Howl in the rear... ??

Discussion in 'Transmission & Driveline Topics' started by fireforeffect, Aug 6, 2020.

  1. fireforeffect

    fireforeffect '78 Trans Am WS6

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    [Asked this over in FB Nation and T/A Country as well... suspect I'll receive same responses, but asking anyway due to similar foundation -- not that I want an echo chamber :D]

    Since before rebuilding the suspension front and rear, I've been hearing a mild cyclical howl from the rear of the car while under load. Thought it was from my tailpipes (driver side rubbing on the left rear tire, pass side stuck tight against the shackles). Took to an exhaust shop yesterday and they heated/bent the tailpipes into position so they're not touching anything anymore. On the drive home heard the howl again but louder. Gets more noticeable w/ greater speed, disappears below 20mph or when taking foot off the gas. No vibrations though. Slow going or take foot off the gas above 20mph and it goes away. Checked the rear tires to see if either are rubbing anywhere else -- nothing. I had the rear end apart when I did the suspension to replace bearings and axles (one axle was chewed up). It's a 3.42 posi and everything seemed clean and in good condition when I had the differential open to replace the axles/axle bearings. I'm stumped...

    Unsure whether this is related... and this is my 1st car w/ a posi. The car shudders when making tight turns into or out of parking spots, just learned this may be because the clutch packs are slipping for the wheels to catch up w/ one another (rears are 275/60/15)? I didn't use posi additive in the rear when I refilled, but used Lucas Oil 75/90 synthetic which Lucas says doesn't need the posi additive. I attributed the shudder to the front tire rubbing at full lock, but now wondering. Research on the world-wide Inter-Lie shows a preference for dead dinosaurs w/ posi additive regardless of whether the lube manufacturer says it's not needed. My course of action right now is 1) add posi additive and drive, see if it changes; 2) dump the synthetic and replace w/ dead dinosaurs and posi sauce; 3) take it in to have the ring/pinion and carrier inspected...

    All thoughts and insights appreciated. Thx.
     
  2. camaro71/holland

    camaro71/holland Veteran Member

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    Did you change the pinion bearings?

    If not, you're saying it was noticable before the rebuild, did you check before or after if the yoke is tight?
     
  3. fireforeffect

    fireforeffect '78 Trans Am WS6

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    No, did not pull the carrier or replace the pinion/ring. Visual inspection didn't indicate to me anything was out of the ordinary (ie, normal wear). Will check the yoke for slop now, hadn't considered. Yes, the howl was mildly noticeable before the fluid change, but my confirmation bias told me it was from the chewed up axle bearing I found when I pulled it down. But much louder now. However, the 1 thing that seems to be the variable is the fluid. I have no clue what I dumped out when I changed out the axle bearings and seals, but what I put back in is likely different than what was discarded. And I have no idea what was in there, only that it was whatever the last owner MIGHT have put in. Car came w/ a chrome go-fast differential cover, so I know the fluid was changed at some point in the past 42yrs. Just bought 3 qts of Lucas Oil 80/90 dead dinos and a tube of Trans-X Posi-Trac additive and will suction the synthetic out and replace tomorrow. Swapping the fluid seems to be the easiest trouble-shoot right now... will report as soon as I get it done and drive it around a little to mix it up.
     
    Last edited: Aug 6, 2020
  4. berg2695

    berg2695 Veteran Member

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    Just to cover all the bases- make sure the rear tire pressures are equal.
     
  5. camaro71/holland

    camaro71/holland Veteran Member

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    The sound you describe (howling) is related to R&P mash. If you didn't mess with the pinion bearings then the first thing I would check is the pinion nut. If it backend up, the pinion could be loose. Or the crush sleeve got beaten up through the years and the pinion is loose.
     
  6. fireforeffect

    fireforeffect '78 Trans Am WS6

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    Alright, new dead dino fluid and posi sauce and drove donuts for 15min to get it mixed in. Still howling. Pinion nut is firm, no slop in the yoke, but gut is telling me it's the pinion bearings. Ugh...
     
  7. dave@ztech

    [email protected] Veteran Member Lifetime Gold Member

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    Had a friends car with that problem, we just kept turning up the radio,to drown out the noise , until it locked up and came to a quick stop, HAA HA ,
     
    Robert stuart Bell likes this.
  8. Fbird

    Fbird Veteran Member Lifetime Gold Member

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    so did you replace ALL the bearings (pinion bearings?)
    I would suspect that if you had an axle that was chewed up.....you have wiped out ALL of the bearings. If they have NOT been at least cleaned i think you are beating a dead horse. I have been down this road before. Lost an axle in my daily driver truck...opened it up..looked like a princess exploded her glitter bottle in it. :( After 4 hrs of cleaning after a 100% teardown....finally got ALL the "glitter" out of the housing. Required ALL new bearings EVEN though they were NOT MAKING ANY noise.... didn't want to do this twice. I was worried the gear set would be noisey since I did NOT re-set it up :eek: just used the factory set-up ...ran a pattern...checked lash...in she went... NO NOISE..:cool:

    Now..4 yrs later.(upped the gear set to 4.56 with new bearings) .same axle gave a little howl :whine:..opened her up...while draining the gear lube I saw NOTHING!!:D so i placed a WHITE clean shop rag in the draining oil to catch some....yup a little bit of glitter BARELY visible.. again full teardown and clean up.. new axles (NOT DORMAN...:mad:) obvious axle bearings.... back together now about 1.5 yrs
     
  9. Vettenick

    Vettenick Vettenick

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    At this point, you might as well look into changing pinion and side carrier bearings. One concern, if the bearings were worn that much, what does your gear pattern look like? If there's a lot of miles, it might be better to replace the R and P too. You might not ever get the noise to go away because you'll never get the correct pattern. Once these gears set their pattern, they're difficult to set up without noise. One other tip, don't use synthetic lube. If you feel that you need extra protection, then use 85-140 dino.
     
  10. 1970_Z28_503

    1970_Z28_503 Veteran Member

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    I am dealing with a similar issue. My rear end is whining at cruise under power. New ring and pinion about 3000 miles ago. Took it to shop and took cover off, found some metal sheen in oil and a small 'chunk' of metal (just changed rear end fluid 2 months prior) Ring and pinion look fine. Shop seem to think its my carrier that is going bad because the say it is loose or sloppy? Overall I wasn't that impressed with their diagnoses skills as they said they could hardly hear the noise on the test drive. I am not sure I want to spend $1700 rebuilding rear end based one a "we think". Going to get a second opinion, I would like to hear if you get your problem solved.
     

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