i have a srx how much sloop should i have in the chain in the gear box 
I like to see a inch back and forth, meaning on the backside of the chain you should be able to move it a total of 1 inch back and forth, thats a half inch to the left, a half inch to the right. This will be plenty tight and not drag the sled down when off the throttle.
I once had this srx come in here for service work and I fixed the engine, I took the sled out in the field to do a little blast on it , when I let off the throttle I almost ate the steering pad on handlebars, was like you just grabbed ahold of the brakes! There was barely any snow so it dragged the sled down right now from speed. Returning to the shop I noticed the sled would barely move with a 1/4 throttle like the brake was on, it wasnt dragging after checking the parking brake and the main caliper so I investigated the cause, here after placing the sled up on a stand and revving it a little the track would come right to a halt, track tension was fine no seized up idlers, so I went to the chaincase.....Low and behold the chain was as tight as a banjo string...really.......tighter is not better in there.
I once had this srx come in here for service work and I fixed the engine, I took the sled out in the field to do a little blast on it , when I let off the throttle I almost ate the steering pad on handlebars, was like you just grabbed ahold of the brakes! There was barely any snow so it dragged the sled down right now from speed. Returning to the shop I noticed the sled would barely move with a 1/4 throttle like the brake was on, it wasnt dragging after checking the parking brake and the main caliper so I investigated the cause, here after placing the sled up on a stand and revving it a little the track would come right to a halt, track tension was fine no seized up idlers, so I went to the chaincase.....Low and behold the chain was as tight as a banjo string...really.......tighter is not better in there.