engine/transmission shuddering badly on 1st gear, Not sure if clutch or transmission mounts Options

[HectortheRican]

So this has been going on for a little while to a small degree, but it recently got pretty bad after a short road trip in the car. First gear on flat pavement and downhill is generally ok, but I'm getting very bad shudders when disengaging the clutch and applying throttle when going uphill. It sometimes happens on a flat, but it's easier to modulate the clutch pedal to avoid the shudders in that situation.

Any ideas what it could be? I have a hard time believing the clutch is slipping because I don't smell burnt clutch (30,000 miles since summer 2012). Perhaps worn transmission mounts? I'll have to get under the car and visually inspect. I did a gear oil flush back in February with Pennzoil Synchromesh, but I haven't checked the levels since the shuddering began. These are the few scenarios I'm thinking of.

This does not happen in any other gear - not even reverse while backing up a hill. Only in 1st gear.

This post has been edited by HectortheRican: Nov 16, 2016 - 6:21 PM

[Box]

You could see how much the O.E. is and if it's astronomical could consider an aftermarket, but yeah tried to do the aftermarket mounts since they were cheaper and it was a '98 Maxima with a crap ton of miles so didn't want to spend more than needed but the aftermarket mounts gave out within a week or two. After replacing the aftermarket under warranty and it gave out again, it's not like he was dumping the clutch and beating on it either, was fed up and replaced with an O.E. that gave no problems. Could've been a bad batch of mounts but still, if anything the O.E. mount made it some 20 years and 200K miles and if it's a car you plan to keep it's worth it.