Under hard acceleration, trying to beat traffic or pulling onto the highway, I get to about 3.5k rpm and then it feels almost like the car popped into neutral for a split second. The revs shoot up to red line and no power is going to the wheels. To the best of my memory this has only happened in 2nd gear. All my shift bushings are newish and I’ve had no other shifting problems beside this. No detectable clutch smell.

I’ve had this happen maybe 3 or 4 times over the past few hundred miles.

Could this be the clutch slipping and on its way out or is second gear getting worn? Last time I replaced the tranny fluid there was a good amount of metal shavings, but nothing too concerning. There’s plenty of slack in the clutch cable.

Sounds like the clutch is slipping. Try the same on a hill. If the rpms go up and your speed does not your clutch is slipping.

+1

Even just 4 or 5th gear from a low speed and floor it, if the RPM's climb out of proportion to your forward speed it is the clutch.

Let us know what you find.

I'm with Tdship, slipping starts with high gears (4 and 5) not first or second....Your shift linkage may need to be adjusted. Mark

Thanks for the input.

It's not slipping in any other conditions than the hard acceleration. Just went out for a ride today and it's driving like normal even in 4th/5th gear at lowish speeds I can't get it to slip. It's not like my 1.8 puts out that much power haha

I am leaning towards a transmission problem and not a clutch problem for this reason.

However, to further complicate things, I just remembered a small leak I had a couple months ago coming from the flywheel area. Is it possible I have a rear main seal leak and some oil is finding its way to the clutch on occasion, causing it to slip?

Just trying to diagnose this as a "Fix this immediately, do not drive further than 2 miles from home" or "get to it eventually" issue. I have no record of the clutch ever being replaced, so it probably should be soon regardless. But I'd like to stretch it another 2 or 3 thousand more miles until I can afford to jump down the "while I'm in there" rabbit hole.

I know of no issue internal to the gearbox which could cause momentary "slippage" such that the engine might rev up suddenly while driving, and then return to normal.
The clutch is the only possible culprit: worn disk, weak pressure plate, or oil contamination.

It's the clutch.

The gears can't slip, under normal conditions you can't strip the gears, grinding, crunching, etc., sounds like that it's the dog teeth and brake bands, not the gears. Other things can also go wrong with the tranny, but it won't slip.

Clutch, probably oil leaked onto it.