Transmission Oil Pump

I thought I would see how big a mess I could make today. Actually, didn't make much of a mess which was good. See the attached picture which is a snapshot of my transaxle oiling system (most of it anyway), while it is running. The basics are 8N line from bottom of tranny to filter, 8N to to pump, 8N to cooler and then 8N to distribution block and eventually six 6N lines back into the tranny. In the picture, that is a little shortened to 8N from tranny (yellow bucket) to oil pump, 8N to distribution block and six 6N lines back to tranny (yellow bucket). I took a picture of the flow out of the six lines into the transaxle. There is pretty good pressure and flow and a steady stream of oil at each of the ports. One thing I was contemplating and had some discussion on different threads with Randy, Rick and others was about the need for a smaller orifice at the output of the lines into the transaxle. I am contemplating not doing that for various reasons (it is a pain to weld the AL fittings and then drill and I am concerned about two of the fittings which NEED to be swivel fittings on the NPT end where they go into the transaxle and I am concerned about the heat from the welding ruining them).

It seems with that good of pressure and flow, a smaller orifice would limit the flow, spray onto the inside of the tranny with higher pressure, but I don't think it would necessarily result in oil getting to places it would not otherwise get. Anyone have thoughts on this?


Randy V

Lifetime Supporter
I think the flow may be different when the fluid is warmed to 200°F
Rather than welding shut and drilling, You could tap the inside of the fitting and thread in a bit of All-thread rod of the appropriate dimensions, locked in with Loctite Red, then drill the steel.
The ideaI had was to great more of a spray to cool each of the gears directly.
My concern would be the possible reduction of flow when the fluid is hot.

Rick Merz

Lifetime Supporter
I agree with Randy, in your test the bar is level and the oil is cool. When the oil is hot and the bar is at an incline then the oil will tend to take the path of least resistance since there is no restriction to equalize the flow to all of the fittings.

Instead of welding the drilled plug (orifice) you could make it so that the outside diameter is about .001" larger than the I.D. (slight taper to get it started) of the NPT end and heat the fitting to 250° and press in the orifice then peen the NPT end over (with a small diameter punch) which will lock it in. Press it in about 1/16" past the bottom edge of the NPT thread. You can re-tap the fitting to clean up the the thread if necessary. You are doing great job on this project but you really need the oil to spray onto the gears to ensure that you get even oiling to all of the gears for maximum benefit. With all of this being said, we are not running our cars in a 12 or 24 hour endurance race so it is debatable if what some of us do is really worth it. To me it is so I did what I felt was right for me.
If you opt for the 01E gearbox, a diff pump housing can be used, which moves fluid to a cooler and back when the vehicle is in motion.