warming up transmission fluid

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Just wondering if anyone can tell me if there is any advantage to warming up an automatic transmission in Neutral as opposed to Park? We just had a cold spell of -40C weather and I was just corious....

Thanks!
 
Does tranny fluid heat up in neutral?
confused.gif
 
I guess I should also ask if the fluid is doing the same thing in park as it is in neutral. One would think that if it wasn't being pumped in park it wouldn't warm up as fast as if it was flowing and in friction with moving parts in neutral....

I really have no idea what goes on in an automatic transmission incase you can't tell!

Thanks everyone!
 
Once the coolant heats up the ATF will eventually warm up.

Putting a load on the tranny will cause it to heat up faster. The load is having the selector in drive or reverse.
 
Park - Neutral...no difference for the fluid. They're the same thing except for the parking pawl engagement.

You're better off warming the fluid by driving the car.

[ February 02, 2004, 10:02 PM: Message edited by: Kestas ]
 
quote:

Originally posted by Kestas:
Park - Neutral...no difference for the fluid. They're the same thing except for the parking pawl engagement.

You're better off warming the fluid by driving the car.


Why do most (if not all) manuals/dipsticks tell you to check ATF in neutral? If it's the same for the tranny I would think park would be safer while the engine is running...
 
I never noticed. I thought the manuals said to check it in park. That's the way I've done it.

Can you see a difference in fluid level when you check in park vs neutral?
 
All of mine say park. I would bet most manufacturers would never get that manual past the risk managers if they said to check it in neutral, too many accident possibilities.
 
quote:

Originally posted by Spector:
All of mine say park. I would bet most manufacturers would never get that manual past the risk managers if they said to check it in neutral, too many accident possibilities.

Says right on my dipstick to check in neutral. Also says the same thing in the manual and my Haynes manual.
 
quote:

Originally posted by ZmOz:

Says right on my dipstick to check in neutral. Also says the same thing in the manual and my Haynes manual. [/QB][/QUOTE]
You must own a Dodge/Crysler.
 
As far as checking the ATF level, the fluid must be at operating temp: at least 20km / 12mi of driving.

For my 2000 GMC Sierra, with the motor idling and the truck on a LEVEL surface, slowly go through the range from Park to One and back to Park, letting it sit for about 5 secs in each range.

Then take out the stick and wipe it, put it back in, pull out and check the level.

This is per the Helm shop manual.

As far as cold weather use, the Brookfield viscosity has a limit of 100 Poise before shift solenoids/springs and the torque converter will fail.

Most conventional Dexron III ATF's reach 100 Poise at around -35 C.

If you operate HD Allison automatics, they REQUIRE a "preheat" in temps colder than -25 C / -13 F. The "preheat" means to use an electric pan heater or to run the motor in P (If equipped) or N for a minimum of 20 minutes.

They warn if you attempt range operation, as in driving off, you could cause transmission failure that would NOT be covered by warranty.

I've seen folks who have attempted to yank the selector into D at -40 and nothing happens. So they floor the pedal, somehow thinking that "helps." They grenade the torque convertor or main pump. I'd let it run 5 min minimum.

So I think it's important to use the correct ATF. If your car takes Dexron III, then in most parts of Canada and the Northern U.S. and Alaska, the regular Dexron III can not be used below -35 C.

FWIW Mobil 1 ATF, which is approved for Dexron III and Allison C4 spec, has a rated Brookfield of 51.5 Poise at -40. This is what I use in my automatics and very good operation, even at -42.

Jerry
 
Actually there is a difference between park and neutral (other than the pawl engagement)
The fluid is pumped through more passageways in neutral. The hydraulic diagrams definitely show this. I don't know enough about automatic transmissions to make a definite comment on why they are set up that way but it makes sense that because of this, the fluid level as read on the dipstick is not the same in Park as Neutral
Ed
 
I think in neutral, there is usually more fluid flow inside toyota the valve body,(the old 80' dodge, chrysler vehicle show big different) so it may show little lower fluid level. , but you should check after driving for awhile, take it ez to warm it up. feel the stick is little warm up to little hot(fluid end ), then park it on a level lot. take a reading. If there is no trans problem I dont worry about the fluid shows a little low or over, Not too much over(less than 10mm is ok). I got a big cooler(12in x 12in x 1/2in) in front of my truck, and the fluid level is still at full cold mark after 30 miles driving on free way in a cold day. In a hot summer day, it blowed over hot mark with a boat behind . I use the right type of fluid on the trans dipstick. Type T4 is handling heat and lube better than any other in T type. 'O' ring and clutch material in T4 fluid trans and Dex III fluid trans are all different in handling of that trans. I dont like mix ATF fluid, I use the same brand name, I like Penzoil Dex III. Mixing those fluid(type T and Dex II or III) may burn your clutch in long run. not right away. drain and refill 3 or 4 times at every other 10 miles trip will take care of mixing problems. Just want to share my thought, my $0.02 . sorry, I dont mean to hijack your topic.
 
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