T-case PTO oil line check valve

[m16ty]

I've had my t-case PTO on my truck for awhile now (running a hyd pump for my dump). When I pulled the PTO off the donor truck I couldn't remove the bottom elbow for the lube line because it hit the e-brake bracket. I just installed a standard street "L" black iron elbow when I put the PTO on my truck and forgot about it.

Since then I acquired another truck with a t-case PTO and sold the PTO. In a attempt to let all the parts go with the sold PTO, I pulled the elbow on that PTO to send with it (oddly enough somebody had done some filing on the edge of the elbow so it would clear the e-brake bracket on this one). When I got the elbow off I realized it was more than just a elbow. It's also a check valve.

I looked in the TM (TM9-2520-246-34) and all it shows is just a standard elbow and makes no mention of a check valve in that location. The two t-case PTOs I've dealt with have check valves there.

So the question is, is a check valve required in the bottom elbow (where it screws into the t-case)? I've still got the donor case that my PTO came off of and the elbow with check valve is still on it. Will the pump work ok without the check valve? As I said above, the TM makes no mention of a check valve there. I just don't want to burn up my PTO.

 

[topo]

When I put the transfer case PTO on my m52a2 I took the oil line off of a m816 wrecker it had the two check valves one in the bottom elbow and the one where it go's in to the PTO .The PTO oil pump , pumps in both direction .I think the check valves work together to keep oil going the right way when the pump pulls the checks open and pull oil.The bottom check may do more to keep oil from going back to the bottom of the transfer case .

 

[m16ty]

I think I've got two check valves up at the pump already. The only thing I can think of that the one in the elbow would do is to keep the line primed (not let the oil drain out of the line when not in use). All the TM mentions is a standard elbow and no mention of a check valve at that location. It does show the two at the pump.

After reading the TM some more it says you can pull the plug on the PTO and see oil moving if the pump is working. I think I'll take a look and see if I've got oil up there.

 

[topo]

I can't check my PTO when it is running it will be interesting to see what you find ?

 

[m16ty]

I think I can check it. My truck has a dump so raising the bed gives you pretty good access to the PTO.

 

[gringeltaube]

So the question is, is a check valve required in the bottom elbow....

Good question!

I know there are different PTO versions out there, but all three I have here take a common elbow fitting only, at the bottom, and then two 3/8", spring-loaded bearing balls inside the pump (head)housing, arranged accordingly, to function as valves. Given the orientation of valve bodies, coil springs are needed to keep the bearing balls seated. (That spring looks kind of fragile to me...!)

Not sure though, if the very same type of check valve, but placed vertically, further down in the suction line would rely on gravity alone, for preload. Also, if there would be any appreciable difference regarding pulsation (= "water-hammering effect)....?

Regardless of position, I doubt that a ball type check valve would prevent hot oil from slowly draining back into the T-case.

Short answer to the initial Q.: NO, if the pump intake port already has a valve.


G.

 

[m16ty]

The elbow check valve is actually oriented horizontally in the elbow. It also has the same fragile spring as the others do. I will agree it doesn't seem like a positive seal though.

I'll take a pic of the valve and post it up.