Cruising in 2nd gear Automatic TL
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Intermediate
Joined: May 2018
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Cruising in 2nd gear Automatic TL
First off I own a 2004 5speed automatic. I have always wondered if it’s ok to cruise in 2nd gear at a normal speed 40-50 while your RPMs hang at 4000-5000 on the highway. I have always figured that it’s horrible for the transmission and scared it can cause it to overheat. But I want to know if it is bad and why it is? The thought of having all that power under your foot while just cruising sounds awesome, but not worth ruining the trans. Any and all helpful info will be appreciated!!
Burning Brakes
Joined: Mar 2017
Posts: 842
Likes: 323
From: Columbus, OH
To give you the most simplistic answer: The higher the speed of moving mechanical parts = the more energy (and heat) it potentially has. Yes, prolonged high RPMs will dangerously heat up your trans fluid on your already fragile '04 AT
Last edited by TheSauceBoss; Jul 16, 2018 at 10:02 AM.
Racer
Joined: Jul 2014
Posts: 386
Likes: 85
From: GTA, Ontario
You'd be unnecessarily be working your engine harder. Your gas mileage would be ridiculously bad.
I'm not 100% sure on this, but your torque converter wouldn't be locked up so that might make the transmission work harder, which in turn would make it hotter inside the trans which would be bad for the transmission fluid and cause it to break down faster.
I'm just not seeing the benefit to "all that power", when downshifting just take a second.
I'm not 100% sure on this, but your torque converter wouldn't be locked up so that might make the transmission work harder, which in turn would make it hotter inside the trans which would be bad for the transmission fluid and cause it to break down faster.
I'm just not seeing the benefit to "all that power", when downshifting just take a second.
Nah. I can't imagine that would be good for anything in the long term. I sometimes cruise at 3000-4000 RPM for relatively short durations (<1 mile) when I know I'm going to be slowing down or stopping soon. The 4G 6AT locks up 2nd and 3rd relatively quickly though so it's not really a problem.
All of the reasons to avoid doing this are extremely valid; the unlocked torque converter may well be the most important. Regardless, you will shorten the life of both the engine and the transmission by doing as you suggest.
Advanced
Joined: Aug 2010
Posts: 74
Likes: 16
From: The Mustard Belt
don't take my word for it; do a science!
It's ok. you have permission from the internet.
your figuring in the right direction. I would need to look back at the FSM to be sure but I don't think that the TC lockup clutch would be engaged under those conditions so you would be adding a lot of heat to the fluid there. you would also be adding a lot of heat at in the trans. pump at those RPM. however, loads otherwise would be relatively low as it doesn't take much power (torque really) to maintain 40-50 MPH on flat or gentle grades. If you prepare ahead of time with adequate cooling capacity/capability it should be feasible to maintain durability. I'll leave the math (and risk) to you.
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