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I have a 1974 d8h it was working fine put in park and now it…

I have a 1974 d8h...
I have a 1974 d8h it was working fine put in park and now it won't move finals are good drive line turns but don't seem to be any pressure in clutches any thoughts
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Customer reply replied 7 years ago
All fluids and filters are good and clean no debre in oil or filter could there be a bad valve or bad pump in tran
Answered in 7 minutes by:
6/2/2015
Mechanic: catmastertech, Technician replied 7 years ago
catmastertech
catmastertech, Technician
Category: Construction and Road Equipment
Satisfied Customers: 4,041
Experience: Field service technician for CAT 19 years.
Verified
Hello, It is possible for the safety valve to stick in the open position and prevent the transmission going into gear.Make sure the shift lever is selecting each gear correctly. F-N-R and 1-2-3.If shifter is working correctly and all detents can be felt, the transmission valve must have some trash in it.Check pump output pressure firsts then check the P1 and P2 pressures.You should have pump pressure even with the stuck valve but P1 and P2 will not.If you don't have pump pressure, check strainer and suction lines for air leaks.
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Customer reply replied 7 years ago
I can feel it shift to all gears I don't have manual for it so pump pressure and port location is unknown to me .is the safety valve the linkage tords the rear of the dozer coming out of the top of trans
Mechanic: catmastertech, Technician replied 7 years ago
Safety valve is an internal load check valve designed to prevent the transmission engaging if left in gear during startup. The check valve is inside the valve sections of the transmission and requires removal of the transmission control valve stack to access it. Since you said this problem began after the machine had been stopped, it seemed a logical explanation. I see many machines with shift lever worn out or adjusted wrong not going back to neutral so, the safety valve cannot reset.I will need the full machine serial number to research the location of the transmission test ports.
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Customer reply replied 7 years ago
OK I am not near machine now will get back at you tomorrow
Mechanic: catmastertech, Technician replied 7 years ago
Ok, thanks. I will be looking for your reply tomorrow night.
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Customer reply replied 7 years ago
Thanks for everything
Mechanic: catmastertech, Technician replied 7 years ago
You're welcome, I am glad to help.
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Customer reply replied 7 years ago
(Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.Trans group number 5m7987 test 39699 arangment 3p4004 numbers of top of trans
Mechanic: catmastertech, Technician replied 7 years ago
I am sorry, I do not have a phone service setup. The live chat and Q&A questions is all I can do. I will look check these numbers to find the related machine serial number and maybe I can find some testing information to help.
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Mechanic: catmastertech, Technician replied 7 years ago
Attached is the test port locations and pressure charts. I also included spec' sheets.
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Mechanic: catmastertech, Technician replied 7 years ago
It will be best to have two gauges to test pressures. I use 500 psi gauges and 1/8" pipe fittings with couplers (use any you like, Hanson couplers is the brand I have) to connect to four foot long hoses.You do not need to do the initial pressure test, this does not normally change.Just record the pressures for direction and speed ports. (P1 and P2) Compare to pump pressure for valve leakage/loss.
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Customer reply replied 7 years ago
couldn't find any Trash in valve I did start it with cover off trans no oil moving in trany I didn't have correct fitting so couldn't check pump but shouldn't there be oil flowing I was expect ing a bath
Mechanic: catmastertech, Technician replied 7 years ago
Yes, you should have seen oil moving out of the valve. It will not spray hard but, it should push out oil.You must have a serious suction leak or a bad pump. Check the suction lines to the pump and replace any hard hoses and seals. You may want to remove the transmission pump anyway to inspect it for wear or damage.
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Customer reply replied 7 years ago
K There is a hose that come of the side of fill tube on Tran its not hooked to any thing on other end is that just a over flow hose or vent ?
Mechanic: catmastertech, Technician replied 7 years ago
Most machines have a vent and some will also vent from the torque convertor to the transmission. I am not familiar with this old machine (a bit before my time) but, I would guess it should be from the top of the torque convertor.I see a steel tube that connects from the torque convertor to the transmission case for a vent but, I cannot find a hose on the fill pipe. Normally this is just an elbow and breather.If this is a cab model, maybe someone added it to vent transmission fuses out from the cab area.
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Customer reply replied 7 years ago
Thanks for all the help I got it going today it had busted gear in pump on for trans
Mechanic: catmastertech, Technician replied 7 years ago
Thanks for the reply. I am glad I could help you.If you need further assistance, please feel free to ask for me. Thanks, Donnie
catmastertech
catmastertech, Technician
Category: Construction and Road Equipment
Satisfied Customers: 4,041
Experience: Field service technician for CAT 19 years.
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