I know you're asking Kenny and I'm sure he'll chime in, but I wanted to share my feedback because I've tested this pretty extensively. Kenny is correct that they are "rated" for 3.5 GPMs, but they can flow much more than that. It will create more heat due to the restriction, but I haven't measured how much. If you're going to run a motor for long periods of time, bigger would be better.
One callout on hydraulic circuits that are powered by gear pumps is that it's a zero sum game. What I mean by that is that the fluid will go somewhere. If the pump is pushing 8 GPMs through that circuit, it's doing one of 3 things:
- All flow will go through the circuit normally (what you want
)
- Some flow will partially go through the circuit with the rest going over the pressure relief valve
- Pump slows down because there is a restriction that it can't overcome and the power unit doesn't have enough power - effectively, you are now pumping less than 8 GPMs because that's all that can go through the circuit. This one isn't likely unless the PRV is set too high or you don't have one.
- Ok, I guess there is a 4th option - something breaks. Hose blows or pump pukes up its insides.
As mentioned, I have not tested temperatures for 3rd function long term use where you're going through 2 sets of 1/4 quick couplers, but I suspect that it's warmer than usual. One other thing I noted when I installed my 3rd function kit is that the 3/8 loader hard line seemed to have a 1/4 or maybe smaller opening in the end. I'm not sure why that is, but it's an additional restriction that can contribute to the heat.
The picture on the left is of the top of the tube closest to the driver. This is what a typical 3/8 ORFS fitting looks like. The other end is a 3/8 SAE O-ring male fitting, but the center is really small. I took the picture back in April when I installed it, but I remember thinking it might be as small as a 1/8. I'm actually building some hard lines as a product for this very reason - and to support non-JD 3rd functions that want hard lines. They should be on the site in late Jan.
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