Ok, here's what happens when I get to putting off my homework and domestic chores...
I wanted stiffer valving in both front and rear shocks on my RS5k-equipped-but-otherwise-unlifted-suspension '86 Toy 4x4 short bed. Being a broke college student, and taking a class in fluid dynamics, it ocurred to me that I could cheat the money=better suspension equation by putting thicker oil in my existing Rancho RS5k shocks. We're in the chapter about viscosity...
After considerable study and analysis of the twin-tube shock design, I decided to drill a 1/4" hole into ONLY the outer chamber of the shock body, just below the seal. After cleaning up the lost oil, I found that the valving between the inner and outer reserviors of the shock kept me from bleeding all of the piss-thin fluid out of the inner compartment/bore.
Another hole, this time much smaller (.045) went through both walls of the shock, as near to the end of the main body, right beneath the eye, as possible. This would only allow flow to let the fluid out and not be big enough to bother valving(compression) too much. The rest of the oil came out in a nice, toolbox-coating(yes, I did) stream when I pushed the shaft in for the final time. It was purged.
I then tig welded a little tiny 1/4" pipe nipple cut in half over the bigger hole, near the seal. While I was at it, I plug welded the little hole in the other end.
While I was at Ace getting the 2 nipples that I cut in half(1 end for each shock), I bought a 1/4" pipe to hose barb.
I threaded the barb onto my new filler port, and looked around the shop for some thicker fluid.
10w-40? no, too thin still. 90w-140 hypoid? yeah,...just right. In a convienient squeeze bottle too.
On went the hose and I began re-bleeding all the air out of the shock, replacing it with virtual molasses. After it was all bled, it felt like a RS 9k set on about 4...pretty damn stiff and ready for airtime.
On went the 1/4" pipe plugs and off to test...stiff, just right tough.
2feet...then 4 feet of air didn't blow out either the valving or the seals, yet.
Has anyone else tried this?