So I had my truck for almost 2 years and put just about 12,000 on it. This is 2 winters of abusive plowing. When I got it, I was told the tranny was rebuilt 25,000 miles ago. Don't know how or what...lol I tweaked the engine nicely and the trans performed great! Solid shifts and in lock up ,no slippage leaving a plume of smoke if I wanted. It would normally run around 140ish degrees normal driving and around 180-200 plowing snow for hours. A couple times I had to run it really hard and I hit 240*.. I let it cool down after those times. After the past 2 winters I decided to have a trans service done at my friends shop. Well... It aint the same! Now I'm running 180-200 normal and hit 220 today driving around town. It feels ALOT more sluggish taking off and shifting.
I'm wondering... If the trans originally had synthetic fluid in it..??? I'm sure regular old fluid was put in for the trans service. Will synthetic fluid make it run cooler and perform better ??? I can't have this for next plow season, I am sure I will cook the trans the 1st storm !!

 

Yes. I would run that for the summer so its not a complete waste, then swap back to synthetic and see what happens....make sure you do it early enough to know if you fixed it in time for snow season.