Transmission Overheating

[aussie370]

As the subject heading states I have a overheating transmission.

Under normal condition the transmission doesn't over heat i.e. City driving, flat road etc. It only overheats under load (towing, full load in the back etc) when going up a hill. On a few occasions the truck went into limp mode.

I have had the transmission rebuilt i.e. Rebuild kit, torque converter, valve body serviced/upgraded (soft parts changed). Oil level is ok. I have an oversized oil cooler. The ATF is correct. The transmission shifts/changes perfectly, well a hell of a lot better than previous that's for sure. The engine temp, oil etc are within normal limits. But the problem still persists.

I should also mention that when the truck went into limp mode the 4x4 and check engine lights came on. I would just pull over and let the transmission cool down and then go on my way. Oh it would not restart until the transmission cool down.

I have taken the truck back to both the place where I have had the transmission rebuilt and to Nissan. Believe it or not no codes were present. The ECU and TCM are talking and are ok so Nissan said.

I'm at a loss.

[disallow]

I'd be checking the plumbing between the Trans and the new cooler. Maybe a restriction/flow issue?

Do you have the radiator bypassed?

[Kestral]

Yes check your plumbing could be a crimped hose.

[aussie370]

Thanks for the suggestions. I never thought about a crimped hose or restrictive flow.

@disallow Yes sir I have a bypass. One of the first things I checked when I read about the problem. When they rebuilt the transmission they mentioned there was no evidence of water mixing with the ATF.

[disallow]

Thanks for the suggestions. I never thought about a crimped hose or restrictive flow.

@disallow Yes sir I have a bypass. One of the first things I checked when I read about the problem. When they rebuilt the transmission they mentioned there was no evidence of water mixing with the ATF.

Did you get rid of the factory auxiliary cooler? It looks small but is very effective. If you put in aftermarket, it may not have the same hear rejection rate as the factory cooler. Most aftermarket coolers I've seen are no where near as good as the factory cooler we have.

Also, if you've replaced your rad, I'd consider undoing the bypass.

[aussie370]

Did you get rid of the factory auxiliary cooler? It looks small but is very effective. If you put in aftermarket, it may not have the same hear rejection rate as the factory cooler. Most aftermarket coolers I've seen are no where near as good as the factory cooler we have.

Also, if you've replaced your rad, I'd consider undoing the bypass.

In all honesty I don't know. When I arrived up here in Phoenix from Boston I needed to upgrade a few parts and that's when I asked about the bypass. They mentioned it was already done into a small black external one (overheating was occurring). I asked for an oversized cooler (overheating still occurring) even after the transmission being rebuilt.

The transmission was slipping. I would see the RPM needle fluctuate and at times see it sitting at 5K - 6K while cruising. So I guess I assumed it was the transmission.

So I really have no idea whether the radiator is the original or has been replaced. I purchased the Pathfinder about 4 years ago and it wasn't until I arrived up here that I learnt about problem.

Interesting that you mentioned aftermarket coolers. I will look into that as well. I'm taking the Pathy to the shop tomorrow to check the hoses etc. They are perplex as I am and want a solution.

[Thupertrooper]

Did you get rid of the factory auxiliary cooler? It looks small but is very effective. If you put in aftermarket, it may not have the same hear rejection rate as the factory cooler. Most aftermarket coolers I've seen are no where near as good as the factory cooler we have.

Also, if you've replaced your rad, I'd consider undoing the bypass.

In all honesty I don't know. When I arrived up here in Phoenix from Boston I needed to upgrade a few parts and that's when I asked about the bypass. They mentioned it was already done into a small black external one (overheating was occurring). I asked for an oversized cooler (overheating still occurring) even after the transmission being rebuilt.

The transmission was slipping. I would see the RPM needle fluctuate and at times see it sitting at 5K - 6K while cruising. So I guess I assumed it was the transmission.

So I really have no idea whether the radiator is the original or has been replaced. I purchased the Pathfinder about 4 years ago and it wasn't until I arrived up here that I learnt about problem.

Interesting that you mentioned aftermarket coolers. I will look into that as well. I'm taking the Pathy to the shop tomorrow to check the hoses etc. They are perplex as I am and want a solution.

I think there was info on someone asking if their radiator was original or already replaced somewhere in this forum.
I second the aftermarket trans cooler might not be working as it should.

If i had to redo mine i would go with CSF aluminum radiator so i could run the trans lines to it.

[aussie370]

I think there was info on someone asking if their radiator was original or already replaced somewhere in this forum.
I second the aftermarket trans cooler might not be working as it should.

If i had to redo mine i would go with CSF aluminum radiator so i could run the trans lines to it.

Thanks. I thought about that, but at this stage I just want to eliminate the problem.

While at the shop this morning, the hoses were not crimped. I'm having the Nissan radiator installed. As mentioned above I just want to eliminate the problem then go from there.

And thank you.

[aussie370]

I am at a complete loss.

The external after market cooler removed and another Nissan radiator installed. The transmission still overheating.

[eieio]

I am at a complete loss.

The external after market cooler removed and another Nissan radiator installed. The transmission still overheating.

how can you be sure the trans is actually overheating?
do you have a trans fluid temp guage installed?
there may be something else (trans temp sensor?) that's fooling the system into thinking that it's overheating?

[HiBRiD109]

Sorry to hear about your troubles. I'm pretty new to the pathfinder but I have a few questions on your problem. How do you know that the transmission is overheating (ie codes or display)? You say they are no DTCs on the ECM. Do you have a aftermarket transmission temp gauge? Could the transmission temp sensor be bad or have debris around causing this? Maybe bad wiring to the sensor?

[aussie370]

I have the Bully Dog installed.

I thought about the sensor but the transmission runs at around 190 in town. It is just under load (400 - 500lbs in the back) when going up long steep hills.

[Thupertrooper]

Torque converter with incorrect stall can make the tranny run hot.

Im thinking its an oil or torque converter issue.

[eieio]

WOW!
Mesa, Prescott, and Phoenix all in one thread!

[smj999smj]

I have the Bully Dog installed.

I thought about the sensor but the transmission runs at around 190 in town. It is just under load (400 - 500lbs in the back) when going up long steep hills.

Is 190 Celsius or Fahrenheit degrees? If it's 190 degrees F., that's normal operating temperature for transmission fluid.