Gearbox oil cooler

[dede911]

Hi,

I would like to build a gearbox oil cooler set-up (915 box) based on an electric pump and a universal oil cooler.

Browsing the forum and the web gave me some ideas.

It looks to me that best place to install the oil cooler would be under the engine grill: good airflow, no risk to damage.

BUT: how to check and adjust the oil level in the gearbox? I assume that if the cooler is installed above the gearbox, as soon as the pump is switched off, the cooler will drain, and the level will be to high...

Am I making a mistake in my thinking, or how to deal with this?

Porsche installed the cooler on the SCRS in the same location...

Thank,

André

[Flieger]

You should post this in the autocross + racing section. They have covered cooler installs there. http://forums.pelicanparts.com/porsche-autocross-track-racing/

[Flieger]

Here's something to think about: 901 Trans Cooling

[Dodge Man]

Since you are in the EU, you may be able to find a factory gear drive unit. Any specific reason for electric? My 915/72 has the stock Euro pump. No wires, relays, or switches to maintain. Takes a while to warm up and uses a little mechanical power but a nice fit & self contained. Is it a track car or Autobahn car? Do you need a large cooler for racing?

[Sboxin]

This is our set up in a 1978 911SC race car with 3.8L and 915

Plate on bottom of 915 is CMS made part - pump is Titan with filter - cooler is Setrab

I have seen coolers mounted under car on this forum . . .









Regards,

[dede911]

Hi,

I know that an electric pump is more complex, but the box has been rebuilt 10K km ago...
A basic set-up can be done in-situ

The car is dual purpose, road and track

I do have a temp gauge, on track temps go to end of scale (150°C)...

André

[safe]

Originally Posted by Sboxin

This is our set up in a 1978 911SC race car with 3.8L and 915

Plate on bottom of 915 is CMS made part - pump is Titan with filter - cooler is Setrab

I have seen coolers mounted under car on this forum . . .

You take out the oil in the plate and return it where, fill plug?

I'm about to undertake this project too, have just got an electric oil pump for the job (originally from a Nissan 200SX rear axle, has a pretty good flow).
I would want to keep the cooler low, under the level in the box, you might not want to run the cooler all the time.

[GaryR]

Originally Posted by Sboxin

This is our set up in a 1978 911SC race car with 3.8L and 915
Plate on bottom of 915 is CMS made part - pump is Titan with filter - cooler is Setrab

Roy - is that plate reproducible? I bet you could sell a few of them, I know I would buy one if they weren't too bad $$ wise.

[Sboxin]

The oil return is into the fill plug hole.

The bottom shift fork plate is made by CMS - California MotorSports in Lake Havasu, AZ
California Motorsports - Porsche transmissions, transaxles, gears, differentials, parts, service, manufacturing
When you call you will be talking to Roger Brown.
I think the part is about $250 and includes the threaded hole for a temp sender.
They manufacture this and other Porsche transmission parts. When I was there they had a real 935 box on the bench - amazing stuff.

Our trans temps run 180F with the cooler running in 100F air temps.

There are more forum threads around that discuss and show pictures of other plumbing options.
We chose to put the cooler in the back seat location - because race car

Regards,

[dede911]

Hi Roy,

how do you check and adjust oil level with the return into the fill plug hole, and cooler higher that oil level?

André

[Sboxin]

Originally Posted by dede911

Hi Roy,

how do you check and adjust oil level with the return into the fill plug hole, and cooler higher that oil level?

André

Well, I have been avoiding your question about how to check the fluid level with the cooler
higher than the trans - - - because so far we haven't done that . . .

But, the way we plan to do it is:
- disconnect the return line at the trans
- run pump and catch fluid in container
- measure fluid amount
- connect return line to trans
- disconnect line at pump inlet
- attach separate made up short line to pump
- put short inlet line into container of fresh fluid - amount same as removed
- run pump to suck fluid into trans and fill cooler until fluid comes out of disconnected
cooler/pump line
- disconnect short inlet line and reconnect cooler line
- disconnect return line to trans fill hole and check level in trans - add fluid if needed

This is the method the tech installer used to fill the system when he installed the cooler/pump.
Yes, this is a time consuming process -- but worth the effort for a cooler gear box.

So, while you are making up lines/plumbing for the pump and cooler just make another short line to fill the system.

Regards,

[KTL]

You should return the cooled oil to the diff housing. Its one of the hottest running locations in the transmission.

Here's a "clean" way to determine the system capacity. First, I would put a check valve in the system just downstream of the "OUT" fitting on the trans.

Fill the 915 with the typical 3L of gear oil. Turn the pump on for a while to ensure steady flow is put thru the cooler. Shut it off & valve will stop the cooler lines from back-draining into the trans. Let the fluid level in the trans stabilize for a while and then fill the trans like you normally do- fill until it dribbles out the fill hole

BTW you don't want to make a habit of running the cooler with cold oil. It's better to have the pump turned on when the oil is warm. It's easier on both the pump and the cooler to pass warm oil.

[safe]

Originally Posted by KTL

You should return the cooled oil to the diff housing. Its one of the hottest running locations in the transmission.

Then shouldn't you take the oil from the diff area, like the drain plug and return it somewhere else, like the fill plug?

[KTL]

Well when you're pulling the oil from the shift fork cover plate, then the opportunity to return oil to the diff housing is there. You have circulation in this way. But if you're pulling the oil from the drain plug which is under the diff housing, you're really not pulling much hot oil out of the gear stack area?

The factory race cars with 915 trans returned the oil to the tail case at the top of the trans. It went into a spray bar that sprayed the gears & the ring gear. All the 915s have the provision for installing this spraybar assembly.

WEVO makes some neat pieces to accomplish the spraybar setup

Welcome to Windrush Evolutions - WEVO - Porsche Products

[dede911]

Kevin,

would you build it in this configutation:

take off point-pump-checkvalve-cooler-return line?
Does the pump not act as a check valve?

Or this way:
take off point-checkvalve-cooler-return line-pump?

Do you agree that under the engine grill is a good lacatio, or other suggestion?

André

[MBruns]

I have one of the Factory setups for the 915, I just bumped it back to the top of the sale page
Thanks, Mike Bruns

[JeremyD]

I currently have mine mounted under the engine grill

I used the WEVO under case





I tapped the case at the top (supposedly the hottest place and the best place to dump the cooled oil) heard one expert describe the differential as a typhoon of gear oil.





Here's my current transmission cooler in the tail (yep, bigger than it probably needs to be)



The pump -


But put a provision in there when I switch out the tail in my car to a IROC tail.



Anyway - hope that helps

[KTL]

Typically in this instance where you're not trying to produce pressurized oil, you place the pump in the system where it does mostly sucking. A sucking system also minmizes leaks (when in operation). So I would place the pump right before the return dump back into the transmission in the following order:

1. Oil out of trans
2. Check valve (if elevation warrants it, keeps the pump primed)
3. Cooler
4. Pump
5. Return into trans

In the sequence above, the pump can't act as a check because its at the "top" of the system.

Another thing to keep in mind is that you don't want to pump the hottest oil. Meaning, you place the pump after the cooler so it is seeing cooled oil. The post-cooler oil is typically better for the pump to keep it from getting too hot.

[Eagledriver]

I have a cooler in my decklid. I just don't consider the oil in the system. Whatever drains out I don't compensate for. I don't think it's much anyway.

-Andy

[Eagledriver]

My system is very simple. I just took off the diff cover and drilled a hole in the bottom and top for the suction and return fittings. I'm sure it could be better, but as far as I can tell it works great. My tranny used to get hot and hard to shift at the end of a session. Now it never gets that way.

-Andy