MI-250 GO-TO
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The main gear can be removed from either the RA or declination axis for cleaning or re lubricating. When re lubricating a gear, keep in mind that the same type of lubrication should be used. Mixing of different lubes can result in poor performance of lubrication. Gassing (hardening) can occur if there is residual lubrication left on the worm or elsewhere. The recommended grease is Jet-Lube MP-50 Black Moly-Paste which can be  ordered from Grainger.com.
1) Remove DEC assembly ;
2) Remove clutch knobs
Remove cover plate
4) Back off worm adjustment screws (not shown in picture)
5) Loosen worm lock down screws (not shown in picture)
6) Drop down worm so that it clears the gear (not shown in picture)
7) Remove inner 4 socket head cap screws
8) Do not let plate fall off. Set aside
9) Carefully lift out gear
10) Perform necessary maintenance and reverse order for reassembly.
11) Refer to worm adjustment section of manual to reset worm.