I'm running an 18" dual pass one mounted on the inside rail on a 32 fully fendered 32-5 window with a 318 poly and 727 auto. Trans convertor was rebuilt just a bit above standard and with normal driving i.e not beating on it the trans temp gauge does not move off it's bottom setting of 140F. Have seen it up to about 160F occasionally, possibily due to idling slowly down our 1k of dirt road to get home on a hot day. Based on Langy's chart above the cooler is doing sufficient to keep the fluid in useable form. I read on here before fitting the cooler that trans fluid should operate between 160 and 250F and I fitted the temp gauge as I had doubts about whether the cooler would do the job.