2002 Jaguar X-Type manual transmission slips out of gear?

My Jaguar X-Type has a 5-speed manual transmission, and when I am driving and shift up, sometimes it starts jerking pretty violently like it might be slipping out of gear, and I have to shift into another gear to get it to stop. It seems to be exacerbated if I am accelerating. I can always get it to stop by shifting, but am afraid at some point that it will not slip into another gear and I’ll be stranded. I had a mechanic look at it but he has no idea what is causing the problem and I don’t want to pay for multiple repairs that may or may not fix the problem! Can anyone help? The car’s got about 125,000 miles. Thanks!

I’m reading this, right or wrong, as an engine that may be cutting out at higher RPMs rather than a transmission problem.

Assuming no CEL is on you might consider having the car scanned for any codes that may be present along with checking fuel pressure and for any vacuum leaks. The latter could have an affect on the MAF sensor.

I agree with Okay…It sounds more like an engine misfire problem than a transmission problem…Next time it happens, let it do it’s thing until the CEL comes on then you can have the codes read which will point directly at the problem…Even if the light goes off, the codes will be stored in the computer…