ALFAGTV6.COM

[kevin]

As the topic suggests, when should the gearbox have an oil cooler ? After looking at most of our production race carsBMW,Seats etc) here they all have coolers and these are all front mounted boxes without having the extra heat of a combined differential as in the transaxle.
The auto delta box had internal sprayers through the shaft with an external pump(the one I have seen).
Some say once the oil is over 112 degrees as the seels become vulnerable but that not an issue in our boxes. Obviously the cooler is accompanied by an electric pump with small inline filter.
Im sure some of you rocket scientists in Volvo territory or Down under can help add some imput to this topic.

[MD]

YO Kevin. Not a scientific answer but more of a general observation.

If the race car is in events that do very many laps as in some time trials or rally events, the oil could build up heat I am sure to a point that may be detrimental. However, the events that our car participates in are of a short duration and the heat is actually beneficial and does not warrant a cooler. Having said that, even race cars that have a combined engine/gearbox sump and sharing the oil don't seem to suffer unduly as a result of simply heat.

The other basic observation is this. Heat is very efficiently transferred by conductivity. When a gearbox is attached to an engine, some of the heat of the engine is conducted into the gearbox and introduces heat values not present in the transaxle as it is remote from the engine and isolated by the rubber couplings. Whilst there is heat from the rear brakes, this would be more fluctuating depending on the nature of events eg, hillclimbs, drags etc

I am about to get out of my depth here but I offer this to think about.

Engine oil coolers are usually fitted to maintain viscosity and stabilise the oil pressure and thereby provide the correct lubrication for the internal moving parts. In EXTREME engine modifications that may develop MEGAWATTS of power the oil cooling could be to reduce oil temperature to prevent its lubricating qualities from getting damaged as well. Somebody from the Shell labs please chime in...

I strongly suspect that in your case, if it ain't broke, don't fix it. More weight, more complexity, more potential for disaster.

[Zamani]

Kev,

I know this is gonna sound dumb, but the SZ has it, so there must be some merit to it. Maybe Alfa discovered that ventilation is a problem even for a road car back there. So on went the vented rear disc and gearbox cooler.

On the other hand lots of people have raced 116 cars without them.

However I just don't see how having a cooler will hurt. For sure it gets real hot down there. The rear rotors get to about 485F (if I can remember correctly) indicated on my laser temp gun.

That and the rear vented rotors are next on my list.

Maybe you won't see an outright improvement, however what you may see is an increase in longevity of gearbox parts especially if you live in hot climates (remember this is just my speculation).

[MR2 Zig]

It might be a good thing to first find out how hot your geabox oil gets. Find a temp probe that will fit in the oil drain fitting. Then check with your oil company and see what they say is max operating temp. If the gearbox gets too hot then there you go.

Cost should be minimal to find out how hot your gearbox gets.....I have no idea how much it would cost to put in a cooler.


hth,

[ar4me]

Kevin,
There is an existing thread on the same topic with some info: viewtopic.php?f=21&t=2670
I have since decided not to add a transmission oil cooler - one more thing to break, and I don't think the temps (I'm seeing) is a problem.
Jes

[Mats]

Yep, read the other thread.

As far as fitting a cooler, I have all the hardware for it now and the plan is to document everything with plenty of pics.

[Giuliettaevo2]

these are all front mounted boxes without having the extra heat of a combined differential as in the transaxle.

where do you think the diff in a FWD gearbox lives ? The diff on a FWD box is just as close(on some boxes even closer) by the gears as on a transaxle box...

I think the FWD boxes run hotter as the transaxe ones, also because of the aforementioned heat-transfer from the engine and the hotter livingspace in the enginebay.

Good quality heatwrap around your exhaust and taking the rearbrakes outboard could give quite a reduction in temperature i think.

I think you should first install a good tempsensor and monitor the temp a while. if it gets over 110 degrees i would start thinking about an oil cooler.

An oil spray on the crown/pignion would be a nice touch if you build a cooling system.

[kevin]

MD, that cleared a lot up for me. I missed that other thread but just read it - thanks Jes. The main reason why i was looking in to this is that we have a race at Phakisa(ex Moto GP track) where it is extremely fast, much faster than any other circuit here and last time I could smell the gearbox fumes from breather into the car which coincided with a whine. I managed to get the car home but broke pinion on next practice session.
I started thinking that i might have 'cooked' the box but that was an over imaginative mind.
So with all the responses from above (Z, Zig)I have bought some probes(very accurate patches) to stick on the box . This should tell me straight away if im in any danger area. The race is only on 23rd this month so must wait.
There were some theories about pinion failures(four other reasons) and one of them was oil that got too hot which caused micro explosion when then crown wheel meshed with pinion. (bull s&#$%)Which all linked to point loading - failure.

[Mats]

Sounds more like a bearing failure -> contact patch walk -> root stress in the pinion goes sky high -> terminal failure.

[TS_turbo]

with proper synt. oils even 150+ degrees are not a problem (75w-140 racing oils)
BUT aluminum long and weak alfa transaxle will not take it for long ... dont forget fact that if average temp is 150 local bearing and teeth contact patches are much higher
i want to try running ATF as transaxle oil with proper cooling(80-100 C)
ATF is much thinner at lower temps and is less slipper than conventional gear oils (better synchro work and feel )

[Mats]

Difficult to make general assumptions about pinion preload due to heat and how ATF type oils work. It is very much down to the specific installation.
Are you sure the ATF oil works for hypoids with out offset for instance? Certainly not the most effective fluid for LSDs either.

I'd love the low-drag side of it though...

[kevin]

Mats, I think you are spot on with my last gearbox failure. I have also used ventillated rear discs and brought the exhaust out the side since then. This should help reduce temp. The bearing on that box which stripped the pinion started turning on the LS unit which intern distorted the shaft. Bottom line I must wait for my temp tests which I suspect will not be in the 'danger' area.

[rz]

hi kev,
with the rz i had a gearbox faillure four times and the sz has one too!
the cooler is not a guarantee that nothing will brake.

reading my own post says "you are an idiot, you brake all the gearboxes"
No, in no other car i have had problems and i am not brutal with the box.
only i drive very long distances early in the morning at 220km/h for at least an hour or more.(6 am on sundays)
that is maybe why i lost my licence several times

[MD]

..now rz's post sort of puts it all back to some scientific approach about temperatures and creeping tolerances. Can't see one could make a decision otherwise.

What an interesting revelation..mmm ?

What I am cosistently finding developing the race car is that people/organisations will often contradict each other when giving so called "expert" advice. I am sick to death of it. The suck it and see mentality is rife out there. Be careful.

[rossogtv]

i was running an Alfa 75 in long distance racing ( 12 and 6 hours ) with almost stock 190 HP 3.0 engine, outboard brakes and exhaust ending by the door, 47% LSD. An oil cooler is needed because temp. vent up to 180 C, and all gear bearings except 5th were damaged after only one race. The bearings ( not the ball bearings ! ! ) were all with a coocked on black film and measuring them detected a play of 0,4 to 0,7 mm, what is way off the original measurements.
The higher temperature was also not very good for the synchronisers, they were all crap after only one race. The oilcooler brings temperature down to 120 C.
Breaking a gearbox is mostly caused by the moving of the main shaft and poor condition of the diff bearings, i use some special non original parts, had no failure since them. But it needed about 5 total failuring boxes, before all reasons for that were found.
I use 80W-140 oil for LSD.