What's up guys

I gotta 92 civic with a GSR tranny grinding on second, but it only grinds if I shift quickly at rpms over 3500 but if I shift slow it goes through fine (yes the clutch pedal is fully pressed)

I should also mention that 2nd also locks out when downshifting I tired double clutching but no use. It only opens at low mph lower than 15 mph.

I going change the tranny fluid and check the shift linkage for play but I am rly hoping its not the synchros Any insight on what might be the cause.

 

I'd look at engine mounts and shifter bushings first.

 

The gsr trans has a 3 piece synchro assembly shabang, it's not uncommon for the assembly to wear down just like any other gear's synchro, more than likely at the very least you'll need that synchro assembly and most of the time 1-2 slider is pretty chewed up if the car has seen any red line 1-2 shifts over the years. I recently just rebuilt my jdm gsr and rather than skimp out like I usually do I went ahead and not only replaced all synchros, but got them in carbon coated option as well as replaced 1-2 sleeve and 3/4 sleeve sliders. Depending on your skill level this can be done by yourself and I'd be glad to help walk you through it. But I'm more than positive based off your description prvoided your synchro assembly is failing to match the input/output shafts spreds appropriately which is what's causing you to be locked out during downshift as well as up shifts with gaps in RPM. Essentially the only time your gear shifts are achieved properly are when the input/output speeds are being Rev matched unintentionally. Even doing this is def detrimental to your gear selector sliders as they are being chewed up because your synchro can't catch the grip it needs to match shaft speeds.

 

You will need a new CS 2nd gear, 1/2 slider and 2nd synchro. Possibly a new 1/2 shift fork and 1/2 hub.