grinding second and third

i have a 89 240 with a rb25det shifying in to second and third the last week or so has been awful. at high rpm going in to second it will make a grinding/ popping noise. same thing in to third just not as bad. stops when i take my foot off the clutch. just changed trans fluid today. hardly any difference... anyone any ideas thanks.

What kind of oil are you running?

Use GL-4.

yeah use gl4, if the grinding still happens it's either your tranny or your syncros

i just put in fresh 80-90 some "high performance stuff. hardly any help at all.

For sure syncros. Prolly from drifting, letting clutch out too soon, before hit the gear. Tranny rebuild time