Corvette C4 gearbox temp
Discussion
Not sure if I've posted this before, but as I went to the tunnel run on Saturday, we sat in the traffic on the bridge for quite a long time, I noticed my gearbox temp going over 200, this hasn’t really happened before, so I was wondering whats the max it should go upto in traffic conditons safely without causing any damage?
>> Edited by mrvette on Thursday 19th January 23:25
>> Edited by mrvette on Thursday 19th January 23:25
I'm assuming you've got an auto - if not then everything that follows is, ermm, completely irrelevant!
Mineral oils degrade at high temperatures so a hot tranny is bad news for your ATF. This leaves the question how hot is too hot? 250F will kill most ATFs and by the time it gets to 230F the fluid's already having a hard time. Under heavy load situations the upper end of this range can readily be attained so doesn't necessarily mean there's anything wrong.
It's difficult to state an "ideal" temperature but 180F is a good figure and anything in the range 160F to 215F seems to be considered relatively normal.
Sounds as though your 200F is nothing too exceptional.
Mineral oils degrade at high temperatures so a hot tranny is bad news for your ATF. This leaves the question how hot is too hot? 250F will kill most ATFs and by the time it gets to 230F the fluid's already having a hard time. Under heavy load situations the upper end of this range can readily be attained so doesn't necessarily mean there's anything wrong.
It's difficult to state an "ideal" temperature but 180F is a good figure and anything in the range 160F to 215F seems to be considered relatively normal.
Sounds as though your 200F is nothing too exceptional.
Yep its an auto!
I gave the car quite a hard time that day, and it was idle for a long time and in a lot of start/stop traffic!
I think I'll change the gearbox oil over the weekend just for piece of mind, although it does smell and look fine colour wise.
They do have a warning light/alarm but it doesn’t go off until about 300F I think!!
>> Edited by mrvette on Thursday 19th January 23:40
I gave the car quite a hard time that day, and it was idle for a long time and in a lot of start/stop traffic!
I think I'll change the gearbox oil over the weekend just for piece of mind, although it does smell and look fine colour wise.
They do have a warning light/alarm but it doesn’t go off until about 300F I think!!
>> Edited by mrvette on Thursday 19th January 23:40
I've not found a satisfactory answer to the change or don't change question for ATF. My "other" auto car is now 8 years old and 120,000 miles yet the dealer swears blind the ATF should definitely not be changed. They reckon once the fluid is knackered the tranny is knackered and vice versa. Same for the diff oil. In both cases just an occasional level check and top-up.
Only thing I've heard about that is that occasionally if your transmission is that had (well, clutches and bands at any rate), then the crap state of the oil and also the debris give the bands a little more friction, but changing to new fluid can make the situation worse.
Auto transmission fluid doesn't normally get changed enough. I'd change it at the first sign of burning, the bearings/bushes/pump/gears/valves will all thank you for it!
Auto transmission fluid doesn't normally get changed enough. I'd change it at the first sign of burning, the bearings/bushes/pump/gears/valves will all thank you for it!
It's easy to fit a tranny cooler to a C5 as GM have a specific kit for the job.
The part numbers are here:
12480080 Transmission Oil Cooler kit
Consists of:
12480081 Pump, Transmission Oil Cooler
This special design electric oil pump is for cooling 6-speed transmissions in HD applications. This pump is designed to direct transmission fluid thro...
12480082 Cooler, Transmission Oil
This HD transmission oil cooler is designed for cooling 6-speed transmissions in HD applications. This cooler is designed to regulate transmission tem...
12480087 Switch, Thermal
This special calibrated thermal switch is used to control the transmission pump. This thermal switch is calibrated to properly regulate the temperatur...
12480088 Package, Hardware Fasteners
This is a complete package of all fasteners and components used to install P/N 12480080 transmission kit.
12480117 Harness, Wiring
This special wiring harness is designed for P/N 12480080 transmission oil cooler kit. This harness is designed for easy installation and has all prope...
The part numbers are here:
12480080 Transmission Oil Cooler kit
Consists of:
12480081 Pump, Transmission Oil Cooler
This special design electric oil pump is for cooling 6-speed transmissions in HD applications. This pump is designed to direct transmission fluid thro...
12480082 Cooler, Transmission Oil
This HD transmission oil cooler is designed for cooling 6-speed transmissions in HD applications. This cooler is designed to regulate transmission tem...
12480087 Switch, Thermal
This special calibrated thermal switch is used to control the transmission pump. This thermal switch is calibrated to properly regulate the temperatur...
12480088 Package, Hardware Fasteners
This is a complete package of all fasteners and components used to install P/N 12480080 transmission kit.
12480117 Harness, Wiring
This special wiring harness is designed for P/N 12480080 transmission oil cooler kit. This harness is designed for easy installation and has all prope...
mrvette said:
is it the same kit for my C4 ?
Nope.....but I'd try someone like Lingenfelter or Doug Rippie as I would think they would have a kit.
Having said that unless you are driving your vette very hard for a long time i.e. Autobahns at excess of 150 for hours upon hours you really shouldn't worry about tranny temperature.
Here's some curious ones.
I reckon auto C5s come standard with a transmission cooler. I'm sure I remember seeing one under there and it looks as though the item was revised in 2003 www.kron4.com/global/story.asp?s=2599676 " All Corvettes with automatics got a new aluminum transmission cooler case."
Shock horror for personal importers! Manual C6s come with a transmission cooler in Europe but base models in USA don't have one. www.corvettemuseum.com/specs/2005/powertrain.shtml "To increase durability in sustained high-speed situations, the Z51 and the base European manual-transmission models have a transmission cooler."
For the C6 auto 260F is the point at which they reckon the temperature is going too high. "For protection from the high temperatures that are generated by high speed, a four-plate oil cooler has been added. When the transmission fluid reaches 127 degrees Celsius (approximately 260 F), the torque converter lock does not disengage, except briefly during shifts. This prevents fluid shear in the torque converter from adding heat to the transmission."
Presumably transmission coolers do precious little when you're stuck in traffic as there's no airflow and no fan. More targeted towards high acceleration and high speed.
I reckon auto C5s come standard with a transmission cooler. I'm sure I remember seeing one under there and it looks as though the item was revised in 2003 www.kron4.com/global/story.asp?s=2599676 " All Corvettes with automatics got a new aluminum transmission cooler case."
Shock horror for personal importers! Manual C6s come with a transmission cooler in Europe but base models in USA don't have one. www.corvettemuseum.com/specs/2005/powertrain.shtml "To increase durability in sustained high-speed situations, the Z51 and the base European manual-transmission models have a transmission cooler."
For the C6 auto 260F is the point at which they reckon the temperature is going too high. "For protection from the high temperatures that are generated by high speed, a four-plate oil cooler has been added. When the transmission fluid reaches 127 degrees Celsius (approximately 260 F), the torque converter lock does not disengage, except briefly during shifts. This prevents fluid shear in the torque converter from adding heat to the transmission."
Presumably transmission coolers do precious little when you're stuck in traffic as there's no airflow and no fan. More targeted towards high acceleration and high speed.
C4 Autos, as per most automatic equipped cars (stock anyway) have a small heat exchanger built into the side of the radiator (right hand side on L98's) - it's got two steel pipes, approx 3/8 in diameter, screwed into that end tank. These are low pressure fluid lines, and you can get cheap air cooled varients to supplement/replace the duty of this heat exchanger. It just swaps heat with the engine coolant.
Air cooled ones are pretty compact, approx6" X 10" I think, if it's put somewhere near the radiator, it'll benefit from both airflow from the car moving but also some from when the rad fan(s) cut in.
In truth though, do you really need one? These boxes don't have a habit of packing up (damn, just sounded the death knell for mine...), it's only hard sustained use that might justify the addition of one. If yours is heating up under normal traffic (should I say overheating) it points to an internal problem, all a cooler will do there is mask the problem, not make it go away.
Air cooled ones are pretty compact, approx6" X 10" I think, if it's put somewhere near the radiator, it'll benefit from both airflow from the car moving but also some from when the rad fan(s) cut in.
In truth though, do you really need one? These boxes don't have a habit of packing up (damn, just sounded the death knell for mine...), it's only hard sustained use that might justify the addition of one. If yours is heating up under normal traffic (should I say overheating) it points to an internal problem, all a cooler will do there is mask the problem, not make it go away.
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