Toyota Repair: Tercel transmission thumping, ball bearings, rims and tires

Question
Mr. Ritter: I bought my trusty 1985 Tercel right out of the box. At 237,000 miles this excellant mechanical servant has had some minor problems but the major components have functioned flawlessly. I have performed all the work this machine has ever received and as a trained and experienced logging mechanic I believe my work has done more good than harm for this Tercel. All the basic work was done according to specs. You asked for specifics so here's the detailed story. In 1998 I had to meet a deadline requiring me to drive about 300 miles with what turned out to be a large bulge in the RF tire. At the time this caused some bad thumping that went away with a new pair of front tires without any other apparent damage. In 2001 the joint in the R half shaft started clacking on R turns and slowly got so bad I changed the R half shaft [a Mexican rebuild from Napa] in 2003. Things went back to normal. Last summer a rumble slowly developed in the RF axel and turn spindel with about a half-inch play in the wheel top to bottom and side to side. Exploratory surgery discovered that the inside race of the inside bearing was cracked clean in half. Some of the ball bearings had huge flat spots caused by rolling over these cracks in the race. I then installed a new set of spindel bearings and happy motoring resumed. About a month ago I detected some new thumping and palsy in the steering wheel. This wheel waggle goes away mostly above about 45 mph when this manual 4-speed is in high, although there is sometimes movement even in 4th. Also the car has a swimming motion up until about 20 mph. My first correction was to rotate the tires both sides, front to back, thinking there was another tire or rim problem. The rims and tires looked ok and the tire rotation didn't fix anything and the problem remains. I then jacked up the RF of the car, removed the wheel and started the car letting it idle in 1st gear. The axel and spindle area seemed to be quiet and tight, the inner portion of the half shaft seemed to have a little run-out and where the half shaft goes into the trans-axel there seemed to be some occasional rumbling and thumping, but nothing startling. I have always kept the transmission 80-90 wt clean and full and I now notice that after driving it there is about one-half teaspoon of 80-90 wt that drips out from the RF half-shaft to trans-axel junction. At the very least the seal is shot. Finally, and thank you for your patience, here are my questions. After long service and some RF trauma, do you think there is a damaged bearing where the RF half-shaft goes into the differential? Is there a bearing there? And can this bearing [or whatever is wrong] be repaired or changed without  removing the entire trans-axel? Can the work be performed by removing the spindel and half-shaft and then unbolting a plate or collar to expose the problem? I'm not too savvy with this computer stuff so could you please e-mail me an answer as I may not be able to find the page on your site that contains the answers, although I will try. Thank you again and sorry about the novel.  

Answer
It's very possible that there is a problem with the differential bearings and gears, the transmission has to be removed to get to the differential unit for inspection, parts are very expensive and it may be more cost effective, considering the age of the car, to try to find a used transmission assembly, there are salvage yards that specialize in used low mileage engines and transmissions directly from Japan, or check with the local salvage yards.