As per the title.

On the last ride home I could not use max effort as the transmission was slipping under full power.

I thought it was the freewheel – 2 & 1/2 year old pro evo. When I took off the cassette and had a look it all looked fine, no obviously broken springs or worn pawls.

It is worth taking out the pawls and turning them around? New springs?

I’ve put it all together and will see how it rides tomorrow, but thought someone might have had a similar experience?

Is the freewheel taking the pedals for a spin?

Are you sure its not the chain slipping on the cassette?

Is the ring drive in the hub worn?

Is the drive ring spinning in the hub shell?

Thanks for the responses everyone.

As the problem is only under significant load, how would I check if the ring drive is the problem?

The freewheel is not moving the pedals

Have you serviced it lately and used grease that is to thick?
This can make the pawls not return fast enough.

Is the drive ring spinning in the hub shell

I once had a hub where this happened, although it wasn’t a hope hub. It would only occur when really trying to put some power through the pedals. Then it was a very smooth slip where no drive was transferred to the wheel.

Has it had a healthy click up until this point? You can usually hear when there are problems with the springs and pawls.

You’re not packing it with too much grease stopping the pawls engaging in the driving ring are you?

Are you sure its not the chain slipping on the cassette?

+1

if you are going to strip it to investigate then it would be worth swapping the pawls and springs anyway.
I dont think the pawls are reversible

As the problem is only under significant load, how would I check if the ring drive is the problem?

If your chainrings start to look anything like that:

Or your cassette resembling anything like that:

That means it is worn out and chain will be sliding under loads.

It do not need to be that dramatic as on the pics but might be significant enough to cause sliding…

Cheers!
I.

You were right Ivan

I think the clue was when the chain whip was slipping to get the cassette off!