Shifting to neutral at stop light . . . Does this help reduce wear on a AT

[nascarnation]

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Originally posted by XS650:

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Originally posted by nascarnation:

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Originally posted by lakeman:
I also shift into neutral at long red lights. The idea is to limit heat buildup in the torque converter.

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BINGO!
We have a winner.
This is a VERY GOOD THING for your auto trans.
The shifts from Neutral back to Drive (assuming they are made at hot idle speed)

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How much did the temperature increae in your TC at idle in gear? The last AT truck I had with trans temp gauge (a good one with 3/4 turn dial movement that was easy to read a 2 degree temp change) I could detect no difference in fluid temp between idle in gear and out of gear over a period of 5 minutes.

There is nearly insignificant amount of power being dissipated in a TC at idle unless you have a fast idle.

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All the heat is in the converter. Most automatics have very little cooling circuit flow when at hot idle. If your gauge is measuring the sump (pan) temp you won't see it. If you have a fast responding thermocouple in the "to cooler" line, you will see the hot oil spike the temp when you get back on the throttle after a long hot idle soak. This is what kills the one way clutch in the stator and also cooks the TCC clutch material over a long period of miles.

 

[Steve S]

The torque convertor has lots of oil going through it the heat is not high enough do damage any components.

 

[Ray H]

I take a two-pronged approach to this conundrum. Though I leave my car in gear at long stops, I at least compensate for the added heat by revving the motor to 5,000 rpm... (Could someone explain why my transmission fluid smells like last week's leftover barbecue?)

 

[nascarnation]

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Originally posted by Steve S:
The torque convertor has lots of oil going through it the heat is not high enough do damage any components.

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I have seen plenty of vehicles where you can disconnect the cooler line at hot idle and no oil (other than the amount in the lines) drains out.
Remember that an auto trans uses an oil flow priority valve circuit to supply pressure to the clutches before any cooler circuit flow takes place. This ensures the clutches won't slip. On a trans with some pump wear and sheared down fluid, it is very common to have minimal cooler flow at hot idle. This means the converter gets hot and may damage the stator OWC or contribute to deterioration of the tcc clutch material not to mention cooking the oil.

 

[crashz]

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Originally posted by Titanium_Alloy:

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Originally posted by crashz:
I used to beleive the same thing. So I would shift to neutral on long lights. Since I installed a tranny temp guage, I quit doing that. I notice no difference in temp at a long light, either in neutral or drive. The most noticable increase in temps are from accelerating. And the longer the acceleration, the hotter it gets. Also ambient temps play a huge role in transmission temps. Yesterday it was in the mid seventies and my tranny held steady at a little below 150 degrees F. This afternoon its 90 degrees and it was holding a little below 180 in traffic and 165 on the highway.

I'm of the opinion now that shifting to neutral in an automatic is just a nusance. Just leave it in gear for the period of time that you are waiting. If you want extra insurance against cooking your transmission, then install a cooler and guage.

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What kind of car do you have? What is the mileage? Do you have AT cooler installed on this car? What ATF are you using? It would be intersting to know all these factors because they directly affect AT operation.

Thank you,

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Sorry I didn't respond sooner. My vehicle is a 2001 F150 4x4, 4.2L V6, 4R70W auto, with 85K miles. I added an aftermarket transmission cooler inline after the cooler in the radiator tank. The sending unit for my gauge is located on a brass T on the output line of the transmission. The gauge is an Autometer trans temp gauge that reads from 100 to 250 degrees F. I am using Motorcraft Mercon V.

[ June 25, 2004, 12:46 PM: Message edited by: crashz ]

 

[mechtech]

Most anyone's auto trans will last 100,000m or so with minimal care.
Consider that clutch plate facings are .010"-.015" when new, and still have some left after countless part and full throtle shifts. There is hardly any wear on them [being in oil], with a no load shift in or out of gear at a stop. You just couldn't measure it.
Consider also that when in gear with the brakes on, you are converting about 5mph or so of energy into heating the fluid, breaking it down, and causing ultimate wear.
So, it won't matter much either way, but if your engine has an objectionable vibration when in gear, it won't hurt to take it out of gear at a light. If you are going to sit longer than a 1/2 minute or so, you can take it out of gear, as well, and let things cool a bit.

 

[Titanium_Alloy]

crashz,

Thanks for the reply. Better late than never

It seems like aftermarket cooler you installed really does its job well. What was the maximum temperature you've observed and under what conditions? I wonder if ATF temperature during towing, high speed or mountain driving (or other kind) is simular to city traffic.

Regards,

 

[seotaji]

i thought shifting from drive-neutral-drive wore out the valve body?

i heard that installing a manual valve body would be better?

honda auto trannys are similar to manual trannys in many ways.