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GEARBOX COOLER SYSTEM Installation and Review

Old 09-27-2012, 05:10 AM
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powdrhound
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Default GEARBOX COOLER SYSTEM Installation and Review

Since a number of you have PM'd me about the gearbox cooling system I have decided it would be easiest to do a quick write up on it. Basically, my decision to do a gearbox cooler was a result of tracking my Rturbo and a number of conversations I had with the builders of these gearboxes like Brian Copans and Gbox. Matt Monson of Guard Transmission who supplied his Guard GT Club LSD for my gearbox also highly recommended a cooler if tracking the car. Since I knew an LSD would raise the temps of the gearbox, especially when running the car hard at the track, for longevity purposes I decided that a cooler was a must. I track my car about 15 days per year.

After doing some research, I realized there were two ways of approaching this project since the gearbox and engine were removed on my car while my coolant pipes were getting welded and while the gearbox case was drilled and tapped for the GT2 slave conversion. One way to do this was to have the gearbox shipped to Gbox or Copans to have it machined and converted to the GT2/3 cooler components utilizing an internal spray bar and an external liquid to liquid cooler that uses the engine coolant to maintain the temperature of the gearbox. This option however would have been quite expensive with many parts required to be ordered from Germany (with several weeks lead time) and price wise at an estimated $6-7K+ and it just did not make sense. The other option was to do it the cheap way and just pull off the oil from the drain hole, run it through a pump and an external air to liquid cooler and return the cooled oil through the gearbox fill hole. This option would have been fairly cheap at an estimated $1-1.5K but I did not like the AN fitting hanging below the gearbox and exposed to potential damage from road debris. As a result, upon consultation with my tech at 3zero3 Motorsports, we decided to come up with a system that falls price wise between the two cooler options but actually offers much more in many aspects.

The one thing that I wanted with my application was to retain the factory drain and fill holes on the gearbox. I did not want to have to draw and return the fluid through those locations so that I would not have to disconnect any AN fittings when doing frequent gearbox oil changes as I normally do when tracking my car. As a result, we decided to drill and tap the gearbox case on the side under the passenger side axle and draw the gearbox oil from that location. This location is very close to the LSD and thus has the hottest oil due to the friction of the clutches. From there, the oil is drawn via a MOCAL oil pump (located on the passenger side of the gearbox ahead of the drive axle) and driven though an oil filter into an external air to liquid cooler located on the driver's side of the gearbox in a location similar to where the factory GT2/3 cooler resides. After the oil passes through the oil cooler it is returned through the top of the gearbox which was drilled and tapped for that purpose. A MOCAL pump, even though it is expensive at around $400, was chosen due to the fact that it is a gear pump as opposed to a diaphragm pump like a Tilton. The advantage of a gear pump is the fact that it is much quieter and more efficient than a pump like a Tilton. When the MOCAL pump is running with the car shut off, you can barely hear it, just a faint whirr. With the car engine running, it is inaudible. The Tilton diaphragm pump by comparison is very noisy due to its diaphram design. All of the hardware like the pump and the cooler is mounted via rubber lord mounts to dampen any noise and vibration.

In addition to the cooler, I also wanted the system to be "hands off", reliable, easy to service, and to provide me some feedback in the car as to the gear oil temperature. To make the system "hands off", it was decided that we would use an adjustable OEM quality automotive thermostat switch to activate the oil pump at a preset temperature which I have set at 200F. I chose 200F since this is close to the coolant temperature that the GT2/3 uses to cool the gear oil with its respective liquid to liquid cooler. In order to use a thermostat switch we needed to insert a temperature pick up probe into the gearbox and did so by drilling and tapping a location in the side of the case near the same spot under the passenger axle where the oil pick up is tapped. Once again, this is near the LSD where the hottest oil is. As a result, when the thermostat senses a temperature of 200F it activates the pump which in turn starts to circulate the gear oil through the cooler. The pump will run continuously until the oil temperature drops to around 180F at which point it stops. There is also a small LED installed (in the lower portion of the center dash below the climate control) which lights up green when the pump is energized and running. In addition, there is also a manual override switch next to the LED that I can use to turn on the pump independent of the thermostat.

The last part of the gearbox cooling system I wanted to employ was some type of an indicator in the car that would give me a temperature readout of the gearbox oil. I looked at many options but one of my requirements was that the install must be very OEM looking. I just did not want to have some gauge stuck in the dash that would look out of place in the car. After much research I decided to employ the Brockway Dgauge with its 996 specific console mount as it is a direct drop in to the 996 console and looks perfectly OEM. The Dgauge has an option to plug in an external sensor for numerous items with oil temperature being one of them. You can purchase the various sensors directly from Brockway and they are OEM automotive quality parts. The side benefit of the Dgauge is the fact that you get a display of countless user selectable data that the unit pulls up through the OBDII port. You have a choice to select up to 4 parameters on the Dgauge display and I chose to have the gearbox oil temp in the upper left, IAT in the upper right, and AFRs for both banks of the motor in the lower left and right. Display colors are also user selectable. The Dgauge is a self contained unit that is powered through the OBDII port and required no wiring besides plugging in the flat connector to the OBD. The final step was to insert one more temperature probe in the gear box and again this was done in a similar fashion as with the thermostat probe by drilling and tapping the case in the location under the passenger axle. If you decide to go with a Dgauge on the 996tt, ask Eric at Brockway to download software V1.24 to ensure the unit Auto shutdown and startup sequence functions correctly in our cars. I sent mine in to Eric at Brockway and we came up with this update for the 996tt since our ECU functions a little differently from other cars.

To wrap everything up, some of the factory coolant hoses that run under the car near the transmission have to be rerouted to make room for the various components of the transmission cooler system like the radiator. This was all pretty straight forward. A few custom brackets had to be made and welded to the crossbar to mount everything up. The last item to complete everything was to add a NACA duct to the bottom of the plastic belly pan cover that is under the transmission. This NACA duct directs air flow over the oil cooler radiator making the system work efficiently. For clarity purposes, the attached pictures do not show the belly pan with the NACA duct installed.

So, how does this whole ball of wax work in the real world? Well, I have to say very well now that I have had a chance to play with it for a couple of weeks including 3 days at the track. During my testing, I discovered that during regular driving which includes stop and go traffic, normal roads, and driving on the interstate, the gearbox oil temp will climb up into the 180s. This is about the same number that I have observed during an hour long drive on the interstate at a constant 80mph. To test the effectiveness of the cooler, I switched it on using the over ride switch and within 2 minutes I saw the temperatures drop 12-15 degrees. This is quite substantial. When running at the track in 85F ambient temperatures I saw the oil temp climb to 200F in about 10 minutes at which point the cooler automatically switched on and maintained that temperature. 200-205F is where I'm seeing the temps generally stabilize at the end of a 25 min track session. The highest temp I ever saw was 221F and that was at the end of the 3rd 25 minute session during mid afternoon when the temps were close to 90F with ambient track temps probably over 100F. When I spoke with Matt of Guard Transmission he told me that you don't want to see temps over 240F or so (if I recall correctly) as this is where the synchros start to swell and the lubricating properties of the oil rapidly decline. Prior to having the cooler, I could definitely tell the gearbox oil was getting hot as it felt quite "watery" from the oil getting so hot and thin when I would come into the pits at the end of the session. BTW, I am running Mobil 1 Delvac 75w90 gear oil.

Overall, I am very pleased how this project turned out and it has exceeded my expectation in every way. My hats off must go to my incredibly competent tech Emery at 3zero3 Motorsports for working out the design and bringing this to fruition. I believe this type of air to liquid cooling system has a greater cooling capacity than the liquid to liquid cooler employed on the GT2/3 as they are using 185F liquid to cool the gear oil. The advantage of the factory system however is that it does bring the gearbox up to temperature quicker especially in the winter. Would I do this project for a street car? No. Would I do it for a car that does one or two track days per year in the lower run groups? No. However, I would absolutely install a gearbox cooler on any car that is taken to the track on a regular basis and is run hard in any of the upper run groups like black or orange. The addition of an LSD will add 15-20 degrees to your gearbox temps due to the friction of the clutches and at that point the cooler will definitely prolong the life of your internal components and make your gearbox more bullet proof and last longer between rebuilds. Couple things of note. While I had my gear box out and taken apart I had the Gbox detent installed and also the 2nd gear synchros replaced as they showed a bit of wear. There was no issue with shifting but since everything was out I figured why not. The one thing I found interesting was the fact that all the synchros in the gearbox were steel. My car is a 2002. There was a rumor floating around that the X50 or GT2 gearboxes came with steel synchros while the normal 996tt had brass synchros but evidently this is false. Additionally, looking at the PET catalogue, all the gears and synchros are the same part number for the Turbo and GT2 so outside of the GT2 cooler the gearboxes are the same.

I believe this gearbox cooler kit is now available in kit form. Hope that helps…….


[URL="http://[ame=http://www.flickr.com/photos/87731073@N06/8028942236/][/ame]
[ame=http://www.flickr.com/photos/87731073@N06/8028942236/]Gear box cooler system[/ame] by [ame=http://www.flickr.com/people/87731073@N06/]pwdrhound1[/ame], on Flickr"]http://http://www.flickr.com/photos/87731073@N06/8028942236/http://www.flickr.com/photos/87731073@N06/8028942236/ by http://www.flickr.com/people/87731073@N06/, on Flickr[/ame]

Looking at the transmission from the passenger side of the car. Note the MOCAL pump mounted in the center at the top of the picture. The oil filter is the red "tube" visible just to the right of the pump



[URL="http://[ame=http://www.flickr.com/photos/87731073@N06/8028946017/][/ame]
[ame=http://www.flickr.com/photos/87731073@N06/8028946017/]Gear box cooler (radiator view)[/ame] by [ame=http://www.flickr.com/people/87731073@N06/]pwdrhound1[/ame], on Flickr"]http://http://www.flickr.com/photos/87731073@N06/8028946017/http://www.flickr.com/photos/87731073@N06/8028946017/ by http://www.flickr.com/people/87731073@N06/, on Flickr[/ame]

Looking at the transmission from the front of the car. Note the thermostat mounted in the upper left of the picture next to the transmission mount



[URL="http://[ame=http://www.flickr.com/photos/87731073@N06/8028942120/][/ame]
[ame=http://www.flickr.com/photos/87731073@N06/8028942120/]Temp probes and AN fitting oil pick up[/ame] by [ame=http://www.flickr.com/people/87731073@N06/]pwdrhound1[/ame], on Flickr"]http://http://www.flickr.com/photos/87731073@N06/8028942120/http://www.flickr.com/photos/87731073@N06/8028942120/ by http://www.flickr.com/people/87731073@N06/, on Flickr[/ame]

AN fitting for oil pick up and the temp probes for the thermostat and Dgauge



[URL="http://[ame=http://www.flickr.com/photos/87731073@N06/8028945921/][/ame]
[ame=http://www.flickr.com/photos/87731073@N06/8028945921/]Gearbox cooler (oil return close up)[/ame] by [ame=http://www.flickr.com/people/87731073@N06/]pwdrhound1[/ame], on Flickr"]http://http://www.flickr.com/photos/87731073@N06/8028945921/http://www.flickr.com/photos/87731073@N06/8028945921/ by http://www.flickr.com/people/87731073@N06/, on Flickr[/ame]

Oil return via AN fitting at the top of the gear box



[URL="http://[ame=http://www.flickr.com/photos/87731073@N06/8028945843/][/ame]
[ame=http://www.flickr.com/photos/87731073@N06/8028945843/]Gearbox cooler (Dgauge:LEDverride switch)[/ame] by [ame=http://www.flickr.com/people/87731073@N06/]pwdrhound1[/ame], on Flickr"]http://http://www.flickr.com/photos/87731073@N06/8028945843/http://www.flickr.com/photos/87731073@N06/8028945843/ by http://www.flickr.com/people/87731073@N06/, on Flickr[/ame]

Dgauge installed in the console. Note the manual override switch and LED in the batwings



http://www.flickr.com/photos/87731073@N06/8042594501/http://www.flickr.com/photos/87731073@N06/8042594501/ by http://www.flickr.com/people/87731073@N06/, on Flickr

Rubber air scoop that is located at the aft end of the belly pan behind the NACA duct and directs air over the air to liquid cooler. The rubber scoop is a Porsche Boxster part.

Last edited by powdrhound; 10-01-2012 at 04:18 AM.
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Old 09-27-2012, 07:30 AM
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32krazy!
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first class writeup! is it 3zero3 that now has the kit for sale?
Old 09-27-2012, 09:37 AM
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Wow, that's an awesome engineering solution! And a fantastic write-up - you should submit it to one of the pcar mags (better than most of the stuff they print).

EOT = engine oil temp?

Why two AFR readouts?

Again, job well done!
Old 09-27-2012, 10:12 AM
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Originally Posted by 32krazy!
first class writeup! is it 3zero3 that now has the kit for sale?
I believe so. Ask for Max.
Old 09-27-2012, 10:16 AM
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powdrhound
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Originally Posted by JG 996T
Wow, that's an awesome engineering solution! And a fantastic write-up - you should submit it to one of the pcar mags (better than most of the stuff they print).

EOT = engine oil temp?

Why two AFR readouts?

Again, job well done!
EOT= External oil temperature (gearbox oil in this case)

The two AFR readouts are for the left side and right side of the engine.

Thanks for the compliments.
Old 09-30-2012, 09:21 AM
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Nice work, keep us posted on long term results. Any pics with the NACA duct installed?
Old 10-01-2012, 04:20 AM
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Originally Posted by Scawt
Nice work, keep us posted on long term results. Any pics with the NACA duct installed?
I added a picture of the belly pan to the end of the original post. The NACA duct is out of view ahead of the rubber scoop. I will take a better picture once the car is on the lift.
Old 10-02-2012, 01:32 PM
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GTgears
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Very nice write up. I am glad that I could be of assistance and am glad to hear that it is working out so well for you.

Your recollection on the numbers we discussed is pretty spot on. And your temps now are near perfect.

The only other thing I will add is regarding the steel synchros. Over the years we have seen this to be very inconsistent and I hesitate to make blanket statements regarding them. Some standard 996TTs do seem to have steel, many others do not.
Old 10-02-2012, 02:42 PM
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Very nice set-up. Well done.

I own an LSD equipped Cayman S with a PDK gearbox. There is a gearbox cooler being installed on my car as I type this as my gearbox side fluid has exceeded it's normal operating temperature in the past.

I'm unsure if the pump being used in my install is a diaphragm or gear type. I'm guessing it's the former as the tech who sold me the system told me that the pump can be on the loud side.

Additionally, the shop will be installing a fan to draw air away from the cooler.
Old 10-02-2012, 07:15 PM
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Originally Posted by rubber_ducky
Very nice set-up. Well done.

I own an LSD equipped Cayman S with a PDK gearbox. There is a gearbox cooler being installed on my car as I type this as my gearbox side fluid has exceeded it's normal operating temperature in the past.

I'm unsure if the pump being used in my install is a diaphragm or gear type. I'm guessing it's the former as the tech who sold me the system told me that the pump can be on the loud side.

Additionally, the shop will be installing a fan to draw air away from the cooler.
If at all possible I would stay away from a diaphram pump like the Tilton. It is very loud especially if you and not using a thermostat switch to activate it and it has to circulate a thicker colder oil. My shop had a track prepped 996 on the shop floor and the Tilton pump was painfully loud when they switched it on. Evidently it becomes quieter once the oil warms up and thins out but I did not want to deal with the noise. To me the noise would take away from the enjoyment of the car. The Mocal in comparison is whisper quiet and well worth the extra cost IMHO. I considered a cooling fan but after my testing realized it was not necessary as long as you provide ducting that directs air flow over the cooler.
Old 10-02-2012, 07:21 PM
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Originally Posted by GTgears
Very nice write up. I am glad that I could be of assistance and am glad to hear that it is working out so well for you.

Your recollection on the numbers we discussed is pretty spot on. And your temps now are near perfect.

The only other thing I will add is regarding the steel synchros. Over the years we have seen this to be very inconsistent and I hesitate to make blanket statements regarding them. Some standard 996TTs do seem to have steel, many others do not.
Thanks for chiming in Matt. Interesting note on the synchros. I haven't thought about the fact that Porsche may have gone back on forth on the synchro material over the years. I expected my synchros to be brass but to my surprise they were steel. Go figure. Your LSD rocks by the way. It completely transformed the car. I'm getting to do a quick write up on it here soon...
Old 10-03-2012, 09:46 AM
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Originally Posted by powdrhound
If at all possible I would stay away from a diaphram pump like the Tilton. It is very loud especially if you and not using a thermostat switch to activate it and it has to circulate a thicker colder oil. My shop had a track prepped 996 on the shop floor and the Tilton pump was painfully loud when they switched it on. Evidently it becomes quieter once the oil warms up and thins out but I did not want to deal with the noise. To me the noise would take away from the enjoyment of the car. The Mocal in comparison is whisper quiet and well worth the extra cost IMHO. I considered a cooling fan but after my testing realized it was not necessary as long as you provide ducting that directs air flow over the cooler.
I appreciate the advice. After some more digging (can't locate my service advisor), I found that the shop uses a Weldon 9200A pump. It's a "slung vane" oil pump which can handle fluids up to 300 degrees. It appears to be a very nice unit:

http://www.weldonracing.com/product/..._Oil_Pump.html
Old 10-03-2012, 05:36 PM
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Originally Posted by rubber_ducky
I appreciate the advice. After some more digging (can't locate my service advisor), I found that the shop uses a Weldon 9200A pump. It's a "slung vane" oil pump which can handle fluids up to 300 degrees. It appears to be a very nice unit:

http://www.weldonracing.com/product/..._Oil_Pump.html
The Weldon is a very nice pump. I looked at this one in particular and the only reason I ended up going with the Mocal 17-311 pump is the fact that the Mocal has a 1.0-2.1gal/min (60-120GPH) flow rate as opposed to the 0.5gal/min (30GPH) flow rate of the Weldon. That's basically 4 times as much which means the Mocal can run the whole 1 gal transmission volume through the cooler at a much faster rate making cooling more effective. Both of these pumps are top notch since they have all metal gears and are built to handle 300F fluid. The Mocal is cheaper at $295 which made it a much better value than the Weldon at $550. Let me know your impression of the Weldon once you get it set up.

MOCAL 17-311
http://97.74.32.155/files/pump.pdf
Old 10-04-2012, 09:36 AM
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I had no idea how much I didn't know about pumps until now. Will report back with impressions. Thanks again for the write-up and all of the info.
Old 10-04-2012, 10:34 AM
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what made you decide to go with a cooler, had you monitored you temps before? Was that just preventive measure or did you have some signs that the oil was getting too hot?

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