ZF Fake Trans Cooler Hookup

[Lynn Miner]

Has anyone come up with an effective way to connect fake lines to the ZF trans that run to the SPF trans cooler (or any other cooler for that matter). I've spoken to a number of people who advise me not to hook it up for real unless I'm racing as it causes premature bearing failure due to cold oil. I need to know how / where to connect hoses that are plugged. I'm obviously just going for the "look" here.

[The Baron]

If you're going to "fake" it you might as well do it for "real" and put a thermostat in there to ensure you always get the right temp oil to your box. That would be best practice anyway surely?

Not sure there should be anything "fake" on an SPF MKII, kind of defeats the object?

[Bill D]

Does anyone have a picture from the rear to show what Lynn is referring to? Or more specifically, where are the lines to the ZF attached? I don't think I've ever seen trans cooler lines on a GT40.

Thanks
Bill D

[Randy V]

The easiest way is to take the input to the pump from the drain plug and the ouput from the cooler would go to the filler plug on the trans.

If you want to "fake it" you could either eliminate the pump or just not switch the pump to the ON position. No pump, no circulation, no cooling.

[Lynn Miner]

I was unaware there "is" an oil pump on the ZF. I thought that was an optional add on unit. I don't think I have an oil pump and if I do, I certainly don't know where it is. I'm concerned about mounting a hose to the drain plug as that is the lowest point on the trans and could get whacked, hence draining all the oil. I thought maybe someone has already done this drill but maybe I'm treading new ground. There are several SPF owners in the same position that have the optional trans cooler and no place to connect the hoses.

[Randy V]

Lynn - I didn't say there was an oil pump on the ZF. Typically you would hook up an electric pump like those made by Setrab, Mocal and Tilton.

Worried about the fitting getting whacked? Check out this place:
BRASS FITTINGS Brass Pipe Fittings Hose Barbs Stainless Steel Fittings Hydraulic Adapters Hydraulic Fittings Grease Zerks Hose Clamps
Look for a Steel 90 degree right angle "JIC" - NPT fitting. JIC is identical to AN 37 degree fittings and threads.

[Lynn Miner]

Thanks Randy, that might just work. I'll post my results

[Bob Childress]

Here is a picture of the back of car GT40P-1077. The bottom oil hose for the ZF is at the bottom center and does looks low. I don't know if it is really as low as it looks or if chassis and suspension components are really closer to the gournd.

[John Fitzpatrick]

Here's a photo of the oil pump on an early ZF 5DS25. The discharge and return are on the underside, and the square tang visible on the end is the speedometer take-off.

[John W]

Nice picture John.
these speedo drive oil pump are not cheap unfortunately (I was quoted $1200+).

Paul (ZF exert here in UK) told me the top cover is drilled for one oil pipe (the return I guess). I can't recall where the other came from, but have a feeling its the rear cover.
Paul does read this site, so maybe he'll clarify when he hopefully reads this thread. If not I'll ask him next time I see him.

[Miles]

Lynn:
I didn't want to fake it on mine. I had R.E.D. provide a differential pump, and it is installed very similar to the photo in the earlier post. I'll try to post photos with this response, but if it doesn't work, just PM me, and I'll forward the photos to you.

Miles

[Ross Nicol]

The previous ZF I had which I believe came from one of the Procar M1 race cars, had a disfunctional oil pump in the rear housing.I don't know how it was driven though.I ended up making an alloy plate to block it off. I find it hard to comprehend why you would fake a cooling pump connection but then again I don't understand why you would need to fit a cooler and pump unless you were long distance racing. One thing that does stay in my memory though is that Lloyd at RBT recommends regular oil changes.Then again I presume that the pump already exists and you guys just have to hook it up.
Ross

[John Fitzpatrick]

Originally Posted by Keith1

If you're going to "fake" it you might as well do it for "real" and put a thermostat in there to ensure you always get the right temp oil to your box. That would be best practice anyway surely?

<snip>
I've been thinking about that-- with a positive displacement gear pump, would you have to use a pressure relief by-pass in your plumbing, or is there a three-port thermostat out there? Also, what temp would you use for the thermostat? Sorry if this is elementary stuff-I know very little about cooling systems beyond "keep the radiator full and don't let the dog drink the antifreeze."
Thanks

[Johan]

Originally Posted by Miles

Lynn:
I didn't want to fake it on mine. I had R.E.D. provide a differential pump, and it is installed very similar to the photo in the earlier post. I'll try to post photos with this response, but if it doesn't work, just PM me, and I'll forward the photos to you.

Miles

Where did you get those neat old oil/air heat exchangers ? I have a few like that and you don't see them that often, but when you do they always seem to be painted gold.

[Lynn Miner]

Those are the coolers that come standard with an SPF GT40. At least the one on the left side is. The trans cooler on the right is a $1500 option.

[wanni]

Why do not you add a dynamic thermostat? How? Easy
You have a pipe exhiting the gearbox going to the cooler and another from the cooler back to the gearbox. Let us assume that you are using a 10 mm piping as diameter.
Connect an additional pipe with about 4 - 5 mm between the exit and the entry in order to by pass the cooler.
When the oil is cold ( fat ) it will take the by pass way thanks to the lower resistance. As soon as it warms up it will go through the cooler because of the lower viscosity.
This system will also decrease the oil pressure, especially in cold conditions, helping a lot the cold shifting ( if synchronised )
Try and let me know.
The GearFox

[John Fitzpatrick]

In theory, the ratio of the flow coefficients of the cooler and the by-pass line will determine what portion of the total fluid passes through the cooler, and since that ratio is independant of the fluid viscosity, I think you'd still need a thermostat in the by-pass line. In practice, I don't know.

[wanni]

But in practice the oil always go through a low resistance channel.
In a cooler there are such a small channels that the back pressure is huge when the oil is cold.
We are using a phisical low. Lamination

[Randy V]

Like anything else, the path of least resistance will be taken.
I do not see how Wanni's suggestion will work.

[wanni]

It is already working, not only on my gearbox but on the AUDI R8 and Lamborghini Gallardo as well.
Of course that when the oil is hot, part of it will go through te by pass, but if you make a calculation, an hole of 4 mm is 12.56 square mm. The pipe line is 78.5 square mm. This means that in hot conditions, only 1/8 of the total flow will by pass the cooler.
In order that a GL5 oil is quiet fat when it is cold, it will not easly pass into the extremely small channels which are in the cooler, contrasted by the viscosity.
More oil is going through the by pass ecause the lamination effect is very low in a 4 mm hole thenin the 1 mm channels of the cooler,
Results of a test made on CIMA T906S.
5.000 revs constant. Gearfox GFX oil in the gearbox.
Total flow at 10°C - 6.8 L/min but only 3.2 L/min are passing through the cooler ( Setrab ).
Total flow at 80°C -15.4 L/min but 11.8 are going through the cooler.
In cold conditions 47% of the oil returns directly into the gearbox but when it is sufficiently warmed up, 77% of the oil is passing into the cooler.
I do not have enough words to get into the detail for a better explanation, but believe that it works.
Ciao
Wanni