Wash 3 pint jars and lids in hot soapy water; rinse with warm water.
Fill canning pot half full of water; add jars and water to cover. Bring water to a boil, reduce heat and simmer.
Place lids in water to cover in a small saucepan; bring water to a simmer. Simmer until ready to use.
Remove and drain jars and lids, one at a time, as needed for filling.
To make the pickles:
Place cucumbers and onions in a glass bowl. Sprinkle with the salt and toss to combine. Let stand at room temperature 2 hours. Drain vegetables, rinse, and drain again. Blot dry using paper towels.
In a large, heavy stock pot, combine vinegar, Splenda Sweetener, mustard seeds, celery seeds, turmeric, and cloves. Bring to a boil over medium-high heat. Add cucumbers and onions and return to a boil.
To can the pickles:
Pack hot vegetables immediately into prepared jars using a slotted spoon, leaving ½” of headspace at top of jars. Ladle pickling liquid into jars, leaving ½” of headspace.
Wipe jar rims and threads. Cover with 2-piece lids; tighten bands.
Place jars on rack in canning pot. (Water must cover jars by at least 1”; add boiling water, if necessary.) Cover; bring water to a gentle boil.
Process for 15 minutes. Remove jars and place upright on a towel to cool completely.
After jars cool, check seals by pressing center of lid with finger. (If lid springs back, lid is not sealed and refrigeration is necessary.)
Store in a cool, dark place for up to 1 year. Once opened, store refrigerated and use within 2 weeks.