Memory that throttles, power draw that sags under load, a card that will not hold the hashrate it used to. Pads dry out and some ship bad from the factory. The card in this example went from throttling to holding 95 MH/s after a pad change.
Search for your exact model and someone who has already been inside it.
What you want from them is the pad thickness, per area of the card.
Buy sheets rather than a kit. A 200 by 200 millimetre sheet is cheap.
Buy a range, from 0.5 millimetre up to 3 millimetre, if you work on more than one card. One card will often use three different thicknesses, sometimes five.
Get a pair of calipers.
Push the caliper down onto the old pad and read it.
It will not be exact, because a used pad has been squashed for two years.
It gets you close enough to pick the right sheet, which is all you need.
Find the four screws with springs on them. Nearly every card has them.
Those four hold the heatsink down onto the GPU core, and they are the ones that matter on reassembly.
Take out the remaining screws holding the cooler to the card.
Note which screw came from where. They are not all the same length.
Lift the cooler slowly.
Watch for the fan headers. Bigger cards also have lighting or a display panel wired to the cooler. Unplug them rather than pulling until something gives.
Look at the pads you removed.
Pads that have gone oily and are leaving a film behind have broken down. Replace all of them, not just the ones over the hot parts.
On the card here the 1 millimetre pads were fine and the 2 and 3 millimetre pads were oily. Thickness and batch both matter, so judge each one.
Do the backplate side first, then fit the backplate.
Flip the card and do the core side.
Peel the film with a plastic tool from a repair kit rather than your fingers. Finger oil on a fresh pad defeats the point.
Keeping one colour per thickness makes it obvious later which pad went where.
Use a stable paste rather than the best performing one.
MX-4 holds up for years. The high end pastes score better on day one and dry out, which is the wrong trade for a card that runs 24 hours a day.
Spread a thin even film with a spreader instead of placing a dot. Mounting a heavy cooler blind is fiddly enough without hoping a blob spread correctly.
Reconnect every fan header and anything else you unplugged.
Start all the screws before you tighten any of them, so the cooler sits square.
Tighten the four spring screws in a crisscross pattern, a little at a time, corner to opposite corner.
Stop when the screw stops. Do not lean on it.
Then do the rest of the screws.
Put the card back in and check temperatures at idle first.
Then run it hard for 10 to 20 minutes and watch the power draw at the wall.
Power sagging under sustained load is the signature of the card pulling itself back, and it is what a pad job fixes.
Once it holds, step the memory clock up gradually and find where it stops being stable.
The example card held 95 MH/s afterward, against about 70 while it was throttling and cooking its own memory.