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Tranny Temp Gauge Shows Extremely Hot

xtmsports

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xtmsports Enthusiast

xtmsports

Posted
Posted

Hi guys,

 

I have a 2002 Chevrolet Silverado 2500HD with the 8.1L engine and Allison Tranny.

 

Just within the last couple of months, my wife has been complaining that the tranny gauge gets to the red zone.

 

I let the truck cool for about 30 minutes and it goes back down to 200 degrees and test drive and it stays on 200 degrees.

 

Well, now she tells me that if she drives the truck for more than 30 minutes, then the temp will get to the 300 degrees red zone.

 

Can anybody please assist with some diagnostic help? i am trying to avoid having to take the truck to the dealer. They want $110 just to look at the problem.

 

What would cause the transmission to run hot if I was not towing anything nor was the truck in 4 wheel drive. Tranny fluid was replaced a year ago and it is at normal levels.

txab Senior Enthusiast

txab

Posted
Posted

I would check to see if the tranny fluid cooler is clean of bugs and debris and fine are not all bent up. You need airflow. I'd also check to see if fluid passages in the cooler are clear and flowing freely and do not have restriction. What's the engine temp like? What does your fluid look and smell like? At 300 degrees you're cooking it pretty good. You could have a sensor or gauge being inaccurate.

Draenor Senior Enthusiast

Draenor

Posted
Posted

 

 

I would check to see if the tranny fluid cooler is clean of bugs and debris and fine are not all bent up. You need airflow. I'd also check to see if fluid passages in the cooler are clear and flowing freely and do not have restriction. What's the engine temp like? What does your fluid look and smell like? At 300 degrees you're cooking it pretty good. You could have a sensor or gauge being inaccurate.
:rolleyes:
masterp2 Enthusiast

masterp2

Posted
Posted

Have you ever replace the spin-on filter? It is in series with the cooling loop. If clogged, it will interfere with fluid flow. Replace it first. Hopefully you don't have a deep pan.

xtmsports Enthusiast

xtmsports

Posted
  • Author
Posted
I would check to see if the tranny fluid cooler is clean of bugs and debris and fine are not all bent up. You need airflow. I'd also check to see if fluid passages in the cooler are clear and flowing freely and do not have restriction. What's the engine temp like? What does your fluid look and smell like? At 300 degrees you're cooking it pretty good. You could have a sensor or gauge being inaccurate.

 

 

The oil is clear red and no burning smell.

 

My wife has said that the gauge will jump to 300 and then drop right away to 200 degrees and then back to 300 degrees and stay there.

 

How can I check the temperature? Where is it located?

 

Thanks

xtmsports Enthusiast

xtmsports

Posted
  • Author
Posted
Have you ever replace the spin-on filter? It is in series with the cooling loop. If clogged, it will interfere with fluid flow. Replace it first. Hopefully you don't have a deep pan.

 

 

I am not sure what the "spin-off" filter is.

 

last year, they dropped the oil pan and replaced the filter inside the oil pan.

 

How would I know if I have a deep pan? It's just the standard factory oil pan.

 

Thanks.

71GMC_3/4T Enthusiast

71GMC_3/4T

Posted
Posted

If the temperature "jumps" quickly, I'd be thinking it was a bad connection or sensor.

 

Find the sensor and unplug it. If it jumps to 300, you're almost there!

 

Temperatures don't usually change rapidly. At least mine doesn't on a cold winter morning while I'm waiting for the bugger to warm up!

dewfpo Senior Enthusiast

dewfpo

Posted
Posted
Have you ever replace the spin-on filter? It is in series with the cooling loop. If clogged, it will interfere with fluid flow. Replace it first. Hopefully you don't have a deep pan.

 

 

I am not sure what the "spin-off" filter is.

 

last year, they dropped the oil pan and replaced the filter inside the oil pan.

 

How would I know if I have a deep pan? It's just the standard factory oil pan.

 

Thanks.

 

 

The red spin-on filter (just like your oil filter) sits next to the tranny pan on the drivers side front corner of the pan. It needs to be changed regularly.

 

DEWFPO

nonotme42 Enthusiast

nonotme42

Posted
Posted

Not unless he has an Allison! If he's just got the 4L80E, the only filter is just going to be in the pan...and since he said they dropped the pan and changed the filter INSIDE the pan, that's a dead giveaway eh?

 

My vote on the issue at hand is bad temperature sending unit...especially if its acting all erratic and the fluid doesn't appear to look like old oil...which it would with a few trips to 300 degrees....which the transmission probably isn't even capable of before something would break.

terryk Enthusiast

terryk

Posted
Posted

Don't Allison's also have an issue with overheating if they are overfilled with fluid? Not sure how that works but it seems to be a common response to a hot Allison.

dewfpo Senior Enthusiast

dewfpo

Posted
Posted
Not unless he has an Allison! If he's just got the 4L80E, the only filter is just going to be in the pan...and since he said they dropped the pan and changed the filter INSIDE the pan, that's a dead giveaway eh?

 

My vote on the issue at hand is bad temperature sending unit...especially if its acting all erratic and the fluid doesn't appear to look like old oil...which it would with a few trips to 300 degrees....which the transmission probably isn't even capable of before something would break.

 

His banner shows he's got a 2500HD.

 

DEWFPO

dewfpo Senior Enthusiast

dewfpo

Posted
Posted
Don't Allison's also have an issue with overheating if they are overfilled with fluid? Not sure how that works but it seems to be a common response to a hot Allison.

 

If it's slightly overfilled it will puke some fluid out (mine has) but it doesn't overheat.

 

DEWFPO

xtmsports Enthusiast

xtmsports

Posted
  • Author
Posted
Not unless he has an Allison! If he's just got the 4L80E, the only filter is just going to be in the pan...and since he said they dropped the pan and changed the filter INSIDE the pan, that's a dead giveaway eh?

 

My vote on the issue at hand is bad temperature sending unit...especially if its acting all erratic and the fluid doesn't appear to look like old oil...which it would with a few trips to 300 degrees....which the transmission probably isn't even capable of before something would break.

 

His banner shows he's got a 2500HD.

 

DEWFPO

 

 

 

Yes, I have the red filter too. It was also changed when they dropped the pan a year ago.

xtmsports Enthusiast

xtmsports

Posted
  • Author
Posted
If the temperature "jumps" quickly, I'd be thinking it was a bad connection or sensor.

 

Find the sensor and unplug it. If it jumps to 300, you're almost there!

 

Temperatures don't usually change rapidly. At least mine doesn't on a cold winter morning while I'm waiting for the bugger to warm up!

 

 

New update. With women, you have to keep DIGGING for all of the information and it always changes.

 

She said that it doesn't just jump to the 300 mark. It slowly creeps up to 300 and then it "bounces" in between the 200 and 300 mark for a second and then stays at 300.

 

She also took it out today and it did not go to 300, but she is claiming because it isn't hot today.

 

I think i'm going to replace the temperature sending unit since it's only $20 from dealer.

 

Do you know where the sending unit resides on the tranny?

 

Thanks.

dewfpo Senior Enthusiast

dewfpo

Posted
Posted
If the temperature "jumps" quickly, I'd be thinking it was a bad connection or sensor.

 

Find the sensor and unplug it. If it jumps to 300, you're almost there!

 

Temperatures don't usually change rapidly. At least mine doesn't on a cold winter morning while I'm waiting for the bugger to warm up!

 

 

New update. With women, you have to keep DIGGING for all of the information and it always changes.

 

She said that it doesn't just jump to the 300 mark. It slowly creeps up to 300 and then it "bounces" in between the 200 and 300 mark for a second and then stays at 300.

 

She also took it out today and it did not go to 300, but she is claiming because it isn't hot today.

 

I think i'm going to replace the temperature sending unit since it's only $20 from dealer.

 

Do you know where the sending unit resides on the tranny?

 

Thanks.

 

 

Most factory transmission temp sensors are in the valve body since that is the best place to measure the fluid. I'm not 100% sure on the allison though.

 

DEWFPO

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