TRD's have been available on dealers lots since Nov 1997.drinkintedbr said:They didn't have TRD's in 99. At least I dont think so. I have had a couple of friends with progressive coils and rear lockers in prerunners. Non-TRD coils are softer riding.
As far as I know, progressive/non-progressive is the only difference between the TRD and non-TRD coils. The TRD coils have a softer sping rate at first, which then progressively builds to a stiffer rate as compression occurs (the first few coil wraps are the softer ones). With the non-TRD coils, the spring rate is the same throughout the coil. I'm not sure what the difference is between the spring rates of the non-TRD's and the TRD's non-progressive section. They may be the same, or the TRD's may be a slightly higher spring rate, which means the TRD's would be the stiffer of the two, just in the main section (not the progressive section).VtFly said:OK, I've done as much searching as I am capable of, aside from being progressive how are trd coils different from non-trd coils, and how do these differences affect performance?