Amazon: Odd transmission issue?

[Faust]

After a bit of advice...

Driving my car home from work this evening (car is a 1970 133 with M41 transmission with overdrive).

In second gear at say 10-15 mph. Accelerate as normal, the trans then kinds of 'jumps' for maybe a second and re-engages. Almost like I'd changed gear... it only does this is 2nd gear at lowish speeds. The gearstick doesn't seem to move when this happens. It's almost like the rear wheels are spinning and not transmitting drive correctly. There is no noticeable clunks or bangs coming from under the car.

Thoughts?

Gearbox oil level is OK, and the clutch seems to be fine with no slipping etc.

My initial suspect was the universal joints in the drive shaft - didn't get back till gone 7 so it's too dark to start poking around. If the rain holds off I'll have a look under the car this weekend, but just wanted to know if there's anything else to check.

Any advice would be appreciated as always.

Mike