HD7G Main Pump
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Construction and other equipment
Forum Description: everything else with orange (or yellow) paint
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=87790
Printed Date: 30 Jun 2025 at 4:38am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: HD7G Main Pump
Posted By: GreaseMonkey
Subject: HD7G Main Pump
Date Posted: 09 Apr 2014 at 7:51pm
| Just starting to investigate a drive problem. Last summer it would go about 50 feet forward or backward and no more. It would stop and would not go any further. The bucket controls work fine and the engine purrs like a kitten, but now no drive at all. I'm thinking the first place to look is a hydraulic pump related to the drive system. Any help you guys can offer would be great. Anyone know where to find the pump? Is there a separate one for the bucket? |
Replies:
Posted By: JC-WI
Date Posted: 09 Apr 2014 at 8:11pm
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OIL? filters? serviced? ------------- He who says there is no evil has already deceived himself The truth is the truth, sugar coated or not. Trawler II says, "Remember that." |
Posted By: GreaseMonkey
Date Posted: 09 Apr 2014 at 9:23pm
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Service pretty sure thats no. Not sure about the filters but oil is new and full. This is a friends machine not mine and I am just starting to try to figure this out. Also I am not familiar with dozers very much. Pretty much an amateur. The post above this one looks like the same problem. I am thinking that when it gets a little warmer it may revert back to being able to travel 30 feet or so before quitting again. So what I am getting here is it may be a simple oil delivery problem due to plugged filers and screens. Correct? Thanks again |
Posted By: gemdozer
Date Posted: 10 Apr 2014 at 5:35am
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The hydrolic pump is in front machine and transmission pump is connect on
the torque housing and the streaner oil transmission must be clog
|
Posted By: DMiller
Date Posted: 10 Apr 2014 at 6:32am
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There are two strainers, one at the bottom of the transmission(square bolt-in with a large line attached to it) then the main unit as you sit in the seat under the left foot and a real bear to get at. The trans. filter is just under the floor plates same area while the strainer has a 1 1/4" hard tube and a similar sized line as the trans. bottom strainer. Both of those lines feed to the transmission pump on the upper right of the torque converter housing. I am going to the farm today, getting ready to swap the trans and converter on my own7g will try to get some photos. |
Posted By: DMiller
Date Posted: 10 Apr 2014 at 4:27pm
These photos are of my spare trans, going in this next few days into the 7G I own:  The small square block at the bottom of the top photo is the trans scavenge strainer, the somewhat round fixture to the right of center with one fitting and a smooth hose tube is the main suction strainer, the hosed connection feeds the steering hydraulics which once cooked from starving the machine will not turn. |
Posted By: GreaseMonkey
Date Posted: 10 Apr 2014 at 6:31pm
| Thanks guys. This helps a great deal. I will check this stuff out and let you know how it goes. |
Posted By: dustydallas
Date Posted: 26 Apr 2014 at 4:10pm
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grease monkey ref hd7g i have a hd7g crawler that has the same problem with the trans pressure it would drive for a while the trans pressure would drop completely and it would not move you come back later it might move for a while and might not i have clean screens took the filter out i even filled it with clear up with oil still do the same thing i took the trans pump off it has some wear but it is a two stage pump with wider gears that are keyed to shaft and two narrower gears but the one narrower gear just floats no keyway or press fit is it a flow divider or bypass the pump has two 3/4 npt lines and two 1''npt lines do you know how much flow the trans pump is suspose to haveand pressure could i change pumps and use a flow divider or priority valve where does the two pressure line go lube and clutch pack??? also under the floor board at your left heal position is somthing that has one oil line on it and a lever on each side of it nothing is hook up to the levers and its a little smaller then the trans pump any help would be really helpful thanks dusty dallas oklahoma |
Posted By: DMiller
Date Posted: 27 Apr 2014 at 4:47pm
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The scavenge side suction draws from the trans case bottom, returns that oil to the left clutch housing of the final housing keeping it circulating and filtering, the main suction strainer is just off that side of the trans case and draws volume from the same point in the finals housing. That side(closest to the seat) of the pump feeds oil to the main filter then the trans shift body, this has a bleed line that replenishes the torque converter as it recirculates oil back to the transmission at the input shaft retainer or left side of trans case. Either strainer, the scavenge side or main gets stopped up or the main filter chokes and you will starve the oil for the trans/torque. These are fairly low pressure, high volume hydraulics systems, normal application pressures are only in the 150-170lbs range with open flow off the pump at 230lbs. Torque converter is checked at 35-45 lbs. |
Posted By: DMiller
Date Posted: 27 Apr 2014 at 5:06pm
| As an add, I am swapping transmissions in mine due to the seals in the accumulators(covers at the ends of the shafts) being gone. I was losing both forwards slowly, the tractor would pull some in lo Forward but would slip in Hi Forward, then had absolutely no Lo Reverse and a strong Hi reverse. Once I had the shift actuator removed I blew air into the ports for the upper shaft(forward)and as I did so the air would blow back from the opposite port, for reverse(lower shaft) the air for Lo would blow into the case. Part of this problem occurred when the previous owner failed to clean the screens and allowed leaks to drop oil levels way too low, he had cooked the steering pump in it as well which was $1300+ when I finally found one. |
Posted By: dustydallas
Date Posted: 27 Apr 2014 at 6:43pm
 to dmiller thank you
what is the housing under the flool board your left foot heel that has a lever or each side
i have a crawler that no rods are hooked up to the unit whatever it is??
|
Posted By: DMiller
Date Posted: 27 Apr 2014 at 8:00pm
| That is an old travel speed governor by my shop manual, not used on many of the later 7G's. If is intact should be a small hydraulic pump mounted to the lower right of the front of the trans case. |
Posted By: dustydallas
Date Posted: 27 Apr 2014 at 8:38pm
| [:tanks I only gave 1400 for my crawler runs good with I can afford to spend a little money on it thanks again for the help I seen a post somewhere that the replacement pump was 1300 from all is and 550 somewhere else thank for the help dusty |