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]

My hypothesis is if it just started getting really bad after arriving in Denver I bet it's a lot colder there than it is in Alburquerque, cold makes the rubber hard and hence the vibration more noticeable.

I'm not sure if they make poly mounts, at least they're not carried on RockAuto that carries the Energy Suspension stuff for most cars. Went through this ordeal on my brother's Maxima, tried aftermarket mounts and they were crap and ended up with the O.E. Nissan mount in the end anyway. Personally I'd go o.e. for rubber, or go to an aftermarket poly.

This post has been edited by Box: Nov 16, 2016 - 9:33 PM

[HectortheRican]

My hypothesis is if it just started getting really bad after arriving in Denver I bet it's a lot colder there than it is in Alburquerque, cold makes the rubber hard and hence the vibration more noticeable.

It's actually warmer in Denver than Albuquerque... for now. It's 80° today, but dropping to ~45° tomorrow. Let's hope that doesn't aggravate the issue too much.
But OE rubber, eh? Well it'll go further in the long run. Thanks for the advice.