2001 Chevy 1500 5.3L ~135,000 miles Stock

The truck is used as a work truck, just hauling light loads, rarely ever a trailer. Drive 200-500 miles a day around town/highway, making multiple stops. Owned it for many years, and only had this issue for about 6-8 months. About once or twice a month it'll throw a P1870, and shift very hard (maxes out line pressure I presume), no CEL, and no other codes.

I installed the Tekpak/Fixall P1870 replacement TCC valve shortly after this first started (installed w/o removing valve body). TCC Solenoid ohm'd out good, pan was fairly clean, no metal debris, and fluid was fine (presumably original fluid, as knew the original owner). It didn't seem to help any. It seems to happen less in the winter months, but that could just be due to driving the truck a bit less.

I have to replace the rear main seal/cover as they're leaking quite a bit, and was wondering what's the likelihood of it just being a bad torque converter? I don't really mind having to remove the transmission again to rebuild it, if it ends up not being the tc, but figured I'd ask for some insight before doing such.

Thanks!

 

If you used the fitzall valve then it would have to be the converter or badly worn bushings, Out it must come.

 

Well that's promising to hear, thanks!