I cram mine into 1st gear all the time then let off the clutch and sqaull the rear tires on dry pavement. Tells me my clutch grips perfectly, my 7.5 is somehow still alive and not giving up anytime soon, and the TK trannies dont give up without a fight. How I havent broken anything yet Im not sure doing this but it will catch up with me sooner or later.
As far as the seals, i replaced mine and they quit leaking............for a week then started up again but not nearly as bad as they were, use to drip on the driveway and doesnt now. I greased around where the yoke comes in contact with the seal and whatnot but oh well, my swap is comming soon.