Servicing the fan clutch seems to be nothing new for many. I picked up the idea after LandTank wrote up how to adjust the temperature for an 80series LC fan clutch (this is NOT possible on a Truck/22RE fan clutch). The fan clutch problem steems from shearing the fluid over time, even just a 10yr period. At 20yrs, like most of our mini trucks, the fluid is pretty much doing nothing. Fresh silicon is the key! Just ensure there is no seeping of the fluid and that the rear bearing turns free without noise. I've serviced four 22RE fan clutches this way with great results. Most noteably the A/C keeps blowing cold at idle and low speed 'wheeling. Previously when I'd be out creeping along in low gear, the A/C would only blow ambeint air untill I got moving again. Now I creep around in cool comfort! Not to mention I hear a slight roar when the clutch engages vs. nothing before, and there is noticeably more air being pulled across the radiator now. Three of the clutches came off two '86 4x4 trucks, an '87 4Runner and the other off an '85 Celica. All of them appeare to be the same physically inside and out. However, each of the top covers have different numbers. Numbers on the oposing side of the spring mounts ranged from a 4k to 6F. While there is another number on the covers such as 10ck or 7ck. I'm not sure what these stand for. After doing some reading, it seems Toyota only used 3, 4 or 10k fluid regardless of market area. So then the 10ck and 4k could represent the fluid, however the numbers are in opposing areas and on opposing clutches. I chose to use 6k fluid on my refills due to the hotter temps here in South Texas. I would guess that nothing less than 4k should be used and nothing more than 8k unless you're in 100+ areas like AZ. Then maybe 10k fluid might be open for consideration, but I wouldn't do a full fill of just 10k fluid. The fluid is mixable to make any range of weights, ie. 10ml of 6k with 10ml of 4k fuild will yeild 20ml of 5k.