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lboy1971

Pow'r max hydrostatic drive questions

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lboy1971
The hydraulic lift works good but the hydro tranny is weak. It will move the tractor in 1st range but won't move it at all in 3rd and barely if on level ground in 2nd. Won't move uphill in 2nd or 3rd and slows down in 1st. I put a new filter on next to the right fender and added 1qt of ATF to bring the fluid up to the level line on the dipstick and no change. Don't see any leaks. Could there be a non-working relief valve for the tranny? Tractor sat about 5 years or more before I bought it.

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Marty-MN
Yes it could be a stuck charge pressure relief valve but you need to check the simple things first. first is thefluid and filter and you said you did that so then check the linkage. if that is ok check the charge pressure with a 0 to 1000 psi gauge with a snubber installed. the pressure should be 70 to 150 with the engine close to high idle . pull the implement lever down and gauge should read 700 to 800 psi. three things you are checking are charge pressure relief valve, implement relief valve and charge pump.

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Ronald Hribar
Did you follow the proper procedure for adding oil? I can not remember step by step procedure. But seems there is a valve to turn and also to turn pump? by hand. Stan D outlined the procedure once.

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StanD
Check the drive belts. Check the bearings in the lower pivot. Check the bushings & shaft in lower pivot. Do not try aftermarket belts. Check free play on clutch pedal. Ten to one belts are shot plus any of other points to check. Stan

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mwells
My 720 also seems to slow down, mostly in 3rd though. It seems to work good, but when you go from nutral to full speed quickly it seems starts to move, then I hear some sweaks and it alomst sounds like something in side is slipping. I will eventually get to full speed, but when you drive up a hill it slows down. I guess I'll try the pressure test.

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D-17_Dave
I'll go with Stan on both the tractors problems. Worn belts will slip easily. Even new belts will slip if the clutch isn't adjusted properly. The main spring must carry the belt load. So if there is no free play in the clutch pedal the pedal may be holding tention against the clutch allowing the main tention spring to not have full force against the drive belts.

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UCD
This tractor has two transmissions, a manual 3 speed in front of a Sundstrand hydro. The weakest link in this set up is the two belt clutch setup. This requires a Matched Set of 2 belts, not just two belts of the same number. Also the clutch pulleys need to work freely and be adjusted correctly. Power Max 4040, MFG# 990705. 4041, MFG# 990953, 990954. 9020, MFG# 1690072, 1690230, 1690283. 616, MFG# 2020185. 620, MFG# 2020303, 2020304, 720, MFG# 1690073, 1690231, 1690288. Drive Belt# 170921 Length 24" Type HA (Matched Set of 2)

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lboy1971
I checked it out today and the two belts are slipping. With the tractor off and laying underneath I could turn the driveshaft from the hydro and the double pulley would spin in the two belts by the engine. It would do that turning it one way then turning it the other way it would grab the belts and turn the engine. I started the tractor and watched the driveshafts through a small space between the bottom of the dash and the frame tunnel and could clearly see the transmission driveshaft come to a complete stop when trying to go fast with the hydro drive lever. I'll try to adjust the clutch and see if that does the trick. I might have to get new belts.

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lboy1971
I finally got around to adjusting the clutch linkage tonight. Now it works great, drives like a new tractor! Well not quite but much more normal :) Thanks for the tip on adjusting the clutch linkage.

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