6l90 Pressure port on side of trans case

[gt1guy]

Does anyone happen to know what the max pressure the pressure port would see when the trans in operation in a vehicle?

Second question: What is the minimum pressure needed for the trans to function.

My reason for the questions is that I'm thinking of connecting a accumulator to the pressure port. Basically like an Accusump for an engine. This is for a offroad rig that can starve the pickup in the trans pan.

Thanks for any light you can shed on the subject.

[hjtrbo]

Around 2000kPa is the pump relief.

Hard to answer min pressure, would depend on shift pressure settings etc, but you'd want as much as possible. At least 1500kPa at a guess if you're going to be shifting in anger.

How long is the suction port in the trans going to be uncovered for? The pump moves allot of volume. I don't know if you'll get that kind of volume back in through that small pressure port.

Other issue is when you're running on the accumulator the pump will be cavitating.

Great question, we have a new member, Robert from Trans Go that pops in and helps. This might be 1 for him. And of course anyone else

[gt1guy]

Around 2000kPa is the pump relief.

Hard to answer min pressure, would depend on shift pressure settings etc, but you'd want as much as possible. At least 1500kPa at a guess if you're going to be shifting in anger.

How long is the suction port in the trans going to be uncovered for? The pump moves allot of volume. I don't know if you'll get that kind of volume back in through that small pressure port.

Other issue is when you're running on the accumulator the pump will be cavitating.

Great question, we have a new member, Robert from Trans Go that pops in and helps. This might be 1 for him. And of course anyone else

I'm only thinking about the oil pickup being uncovered for a few seconds or so. Just to throw a number out, I'd say 5 seconds max, because that's a long time knowing something isn't right.

Wouldn't be shifting in anger in the scenario I'm thinking about. No shifting at all actually. It would be more like trying to make a 5'-10'(2-3m) vertical climb. So no real speed involved.

Let me ask this, what is the minimum pressure needed to keep driving forward in gear. No shifting up or down, just turning the wheels.

I guess my first question should have been....Will an accumulator allow me to keep me moving forward for a short period of time with the pickup in the pan not sucking oil?

The plan would be to use an elect solenoid valve on a pressure switch connected to the accumulator. So the accumulator would be out of the equation under normal driving.

[hjtrbo]

Geez, if you can keep the flow up, 500kpa should keep the clutches together. You're breaking new ground, for the time I've been around and all the

[hjtrbo]

..... searching I've done, I've never heard of an accumulator being used. I'll dig a drawing out later to see how it might work.

[TheMechanic]

Been a long time ago when I worked for Nissan factory off road racing team. Lucky to be living in the off road racing capitol of the world. If you know you know.
Anyways we did have one class 8 that we dry sumped. It used one of the stages of a dry sump system as a scavenge. Just ran some AN lines. Easy peezy.
Personally I think with a semi baffled deep sump you just don't need it. A few one way doors like they use on road racing engines would be the key

[TransGo Robert]

The maximum line pressure is 310 psi or so stock, but forward it will never command it that high with stock programing, it never goes above 275 psi. As for how much minimum you need to keep the 1-2-3-4 clutch from slipping it all depends on the load. 80 psi under very light load is all you need, 140 under medium load would be my guess for minium. As for using the line tap to add an accumulator that would send fluid back in the unit if/when the filter pick-up gets exposed to atmospheric pressure that's an interesting question. It would be much easier to simply address the suction issue in the pan with baffles, extended and relocated pickup and alike instead. The first challenge I see is the volume that would be needed. You would need one big accumulator I think to be able to maintain the pressure. Figure a flow or roughly 2 GPM at a very minimum, that would be about 2 quarts during that theoretical 5 seconds you mentioned. The other issue is that comes to mind is how you would regulate that pressure you are pushing in to not exceed the command by the computer? If you go higher then what the EPC pressure command is then the PR valve will simply open and dump all your volume back in the pump quickly to drop it where it wants it to be. Then you would have all that air that is put in the circuit by the pump turning and drawing only air from the sump, that would aerate the fluid like crazy, make it get very soft shifts until it gets all bleed and generate lots of heat. There might be more issues, those are just a first things that come to mind, so I really don't think it is a good idea to try and do something like that.

[gt1guy]

Been a long time ago when I worked for Nissan factory off road racing team. Lucky to be living in the off road racing capitol of the world. If you know you know.
Anyways we did have one class 8 that we dry sumped. It used one of the stages of a dry sump system as a scavenge. Just ran some AN lines. Easy peezy.
Personally I think with a semi baffled deep sump you just don't need it. A few one way doors like they use on road racing engines would be the key

Ya, a deep pan with trap doors would be great.....I just don't have the room for the pan to go lower though. The skid is just below the pan and the triangulated lower suspension links sit just to the sides of it.

[gt1guy]

The maximum line pressure is 310 psi or so stock, but forward it will never command it that high with stock programing, it never goes above 275 psi. As for how much minimum you need to keep the 1-2-3-4 clutch from slipping it all depends on the load. 80 psi under very light load is all you need, 140 under medium load would be my guess for minium. As for using the line tap to add an accumulator that would send fluid back in the unit if/when the filter pick-up gets exposed to atmospheric pressure that's an interesting question. It would be much easier to simply address the suction issue in the pan with baffles, extended and relocated pickup and alike instead. The first challenge I see is the volume that would be needed. You would need one big accumulator I think to be able to maintain the pressure. Figure a flow or roughly 2 GPM at a very minimum, that would be about 2 quarts during that theoretical 5 seconds you mentioned. The other issue is that comes to mind is how you would regulate that pressure you are pushing in to not exceed the command by the computer? If you go higher then what the EPC pressure command is then the PR valve will simply open and dump all your volume back in the pump quickly to drop it where it wants it to be. Then you would have all that air that is put in the circuit by the pump turning and drawing only air from the sump, that would aerate the fluid like crazy, make it get very soft shifts until it gets all bleed and generate lots of heat. There might be more issues, those are just a first things that come to mind, so I really don't think it is a good idea to try and do something like that.

Sounds like this could really get complicated fast.

Just to help me understand what exactly would be going on. When the PR valve bleeds off excess pressure, that fluid gets dumped into (in front of) the suction side of the pump? Or is it dumped out into pan?

Then you would have all that air that is put in the circuit by the pump turning and drawing only air from the sump, that would aerate the fluid like crazy, make it get very soft shifts until it gets all bleed and generate lots of heat.

Would the excess fluid being bypassed into the pump make this situation worse? Because remember, I'd already be at this point.

[TransGo Robert]

Sounds like this could really get complicated fast.
Just to help me understand what exactly would be going on. When the PR valve bleeds off excess pressure, that fluid gets dumped into (in front of) the suction side of the pump? Or is it dumped out into pan?

When the PR valve starts to regulate it sends the excess pump output to the converter. Once that requirement is met, it then sends any excess pump output to the decrease side of the pump slide which then reduce the pump output.

Would the excess fluid being bypassed into the pump make this situation worse? Because remember, I'd already be at this point.

It would make it worse because normally nothing would go in since it would stop pumping completely, but sending fluid in now it would be blending air into it and causing all kinds of issues. Either way, makes no difference the pump drawing air is the kiss of death, you can’t have that not even for a split second.

[gt1guy]

When the PR valve starts to regulate it sends the excess pump output to the converter. Once that requirement is met, it then sends any excess pump output to the decrease side of the pump slide which then reduce the pump output.

It would make it worse because normally nothing would go in since it would stop pumping completely, but sending fluid in now it would be blending air into it and causing all kinds of issues. Either way, makes no difference the pump drawing air is the kiss of death, you can’t have that not even for a split second.

Understood.

Thank you Robert for taking the time to help me understand how things work.

I'm going to can this idea. Just sounds like it would only create problems and wouldn't even do what I wanted to accomplish. My lack of knowledge make me dangerous, so my best move is to back away quickly with my hands in my pockets.

[TransGo Robert]

Understood.

My lack of knowledge make me dangerous, so my best move is to back away quickly with my hands in my pockets.

LOL Well I do like the thinking out of the box approach even if in this case it would not really work. I think finding a way to extend the pick-up for the filter to the back of the pan would be a better approach in my opinion.

[TheMechanic]

LOL Well I do like the thinking out of the box approach even if in this case it would not really work. I think finding a way to extend the pick-up for the filter to the back of the pan would be a better approach in my opinion.

Unfortunately with off road stuff the fluid is pushed everywhere. Front of the pan, back of the pan, side of the pan and vertical. Hahahaha. I really think a deep sump and gated baffles will do the trick. Although I have never had an issue before and have dome many class 4, 7, 7S, 7S 4x4, and class 8. Cooling issues are the ones that are the most prevalent