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bersh

Jerky 7117

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bersh
I have a 7117 that has been acting up lately. It runs great, and typically mows great, but lately it doens't seem to want to move very well. The tractor is very jerky, like something is slipping or not engaging fully. It gets worse on hills and after turning. I've checked the fluid levels in the bevel gear box and the hydro, and both seem fine (though the BGB does have a leaking seal around the shaft that drives the PTO). Any input, suggestions, things to look for would be appreciated. Thanks, Scott

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SmilinSam
The bolts holding the frame plates to the bevel gear box are loose most likley. Check all of them for tightness. 3 on each side and 4 in the front. When these get loose the tractor tends to get jerky, slow down or speed up in turns on uneven ground because therear end scissors enough from being loose at the gearbox to change the position of the hydro control.

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D-17_Dave
Check for a sticking clutch pedel that's stiff not allowing the drive belt to stay tight. A loose belt will cause all sorts of hydrostatic tranny problems. Stiff linkage since the clutch rarely gets used can sometimes hold the belt juft off of complete engagement.

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bersh
quote:
Originally posted by SmilinSam
The bolts holding the frame plates to the bevel gear box are loose most likley. Check all of them for tightness. 3 on each side and 4 in the front. When these get loose the tractor tends to get jerky, slow down or speed up in turns on uneven ground because therear end scissors enough from being loose at the gearbox to change the position of the hydro control.
Thanks for the info. I checked the BGB and the bolts are all tight and the unit itself is pretty much fused in place. Scott

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bersh
quote:
Originally posted by D-17_Dave
Check for a sticking clutch pedel that's stiff not allowing the drive belt to stay tight. A loose belt will cause all sorts of hydrostatic tranny problems. Stiff linkage since the clutch rarely gets used can sometimes hold the belt juft off of complete engagement.
I will look at this tonight while I'm changing the fluid. Thanks, Scott

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Kenh
I use a universal transmission fluid (UTF) in the hydro. Same fluid as used in farm tractors. UTF is made to be used in final drives and hydrostaic applications. The BGB can use the same fluid, but I use 80W90 gear oil in mine. I like the extra protection this gives the gears. Ken

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bersh
quote:
Originally posted by Kenh
I use a universal transmission fluid (UTF) in the hydro. Same fluid as used in farm tractors. UTF is made to be used in final drives and hydrostaic applications. The BGB can use the same fluid, but I use 80W90 gear oil in mine. I like the extra protection this gives the gears. Ken
I was going to get some of the UTF, but can only find it in 5 gallon buckets around here. Thanks, Scott

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PatRarick
quote:
Originally posted by bersh
quote:
Originally posted by D-17_Dave
Check for a sticking clutch pedel that's stiff not allowing the drive belt to stay tight. A loose belt will cause all sorts of hydrostatic tranny problems. Stiff linkage since the clutch rarely gets used can sometimes hold the belt juft off of complete engagement.
I will look at this tonight while I'm changing the fluid. Thanks, Scott
Be sure to also check the CONDITION of the belt. I have a 716 that was jerky and would have problems climbing the ditch banks. I checked everything mentioned in this thread, and also changed the fluid and filter without any change in performance. The belt looked good and seemed tight. It showed no signs of deterioration. Upon closer inspection I found it to be badly, but evenly worn. It was just a hair over 3/8" wide, nearly 1/8" narrower than a new belt and worn to almost a sharp "V". It was also badly glazed, indicating that it was slipping. Replaced the belt and the problem was solved. Pat

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MrSteele
My landlord is not a hydro, but your problem sounds like it is unrelated to hydro, just happens that your tractor IS a hydro. Check the tension of the drive belt. It sounds like it is slipping, and will cause the jerking motions you describe, with either a mechanical or hydro unit. On a mechaincal unit, this is completely adjustable, and I assume it should be on a hydro as well. When your tractor is in a 'bind', such as pulling up a rise, or turning, if the belt slips at all, the tractor will jerk, then, as the belt grabs, will move forward.

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Al
Hi, Usually when we see this problem it is the bolts from the side plates to the rear end assy being loose. This lets the gear case move back and forth the amount of slack in the holes. The hydro cam is mounted on the side plates and when the case rocks it moves the roller in the cam. Al Eden

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