why CR ARRV not upgrading chieftains ?

If you mean, why Challenger ARRV and not Chieftain, I would guess: because the Chieftain's very old; because if you base your ARRV on your current MBT, you only need one load of spare parts; and because the Challenger is a more up-to-date ARRV that's better matched to the current work. Also, isn't Jordan almost all Challengers and M60s now?

Out of interest, why do you ask?

Thanks, there are some ideas for upgrading ,like to upgrade old chieftain recovery vehicle by new engine ,new crane,new main wench,,why didnt the UK army go with an upgrade like this and instead it went with a new recovery vehicle?

Because it will ahve been quicker and cheaper to introduce a ARV bassed on your current mbt, like the the prevous Sean says.
This means 90% of the parts are identical, so its not as costly. Plus you also have to factor in the budget for a upgrade.
To upgrade a chieftan ARV would you ahve to first design and plan them, then build and test, this could take much longer than simply going with what the contractor was already drawn up.

Thanks for your reply,
I am interesting by Cheiftain Recovery vehicle mainly , do anyone know it setbacks ?
I have read that it has a problem with Transmission , is that right?