Great to see you fit it!
Its not 4:1, its 6,4:1 !
And i think the reason you wer not able to pull 106 pounds is in your motor! Try stronger motor, 55T doesnt have enough power, and now you need power to get the best results with GRU.
Its simple, you can find out how much GRU can pull when you brake it. Try stronger motor, 27T maybe, or 23T if you have. You will have to brake something under load. Trewq broke 2 driveshafts allready and something in the gearbox, but GRU is still in perfect condition.
If you want to test, try it, if you brake something on GRU, I will send you free replacement parts
