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Case 450 3056051
- Thread starter Nelsonkl
- Start date
Bill Edwards
Well-Known Member
Do the gauges on the dash for the oil pressures work?
Correct amount of oil in the transmission?
Does the propshaft under the floor plate turn when it's in gear?
Does it make any attempt to move, and does it behave the same in all gears?
More information would be helpful.
Correct amount of oil in the transmission?
Does the propshaft under the floor plate turn when it's in gear?
Does it make any attempt to move, and does it behave the same in all gears?
More information would be helpful.
Coy Lancaster
Senior Member
It sounds like the trans pump may be bad. After the oil warms up it quits pumping enough oil to keep pressure up.
Bill Edwards
Well-Known Member
I too would look at the charge pump and suction line - could be a coincidence but pointing uphill at the time of it starting to give trouble would tie in with this being the problem as it'll make it harder to suck, and a leak in the suction line or a knackered pump would find this too much to deal with.
mcprp
Senior Member
Bill , since no one else will respond to my post I wanted to ask you a question . I also have lost all pressure on my trans and torque converter on my case 450 dozer . I brought the pump home and took it apart . Seems like a very basic component . Four aluminum bushings that they call bearings , an oil seal , two o rings , and of coarse two gears . I replaced the o rings and put a new oil seal in it . The gears look perfect . It spins fine . Anyway I put it back in and still no pressure . I can understand o rings drying out or going bad . I can understand oil seal being bad . I can understand sloppy bearings or bad gears but other than that I can’t understand what could go wrong with these pumps . What stops it from working properly ? Is there a way to test it . I filled the suction line with Tran fluid and it goes in fast but then fills to the top and weeps down slow . Does the pump create the pressure . I’ve cleaned all filters , checked everywhere for cracked or open suction lines , tried pumping air into the Tran fill tube to create pressure . Still nothing . I would appreciate and feed back .
Bill Edwards
Well-Known Member
Generally with gear pumps the issue is clearance between the gear faces and the pump body, allowing oil to leak down the side of the gears. Fitting new seals can often finish tired pumps off because it increases the gap. I find small pumps often aren't worth the trouble of trying to fix, but I've never tried with these particular ones.
As to your problem, have you got a flowmeter that can be used to check the output of the pump? I expect the issue is to do with the charge pump in some way, but it's good to test things properly before condemning anything.
The oil is drawn from under the transmission, through the suction filter (you've remembered to check this?) into the charge pump then to the proper transmission filter, then to the control valve and torque converter. I would say you've either got a problem in the suction line, bad charge pump or the only other option would be a very big internal leak which I think unlikely.
Have you checked that the suction line hasn't collapsed internally, blocking off the flow to the pump?
As to your problem, have you got a flowmeter that can be used to check the output of the pump? I expect the issue is to do with the charge pump in some way, but it's good to test things properly before condemning anything.
The oil is drawn from under the transmission, through the suction filter (you've remembered to check this?) into the charge pump then to the proper transmission filter, then to the control valve and torque converter. I would say you've either got a problem in the suction line, bad charge pump or the only other option would be a very big internal leak which I think unlikely.
Have you checked that the suction line hasn't collapsed internally, blocking off the flow to the pump?
mcprp
Senior Member
T
thank you so much for getting back to me . I have checked the suction line going back to the trans. Rubber hose is also good . I do not have a flow meter as they are like 3000.00 for a 30 gpm small one . I was thinking about how I could make one . The way this started is I got stuck in the mud really bad . The fan belt broke and the engine temp got up to 220 . I shut her down and got pulled out by a friend with another dozer . When I backed up about 30 feet ,everything just stopped working .meaning controls . I noticed a lot of tranny fluid on the ground and saw that it was coming from the driveshaft seal going into the tranny . I fixed that but still no pressure . I made sure the tranny was full again and tried pouring fluid into the suction line . About a gallon would pour in and go down pretty fast but then the hose would fill up and just weep down slowly . I would think that if the pump was working correctly , that it would just keep sucking that oil till it made a full circuit and came out the suction filter that I took The one end of the hose off of . I tried pumping air with my compressor into the fill spout for the tranny to see if I could build up pressure but no pressure at all . Boy I sure hope your not right about the big leak in the tranny . I’ve been shopping all over the country for a charge pump but it is a very rare item . I do know I can buy a new one for 800.00 but I’d really like to feel confident that it is the problem before I do . The thing with the flow meter is how would I get any reading when there is no oil to pick up ?
mcprp
Senior Member
Also is it the charge pump that creates the pressure in the system ?
A flow meter will tell you the condition of your pump which is the main component. You really need to know if your pump is in proper working order or you are going to chase your tail until you pull your hair out. Your Case dealer should have a flow meter and it would be a lot cheaper to have them come out and check your pump versus buying one.
mcprp
Senior Member
mcprp
Senior Member
Ok , thank you . At least now I understand how a gear pump works . I just read about the external gear pump and have finally figured out that the tolerance between the pump housing and gears is critical and very close tolerance . Now I see how one good wear . It could be why my tranny fluid was always 20 psi lower than it should be . Maybe it was going slow and it finally went . Actually as expensive as they are it would be a lot worse if it was the tranny or torque converter . Keeping my fingers crossed . But again , I don’t see how they can even test the pump if there is zero pressure . It’s not pulling fluid from the tranny so I guess it’s shot . Like I said if I pour Tran fluid into the suction line , it should pull just as much fluid as I am pouring and it doesn’t . The hose fills up and weeps down very very slow
Coy Lancaster
Senior Member
d be stuck. Also the brake declutch valves in the control valve could be giving you problems. Items 10 is the brake spool and item 21 is the brake piston. Unusual for both brakes to go down at the same time but anything is possible.And oh by the way a general rule of thumb to test trans pump is disconnect hose from trans filter coming from pump and put your thumb over the fitting and crank engine over without starting. If the oil pushes your thumb off then pump is good if not then it's bad.
mcprp
Senior Member
So , these items , relief valve and regulator valve or the control valve brake pistons could cause all pressure to go down ? Can you explain how so I understand more .Items 48 and 50 are relief valves one or both could View attachment 218773d be stuck. Also the brake declutch valves in the control valve could be giving you problems. Items 10 is the brake spool and item 21 is the brake piston. Unusual for both brakes to go down at the same time but anything is possible.
And oh by the way a general rule of thumb to test trans pump is disconnect hose from trans filter coming from pump and put your thumb over the fitting and crank engine over without starting. If the oil pushes your thumb off then pump is good if not then it's bad.
Coy Lancaster
Senior Member
The ones in the torque convertor control the pressure in the convertor itself and the trans control valve just like the relief valve in the hydraulics on the machine. The brake declutch valves work when you want to turn with one brake or stop all together, they disengage the transmission by dropping pressure in the control valve.
One other thing that will cause a complete pressure loss is the seal rings on the forward and reverse shaft. They are located in the rear of the trans housing behind the cover that looks like a PTO shaft if they are broke or damaged the trans will not have pressure.
One other thing that will cause a complete pressure loss is the seal rings on the forward and reverse shaft. They are located in the rear of the trans housing behind the cover that looks like a PTO shaft if they are broke or damaged the trans will not have pressure.
mcprp
Senior Member
Great knowledge , thank you very much !
Coy Lancaster
Senior Member
You’re welcome
mcprp
Senior Member
Hey coy , I see the forward reverse oil seal seems pretty easy to change but how will I know if it is leaking ? Wouldn’t I see oil coming out of that pto thing on that you take off to get to the seal ?