I need An Answer

I have a 83 chevy stepside pickup it has a 700 r 4 transmission in it it is slipping in high gear does it need a vaccum on the transmission

By 'vaccuum', do you mean a flush and fill?

Imho those services are mostly useless at fixing performance problems in a transmission. They do nothing to remove debris from the pan or clean the filter... and these are where many problems originate from.

(BTW if your mechanic tells you the flush is the best way... he is LYING. Mechanics make more money doing the suck and flush than they do for proper transmission maintenance)

The most important thing is to drop the transmission oil pan, drain the fluid, change the filter (make sure the old O-ring comes out along with the filter neck) and take a look at the debris that you have in the pan.

A modest amount of sooty debris in the pan is notmal. Huge amounts of thick, gloppy brown debris and/or sparkly metal shavings is not normal.

Clean out the pan, install a new filter and gasket, then reassemble. Make sure the big round magnet goes back inside the pan. If the magnet is missing, get one and put it in.
(for some reason, many mechanics love to throw these magnets out, instead of cleaning and reinstalling them.

I find a fluid and filter change along with a pan clean-out fixes these slipping problems about one-third of the time. Two thirds of the time, the problem lies elsewhere.... usually requiring a trans rebuild.

Finally, are you sure the trans is slipping, and its not just that the converter has failed to lock-up.