good grappling and natural attack classes

[Kimras]

just looking for good classes to help my troll be better with his natural abilities.

[NoACWarrior]

Druid - the self buff spells are pretty good. Also Wild shape gets you much more strength on top of whatever you already have from troll. You can make your "natural" weapons even larger with a few select spells. Your capstone should be warshaper, so you get that good FH and the ability to make your natural attacks even bigger.

Cleric - buffing yourself to the extreme. Also you get heals and the ability to toss on high energy resistance so that they must do enough subdual damage to down you. Note that magical healing heals subdual damage while also healing regular damage - where as FH will only heal one or the other - it just gives you the option to have 2 health pools.

Totemist - get additional claw attacks, and grapple like a god. Or at least grapple high enough to auto grapple a terrasque. On top of your large size, and your regular claws you can get so many more claws, and get pounce via soulmeld.

[morkendi]

Psychic warrior as well.

[eggynack]

Also Wild shape gets you much more strength on top of whatever you already have from troll.
That's not really accurate. Wild shape's ability score alterations are a replacement effect, rather than a bonus effect. It's usually a boon, but here it is not. I suppose you could always do something like shapeshifter or aspect of the dragon, but those are really mediocre, even here. Aspect of the dragon less so, perhaps. Your cleric plan is a somewhat better one, though I'm somewhat uncomfortable with any caster build that sacrifices eleven levels of casting progression. I'd thus go with the totemist. It's a pretty front loaded class, which is important when you have so few levels to work with.

[Kimras]

are there any other classes

[Urpriest]

are there any other classes

Warblade has a few stances that add damage to every attack, which is good when you have lots of naturals.

Thayan Gladiator is kind of cute, though I've always been a bit skeptical about it actually being good.

Warshaper is gold if you can swing it, but you probably can't.

Black Blood Cultist is basically required if you're making a natural attack-focused grappler, unless it's Totemist-based.

[infomatic]

Wizard, of course, or even Better Wu Jen for Giant Size. Casters also have plenty of options for spell-grappling.

Barbarian/Bear Warrior or Runescarred Berserker can work (pop an Antimagic Field runescar to block the usual escapes).

Druid's best, though, as they can change into ridiculous grapplers via wild shape and also have good grappling spells like entangling staff/kelpstrand, and have a backup grappler with their animal companion.

[eggynack]

Druid's best, though, as they can change into ridiculous grapplers via wild shape and also have good grappling spells like entangling staff/kelpstrand, and have a backup grappler with their animal companion.
As I've noted above, while druids are normally the best grapplers in the game, and they might still be here (man, spontaneous summons are sweet), it's not a plan that makes any use of the many lost levels of troll. I suppose the OP could always swap troll to something more reasonable, like dragonborn desert half-orc, or even, if I'm really going with an off the wall suggestion, goliath, but there's little current indication that that's in the cards. That goliath plan actually sounds sweet, because while it's generally one of my least favorite druid archetypes, it's miles ahead of troll druid.

[Angelalex242]

Monk would be the traditional answer. In practice, though, there's a reason they're only Tier 5.