transmission overheating

hi all,
i have a cat it38g serial jan 00443 which i bought not long ago.
the transmission filter gets so hot even at idle, machine not in operation and even hotter when its working.
put a new filter and a new bypass valve but still no difference.
one thing i noticed when having a check on the modulating valve pressures,valve number 5,last one on the bottom reads 240 psi with gear in neutral.is that normal?
any advice what to do next woud be great.
cheers

naheed said:

any advice what to do next would be great.

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Maybe get a Service Manual..?
https://www.ebay.com/p/CAT-Caterpil...anual-RTB-CRD-PHN-CSX-B9y-Volume-1/1838043939
Although this one does not include JAN-prefix when I cross-referenced some of the S/N prefixes on the spine of the cover (e.g. CSX) it took me to the same document reference, so it would work for your particular machine.

Clutch #5 is engaged when the transmission is in neutral, so you should have pressure. Actual pressure is low though. Spec is 325+/-10psi for ALL clutches except #3 which is 240+/-10psi.
Table of clutch engagement below.


Next thing I would suggest is to run a calibration of clutch fill times and of clutch engagement pressures - 2 separate calibrations. This process can only be done with Cat ET.

Hi,I would check the main transmission pressure and the torque convertor outlet pressure and report back
A number of issues can cause overheating
Faulty main relief main
Worn transmission pump will allow very little flow to cooler
torque convertor outlet relief valve set to high will also allow overheating issues
large internal system leak can also contribute to overheating
i

Hi nige,
Actual pressure at solenoid 5 in gear 3/4 is 320 psi but in neutral it shows 240.will borrow et next week and do calibrations.
@MARK
What pressure is transmission relief at?
And torque conv outlet?
Will have a check.

here is the test procedure
from memory the torque convertor outlet test port is behind the no 5 clutch solenoid
Mark

done pressure tests today and this is what i got,
torque converter inlet idle-20 psi
full rpm-100 psi
torque conerter outlet idle-10 psi
full rpm -40 psi
lubrication pressure idle-10 psi
full rpm-40 psi
all these above tests i found the pressure gauge to move pretty slowly, especially lub pressure which i thought would immediately jump to 40 psi.plus i did a oil change(shell tc30) ,new transmission filter and checked the strainer9(ok).will do a stall test and report.

main relief valve pressure idle-320 psi
full rpm-360 psi.

Transmission filters will run as hot as the oil is. They don't cause heat. That comes from a leaking torque converter, slipping transmission or plugged coolers. Does the gauge and alarms say that the oil it hot? Have you used an infrared thermometer so you know the exact temperature the oil is running at.
You may be chasing something that is normal.

Torque converter inlet pressure should be no more than 140psi with oil cold and engine at High Idle speed.
You need to be measuring the converter outlet pressure with the transmission stalled in 4th speed and the engine at the maximum throttle position (you won't get full RPM, probably only somewhere around 2100 RPM). Usually it will be somewhere around 50+/-5psi. I can't lay my hands on definite information, maybe Mark can..?

@John
There is no clutch slippage,torque converter leakage would mean loss of power yet I tried and the wheels spin under load.will have a check with cooler.
Nige,
Will do a stall test and calibrations tomorrow to see what happens.
Cheers guys

Nige said:

Torque converter inlet pressure should be no more than 140psi with oil cold and engine at High Idle speed.
You need to be measuring the converter outlet pressure with the transmission stalled in 4th speed and the engine at the maximum throttle position (you won't get full RPM, probably only somewhere around 2100 RPM). Usually it will be somewhere around 50+/-5psi. I can't lay my hands on definite information, maybe Mark can..?

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Stall speed is 2085 +/- 65 rpm
Have you checked that the oil cooler bypass valve is plumbed correctly and is functional
Mark

Cooler bypass valve I had put new

I was getting confused by the single/double stall test procedure (attached) where the instructions are to install a 0-to-58psi gauge to the TC outlet pressure test port. With the TC Out pressure at converter stall being 60+/-20psi as quoted above by Mark that doesn't make sense, not to me anyway. You're being told to install a gauge which is not capable of measuring the maximum specified pressure of 80psi without going pop.

Nige said:

I was getting confused by the single/double stall test procedure (attached) where the instructions are to install a 0-to-58psi gauge to the TC outlet pressure test port. With the TC Out pressure at converter stall being 60+/-20psi as quoted above by Mark that doesn't make sense, not to me anyway. You're being told to install a gauge which is not capable of measuring the maximum specified pressure of 80psi without going pop

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hi nige,
specified torque converter outlet pressure at stall test should be min 40 psi and i got 50 psi off my test!
i wonder what the max permissable would be? so mark is correct in that stating 60 +- 20 psi,maybe a mistake on the pressure gauge size.
i cleaned out the torque converter inlet relief valve(that sits under the main transmission control valve),it had a worn o ring which seemed like some pressure would be lost there,the stall test and calibrations went well.im very happy after the fill calibration as the transmission sounds different now and gear change is so much smoother.
and great im not sure what made the difference the calibration or the worn o ring on the valve,but after the calibration seems the transmission and filter arent getting hot anymore and after a good run the max temp i saw was 170 deg f.
so finally another problem solved and thanks to all you guys for helping out!
last question on this, if the fill calibration is out will it overheat????
cheers guys

Good to here you got it sorted out.
I suspect the low gauge is a typo they do happen
Mark