2017 GMC 6.0 Vortec - Manual Shifting?
I notice when I am towing my RV, my truck seems to try and down shift sometimes when climbing a hill before it should. Do any of you guys manually shift to get more power or save gas in these situalt...
Forum Discussion
transamz9 wrote:SidecarFlip wrote:transamz9 wrote:SidecarFlip wrote:
Always keep in mind that when an automatic trans up shifts or down shifts, thats is when the box makes the most heat.
It makes heat through hydraulic actuation and it makes heat as the clutch packs engage under heavy load and gear ratio selections are programmed to feel smooth. It's the smooth feel that makes the heat (and wear) because the clutch pack hydraulic pressure is modulated for smoothness. That slipping makes the heat.
While I don't have a GM, I manually downshift out of OD into direct prior to ascending a hill when the motor isn't producing a gob of power (Torque) and the clutch packs can engage with less residual heat. I run a shift kit as well and my shift kit increases the hydraulic pressure and how fast it rises, thereby clamping the packs quicker.... less heat
I might be wrong but you don't ever want your clutch packs to slip. You want your torque converter to do the slipping. That's what it's for.
Your clutch packs always slip to some degree as the internal ratio's change. They aren't an on-off switch. If they were, you'd rip your universals out or twist the drive shaft. The more they slip, the more heat produced and conversely, the smoother the shift is. How an automatic transmission works.
When my TC locks there is no slippage.;)
When the TC locks here is no torque converter slippage, but when the transmission shifts, the clutch packs DO slip as it moves from one gear to the next.
I toasted the 700R4 in my 92 GMC conversion van by towing overweight, and when I had it rebuilt, I told the shop--a performance oriented place--what I was doing, and what I wanted, which was lower temps and a trans that would last. The difference when they got done was like night and day. The improved trans shifted like it meant it, the shift points were higher when I got on it, and the temps were nice and low.
But yeah, Sidecarflip is correct, the clutches do slip, by design. Those buttery soft shifts are nice, just not for towing.
