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I just changed the trans fluid and installed new filters and a BD pan. Getting the oil level correct on the 68RFE seems to be more difficult than any other transmission I’ve worked with in the past. Looking on the internet I have found charts that give exact oil level measurements from the tip of the dipstick that are proportional to the transmission temperature. I am hoping TransEngineer and any other knowledgeable members will chime in and answer a few questions I have.

1. The first set of holes on the dip stick are for a “cold” measurement 70 degrees F (21 degrees C). I live in a cold climate where it is consistently much cooler than 70 F. Therefore if I set my fluid level correct at 70 degrees it is much much lower than the two holes when I initially start the truck on a cold morning. Will this cause issues? Can the fluid level drop below the pump pickup thus starving it of oil?

2. I now have increased volume of oil due to my deeper transmission pan. I will obviously have more volumetric expansion and contraction now. Should I be aiming for the lower limit of the acceptable fill range to try and prevent an “overfill” condition when the transmission is hot and my increased volume of oil has expanded more than what was initially engineered?

3. Is the onboard transmission temperature reading accurate enough to use when adjusting the fill level.

This is my first post so hopefully I have put it in the correct place and not broken any rules….if I have please go easy on me.
 

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I just changed the trans fluid and installed new filters and a BD pan. Getting the oil level correct on the 68RFE seems to be more difficult than any other transmission I’ve worked with in the past. Looking on the internet I have found charts that give exact oil level measurements from the tip of the dipstick that are proportional to the transmission temperature. I am hoping TransEngineer and any other knowledgeable members will chime in and answer a few questions I have.

1. The first set of holes on the dip stick are for a “cold” measurement 70 degrees F (21 degrees C). I live in a cold climate where it is consistently much cooler than 70 F. Therefore if I set my fluid level correct at 70 degrees it is much much lower than the two holes when I initially start the truck on a cold morning. Will this cause issues? Can the fluid level drop below the pump pickup thus starving it of oil?

2. I now have increased volume of oil due to my deeper transmission pan. I will obviously have more volumetric expansion and contraction now. Should I be aiming for the lower limit of the acceptable fill range to try and prevent an “overfill” condition when the transmission is hot and my increased volume of oil has expanded more than what was initially engineered?

3. Is the onboard transmission temperature reading accurate enough to use when adjusting the fill level.

This is my first post so hopefully I have put it in the correct place and not broken any rules….if I have please go easy on me.
Yes, setting the oil level on a 68RFE can be tricky, primarily because, after adding any fluid down the filler tube, you must WAIT several minutes for all the oil to run down off the inside of the tube. Otherwise, it smears on the dipstick and can give you a false "high" reading. Look at the holes in the stick to confirm for sure whether the "real" oil level is at (or above) the hole.

To answer your questions:

1. At really cold temps, the fluid may indeed be below the tip of the dipstick, however this is NOT a problem. The dipstick rests on a shelf / step on the side of the pan. The sump filter inlet is BELOW this level. You typically need to be about 4 quarts low before you start sucking air.

2. Good point! Hadn't thought about that before (I don't normally deal with deep pans). Probably not a big concern, but yes, I think it would make sense to set it near the MIN spec when cold, and then RECHECK it when hot. The hot level is what really matters. So check it once you get to normal operating temp, and if the level is OK then, it really doesn't matter whether it's at the high or low end when cold. But you're right... setting it near MIN when cold (with a deep pan) will probably make you more likely to hit the correct range once you warm it up.

3. Yes, the trans temp display in the cluster is the same number you would read with a scan tool, and it should be accurate within the sensor error (a couple degrees maybe?).

Hope that helps....
 

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Yes, setting the oil level on a 68RFE can be tricky, primarily because, after adding any fluid down the filler tube, you must WAIT several minutes for all the oil to run down off the inside of the tube. Otherwise, it smears on the dipstick and can give you a false "high" reading. Look at the holes in the stick to confirm for sure whether the "real" oil level is at (or above) the hole.

To answer your questions:

1. At really cold temps, the fluid may indeed be below the tip of the dipstick, however this is NOT a problem. The dipstick rests on a shelf / step on the side of the pan. The sump filter inlet is BELOW this level. You typically need to be about 4 quarts low before you start sucking air.

2. Good point! Hadn't thought about that before (I don't normally deal with deep pans). Probably not a big concern, but yes, I think it would make sense to set it near the MIN spec when cold, and then RECHECK it when hot. The hot level is what really matters. So check it once you get to normal operating temp, and if the level is OK then, it really doesn't matter whether it's at the high or low end when cold. But you're right... setting it near MIN when cold (with a deep pan) will probably make you more likely to hit the correct range once you warm it up.

3. Yes, the trans temp display in the cluster is the same number you would read with a scan tool, and it should be accurate within the sensor error (a couple degrees maybe?).

Hope that helps....
Good info here ^..

Thank you! I do have one question myself..

If the fluid level is above the top hole on the dipstick at operating temperature, my pan is indeed overfilled? Will this cause any major problems?

Hopefully I'am not hi-jacking this thread!
 

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Good info here ^..

Thank you! I do have one question myself..

If the fluid level is above the top hole on the dipstick at operating temperature, my pan is indeed overfilled? Will this cause any major problems?

Hopefully I'am not hi-jacking this thread!
Yes, if you're above the top HOT hole at operating temp, you are overfilled, so you might want to adjust the level down. Most shops have suction guns with hoses that can suck oil out through the filler tube (or you can probably buy one at a parts store), which is a lot easier than dropping the pan and refilling.

The problem with overfilling is that if the oil gets high enough to reach the rotating parts, it will get churned up and foamy. This will cut your fuel economy (due to increased drag on the rotating parts) and it can also adversely affect trans operation, since foamy oil won't allow accurate control of clutch engagement. So check your dipstick and see if the oil has bubbles in it. If so, then you should definitely adjust it down to the correct level. Even if you have no foam in the oil, setting it at the proper level is best.
 

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Yes, if you're above the top HOT hole at operating temp, you are overfilled, so you might want to adjust the level down. Most shops have suction guns with hoses that can suck oil out through the filler tube (or you can probably buy one at a parts store), which is a lot easier than dropping the pan and refilling.

The problem with overfilling is that if the oil gets high enough to reach the rotating parts, it will get churned up and foamy. This will cut your fuel economy (due to increased drag on the rotating parts) and it can also adversely affect trans operation, since foamy oil won't allow accurate control of clutch engagement. So check your dipstick and see if the oil has bubbles in it. If so, then you should definitely adjust it down to the correct level. Even if you have no foam in the oil, setting it at the proper level is best.
Thank you! Well, I just went outside and checked the fluid level cold. The fluid level looks to be over the top two hot check holes.. This can't be good! :doh:

Happy to say, I do have an AFE deep pan with a drain plug. So, I will just loosen the plug and drain some fluid out.
 

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Discussion Starter #7
You are checking it with the engine RUNNING (in Park), correct?

Engine must be running, otherwise you'll get a way-high reading.
Thank You for the quick reply and the excellent knowledge you share!!!

Does it matter whether its in "Park" or "Neutral"? The Dipstick says "Neutral"?
 

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Thank You for the quick reply and the excellent knowledge you share!!!

Does it matter whether its in "Park" or "Neutral"? The Dipstick says "Neutral"?
Okay, so I made the mistake of checking the fluid level with the transmission in park. You definitely want to check the level with the transmission in neutral!!

This is how you get the most accurate reading!
 
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Okay, so I made the mistake of checking the fluid level with the transmission in park. You definitely want to check the level with the transmission in neutral!!

This is how you get the most accurate reading!
Actually, for the 68RFE trans, Park and Neutral are identical hydraulically, so you can check it in either position. I prefer Park for safety reasons.
 

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Actually, for the 68RFE trans, Park and Neutral are identical hydraulically, so you can check it in either position. I prefer Park for safety reasons.
Why does it say on the dipstick "check level in neutral"?
 
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