8 speed eaton fuller transmission

It depends on a lot of things, including the engine and the gear ratios. It took me about 6 months to eliminate 60% of my grinding and 12 months to eliminate 90%. In retrospect, 85% of my grinding was due to trying to shove it into the next gear too quickly, instead of giving the truck a moment to let the rpm''s wind down after shifting out of the prior gear. Ultimately you want to shift based on rpm's, not mph. Every truck will have a different sweet spot, and the sweet spot can vary based on the circumstance.

 

I concur with above, shift by RPM not speed. Keep the engine in its powerband as much as possible.

General rule: there's about a 400 to 450 RPM spread between full gears on most transmissions. If you can keep it somewhere between 1100ish and 1700ish you're generally ok. There's no real hard and fast rule. Some trucks like the RPM a little lower and others are happier when its a little higher. Its all in getting in tune with the truck you're driving.

 

Don't forget when going up a steep grade in the lower gears to wind it up more bc you lose speed. For me with the macks being slow shifters in 1st I'll wind it up to 2000 and it'll fall in at 1200 if im going up a steep grade. So that 400 rule doesn't always apply. Same with going down hill your gonna need to shift it quicker since your gaining speed between shifts. Once you get into high range then you can follow the 400-500rpm rule