Shift Firmness

axlehead · #1 Tue, April 21st, 2009, 04:08 AM

I was wondering if there was any downside to increasing shift firmness. I like hard shifts. I have mine set at 13 right now but was thinking about bumping it up a little more. But I wanted to know if it safe to do so or not. Not looking to damage my tranny.

***cleatus12r*** · #2 Tue, April 21st, 2009, 07:20 AM

"Six of one, half a dozen of the other."

As with most things there is a trade-off when it comes to shift firmness. For modest power levels in a mildly modified vehicle, firmer shifts will ultimately be better for the friction elements (clutches) in the transmission. The less time that the clutches slip during a shift, the longer they will last.

However, most mechanical parts inside the transmission will suffer. These parts are namely one way roller clutches or sprags (which are usually used for 1-2 shifts in most transmissions), friction element drive splines, and the tiny planetary gear sets. Any time there is a near-instant reversal of rotation, near-instant stopping of rotation, or near-instant starting of rotation, the longer the time that these actions can be drawn out, the longer the life of the hard parts. Automatic transmissions function by these principles.

The rest of the drivetrain will remain mostly uneffected by firmer shifts, mostly because there isn't enough time during the shift to "unload" the drive components. The less "on-off-on" power transition time between shifts, the better.

***Jackpine*** · #3 Tue, April 21st, 2009, 08:25 AM

Nice answer Cody -

I couldn't help but think there was a downside to the "harsh" feel of a super-firm shift. That shock had to be bad for something, I reasoned.

Because of that, I've simply left my shift firmness settings the way Bill set them in my custom tunes. I can still get serpentine belt squeak in WOT upshifts at times (which seems plenty firm to me).

- Jack

axlehead · #4 Tue, April 21st, 2009, 01:09 PM

I have belt squeal too, but I plan to replace the belt to fix that problem. I was just wondering what the firmest setting I could use without causing problems. I plan to leave it at 13 for now. I will send a PM to corey to get some more input though. Thanks.

***88Racing*** · #5 Wed, April 22nd, 2009, 01:26 AM

Quote:

Originally Posted by axlehead

I have belt squeal too, but I plan to replace the belt to fix that problem. I was just wondering what the firmest setting I could use without causing problems. I plan to leave it at 13 for now. I will send a PM to corey to get some more input though. Thanks.

Try a goodyear gatorback belt if that doesn't help there are performance tensioners out there. But over all its the nature of the beast with the automatic/serpentine tensioner.

Lars