Yes, they do make a T52, but are you sure it's coming from the tranny / T-case area? Just asking because knocking noises seem to travel up drive lines and into passenger area when heading down the road. Even at 15mph... or so. Also, having worn drive-line joints making noises (that I never would have thought were u-joints gone bad) and most recently a broke front ring gear (expensive Christmas tree outing!) that I swore was a tranny /t-case problem. As I increased in speed, the knocking...thumping got faster and louder. Keep in mind, this will happen in 2wd unless you changed over to locking hubs. To isolate the problem, jack up the rear on jack stands, start the vehicle and put into gear. If there is NO noise or knocking in first, second and third gear in 2wd (low rpm...it's not a race... and your on jack stands!) then the problem is most-likely NOT coming from the coming from the tranny/t-case/rear-end. It is most likely the front axle. If you have four jack stands, I would jack up the front and rear, start the vehicle, put in 4-wheel high and let the clutch out. If it starts making noise, now you know it's the front axle. To confirm, put back in 2wd and let the clutch out, then back to 4wd high and let the clutch out. If the noise happens in 4wd, I would start by pulling the front differential cover and inspect the ring and pinion teeth. Always check the oil in the bottom of the pinion for metal shavings. If not, you could try pulling the rear drive-line to see if the noise still happens and to try and isolate the problem even further. I would think you could get lucky by hearing a difference and possibly isolate the problem to the rear-end or not. At least that might isolate the problem.