How hot does a manual trans run?

[SecondMonkey]

Never really thought about this before until I saw it for sale on ebay. A trans cooler for a manual truck transmission that bolts onto the PTO outputs on both sides. Supposedly adds 2 quarts of fluid and is made out of aluminum with cooling fins.

Being the oil geek that I am I instantly thought "I want one of those!", but really, would it do me any benefit? How hot does a manual trans get? I have a '79 1 ton Chevy truck with a manual trans that's geared like a tractor, which I plan on filling with Amsoil 75w90.

 

[JohnBrowning]

Some small Mitsubishi car's had trans coolers on their manual transmissions too. Usually you only see these on large heavy equipment. Seldom do you see them today on 1 ton and lighter vehicles because they can just use a high grade synthetic and accomplish much the same thing.

If you are working a set of gears hard enough you can get them hot enough to blister the paint and if taken to failure you can melt the gears and aluminum and yellow metal inside but the noise it would be making would be all the warning anyone that can hear would need to shut down!

It is a another pontiela leak point so on a truck it is a really bad thing to add if you do not need it. If you puncture it with a branch or a rock guess what?

 

[Doug Hillary]

Hi,
SecondMonkey - In the world of "real" (Class 8) trucks gearbox coolers are a reality. Some are also fitted (on spec.) to differentials

My average oil temps are as follows;

Gearbox - SAE50 synthetic lubricant = 86C (Normal >120C, Warning 149C)

Diffs = 75W-90 GL5 synthetic + 94C (Normal >120C, Warning 149C)

 

[Audi Junkie]

Just get a $20 IR thermometer.

 

[jaj]

My 2008 BMW E92 M3 has a thermostatically-controlled transmission cooler on the six-speed manual transmission.

The thermostat runs an electric pump that circulates gearbox oil through the exact same oil-to-air radiator that a BMW 335i twin-turbo uses as an engine oil cooler.

 

[d00df00d]

Originally Posted By: jaj
The thermostat runs an electric pump that circulates gearbox oil through the exact same oil-to-air radiator that a BMW 335i twin-turbo uses as an engine oil cooler.

I will remember that next time someone compares a chipped 335i to an M3...

 

[mechtech2]

Some expensive cars use a surprisingly small manual gearbox lube capacity.
1 1/2 qts or so.
This makes things more critical.
But I'd change the fluid more frequently before adding a cooler that was not factory implemented. For sure.

 

[tdi-rick]

I have an oil cooler for one of my vehicles that specced ATF as the fluid in previous incarnations (same g/box) and the t/stat starts to open at 74*C.
Later versions that specced MTF's did away with the cooler, but within a short space of time the cooler reappeared in ROW spec vehicles, although European spec vehicles still run without.

 

[Nick R]

Originally Posted By: mechtech2
Some expensive cars use a surprisingly small manual gearbox lube capacity.
1 1/2 qts or so.
This makes things more critical.
But I'd change the fluid more frequently before adding a cooler that was not factory implemented. For sure.



I know its not an AT, but what on earth car out there uses only 1 1/2 quarts of oil? That is like a diff, probably less even.

 

[Nick R]

Originally Posted By: Doug Hillary
Hi,
SecondMonkey - In the world of "real" (Class 8) trucks gearbox coolers are a reality. Some are also fitted (on spec.) to differentials

My average oil temps are as follows;

Gearbox - SAE50 synthetic lubricant = 86C (Normal >120C, Warning 149C)



Diffs = 75W-90 GL5 synthetic + 94C (Normal >120C, Warning 149C)


Do Diffs really get that hot? wow.

 

[Doug Hillary]

Hi,
rudolphna - The highest temps I ever recorded was 102C in the rear diff of my tandem drive trucks

In my 928 Porsche (V8 - rear transaxle) the normal diff temp was 75C. In some Japanese utes ets this is around 55-65C. Usually differentials run cooler than most people imagine

Sulphur-phosphorus based diff fluids tend to deteriorate rapidly above around 100C.

Synthetic gear lubricants flow better when cold and cover the operating temperature range much better remaining stable up to around 150C. They also tend to lower the normal operating temperature by up to 10-20C thereby extending seal life.
They also contribute to better fuel economy

The maximum gearbox temp I ever recorded in my trucks (18spd Roadranger with cooler) was 100C. This was using a synthetic SAE50 prescribed lubricant

 

[Brett Miller]

Originally Posted By: rudolphna
Originally Posted By: mechtech2
Some expensive cars use a surprisingly small manual gearbox lube capacity.
1 1/2 qts or so.
This makes things more critical.
But I'd change the fluid more frequently before adding a cooler that was not factory implemented. For sure.



I know its not an AT, but what on earth car out there uses only 1 1/2 quarts of oil? That is like a diff, probably less even.


That's about what my 2003 Civic holds.

 

[d00df00d]

My car's transmission holds 1.25 quarts (and it's ATF to boot).

 

[4wheels]

My Z06 6spd manual holds approx 4.5 qts of transmission fluid & has a cooler/pump. Makes it fun when trying different fluids...

 

[38sho]

some of the SHO's with gauges run about 200f on the highway and 250+ on the track.... some of the higher numbers on the track are people using a quaife differential that brings a lot of heat with it when its works hard.....

most people run ATF in our trans

i think this is 3qt capacity