Remote oil cooler on manual transmission

[PEW]

I have a small car (a Liege) which uses an 850 cc engine and a small 4 speed gearbox, the latter "not being known for its reliability". At Mallory Park racetrack during an endurance event the oil badly overheated and the gearchange became more tricky. The car eventually suffered a bad gear downchange (not me driving) which broke some teeth off the layshaft. To give you some idea of the pressure we put our little cars under, our team came 5th out of 26 teams involved and we beat a team driving a pair of 6 litre, 500 bhp cars; one a Cobra Replica and the other a Lola T70 replica.

I now wish to fit a small oil cooler to the gearbox using an electric pump. I have sourced the cooler and gear driven pump. I intend to use a thermostatic switch to control the pump.

Has anyone here relevant experience of this type of project and what are the pitfalls, if any?

I've found very scant information on the web and I've tried the search facility here with no success.

Thanks in advance for any advice, as long as it's not "use a better gearbox" because I'm hoping to keep the car original.

Paul W.

 

[romke]

use of a ATF might be a good alternative. ATF's are very oxidation resistant and that could help you. if you want to try it, you are advised to use a topquality synthetic ATF.

You can get an idea of the types that are suitable here:

http://www01apps.zf.com/kst464/ZF_I...?doStatistik=1&doMode=1&mode=3&doID=1&id=2371

you should choose a product listed for one of the 5 or 6 speed automatics. these products differ somewhat in frictional characteristics, but all have a very high oxidation and thermal stability. getting them could be a problem since they are only used when rebuilding the transmission and for factory fill. you might try a firm that specializes in transmission rebuilding. they might be willing to sell you a few litres.

another suitable product group are the products used in aisin 6 speed automatics installed in or example volvo, peugeot and alfa romeo cars. they have similar characteristics as the ZF-advised product. obtaining them is just as difficult unfortunately.

 

[PEW]

Romke, thanks. The link didn't work but I think I found the correct website.

There's a very good motor factor near me and also a transmission specialist so I'm sure I can find a good quality fluid.

 

[romke]

I noticed that ZF has taken part of their site down for maintenance. The link might work again next week.

 

[thundair]

Paul
FWIW I have done a lot of work with PSRUs (transmissions for aircraft) and I have always designed in a cooler with a return spray at the gears and bearings that are loaded.The big advantage for remote reservoir w/cooler is (as was mentioned) not having a box whirl around a lot of oil. The caveat with an on/off switch is; where does the oil in line go? Does it drain back into the box and overfill it, or is there a reservoir that can be brought back on line? Just a few thoughts as I have never designed a gear box other then dry sump.

Cheers

I don't know anything but the people that do.

 

[PEW]

Thankyou for the idea.

I understand the advantages of a properly designed dry sump system (I'm a helicopter pilot with some engineering background) but speaking from a practical point of view I don't have the resources or time to research/experiment this avenue.

My concern would be that in an essentially "empty" dry sumped gearbox I couldn't guarantee correct oil supply to all areas needing it. I don't think it's been done before on this type of gearbox so I would definitely be out on a limb.

The use of ATF plus a cooler & circulation pump is, I regret, all I can reasonably do.

Paul W.

 

[PEW]

A couple of extra thoughts. I spoke to my local transmission specialist yesterday; he is changing some parts over for me.

Having discussed the issue this with him he advised me to use a top-quality 15W/40 engine oil instead of ATF because from his own experiences.

He does think that the gearbox oil cooler is a very good idea; he rebuilds transmissions for a number of local car racers and he said he is now trying to get them all to fit oil coolers. He says just use a manual switch to run it as soon as the car warms up, period. I may still fit a thermostatic switch for a couple of reasons.

The engine oil issue makes my life easier because that's what the engine uses; because of the small engine size I can change both oils at the same time and the whole lot will use up one 5 litre can ;-) .

 

[evelrod]

Sounds like you have it all under control, Paul. I see no reason that a good quality engine oil will not perform adequately, after all, I race a '63 Austin Cooper Mini in vintage ( 115 hp at the wheels 1380cc ) and the little close ratio four speed box works well with my Redline 50 .

Hmmm. Looking at the Mini's gearbox, I guess I already have a transmission AND differential/final remote cooler. ;-)

Rod

 

[romke]

the engine oil might be an alternative. bear in mind though that the viscosity is higher then ATF and that will problably result in a higher oil temperature. that then compensates somewhat for the higher viscosity, but introduces additional frictional losses that generate heat that must be dissipated.

do you have the possibility to test both oils and do some temperature measurements?

i still prefer the ATF, most applications use an oil that is rather too viscous.

as far as wear is concerned: both types of oils contain anti-wear additives - so there you should not worry.

the best way to sort things out is to run the vehicle on a rolling road and do temperature mesurements with both types of oils under identical circumstances. that problably would show which type works best.

 

[evelrod]

romke, in years past, we have taken 'on track' readings for all things ' hot' including the gearbox. In the early 80's I found that the ATF was SUBSTANTIALLY cooler than the 80W-90 OR the Castrol (40 I think)engine oil. That was one of, if not THE, determining factor in my switching the Lotus/Ford gearbox to ATF. Yes, Mildred, I had to "prove it" to myself...ATF is what I still use today. (Raced the car last weekend, track temp was 70ish and temps were barely readable...gearbox was only 140f after 12 laps at Willow Springs.

Rod

 

[PEW]

Engine oil or ATF? Decisions, decisions!;-)

Whatever it is, it will be properly cooled sooner or later.

Great thread, btw, I'm enjoying hearing all these different opinions.

Paul.

 

[romke]

evelrod:

what shifting problems do you experience in your mini and what oil do you use in the engine/gearbox/diff combo?

i remember that those gearboxes had a tendency to shift well with fresh engine oil, but shift performance deteriorated when the oil was longer in use. the most likely cause for that was the breakdown of the type of VI-improver used in the 60-ties and 70-ties and the limited detergency of those products that caused some deposits (not visible to the naked eye) on the synchromesh mating faces essentially changing the rictional characteristics.

i guess modern synthetics based engine oils with much less (and better quality) VI-improver and far better detergency may well improve on that.

in regard to shift performance it might be interesting to compare engine oils designed for 4stroke motorcycle engines. basically there are to types: MA and MB, that differ in frictional characteristics. The MA types give high static and dynamic friction when used with wet clutches, the MB type gives lower friction. although the frictional characteristics are engineered to work well with clutches, they might also influence synchromesh behaviour. the frictional characteristics are managed through the inclusion of friction modifiers in the MA types, the MB types do not include a friction modifier.

apart from being "MA" or "MB" the oils further meet the standard automotive engine specs and are available both in synthetic, partly synthetic and mineral types.

you therefore could experiment with synthetic types with distinct frictional characteristics.

 

[evelrod]

romke, the shifting problems in my Mini Cooper race car can usually be attributed to the dumb ass rowing the shifter about...usually. Of course the antiquated "remote shifter" of the early Minis is not exactly "state of the art", even for 1963. As far as the gearbox/synchros...I really have not had a problem, at least with THIS gearbox, a straight cut close ratio synchro box. Of course I change the lubricant after each race weekend, Redline Racing 50.

As all this relates to motorcycle gearboxes...I have experience with a few, most notably the Hodaka style "ball change" constant engagement type, the early BSA and Norton non synchro and, My KZ which was closer to at true "dog box". All very close ratio, all could be shifted without a clutch with ease...NOT typical of automotive synchro or dog box. Where a bike can live on just about any lubricant, that may not be the hot setup for a car.

Trust that if I could isolate the Mini's gearbox, it would be using ATF ! AND, NO I'm not even going to try !!! ;-)

Rod

 

[drwebb]

That's backwards- MB oils are friction modified and MA oils typically aren't.

Actually, MA oils (subsequently split into MA2 (higher) and MA1 (lower) classes) have high friction suitable for wet clutch applications, and MB oils have lower wet clutch friction which typically makes them less suitable (though OEMs can spec whatever class they choose to). Traditional 'friction modifiers' _reduce_ static friction, so MB oils typically contain high doses of these.

There have been papers published describing friction _increasing_ modifiers in motorcycle oils, so describing either performance classification as containing or not containing FM ingredients may not be accurate.

 

[PEW]

The gearbox modification has been done. I've sited an oil "suction" pipe from a position near the bottom of the casing and the return outlet near the top.

I've fitted the return flow outlet where it should avoid throwing oil at meshing gears; I am concerned about causing undue aeration of the oil. I've decided to slow the pump, too. The reason for this is that in standard form it can move 3.7 Imperial gallons per minute and the gearbox only holds about a pint so it will have a very quick "turnaround time".

For this reason I've taken advice and decided to use Silkolene "SilkTran" oil which apparently has a very good resistance to aeration. I must admit a bias to their products as my grandmother was their company secretary for many years and I know their head chemist. Seeing him stop to oil up the exposed valve gear on his 3 wheeler V twin powered Morgan as a schoolboy was probably one of the reasons I became interested in wacky, off-beat vehicles.

All I have to do now is install it. I'll report back when it's all done and the car is back on the road.

 

[PEW]

The oil cooler and electric pump are now installed. The pump is wired through a fused relay and a resistor to slow down the flow a little. The relay circuit is triggered by a thermal circuit breaker rated at 70 degrees C, which I've fitted to the outside face of the gearbox casing.

I've filled the box with the Silkolene SilkTran synthetic lubricant, as previously mentioned. It took 25% more fluid to reach the level plug due to the extra capacity of the cooling circuit, which is probably a bonus in itself.

Hopefully there will be nothing more amiss to report so thanks again to all those participating in the discussion.

 

[romke]

Hope I do not disappoint you, but as far as I know the lubricant mentioned is (a high suality) SAE 75W-90. That might still give rise to higher temperatures (but it is better then what you used to have), when compared with a high quality ATF.

I suggest you try the Silkolene and if overheating still occurs, try ATF.

Good luck.

 

[PEW]

Thanks, romke.

Hopefully the cooler will now keep the temperature under control and as you say, the SilkTran lubricant is certainly much better than the plain vanilla mineral based stuff I used before, at any temperature (it must be, it costs much more than best beer per litre. But will hopefully last somewhat longer).

I certainly will try ATF next if there are further issues.