Not trying to be-labor the forum with another “what’s this noise thread” but I wanted to poll people’s thoughts so I’m not missing anything.

Symptom: High pitched ring/whine when in all 5 gears, when the engine is coasting/ not under load; most commonly rpm ~2500. Goes away when load is applied or when I depress the clutch. Truck is silent in all speeds when in neutral and coasting.

Differential diagnosis list:
- Synchros; just rebuilt my transmission myself with new synchros, bearings, etc; everything was within spec to FSM
- throw out bearing (seemed fine when I spun it by hand, that and clutch was replaced 20K miles ago) and would expect sound to get worse when clutch is applied
- pilot bearing (no issues shifting, sound not linear with RPM)
- serpentine belt pulleys? (Cannot replicate the sound with car still and revving engine with stethoscope)
- belt tensioner? (No rattling coming from engine or valve cover with stethoscope; no chain play when I redid valve lash 2 mo ago)
- pinion bearing? (Not present when coasting which is what I would expect if it was)


Y’all have any other thoughts on what it could be? Or feedback on my reasoning if it’s faulty.

1987 4Runner SR5, 22RE

 

Was the noise there before the trans rebuild?

 

Thanks for the reply. The sound was there before the rebuild.

I am pretty sure I found the cause and it’s a bad CC. I had been running rich for a while before fixing a faulty AFM. I’m pretty sure that expedited the CC breakdown. Hopefully this will be helpful for people in the future.

 

Magnaflow?

 

It is a walker, I had it replaced a couple years back but never got around to fixing the rich condition until recently.

 

Is everything good now?

Edit: Seems yes.