Help! M/ Transmission grind when upshift to 5th or downshift to 4th from 5th

[adrianfromthecastle]

okay, just recently, I've noticed on the freeway, when I shift to 5th, it will sometimes grind, same goes when I downshift to 4th from 5th. I just recently changed my transmission oil, to maybe see if that was the issue (because its been more than awhile)... but it still happens (well, less often than before the transmission oil change).

I just want to know what my possible options are. Is there some kind of additive I can put in my transmission that would help this? Or are my synchros already effed up to where I need to either rebuild or source out a new transmission?

[the converted]

What did you put in for fluid? I've put syncromesh fluid in every transmission that I have had with light grinding and it usually clears it up.

[Koshin]

synchros...mine does the same exact thing, you need synchros

it probably cheaper just to buy a new transmission...Im going Z32 transmission so Im gonna tuff it out till then

I use royal purple/mt90 in mine and it didnt clear it up...you should try this before you buy a new one...just to make sure

[CSUPUEBLOTIM]

Odds are the dog teeth on the syncro or the collar are becoming rounded so no oil is going to replace the material wear. Either swap in a replacement or do a rebuild.