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D8 "JJ8" Transmission overheating"
- Thread starter Sameh
- Start date
Welder Dave
Senior Member
Or Bro Nigeria.
Not sure what Captain Manering or Awkright will think of being called Bro
.
Don’t tell ‘em yer name Pike!
Bit of English humour lads.
I’m sure the Nige will understand the bits that get lost in translation with our African friends
Makes me smile though.
.Don’t tell ‘em yer name Pike!
Bit of English humour lads.
I’m sure the Nige will understand the bits that get lost in translation with our African friends
Makes me smile though.
Why all these comments on my reply? I think it is enough. If you have no useful info please don't add reply.Not sure what Captain Manering or Awkright will think of being called Bro
Don’t tell ‘em yer name Pike!
Bit of English humour lads.
I’m sure the Nige will understand the bits that get lost in translation with our African friends
Makes me smile though.
Welder Dave
Senior Member
No disrespect was intended for anyone. There's a lot of knowledge on this forum.
The scavenge is working efficiently. I don't know if the problem with the manufactury material.
Nige
Senior Member
And yet in an earlier post you stated that you drained 40 litres of oil from the converter housing. On the face of it that indicates the converter housing is not being scavenged correctly.
As per the earlier question from @ahart - what is the dealer saying/doing about the problem.?
The dealer has no more solutions. They communicated with CAT and waiting.
JAJ
Well-Known Member
I believe that this should be a dealer problem not a @Sameh problem to fix.
I am not familiar with this model dozer and don't claim to know anywhere near as much as the other guys help you on this, but this seems very odd to me... how did you come to the fact of overheating... dash temp gauge, service codes?
Does it have trans temp gauge, if so what is it reading? Has that been verified with an IR temp gun on a pipe near the temp sender?
You said earlier that the engine coolant temp is only 83*C.... others have already pointed out that coolant should be a lot hotter if the transmission is overheating. So my thinking is are you sure it is actually overheating and not a bad sender giving a false reading?
This may have already been ruled out and I have missed it in reading though but wanted to ask just in case.
I am not familiar with this model dozer and don't claim to know anywhere near as much as the other guys help you on this, but this seems very odd to me... how did you come to the fact of overheating... dash temp gauge, service codes?
Does it have trans temp gauge, if so what is it reading? Has that been verified with an IR temp gun on a pipe near the temp sender?
You said earlier that the engine coolant temp is only 83*C.... others have already pointed out that coolant should be a lot hotter if the transmission is overheating. So my thinking is are you sure it is actually overheating and not a bad sender giving a false reading?
This may have already been ruled out and I have missed it in reading though but wanted to ask just in case.
Look, First the operator claim was about high trn temp. And by tracing the problem we found that all trn oil drawn and sent to torque and not exit back to trn. So the high temp is result and the engine coolant rises temp in final. We checked hoses, Pipes, TC oil cooler for any plug but found nothing.
.RC.
Senior Member
I would nearly bet my balls the problem is in the torque converter.
JAJ
Well-Known Member
It would seem so but I couldn't find the temps anywhere and that should have been double checked early on I was thinking.
On the torque converter, I think the OP means that the housing is indeed flooded with 40 Lts and that the pump has been checked and it is up to spec, but cant keep up with the leakage.... not sure though??
As a nail in the coffin for the Torque converter leakage, the trans lube pressure should be checked if not already and one would expect it to be very low. The port should be after the cooler in the circuit somewhere, flow creates the pressure for it and so low pressure means low flow... that is how the older non electronic machines that i have had experience with work anyway, someone would have to confirm if I am correct on this in relation to this machine.
I could be completely incorrect and don't mind being corrected at all.
Look dear, the problem first was a complaint of high trn temp occur after 3 or 4 hour work. When I checked the oil levels all oil levels was correct except trn oil was low, I adjusted it and measure inlet pressure of TC when the oil is cold, it was 30 psi higher than specs. I tested the machine for 2 hours, it was good. But when I came the day after and checking the trn oil level, I found no oil. I drained the TC oil to see the screen and found too much oil exiting from TC, more than 40litres. So all these days I was wondering why oil doesn't exit from TC. I checked lines if it fitted in the wrong place or plugged but all correct and clear. I checked the Powertrain oil cooler and found it OK. I checked the TC outlet relief pressure, it was as specs 55psi. The question I want to know is TC has internal passages between the oil path which rotate the turbine and the TC sump? or what make oil not to drop to sump and complete path to the outlet relief then cooler then trn path? The oil on TC sump collected in which condition? @nigvPlease advise.
Nige
Senior Member
You may not be aware of this but the outlet relief valve for the converter controls the MINIMUM pressure of the oil leaving the converter, not the maximum. I wouldn't worry too mcuh about the inlet pressure at cold startup being up a bit above specification. It may be an indication of something but I would say "not proven" at this point.
What type & grade of oil is in the powertrain system.?
Oil entering the torque converter has two paths. First is the oil passing through the converter assembly and out via the outlet relief valve to the powertrain cooler. This oil flow is what takes away the tremendous amount of heat generator by torque converter operation. The outlet relief valve maintains the minimum pressure inside the torque converter assembly.
Second is internal leakage within the converter components - quite a lot of it in fact. All the oil that leaks internally from the converter finds its way into the bottom of the housing and is sucked away by the scavenge pump. If a converter has excessive internal leakage the quantity of oil in the converter housing can exceed the capacity of the scavenge pump. Eventually this could cause the oil level in the transmission/rear case to fall because the oil is accumulating in the converter housing and not being returned. If this situation continues it could starve the suction side of the powertrain oil pump transmission charging section and result in cavitation.
TDTO 50
Many thanks, Nige for your great priceless data.
Another question to be fully understand. According to your words if the torque outlet pressure is low, it will lead to cavitation as it controls the pressure inside torque and the inlet pressure affects only in cold start up. Am I right?
Nige
Senior Member
That could be a reason for the high inlet pressure when cold. If you have TDTO 30 available change the oil and try a test with that oil. I was once a big believer in 50 oil in transmissions in hot climates but after a lot of testing I have changed my opinion and would now only recommend to go with 50 in cases of extremely high ambient temperatures - probably over 50 DegC.
No, that is not what I was saying. In the case where a large quantity of oil accumulates in the converter housing for whatever reason the result is that the oil level measured on the transmission dipstick goes down. You found this yourself. If the oil level in the transmission case goes down far enough it can potentially create cavitation in the suction side of the section of the transmission pump (remember that it is a 3-section pump) that supplies the transmission and its controls.