Buzz from transmission

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KC masterpiece

KC masterpiece

Joined
Dec 14, 2018
Threads
12
Messages
389
Location
Silverthorne, CO
Evening folks,

I have a 1997 with 177k. After a recent trip of about 2000 miles I noticed a noise that I finally narrowed down to the transmission bell housing.

It is best described as a metal on metal buzz. Based on my forum digging I have narrowed it down to a few options and hopefully provided enough info. I would love some input. A local shop just quoted me $4500 for a transmission rebuild which is nonsense. Their specific diagnosis was "failed transmission fluid pump". I am suspect....

  1. The sound is rotational and directly tied to RPM.
  2. The noise is constant and present in D, N, R, and with the x case in neutral.
  3. Worst when cold on startup. Gradually becomes less apparent.
  4. Transmission fluid looks brand new from PO. Bright red and correct level.
  5. Noise is still present after driving at operating temp for a long duration.
  6. I have driven over 1000mi since it began roughly two weeks ago. Transmission operation is unaffected. Shifts fine, no apparent slipping.
  7. No mods to drivetrain
  8. During the winter the starter would occasionally grind below 0F. This could be related (flex plate)
  9. Louder when bell housing inspection port is open.
  10. Engine has been running a little hot, but my radiator is gross and a replacement / flush is on the list after this.


My thoughts...
  1. Failing torque converter?
  2. Failing or cracked flex plate?
  3. Transmission has internal failure?
  4. A rock is somewhere?
Any input is appreciated.
 
Last edited:
Could be the starter not disengaging.
 
ppc said:
I would pop the inspection cover off the bell housing and examine the flex plate for cracks or damage as best you can.
Click to expand...

Gave that a shot after some reading and was not able to see anything. I have a borescope coming from Amazon that should help look for things.

What is the easiest way to rotate the flex plate to check? Trans in neutral with a breaker bar on the crank and a helper?
 
That is how I would rotate the motor. Using the starter to turn the motor would be random and may not see a 360 degree view unless you mark each area examined. Pulling the plugs is a lot of work but make spinning the crank easier and a good time to replace the plugs.
 
ppc said:
That is how I would rotate the motor. Using the starter to turn the motor would be random and may not see a 360 degree view unless you mark each area examined. Pulling the plugs is a lot of work but make spinning the crank easier and a good time to replace the plugs.
Click to expand...

Thanks for the tip.
 
Starter not disengaging meaning the starter drive dragging and not returning to neutral position. If it's hanging where the drive is engaged the drive will spin, not the starter motor and solenoid still trying to start it.

Just a thought. Not common, but possible.
 
BILT4ME said:
Starter not disengaging meaning the starter drive dragging and not returning to neutral position. If it's hanging where the drive is engaged the drive will spin, not the starter motor and solenoid still trying to start it.

Just a thought. Not common, but possible.
Click to expand...

I am starting to lean towards this as the cause. Thanks for the tip.

The noise has been about the same, but yesterday I noticed some fine metal shavings in the bottom of the bell housing. I have checked the flexplate for cracks and all of the bolts are snug.

Finally had time to think about pulling the starter today and noticed this.

1997786


Am I correct that this is the lower starter mounting bolt that was broken off? I am assuming this could contribute to misalignment and the starter drive dragging as mentioned above?

Here is a shot of the flexplate. I hope this can be fixed with a starter replacement and not a new flexplate. How do my teeth look? (Notice the fine metal shavings clinging to a few.)

1997787


And finally one more video shot today for reference. Right after the first cold start of the day when the noise is most apparent.

 
Starter may be the culprit. Looks like it may have been hitting the flexplate and not retracting fully. Are these marks on the drive gear normal?

1997866


Going to drop a reman denso in and see if there is improvement.
 
Do some Google Fu and lookup Denso Bendix drive and go to images, You will see many new ones with that chamfer on the outer edge of the teeth.
 
Take the starter to O'Reillys and have it bench tested. You'll see if the starter drive retracts immediately or if it's hanging out.

Teeth look normal both on the starter and the flex plate.
 
I had the starter tested and it is working okay so it was reinstalled.

Since I already had lots of ATF around from a recent power steering flush I decided to take the 30 min for a quick drain and fill. Figured it could not hurt and that was one of the fluids I have not changed yet.

1999462


Not nearly as dark on a paper towel. Definitely needed changing but does not appear or smell burnt. Strange since it looked much better on the dipstick.

4.75 qt out and 4.75 back in. Waited for a cold start this morning and no change in the noise. I did run a magent through the old fluid and it is clean, no metal shavings. Is it worth sending the used ATF to Blackstone for an analysis? I'm pretty sure the issue is not internal.

If @Cruzilla is right and it's just a backed out bolt I am having a hell of a time finding it.
 
KC masterpiece said:
I had the starter tested and it is working okay so it was reinstalled.

Since I already had lots of ATF around from a recent power steering flush I decided to take the 30 min for a quick drain and fill. Figured it could not hurt and that was one of the fluids I have not changed yet.

View attachment 1999462

Not nearly as dark on a paper towel. Definitely needed changing but does not appear or smell burnt. Strange since it looked much better on the dipstick.

4.75 qt out and 4.75 back in. Waited for a cold start this morning and no change in the noise. I did run a magent through the old fluid and it is clean, no metal shavings. Is it worth sending the used ATF to Blackstone for an analysis? I'm pretty sure the issue is not internal.

If @Cruzilla is right and it's just a backed out bolt I am having a hell of a time finding it.
Click to expand...

But you didn't do the full fluid exchange thing though, through the trans cooler? Doing it that way will clean ALL the fluid including the torque converter. You only swapped about 1/3 of the total fluid.
 
BILT4ME said:
But you didn't do the full fluid exchange thing though, through the trans cooler? Doing it that way will clean ALL the fluid including the torque converter. You only swapped about 1/3 of the total fluid.
Click to expand...

I was aware it would not do a total exchange and had looked at the flush method using the cooler hoses. At least I know there was no metal in the pan?

My hope was that a quick drain and fill would provide at least some change in the noise IF it was fluid related. A full proper flush with the rest of the driveline fluids, and an axle rebuild, are on the list in a week or so when I have the time.

I drove about 30 minutes afterwards and assumed that is enough time to cycle the new fluid through the TC and other bits?
 
KC masterpiece said:
I was aware it would not do a total exchange and had looked at the flush method using the cooler hoses. At least I know there was no metal in the pan?

My hope was that a quick drain and fill would provide at least some change in the noise IF it was fluid related. A full proper flush with the rest of the driveline fluids, and an axle rebuild, are on the list in a week or so when I have the time.

I drove about 30 minutes afterwards and assumed that is enough time to cycle the new fluid through the TC and other bits?
Click to expand...

Yes, that's enough to cycle and mix. May or may not notice a shifting or noise difference.

I listened again to the noise and with headphones in, I'm not sure I'm picking up the CORRECT noise. When I used the speaker on my phone, it sounds like the engine is coming apart, so I'm not sure I'm getting the right thing.

Are you sure you're not just hearing an idler pulley going bad?
 
BILT4ME said:
Yes, that's enough to cycle and mix. May or may not notice a shifting or noise difference.

I listened again to the noise and with headphones in, I'm not sure I'm picking up the CORRECT noise. When I used the speaker on my phone, it sounds like the engine is coming apart, so I'm not sure I'm getting the right thing.

Are you sure you're not just hearing an idler pulley going bad?
Click to expand...

Pretty sure. Phone microphone is clearly not great at picking it up. It seems localized to the bell housing. Definitely not coming from the front end of the truck... But I know vibrations can mysteriously travel.

I recently replaced an idler pulley that was just starting to make some noise.

I'll go take a video of the noise from inside the cab maybe that will help.
 
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