Confused about ATF levels

[LagunaH1]

Hi guys,

Yesterday I decided to do a routine check of my ATF levels after having been driving around town for about 30 - 45 minutes. The engine was definitely up to normal operating temperature, and I assumed the transmission was, too.

I stopped, set the parking brake and put the truck in neutral (left engine running of course) and pulled the dip stick and it was slightly above the "cold fill" mark. I thought that seemed low so I added about half a quart of ATF and drove about 5 miles home.

Today I wanted to see what the cold levels were after the truck sat over night and all day. The ATF levels now seem *very* high, above the "hot full" mark on the dip stick.

I'm confused. I thought ATF expanded when hot, so when I saw what appeared to be a low level of ATF with a (presumably) warm transmission, I added ATF and did not expect the level to be so high today.

How long should I drive the truck to be certain my transmission is at operating temperatures so I can get a reliable reading of the ATF level?

 

[f5moab]

To check cold levels, the engine must still be running and the trans shifted between gears. Fluid still not hot, but the pump will resupply the passages and the torque converter. The TC and passages will drip fluid back into the pan overnight.

Also, on a hot trans you might need to check in Park, not neutral.

Do you have the 3 or 4 speed trans in your H1? I'm never too sure about H1's and what trans was used in what year.

 

[LagunaH1]

Thanks Doug. My truck has a 4 speed transmission (4L80E). I'll test with the engine running while cold and see if there's any difference between park and neutral

 

[f5moab]

For a 4L80...


• Wait at least 30 minutes before checking the transmission fluid, if the vehicle has been driven under the following conditions:

- Outside temperature is above 32°C (90°F)

- At high speed for more than 15 minutes

- In heavy traffic during hot weather

- While pulling a trailer

• In order to get the correct reading, the fluid should be at a normal operating temperature, which is 82°C-94°C (180°F-200°F).

• Do the following for a hot check:

Warm up the vehicle by driving about 24 km (15 miles), when the outside temperature is above 10°C (50°F).

If the temperature is colder than 10°C (50°F), you may have to drive the vehicle longer.

• Do the following for a cold check:

Do a cold check when the transmission temperature is 24°C-29°C (75°F-85°F).

Let the engine run at slow idle for 5 minutes, if the outside temperature is 10°C (50°F) or higher.

If the outside temperature is colder than 10°C (50°F), you may have to idle the engine longer than 5 minutes.

• Do the following for a hot or a cold transmission fluid check:

1. Idle the engine.

2. Park the vehicle on a level surface.

3. Place the shift lever in the P (Park) position.

4. Apply the parking brake.

5. With you foot on the brake pedal, move the shift lever through each gear, pausing for about 3 seconds in each range. Then, put the shift lever in P (Park).

6. Idle the engine for 3 minutes or more.

• Now, do the following in order to check the fluid level:

1. Pull out the dipstick. Wipe the dipstick well with a clean rag or a paper towel.

2. Push the dipstick in all the way. Wait 3 seconds. Then, pull the dipstick back out again.

3. Check bolt sides of the dipstick, reading the lower level.

• For a cold check, the fluid level must be in the COLD area.

• For a hot check, the fluid level must be in the HOT or crosshatched area.

4. If the fluid level is OK, push the dipstick back in all the way.

Notice: Check the transmission fluid level immediately after adding fluid and before vehicle operation. Do not overfill the transmission. An overfilled transmission may result in foaming or fluid to be expelled out the vent tube when the vehicle is operated. Overfilling will result in possible damage to the transmission.

5. If the fluid level is low, add only enough DEXRON®-III (or, if unavailable, DEXRON®-IIE) to bring the fluid level up to the COLD area for a cold check or the HOT area for a hot check.

Generally, this will require less than a pint of fluid. Do not overfill.

6. After adding the fluid, recheck the fluid level as described above. When the fluid level is correct, push the dipstick in all the way.

• Transmission fluid should be red in color when the fluid is new.

 

[LagunaH1]

Update:

Started the truck.
Went through all the positions on the shifter with at least 3 seconds at each position.
Read the dip stick

It's still a little bit above "hot full" while cold, but not nearly as high as before when the engine wasn't running and I hadn't cycled through all the shifter positions.

 

[3Hummers]

Yep.

 

[LagunaH1]

After a quick stop by Tustin Hummer all is now better and I am a lot less confused, LOL.

Thanks again to Mike and Patrick

 

[HUMMER INVESTMENTS]

They are very helpful at Tustin. They are helping me set me up for my lift

 

[Kurt]

What lift are you going for? Duck or predator? Or something custom...?

 

[HUMMER INVESTMENTS]

What lift are you going for? Duck or predator? Or something custom...?

Ive got a friend in CO that has a custom lift. I just bought some springs and 2 spacers for a 2" Lift Kit and plan on running 41" Irok SS tires or 40" Goodyear MTR Kevlar