Tranny temp question? helppp???

[dirtbiker109d]

hey guys. i have a 96 PSD eclb. I just rebuilt the whole transmission. Put a reman TC in it with a suncaost super duty master rebuild kit. I also put in pyro. boost and trans. temp gauges. I have a ts 6 pos. chip with wildman tunes. I also have a bigger 6 pass tranny cooler from XDP. So on my long road trips the trans temp gets up there. between 190 and at times almost 210. Why dose it get so high? i cruse around 70 MPH. I have highway gears in the rear end?

Can someone answer my question? thanks!