I'm curious to know if anyone has any idea of what temperature their manual transmission gear oil reaches. While on the dyno a couple days ago, my charge pipe blew off and while reconnecting it I bumped the final drive area of the transmission and noted it was very hot leading me to suspect manual transmissions behind loads in excess of what they were designed for might benefit from an oil cooler and electric pump looped into the drain and fill holes.
If the oil temps are reaching 200+ deg I think it would be worth it as the F40 has been known to show more shift resistance when cold even with the engine off to suggest possible tolerance variance with temp change. Perhaps using synchromesh in my first tranny was part of the failure equation in the same manner that too thin or too hot an oil in a hard run motor can compromise durability.
Now I wonder if running the tranny at a lower oil level than initially prescribed to combat shift resistance problems is a good idea as a result of the reduced heat capacity that will result.
The heat they do have would probably be from the engine being bolted to them and exhaust nearby. Does the tranny oil even get pumped? I dont think there is much of a way to cool it?
Running the fluid level low could probably never be advised for any reason.
[This message has been edited by 2.5 (edited 08-21-2013).]
It may be something to consider. I can't imagine gear oil remaining near normal operating temps being subjected to loads far in excess of what the motors they were attached to from the factory generated, especially in the absence of any proof to the contrary.
Some of the WRX and Saab owners have switched to more shock resistant oil for hard driven manual cars that also see more power output than stock and some also change the gear oil at intervals far more frequent than factory recommendations.
Originally posted by 2.5: The heat they do have would probably be from the engine being bolted to them and exhaust nearby. Does the tranny oil even get pumped? I dont think there is much of a way to cool it?
Running the fluid level low could probably never be advised for any reason.
I was first told by a Saab tranny builder that lowering the oil level was the fix for the F40 cold shift complaints followed later by some one stating that GM mandated it, but that's for a stock application. I run the full dose.
What I felt was definitely not engine or exhaust heat derived.
[This message has been edited by Joseph Upson (edited 08-21-2013).]
I used to run a loose-bearing Muncie 4 speed behind my 3800, and when drag racing it it would get hot enough to shoot oil out the vent. The Isuzu behind it now is much tighter and newer, and barely gets warm. I suspect that the slight tolerance and angle change that results from bearing wear in the trans (especially in the differential bearings) leads to a significant increase in friction and heat.
From what I understand, oil is pulled thru the shafts when the gearsets are spinning; they act like a centrifugal pump.
Keep in mind that the transmission (even a manual transmission) absorbs some of the engine power, due to frictional losses. That absorbed energy is mostly turned into heat. The more powerful the engine, the more heat is dumped into the gearbox.
The big question is whether or not not you can get to a point where the gearbox absorbs enough heat to cause negative effects. I think the only way to determine that is through experimentation.
I was first told by a Saab tranny builder that lowering the oil level was the fix for the F40 cold shift complaints followed later by some one stating that GM mandated it, but that's for a stock application. I run the full dose.
Interesting. Hard to shift when its cold, wouldnt the answer be (example) instead of say 5w30 use 0w30?
[This message has been edited by 2.5 (edited 08-21-2013).]
Interesting. Hard to shift when its cold, wouldnt the answer be (example) instead of say 5w30 use 0w30?
You would think, but apparently it's not that simple. The problem was first complained about in stock G6 cars where some owners were practically locked out of 1st and 2nd gear except for starting the car with the gear engaged until it warmed up a little. Even with the motor off, on a cold day I can feel considerable stiffness in the gear shifter although you would think much of the oil is in the bottom of the transmission away from most of the gears.
I did read mention of high gear tooth temps as one source of considerable heat not unlike the engine oil coming off the bearings at a higher temp than what's in the pan. I've also seen a number of late model rear end failures mainly involving SUVs which I thought in the past was a rare incident. Can't attribute it to poor install at the factory because when they're wrong they whine from the start. Some production cars have temp sensors in the differential.
[This message has been edited by Joseph Upson (edited 08-21-2013).]
Originally posted by Joseph Upson: ... Some production cars have temp sensors in the differential.
A lot of "track ready" cars like the new Z28 and others also have differential oil coolers. Can't say I've heard of a manual tranny cooler, but that doesn't mean they're not out there.
It occurs to me that the 90 degree angle between the ring and pinion in a conventional rear end may generate a lot more heat than transmission gears.
Weve used Holley Black fuel pumps to pump oil out of the trans to a cooler and back into the trans. the main line has to have a orfice in it to slow the oil down long enough to stay in the cooler to cool the temp down. Just use the Lower drain plug as a pickup and the side check plug as the return. Holley black pumps push oil good so i dont know about any other pumps that would.
Weve used Holley Black fuel pumps to pump oil out of the trans to a cooler and back into the trans. the main line has to have a orfice in it to slow the oil down long enough to stay in the cooler to cool the temp down. Just use the Lower drain plug as a pickup and the side check plug as the return. Holley black pumps push oil good so i dont know about any other pumps that would.
That's exactly the kind of arrangement I was imagining as I already have a Holley Black fuel pump in place from temporary use with my turbo oil return, used until it was clear the oil return was sufficient without it. You just have to remember to remove the stainless mesh screen so that there's no problem with oil pickup flow during really cold weather when the oil is thickest.
It just seems to me that if by chance oil temps are reaching and exceeding 200 deg at any time, a cooler might benefit structural integrity by reducing tolerance changes due to heat in applications that far exceed component rated limits, by nearly double in some cases.
One could also run a larger capacity of oil, probably would need to anyway for how much the cooler holds, but a larger reservoir could help with cooling.
I shot the case with an IR gun. 83* outside about 30 miles a few runs over 100mph. The diff and the top of the trans case both read 160*f. Oil pan reads 211*. It was too hot to touch for more than a split second.
Originally posted by Justinbart: I shot the case with an IR gun. 83* outside about 30 miles a few runs over 100mph. The diff and the top of the trans case both read 160*f. Oil pan reads 211*. It was too hot to touch for more than a split second.
In that case it's hotter than that coming off the gears and inside the case. I imagine putting synchromesh in the first F40 I installed instead of the high dollar full synthetic recommended for it probably didn't help my situation and may have contributed to the eventual failure.
A candy thermometer might work lowered into the oil fill hole. I use K thermocouple probes on my rider lawnmower. The thermometers are $30 and up on line and some are junk, but others are very good. The K thermocouple is extremerly accurate and widely used for exhaust gas temp , cyl head temp , lab work etc. Some VOMs include the function. I think I saw a Harbor Freight unit with it cheap. I made an oil sump probe from brake line and K termocouple wire. Not too hard. The guns probably are picking up case temps when aimed? For those interested the AC rider I have runs sump temps of 290-300F doing hard work. I put on a fan-cooled oil cooler.
