im wondering if a 2001 tacoma rear 8.4 rear end spooled will be alittle scary with 38" swampers? will it be strong enough? remember i have been running a locked d35 for a year with 35's and i havent broke a shaft, so im not known for goin crazy on the gas. but i dont want to have to worry about it like i do the d35.
You need 35 spline axles to run 38's, period. You will always be worried about breaking a shaft, as they are equal in strength to a 44 shaft. Both are 30 spline.
The constant torque loading that a spool produces will cause the fatigue life of the shafts to be severely curtailed.
In other words, you will experience twisted splines in short order. Big, soft tires and the torque produced by a 4.0 will eat those shafts alive.