Powermax Hydro Rebuild
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Garden Tractors
Forum Description: A great place to discuss the Simplicity and Allis Chalmers Garden Models
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=146211
Printed Date: 04 Nov 2025 at 5:23am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: Powermax Hydro Rebuild
Posted By: IBWD MIke
Subject: Powermax Hydro Rebuild
Date Posted: 06 Jan 2018 at 5:35pm
I've got a line on a Simplicity Powermax not sure which model exactly, but it's the same as a 720. It has a bad hydro in it, how much would it cost roughly to get this thing overhauled?
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Replies:
Posted By: ac720nut
Date Posted: 07 Jan 2018 at 5:38pm
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I don't know the exact cost but finding the parts would be the big thing. A gentleman from Canada just recently did one and has it documented on here.
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Posted By: IBWD MIke
Date Posted: 07 Jan 2018 at 7:02pm
I seem to remember that thread. Thanks for the reply.
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Posted By: orangeman
Date Posted: 08 Jan 2018 at 10:28am
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IBWD Mike: I think if you do a search using Rustydollar that will bring you a wealth of information on the hydro rebuild that he tackled.
Lots of good information and much can be learned through the work that he did and was kind enough to post.
Orangeman
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Posted By: IBWD MIke
Date Posted: 08 Jan 2018 at 11:09am
Ok, next question. I have done business with the potential seller a couple of times already, great guy. I don't want to insult him on an offer but don't want to overpay for this thing either. What's a fair price for a good running (original Onan) Powermax with a bad hydro? Has great tires on the back fronts aren't much.
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Posted By: Brian S(NY)
Date Posted: 08 Jan 2018 at 1:41pm
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is it complete with front and rear pto? does it have the three point hitch? any attachments?
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God made man.Sam colt made man equal.
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Posted By: AC720Man
Date Posted: 08 Jan 2018 at 5:10pm
Before you assume hydro is bad I would at least verify oil level by unscrewing the stick to check. How fresh of a filter and oil? My 720 would barely move when I first ran it as it had been setting for awhile before I purchased it. New oil and filter resolved it. Those things are fairly bullet proof if proper care is given. Has it been professionally diagnosed?
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1968 B-208, 1976 720 (2 of them)Danco brush hog, single bottom plow,52" snow thrower, belly mower,rear tine tiller, rear blade, front blade, 57"sickle bar,1983 917 hydro, 1968 7hp sno-bee, 1968 190XTD
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Posted By: IBWD MIke
Date Posted: 09 Jan 2018 at 10:06am
I will have to get back with the seller in the spring as he has went South for the winter. I'm pretty sure the oil level and filter are good. He is a good AC man. If it was something simple I think he would have caught it.
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Posted By: injpumpEd
Date Posted: 13 Jan 2018 at 9:47am
I had the hydro "go out" on my 720 about 10 years ago. I pulled it out and apart, and all that was wrong was the roll pin that connects the shift lever to the swash plate had sheared off from years of back and forth use. I was able to get all the seals, gaskets and needle bearings, and pins from a Simplicity dealer. The pump group looked really nice and clean still, though the charge pump was a little rough, and it was very expensive, so I just re-used mine. When using it hard, it does get slow to lift when really hot, but it still moves and raises the deck ok. The charge pump provides the hydraulics for the lift.I run Dexron in mine, just like called for in owner's manual.
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210 "too hot to farm" puller, part of the "insane pumpkin posse". Owner of Guenther Heritage Diesel, specializing in fuel injection systems on heritage era tractors. stock rebuilds to all out pullers!
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Posted By: IBWD MIke
Date Posted: 13 Jan 2018 at 11:41am
Thanks Ed, I hope I can get this thing bought. After getting my 720 last year and using the front blade I would like to have one tractor for that and one for the mower deck.
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Posted By: rustydollar
Date Posted: 13 Jan 2018 at 8:40pm
Posted By: IBWD MIke
Date Posted: 14 Jan 2018 at 9:23am
Thanks, if I get this thing bought in the spring it will be interesting to see what's actually wrong with it.
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Posted By: rustydollar
Date Posted: 14 Jan 2018 at 11:09am
Posted By: IBWD MIke
Date Posted: 15 Jan 2018 at 11:02am
Posted By: bill(soh)
Date Posted: 24 Jan 2018 at 9:57am
I have 620 mower that just stopped moving, figured hydro went out. To make a long story short finely figured out all splines on stub axel were worn clear off one side.
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D-15,CA,I-400,C,180 2-620's,2-110's,112,718,716,
5015, agco 1718
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