Muncie Whirring noise in neutral

['71StreetZ]

Hello all,
Recently swapped out my old saggy and put my rebuilt M21 Muncie in my car all went well but it makes a rock crusher type noise and even does it while in neutral. I’ve replaced the throwout bearing and have had the trans in and out a few times now the only thing that keeps it from making the whirring/gear noise is pushing the clutch pedal in. The car runs good and the trans shifts smoothly and stays in gear but the noise persists in 1-2-3 and reverse but not fourth. When driving around it seems to quiet down
Could this be a pilot bearing or a clutch / clutch-linkage issue?
Or is something inside my gear box wrong?

 

[tom3]

I'd suspect bad bearings inside the trans. Maybe in the cluster gear? You do have 90wt lube in it? Not ATF.

 

['71StreetZ]

I'd suspect bad bearings inside the trans. Maybe in the cluster gear? You do have 90wt lube in it? Not ATF.

75-90 GL4 in it

 

[Dave Nelson]

Sometimes a whirling noise usually only in first gear is when the 1/2 slider slightly makes contact with the reverse idler gear. When in first gear pull slightly back on the shifter and see if the noise goes away, but this noise only happens in first gear.

 

[COPO]

I would suspect the front or mid plate bearing. Make sure the gear oil is at the proper level and never use synthetic gear oil in a Muncie. I use 80w-90 GM GL4 gear oil.

 

[Gary S]

I've used only synthetic oil in my Muncie for most of its life. Because of that, the tranny has never been opened up or worked on in 49 years. I would never use dino oil in a manual tranny again.

 

[COPO]

You got to drive it in order for parts to wear. My cars got somewheres around 155,000 mi that I've put on. It had about 76,000 when I bought it in 1981. If you don't put miles on it then, it'll last forever which isn't a true test for synthetic oil.

 

['71StreetZ]

I pulled the trans out the other day and the oil that came out of it looked like grey metallic paint so it got taken down to the local transmission shop to get rebuilt (guy is very good and has a great reputation)
the counter shaft was sliding forwards and backwards for some reason???
I'm no expert but I know when to call one!!!!

 

[COPO]

The case will need to be bushed with brass where the counter gear shaft ends sit.

 

[dave@ztech]

This guy has some great parts to upgrade that transmission while it apart, like a better mid plate, and the upgraded center shaft , just a thought, and they sell the better steel bushings for your shifter
https://www.5speeds.com/