Rawze.com: Rawze's ISX Technical Discussion and more

2011 prostar, cm871, 10 Spd Eaton fuller. I'll be changing the tranny oil soon, never done it before but seems fairly straight forward. Just wondering if there is anything I need to do, other than just draining and adding new oil? TIA

That's about all there is to it as far as I know. Use synthetic 50 weight and you'll be good to go.

I use 75-90 or 80-90 in mine. Always have. Tranny has more than a million miles on it and still is tighter than most I have driven with half the miles.


there are many who disagree with this, claim lower fuel mil,eage and such. I have not seen lower fuel mileage on mine, maybe it is because I don't run 70+ mph. 50-wt makes them wear out much quicker.

Just my own opinion, no one has to agree.

I have 80-90 in mine, Rawze suggested it when he was test driving the truck. I am glad I listened to him, the transmission is night and day, really smoothed the shifting out. Those little hang ups are gone, and feels much better all around. I would recommend it, we shall see how she does in the winter, I don't think it will be an issue once she is warmed up.

The only thing I've seen a problem with when switching to thicker oil in the transmission is that in really cold weather or really cold morning startups the range selector will sometimes be slow and may also sometimes stick. But once it's warmed up everything moves real nice again.

What brand of oil would you recommend, how often do you change your tranny oil? According to the manual, it says 500,000 mi/5 yrs. for synthetic. Is that fairly accurate?

Synthetic is way overpriced in my opinion and not necessary in a standard transmission. Maybe it's needed in an automatic or auto shift. But I've never owned one of those

I go to Tractor Supply and buy 5 gallon buckets of Super-Tech non-synthetic 80-90 in the trans and 80-140 in the rears it's the best price I could find. It's also where I buy my 5 gallon buckets of Rotella t4 15w 40 engine oil if Walmart isn't the cheapest. I also go to one of those el cheapo tool place around my area that sells sta-lube 80-90 or 80-140 dirt cheap when they get it in. I change it every 250-300,000. It's cheaper and I get to see if there's any excessive metal shavings or chunks in the oil more often.

(06-12-2018 )rapidisimo Wrote: [ -> ]What brand of oil would you recommend, how often do you change your tranny oil? According to the manual, it says 500,000 mi/5 yrs. for synthetic. Is that fairly accurate?

you can go 500k miles, but if you care about it, 250k miles or every 2 years (whichever is first) is more reasonable to stave off additive separation and possible condensation issues..

Any major difference in the winter months with 80-90 in the tranny? I'm in the north east and we had a tough winter last season, just wondering if it feels any different.