Engine torque
After the engine in our '09 V10 6.8L F250 'sploded 3 days ago, we ended up with a new-to-us replacement '12 GMC 2500HD that we were able to find on very short notice. The V10 6.8L was rated 362HP w...
Forum Discussion
RoyJ wrote:myredracer wrote:Lynnmor wrote:Around 4K is about all I can remember. It was kicking into a lower gear and up to around 5K at times but that was on inclines that weren't as steep. Like the F250, I thought if I slowed down on steeper hills and pushed the peddle to the floor it would kick into a lower gear but it wouldn't and I was stuck with lower rpms and less power.
Maximum horsepower is at 5400 RPM, how close to that were you running when you couldn't hold the desired speed?
Not sure what sensor(s) makes the tranny shift? Air flow or... ?? Maybe a sensor needs cleaning or an adjustment is needed on something?
Do you recall what rpm you were spinning in the V10? I wonder if the V10 happened to be geared perfect for the Coq and the GM 6 spd is stuck at a less than ideal rpm (4k). Less torque makes it more crucial to be perfectly geared.
Also, is this only during the steeper hill (8% one at the snowshed), or at the 6% hills as well?
IIRC, the V10 was running near or at 6K rpms at 65 mph, and maybe a little more. The new tires are 31.1" dia. They're a 70 profile compared to the OEM spec 75 and rmps would be a wee bit higher.
The 2500 was struggling on the inclines heading west out of Kamloops and again heading west out of Merrit. The 8% grade I believe is on the section heading east from Hope and up through the snowshed. The V10 easily made it up the 8% grade section.
Odd that when the grade wasn't as steep (like around 6-ish %), the 2500/V8 kicked into a lower gear and ran at higher rpms okay and could maintain 65 mph. But on steeper grades it didn't change gears and I really slowed down - presumably in part because it was putting out lower HP at the lower rpms.
