Bell housing grinding sound

[Friz]

1999 k2500 suburban 7.4 vortec 4l80
When under load deceleration down steeper grades I am getting a grinding sound from the bell housing. It sounds like metal on metal brakes. The sound is tied to engine rpm. The sound stops as soon as I tap the throttle. The only time I have had it happen is longer downhill steeper grades 6% or higher when pulling a trailer with fairly heavy loads. Any ideas as to cause would be appreciated.

 

[EJ_74]

What did you see inside the bellhousing? Torque converter bolts tight, nothing rubbing flexplate?

 

[Friz]

What did you see inside the bellhousing? Torque converter bolts tight, nothing rubbing flexplate?

Nothing visible rubbing, torque converter bolts were tight. I did find a few metal shavings in the bottom cover. Have no clue from where.

 

[NickTransmissions]

Nothing visible rubbing, torque converter bolts were tight. I did find a few metal shavings in the bottom cover. Have no clue from where.

Maybe starter interacting with the flywheel...pull the starter to see if the gear shows any damage. Check the flexplate for cracks. You may need to yank the transmission out to find and fix. This assumes its actually coming from the bell housing and not somewhere else in the front like the front diff (spider gears, excessively worn coast side of ring and/op pinion gears) or wheels (bearings, brakes, etc).

 

[Friz]

Maybe starter interacting with the flywheel...pull the starter to see if the gear shows any damage. Check the flexplate for cracks. You may need to yank the transmission out to find and fix. This assumes its actually coming from the bell housing and not somewhere else in the front like the front diff (spider gears, excessively worn coast side of ring and/op pinion gears) or wheels (bearings, brakes, etc).

Starter and flex plate are undamaged. The noise is rpm related not speed related so I don’t think it’s the front differential.

 

[NickTransmissions]

Starter and flex plate are undamaged. The noise is rpm related not speed related so I don’t think it’s the front differential.

Gotcha, I was just thowing darts against the wall...think you're going to have to get your hands dirty...unbolt the TC from the flexplate and spin the converter - see if any unusual noises are heard...if not, bolt it back up and continue your search.

 

[Friz]

On an RV forum I found a couple posts talking about torque converters expanding under engine braking pressure and rubbing on the bolts for the transmission pump. Have you ever heard of this happening?

 

[NickTransmissions]

On an RV forum I found a couple posts talking about torque converters expanding under engine braking pressure and rubbing on the bolts for the transmission pump. Have you ever heard of this happening?

I've heard of it a couple times in the past from my converter builder. He said that sometimes converters come in with covers that are extremely warped from overheating and sees evidence of contact with the pump bolts.

The only way you can confirm or deny is to yank the transmission...When comes to noises, there's only so much diagnosis folks can do over the internet...At some point, you have to grab the bull by the horns...Perhaps take it for one more drive with someone else in the passenger seat (preferably someone who is either a mechanic or advanced, knowledgeable DYIer) and get that person's opinion before you begin tearing into it.

I wouldn't drive it too long; just enough to duplicate the condition so your mechanic/DYIer helper can offer his thoughts. If no such friend or mechanic exists, take the logical next step and yank the trans so you can confirm or deny your theory.

 

[Friz]

Thanks for your help.