Transmission Heating, EXPLAINED
- A Hawas
- Jun 24, 2020
- 5 min read
What you need to know ?
Overheating is the main cause of transmission deficiency, accounting for around 90 per cent of all failures. Your transmission can never run too cool (unless you’re in the snow).
Regular stock transmission coolers work by using the vehicle’s radiator, which is usually hot.
The impact this will have on transmission temperatures is not rocket science.
Like engine oil, automatic transmission fluid (ATF) absorbs the heat produced by moving internal parts. This heat gets released as the transmission fluid passes through a cooling chamber at the bottom of the radiator. Under normal conditions, this would sufficiently cool the ATF before it gets re-circulated back into the transmission.
However, if you add more strain to the gearbox, for example, when towing, if your car is loaded with accessories, long inclines, desert driving or hot summer days, then components have to work harder, which creates more heat than the stock transmission cooler is designed to handle. This additional heat causes the transmission fluid to break down, reducing its ability to perform smooth gear changes as well as causing irreversible damage to the transmission.
Generally, you would use a transmission cooler in a towing vehicle, or in a vehicle that spends a lot of time in traffic, and other conditions.
What you shall know when it comes to Trans Coolers?
Adding an aftermarket transmission cooler to your car is always a good idea. Here are some tips:
Always mount the cooler in a place that has good air flow
If you are mounting it in front of the radiator, always make sure the fin’s in the cooler are parallel with the fin’s in the radiator. This prevents restricting air flow to the radiator.
If you place the cooler in and area with little air flow, a fan is a must
When installing coolers, make sure lines are clear of anything that can rub them
Always use line that is approved for transmission/hydraulic fluid
Fuel line will not work and will break down in transmission fluid.
Bypassing the radiator is the way we prefer a cooler be set up. The transmission will generally run cooler this way
Additionally, this may take some of the load off the radiators job of cooling the engine.
When hooking up multiple coolers several things should be noted
The cooler itself is a restriction of flow and this restriction while not a problem for the cooling or lube to the transmission can cause excessive pressure inside the converter. This can force the converter against the flex plate more so than normal and cause wear to the engine thrust bearing. A stopped up or severely restricted cooler or cooler lines can do the same.
When installing more than one cooler, its advised to put them in parallel with each other, This means one line from the transmission is split with a Y and one line run to each cooler then out of each and into a Y back to a single line running to the transmission. This will assure adequate cooling while reducing the wear to the engine thrust bearing.
Always use line that’s at least as large as the inlets in the cooler, Avoid extreme twist or turns in them particularly with rubber lines.
Type and brands of coolers
No preference here as far as brand. From experience, an expensive brand name unit or a generic one seem to do the same job.
For sure the stacked plate (flat tube) types tend to be more efficient in the same dimensional sizes with a greater temperature drop.
Always be sure that the metal lines coming from the transmission under car do not contact the headers or exhaust
This is not specifically about a cooler but about cooling. If the cooler lines were in contact with the headers, it would super heat the fluid when the headers get hot. Make sure there is no contact so you won’t have a problem.
Always keep transmission cooler lines factory or otherwise as far away from the exhaust as possible.
Transmission temperatures – This question gets asked a lot. What’s TOO HOT?
Well, ideally you want your average temperature to stay under 90 Celsius degrees. However, we would not get too concerned until the temperature gets to or over 110 Celsius degrees.
Heat can damage a transmission by breaking down the fluid and causing rubber seals to harden and break.
What you need to consider in your maintenance ?
Never attempt to remove fluid from your transmission by starting the engine
Never attempt to flush by catching fluid in a pan while adding fluid in the dipstick hole
When this is done, no lube is being sent to the gears and bushings. They can go dry and melt down very quickly, destroying or significantly shortening the life of your transmission.
It is advisable to fully and properly flush a cooler, especially when a converter failure is involved
A transmission internal failure is unlikely to put debris in the cooler, because all fluid coming from the transmission must travel through the trans filter.
Its always a good idea to power flush a cooler or replace it after a failure. It is particularly important in the type of failure. Anything that’s in your cooler or lines will end up in your valve body, bushings and gears.
A cooler cannot be properly cleaned simply by blowing air through it. A can of cooler flush, which most shops have, followed by being blown out with air is the correct way to do it.
When installing rubber cooler lines to metal lines always put a small flair at the end of the metal line
Not too big because you will tear the line on the inside during install. Then place a clamp just ahead of the flair.
Roughening up the outer surface of the metal line with coarse sand paper in the area where the clamp will ride will help assure a good seal and reduce the possibility of blow off.
Never over tighten clamps to the point of the rubber oozing through or being cut this will cause a failure too.
Why You Need a Transmission Temperature Gauge ?
installing a transmission temperature gauge is the best way to prevent overheating as it allows you to track the transmission temperature to ensure it is working at peak efficiency. The ideal fluid temperature is between 80°C to 107°C, where temperatures above this can start to lead to damage.
The Temperature Gauge can warn you when excessive heat is reached and may possibly be ruining the transmission fluid or damaging the transmission.
This can be a helpful tool for any vehicle with an automatic transmission, as well as diesel trucks that tow heavy loads over long distances.
The best place for temperature sending units is in the pan
This is because it will give the best average temperature which is what’s important.
Using the pressure port is OK, however, you will show temps 10 to 20 degrees higher than in the pan.
We do not suggest placing temp senders in either the inlet or outlet from the cooler. This is because it will increase cooler restriction and increase the odds of a leak.
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