Funny, I can't stand trying to crawl with a sensorless brushless. Seems all jittery and tries to run at a minumum speed, wheras I expect to be able to truly creep along at mm by mm.
I'm running an older gen 1 Tekin Redline 17.5 on 2s and 3s geared 24/82 for summer and 27/78 for ultimate snow bashing. It's been great, but I wouldn't run the newer gen 2/3 because the cans are vented, which seems silly for any offroad motor.
IMO any decent 17.5 or 18.5 on 3s is plenty of pep for the TH. If you like overkill check out the Tekin Roc412, or Holmes Hobbies puller lineup if you want to ensure CVD failures.
The Castle 4 poles are hard to beat as far as raw power to dollar ratio. My brother has the 5700 in a TH on 2s geared 21/82. On 2s only its as fast as my 17.5 on 3s geared 24/82. But it doesn't crawl. We'll play on stonewalls and he'll keep falling off because of small throttle control issues inherant to the startup of a sensorless motor under load. I tried it and got frustrated quickly because even geared low it wants to go 1mph minimum. Fine for driving on most trails and through the woods, but it just doesn't cut it when the rocks get technical.
Its more initial investment to go sensored, but if you actually crawl it's completely worth it.
The servo is a bit of a pain to replace since you must mockup install it with the mounting brackets just ever so slightly snugged up against the servo. Then install the servo onto the chassis so the brackets get pulled snug against chassis by the 2 chassis bolts before fully tightening the 3 accessible bolts, powering everything up to set your servo horn position, so you can remove it to tighten last bolt, and horn bolt. Then reinstall. In order to not play that game often, you really want to get a really good servo from the start.
I'm running a Hitec 7950, my brothers got a Promodeler 420. Their both great, only complaint with the Hitec is the price. If you think you'll get away with a $30 servo, then you'll end up buying multiple underperforming servos. Take your newfound slop-free steering and Al servo horn, add a little brushless speed, and you have a recipe for stripped servo gears.
You can get away with almost any mini servo for shifting though.
I'm running 2200 40c Turnigy 2s and 3s in most of my fleet and can't complain. The stock battery location rewards running a smaller battery in the form of lower cog, which means better everything.
