HI,
Looking for some ideas of causes for an issue I am having. I have a 1970 Convertible, 3-speed automatic TH400, base 350 engine. I'll try and explain what's happening without writing a novel...

If I go for an extended drive (2+ hours) on the highway (50-60-70mph), then I come to a complete stop, and have to turn right, i can hear a loud noise (like a popping noise) which appears to come from the rear tire area on the driver side. I can't say for sure if I've noticed this same noise turning left from a complete stop though, and I don't believe the noise is happening on the rear left tire either. I've only ever heard it from the rear driver side.

If I am leisurely driving around home for a few hours (20-30-40mph), and stopping and turning multiple times I have not noticed any noises from that area... it's only if I am driving for an extended period on the highway, then come to a stop.

I have already tried changing the oil in the diff and adding an additive, then driving in circle 8's but I am still having this issue after that.

I am wondering if something is sticking (brakes/emergency brakes), then when it releases, I hear that noise...

Anyhow, just looking for some suggestions as to some possibilities.

Thanks.

 

I would try sending a PM to Gary Ramadei GTR1999.
He is the rear differential expert and he can probably pin point what is going on better than anyone else.
It could be the posi is going out or any number of things.

 

I would put my hand on both rear wheels near the hub after a extended highway drive. Is one or both Hot?

 

Sounds like it maybe a wheel bearing. But this is your best option >>>>>>> I would try sending a PM to Gary Ramadei GTR1999.

 

Yes, good idea, but just tap them first...I once sort of grabbed a motorcycle hub to check for hot bearings, lost my finger prints for a few weeks...LOL...they can get real hot... Bearings generally make a sort of roaring sound, you might want to check out the U-Joints on the axles, they can make a popping/clicking noise when dry and going bad...

​​​​​​​60

 

Last spring a similar story such as this popped up.
Upon removal of one of the rear tires, the owner noted the brake pad locking pin,
completely gone!

 

The symptoms described above sound like posi chatter. Correctly setup posi's should not chatter, no matter how long driven. The only oil and additive I use and recommend is GM limited slip additive and Lucas non synthetic gear oil, I use 85-140 in diff's used between temps 30-100*F. I don't use any other products, while there are plenty out there, this is what has worked for me for the past 30 years, prior to that I used 90 wt gear oil and additive again GM brand. I have NEVER had issue using 85-140 Lucas, not once, and I have recommended it to 100's of people I built diff's for.

If the parking brakes were hanging up, the rotor hats would be hot to the touch in a few miles. Driving will only create more issues if the brakes are hanging up. Bearings typically will make noise and them lock up. U-joints will show rust trails or click and have play in them. Given the explanation of the issue I suspect the diff is the issue.

If the posi was ever rebuilt, then it depends on how it was rebuilt and what clutches were used. For example, I never use the spring pack. I tune the posi, run it in on a machine I built, and have no endplay, no lash, no binding, and no chatter. However, few know how to correctly tune a posi and if the diff was rebuilt by common vendors or shops more than likely it is a spring pack setup. New out of the box Eaton posi's, (I never use Yukon posi's) are sloppy. I rebuilt new posi's, replacing the fiber clutches and spring packs. Fiber clutches will not chatter but you can NOT tune them either and they smudge at every turn.

If replacing the gear oil with the Lucas and 2 bottles of additive doesn't work the only option is to live with it or drop the diff for inspection.

 

"I don't believe the noise is happening on the rear left tire either. I've only ever heard it from the rear driver side."
Just to clarify. The driver's side IS the left side.

 

Thxs GRT1999...
I performed the flush and put in the Lucas 85-140, and 2 bottles of AC Delco additive this weekend...
Now I need to go for a long drive to see if I can still hear the noise or not...

 

You can do the parking lot deal of figure 8's but driving will do the same thing. Hope it resolves your issue.

 

I've actually done both... did several figure 8's in a parking lot, and also drove... still not sure if I drove far enough and fast enough, but I haven't heard anything yet... I may have a multiple hour highway drive coming up this weekend, so I'll listen for sure.
Thxs.