The fluid was Redline 75w90 at 45k and 83k. I just put Motul Gear 300 75w90 in it last week. If not that, what should be in it?

A few questions:

1.) Did you see actual pinion damage? I just re-read this. I was shocked to hear that pinion damage was occurring on a street car. If this is a noise based concern, it is most likely a bearing. You could always remove the limited slip diff and look in and inspect the pinion shaft. I could be wrong but I would assume that the parts from the OE supplier are still good as far as the ring and pinion.

2.) Are you looking to solve the problem or upgrade the gearbox or both? These are some of the most reliable transmissions around and the biggest difference I know of is the syncro material.

3.) Just out of curiosity, why the decision to stray away from Mobil 1?

I wouldn't put anything but the factory fill in your car. It isn't a racecar and the factory formula is engineered to give you the best shift quality.

New sounds over the past two days that may help solve this. - fun times lol

Once the temperature really dropped there has been a spinning sound at startup.

While in neutral I can hear it. If I press the clutch pedal in the sound raises in pitch.

What is still spinning while in neutral, stationary and with the clutch pedal pressed down?

The throw out bearing.

Can you post a vid of car and sound? Sounds like a release bearing, they are sometimes noisy whilst still being perfectly ok.

Might be tough but I will see what I can do.

Again, has anyone qualified looked at/listened to/driven this car to diagnose it?

If not, It seems the gearbox is coming out at some point to properly diagnose. I think you likely have a TOB issue based on your description. But you can't be 100% certain until you get a look at it. If it is a TOB, gearbox needs to come out. If it is internal to the gearbox, the gearbox needs to come out.... So, pull the gearbox and inspect the external rotating parts. OR;

spend 100.00 and take it to someone who knows these cars and see what they think. Report back with what they say.

Cheers

Long time since posting. I finally got the transmission back in the car. I replaced the clutch, flywheel, pressure plate, release bearing, guide tube, slave cylinder, fork and all the other little bits in the bellhousing. I took it for a 30 minute drive today and there is a lot of the loose grinding rattling sound in gear under load still.

Edit: I just drained the fluid after only a few thousand miles. The drain magnet was black and there were very tiny shiny metal specs in it. Honestly it looked just like an oil magnet typically looks like from the motor. They could have been in there for a while since the magnet is new but who knows. Can the pinion be checked without taking the trans out?

What's next to look at at this point?

Pull the side cover and remove the differential. Ring gear will be attached and you will be able to see the pinion in the case with a flashlight.

side cover is off but the diff is stuck onto the opposite axle hub. Do I reverse thread that off first as well or do I undo the hex bolts on the diff cover?

Got it. I did not want to force it.

See photos.

You want to look very closely at every pinion tooth. Your photo shows detail of the braking side. You want to look at the drive side. That's where they wear.

Also spin and wiggle the pinion. If the bestimg is bad you may be able to hear/feel the issue.

Like this?

See photo.

I tried to move the pinion in all directions. It felt really solid.

Ah I am starting to understand. Drive/Coast sides like in this document.

https://www.ringpinion.com/content/b...h-patterns.pdf