Grinding issues after rebuild.

[MADMODDER]

Rebuild thread found here.

Post in thread 'Rebuilding a M50D-HD'

Aug 28, 2025

Okay yeah, I'm an idiot, I see it now. IIRC the big outer race on the new 30207X is what I've always seen. I don't know what's going on with the outer race on the original input shaft bearing.
I don't understand how it's possible both those races are supposed to spec the same dimensions when the tapered bearings are exactly the same and the races are so completely different looking.

So is the wider-looking outer race from the last pictures, -X4/80EW, overall larger OD than the skinnier-looking outer race from the first pictures, -X3EW? And the original race is too small for the...

• MADMODDER

During my rebuild I inspected all of my components and got new bearings, seals, shift bushings and shims all from a highly recommended shop in the PSW. Transmission Exchange, I believe it was. The gentleman that helped was amazing. My syncros, gear teeth, forks, dogs, ect, all looked great.

About a month ago, my pedal dropped to the floor and would not return. Master cylinder went bad, no big deal. Repalced it with a new, bench bled, OEM piece and everything was good as gold. For about 2 weeks. Then my trans started grinding going into 3rd. Roughly 10k on the rebuild and I'm not leaking any fluids and no loose hardware.

I did replace my trans mount while I was in there but have yet to replace my engine mounts. I know unevenly worn mounts can cause shifting issues in European cars (I'm a euro tech) but I have not found this to be the same with domestic models. Admittedly, I do have a lack of domestic experience.

I've also found a few online sources saying when they encountered this, they would drain the ATF and replace it with a 50/50 split of Redline lightweight Shockproof gear oil and MTL or MT90.
Is there any truth to this?

I do have a brake flush machine that pushes and pulls fluid. I will be doing that just to see if it helps.

Thanks in advance.

 

[85_Ranger4x4]

They are pretty particular about atf or similar.

 

[MADMODDER]

They are pretty particular about atf or similar.

Thats all I've been told and found through my research on here.

So I thought it was totally backwards. But results are results.