1971 conv 442 TH400 455. Driving very nicely but occasionally upon deceleration typically at 50 MPH I get a metallic grinding. Not always and can happen at lower speeds too. Cannot replicate on demand.

Forgive the redundancy - I have utilized CO search feature but couldn’t find what I thought I had read previously, any help would be appreciated. I initially thought wheel bearings or U joints - thanks again in advance for any help.

Also, any ideas regarding significant damage happening while I’m driving it? Of course nothing gets better on its own, but it’s been so beautiful out I’m enjoying it.

 

Try to narrow down the source of the metallic grinding noise. Post an audio on the forum if possible.

 

first thought ... rear axle shaft bearing
u joint
muffler rubbing on drive shaft
e brake cable on driveshaft
front wheel bearing ...
look for a shiney ring on drive shaft where something may be rubbing under deceleration ..
look from the rear of the car at inside of the rear brake backing plates ... see a shiney area or real black dust near ir
at the bottom of the backing plate by the brake drums edge ?
is it a 4 speed ?
any work done on it recently that may be a clue ?

 

Thanks for replies. I tried to video but it’s more a feel than sound, but I can hear it. Ok so saw some oil under right rear shock/ on inside of RR lower tire not long ago. Thought it was from the shock but now thinking it was the wheel bearing/seal. Just a few drops not huge puddle. Hmmmm

 

Examine the brake caliper piston seal, as well.

 

Thanks VC brakes look pretty clean, with no brake fade or issues and MC fluid is good. Tried to grab a photo but this is the best I could do, everything looks pretty dry now.
If in fact I’ve got a wheel bearing /seal issue would it be both at the same time or could it just be the seal - and what damage am I doing driving it.

Thank you again for your help.

 

Well, I would never be able to determine the caliper piston seal was any good w/o removing the wheel. The fact the MC fluid is good doesn't suggest anything relative to a leak at a caliper piston seal. Additionally, you're catching this probably very early (hopefully) don't expect the brakes to "pronounce" themselves as having no brake fade until the brake caliper piston seal is no longer functioning. Personally, I'd have to remove the wheel to inspect anything associated with that leak.

EDIT: Doh, on my part - you probably have drums on the rear. Pull the wheel and look for oil anywhere.

 

I would suspect the first thing to occur is the wheel is going to begin to wobble, then it will wobble more and more. It will definitely increase in the grinding noise. If you're driving along at 65 mph and the seal disintegrates then the bearing disintegrates, you're not going to be a happy camper sitting alongside the freeway with either no wheel or a completely locked-up wheel.

A couple months ago I saw a gentlemen with nearly your same situation pull into the driveway area next door to me - I could hear him coming down the road (grinding), but it was his boat trailer. He stopped in time (obviously he had no proper tools with him). I dragged out my floor jack, hoisted the trailer, we pulled the wheel, examined the hub and the seal and bearing were literally gone. Luckily there are tons of boat supply houses nearby. He made a couple quick purchases, he did the R&R, we dropped the trailer and he was gone in less than 45 minutes.

If you know there is a grinding sound, my advice is not to drive it. If you don't want to pull the wheel to have a look-see, take to a shop ASAP.

 

Thanks VC I expected your response from my idiotic comment about the brakes looking dry without pulling wheel. I recently had hernia surgery and have bilateral rotator cuff issues, so my ability to work on this thing myself is drastically limited.

Sounds like I need to fix this ASAP, and it’s beyond my scope/ ability.

Any other insights or guidance? I appreciate you guys sharing your knowledge

 

No worries. You'll have to pull the wheel to have a proper look. A good mechanic can visualize this for you in no time. I wouldn't drive it down the highway at highway speeds for a leisure trip of any duration. I'd drive it to one or several mechanics to have it examined. Chances are the wheel will not fall off - it would have to be violently wobbling, then the violent wobbling might brake the wheel lugs causing the wheel to separate. In most cases, the wheel won't fall off if you're driving slowly, pull over in time. Best to address before it gets worse though.

I had a bilateral inguinal hernia repair several years ago. Recovery is no walk in the park. GL

 

It sucks getting old doesn’t it! My surgeon said right side looked good when he repaired the left hernia - now I need to look at getting my shoulders done.

I will search on here for rear bearing replacement info - would you recommend I do both sides and seals as well. Sounds like the rear axles have to come out. Thanks again

 

Tough call on whether to do both sides. I've owned my '71 CS for x2 years - I've had the wheels off numerous times. I have no issues w/ leaks or grinding and I can't say if anyone has replaced any seals and/or bearings before me but I suspect someone probably has. If you don't know if anyone has replaced bearings seals previously, you might have both sides done for peace of mind. Yet, IMO, it's tough telling if they're going to fail until they start to grind, squeal and whale while driving has been my experience. I will have to say though, there's nothing like complete peace of mind knowing your wheels have brand spanking new seals and bearings. It's not a tough job why not go for it.

 

Thanks again VC, and by the way I love your color combo. My first Oldsmobile was a 71 CS, bamboo with sienna interior - that thing was such a sleeper when I was a junior in high school! Power bench, cruise AM/FM stereo AC tilt wheel. Six months after getting it - got hit a drunk driver coming back from the junior prom about 2am in Pennsylvania — where my learners permit was only good till midnight - but everything worked out, even though the car was totaled. It led me to my 72V code purchase👍

I also like your thought process and think I’ll do both sides, bearings and seals, if I can find the right guy to do it. Also not sure this is the original rear can anyone idea from these pics?

I purchased car knowing motor was original, not being able to verify trans or rear as original, and made offer accordingly. Thanks again!

Wow I just looked at that second photo and the driveshaft looks awfully close to the one exhaust pipe, is that because it’s on a lift or is that trouble

 

If you do drive it again, decelerating after put in neutral or separately, downshifting, might help eliminate things. More extremely, neutral, shut off engine, and coast for a bit.

 

IMHO that exhaust job looks like crap, and your driveshaft is way too close, I would have the pipes between the down pipes and the mufflers remade, crappy work.
just my .02

 

That exhaust pipe is really close to the driveshaft. Look for shiny spots that would indicate rubbing; if there are some, it may be your issue.

The rearend doesn't look like a 71-72 Olds 10 bolt. Post pics of the sides of the center section for better identification.

All of the times when I had axle bearings failing, they made a rumbling vibration while driving. Your issue of a grinding only upon deceleration seems to be something other than axle bearings to me.

I would recommend you get that drivesahft to exhaust pipe clearance corrected and see if the noise goes away before doing anything else.

 

Thanks for the input guys, yup she’s got plenty of warts but shes still fun - until something breaks, or my driveshaft hits the driver side exhaust pipe. Just crawled under there, I can fit my fingers between the shaft and the exhaust but that’s about it.

Here’s the best photo I could get of the driveshaft side of the rear. And oh yeah I have a small leak where the speedo cable comes into the trans and also a small power steering leak. Lots of warts.

The guy I bought it from trailered it and never drove it, which was a damn shame. I put more miles on the first week than he did in five years.

Thanks again for all your input, it’s very appreciated.

 

To me it looks like the left exhaust pipe is hitting the driveshaft.

 

That first picture looks like the exhaust is rubbing on the shock'
'
If you're getting the rear axle inspected, have them check for pinion movement.

 

Great input guys, really appreciate it, I will get to work on things next week.

Anyone ID the rear?

 

I'm leaning towards a Chevy 8.2" 10 bolt, but that is just a guess.
- Two parallel ribs on side of center section.
- Brake line bracket attached to upper cover bolt.

Hopefully monzaz or someone with a lot more knowledge than I will post.

 

x2
first thought ... rear axle shaft bearing
u joint
muffler rubbing on drive shaft ...... ok the header pipe


those black lines on the inside of your tire is oil being centrifically flung from brake fluid or axle grease ...
its not a 71 72 8.5 10 bolt

 

Thanks again to all for sharing your knowledge - taking it to a recommended mechanic this week for evaluation.

 

What about that scrape on the passenger side shock. Is the tailpipe contacting it? Those pipes look low and the angles are off a bit..to me.

 

^^^

 

Exhaust job mediocre at best, will redo first. As fun and dc2 initially point out, right rear shock rubs when on lift and too close for comfort when all four tires are planted.

Also noticed no rubbing on driveshaft but will fix as well. After that rear wheel bearings/ seals and rear brakes.

Thanks again to all the knowledge on this website and the good people that take the time to share 👍

 

Tom- When you have the rear axle/wheel bearing(s) seal(s) evaluated, have them check the fluid level in the differential. Also, ask them to evaluate both item 'A' (broken missing edge) and 'B' oil deposit. As has been mentioned, the rear axle/differential is not OEM (probably not Oldsmobile, as well) and possibly a Chevrolet 8.2 - anyone's guess. None-the-less, the right time to evaluate items 'A' & 'B' (including differential fluid level) is when you take it in for rear axle/wheel bearing(s) & seal(s) inspection.




Better image (below).

 

Thank you Norm, I hope that eagle eye of yours leads to many birdies and eagles on the links!

Yes rear is Chevy 10 bolt 8.2 with C clip axles. One day may look for bolt in axle Oldsmobile rear - but this is a cruiser (with some originality) and really just want to keep it safe and drivable.

Thanks again for your help.

 

I did some internet searching and apparently the Chevy 8.2" 10 bolt cover has that notch on the left side from the factory.

https://www.onedirt.com/tech/drivetrain/10-bolt-chevy/

 

Nice. Great catch, Ken.

 

Hi Ken, I read that article as well it’s very informative but I think the photo you posted is of the beefier 8.5 Chevy 10 bolt. Note the protrusions at the 5 and 7 o’clock positions on the carrier.

From that same article here is the rear in my car, the 8.2 10 bolt Chevy.

 

According to that site, all the emblems being sold are incorrectly spelled.

 

Good evening, I hope everyone’s doing well during these extraordinary times.

Wanted to circle back regarding my grinding issue - looks like it was the rear end /axles. Open carrier probably could’ve been salvaged but I upgraded to anti spin and replaced axles as well. New rear brakes too.

Also reworked the exhaust, so should be good to go - until the next issue.

Best way to flatten the curve/ social distance while self isolating: taking out your Oldsmobile and enjoying the ride! Stay smart and safe everybody, God bless us all.

 

Tom - Thanks for circling back. Glad it's fixed and buttoned up. Enjoy the ride.

 

Glad you got it figured out, but I'm wondering if it was the axle bearings or something else?

 

Glad its fixed, just never had an axle bearing make noise on deacceleration, always the opposite.

 

Most probably the rear carrier, but not confirmed. Rear axle seals were shot and replacing axles/bearing/seals added minimal cost. So, rear end rebuilt kit w/ new anti spin carrier and new axles.

 

Agreed. I wonder if it was a pinion bearing?

 

My money is on you guys relative to cause, the shop where the work was done seemed competent, but you just never know unless you do it yourself.

Thanks again for all the input and help - it’s really appreciated

 

Yes, TX for the follow-up.

Can you describe the specific defective parts?
So the whole rear end is new(rebuilt)?

In my experience bearing noise on accel, decel or coast. is always pinion related.
Axle bearings will grumble and buzz at various speeds and change pitch per loading(cornering vs straight line).
Never experienced inner carrier bearing failure, knock on wood.