permanent solution involves R&R of the half shaft to get a brush and wd-40 into the splined hub for a good cleaning and then a little synthetic grease upon reassembly. There is also a teflon coated washer (it is mounted inboard and the axle has to come out) that is recommended to be replaced (along with a fresh axle nut probably), but I never had to buy those parts for a low mileage car.

Even the C5's and c6's do the same thing- pretty much all labor and no parts kind of a job. you may choose to do new u-joints while the axles are on the table- if so, use genuine Spicer parts, not the imported ones...they fit sooo much better.

[Schrade]

You say up and down the driveway.
Does the noise happen going forward only ?
or backward only ?
or both?

Both.

No mention by the guy who drove it for me, following me, on the 60 mile trip home last week, at around 65mph...

It DOES resemble the clunking of a 4WD vehicle, with FRONT hubs locked, on pavement in a turn (something you're not supposed to do)...

[scottfab]

Both.

No mention by the guy who drove it for me, following me, on the 60 mile trip home last week, at around 65mph...

It DOES resemble the clunking of a 4WD vehicle, with FRONT hubs locked, on pavement in a turn (something you're not supposed to do)...

Does not sound like a hub. Easy enough to rock the half shaft back and forth to check for slop in the U-joint. You'd want to lift such that the full weight in on the tire (ramp it up or lower it onto some wood)

[Schrade]

I found 2 of these in my driveway in the recent past - look like needle bearings, spec @ 10.63mm...

Any of them in the rear hub / half-shaft assemblies???

https://lh3.googleusercontent.com/-sD0mzVIuO4k/Ub4S-IRMXkI/AAAAAAAABcY/XDZ692B26LM/s1280/HPIM6981c.JPG

[Bearly Flying]

Looks like a needle bearing from a U joint.

[Schrade]

Looks like a needle bearing from a U joint.

Sounds good there BF; now if only one other would concur - I'd think it too good to be true (depending on how accessible the U-joint is)..........................

[mike100]

There is no way a u-joint needle roller is gonna be on the ground and your drivetrain still driveable. That would be so far gone that you wouldn't be able to drive 20mph without the worst noise you ever heard.

Maybe that's from someone else's car??? Probably need to take a quick peek under the vette.

[Bearly Flying]

Actually over the years, I have had several that have failed and spit out the needle bearings before showing any signs of failure.

I agree, a peek under the car is the best.

[scottfab]

Actually over the years, I have had several that have failed and spit out the needle bearings before showing any signs of failure.

I agree, a peek under the car is the best.

Yup, me to. It wasn't on my Z but have seen depending on the position of the U joint missing needle bearings and very little noise. Time to stop driving it till you find the root cause.

[Schrade]

This hub nut is loose - VERY SLIGHTLY loose.

Is there a torque spec?

How does it get measured?

https://lh5.googleusercontent.com/-J93HoSSUngc/Ub9p2lqLfAI/AAAAAAAABcs/TpexjqDLbjw/s1280/HPIM6982.JPG

Looks like 42.80mm across the flats???

https://lh4.googleusercontent.com/-F5NGR03EuF4/Ub9rgpdadMI/AAAAAAAABdQ/1qKLa5TvIIg/s1280/HPIM6986.JPG

[Jagdpanzer]

Remove the cotter pin pull the locking hat off and you find 36 mm hex nut underneath. Set emergency brake and Torque to 200 lb ft

[batchman]

FSM calls for 168 lb ft if I recall. I find they sometimes loosen up so perhaps I should try 200...

Thanks!
- Jeff

[scottfab]

FSM calls for 168 lb ft if I recall. I find they sometimes loosen up so perhaps I should try 200...

Thanks!
- Jeff

That number rings a bell. In about 2000 I retorqued my left rear and I still
had movement. Turned out to be the hub.

[Schrade]

I found nothing, and can't replicate. The rear axle(s) spun freely with the back in the air, forward and reverse. Shaft is tight, hub nut is tight.

I did find a bunch of acorns and small sticks in the driveway. Funny tho', I couldn't hear the crunch, but I sure felt in in the back left, rolling down the driveway engine off...

Kind of bothers me when problems go away by themselves... :confused:

[WARP TEN]

When I first got my 95 I encountered a clunking sound in the left rear when I turned into my driveway. My driveway is slightly up hill so the body was being torqued a bit as the one front wheel first hit. When it was down at Marc Haibeck's for some servicing he thought the sway bar bushing might be the culprit as they looked quite dried out. (18 year old 20k mile car living in So.Cal) He replaced them and retightened them but said the old ones turned out to look pretty good after all. But I went home and sure enough the noise was gone. We were both surprised but it hasn't reappeared in a year. --Bob

[WARP TEN]

I found nothing, and can't replicate. The rear axle(s) spun freely with the back in the air, forward and reverse. Shaft is tight, hub nut is tight.

I did find a bunch of acorns and small sticks in the driveway. Funny tho', I couldn't hear the crunch, but I sure felt in in the back left, rolling down the driveway engine off...

Kind of bothers me when problems go away by themselves... :confused:

Hey Schrade---Did you ever find what was causing the noise or did it just go away? --Bob

[mike100]

Good chance it was the loose axle nuts. I've had a 91 C4, a 95 C4, and a 2008 vette and they all had a similar axle spline noises.

[Schrade]

Hey Schrade---Did you ever find what was causing the noise or did it just go away? --Bob
Don't have much of a clue on it there Bob; I cannot replicate, coasting, accelerating - reverse, turned right or left, forward, turned right or left.

Hub nut was tight, hub is tight, shaft is tight.

Only thing left was small Oak tree debris in the driveway, crunching under F1's @ 48psi

[cvette98pacecar]

I got a new sound in the drivetrain - a heavy 'clunking' in the left rear, as I roll up and down the driveway.

The speed shop that did the auto conversion had the wheels in the air, testing the speedo link. I said, "Isn't that bad for the U-joints?"

They said no. They spun it up to 50 - 55 on the speedo.

Car only has 32k on it here.

Thoughts? Opinions?

The u-joint in the Ear of the Half shaft on the spindle is sloppy. when you accelerate you hear it moving.