# Need info, 88 JD 2555



## Bigtubz (Jul 1, 2021)

Need to find the proper name of the rabbit/turtle function on the right hand side just below the throttle lever on a 1988 JD 2555 with cab and 4wd. What purpose should it be used for since the tractor has a throttle lever? Thanks for any and all replies.
Have a blessed day 🙏


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## pogobill (Jan 31, 2012)

Welcome to the forum.
Not sure what your function is, but mine lets me switch between high and low speed in either high or low range, giving me basically four transmission speeds.


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## Bigtubz (Jul 1, 2021)

That's what I thought but have lost that function. Was trying to figure the proper part name so I could research possible fixes. There was another post on a different site that said the true function was to moderate the speed of the hydraulics going to the back of the tractor, that's the reason I asked about its function. Have pulled different schematics but none reveal the part name along with multiple searches using different key words.
Thank you for your reply.


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## Tx Jim (Jul 28, 2020)

Welcome to TF
Proper name is hyd hi-lo. Sounds as if supply tube or seal has failed not allowing hyd pressure to engage clutch. One test is remove cab floor then remove shift cover & blow compressed air into tubes & listen for escaping air. One can also check hyd trans pump pressure on RH side of shift cover. Trans pump pressure should be around 155 psi. The person that stated that lever you encircled in red controls speed of hyd SCV is incorrect. Handle(see photo below) circled in green controls scv speed.
HTH's Jim( PS: I served as a JD dealer service manager from '74-'87)


https://partscatalog.deere.com/jdrc/sidebyside/equipment/60847/referrer/navigation/pgId/392089835


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## Tx Jim (Jul 28, 2020)

pogobill said:


> Welcome to the forum.
> Not sure what your function is, but mine lets me switch between high and low speed in either high or low range, giving me basically four transmission speeds.


I disagree about hyd hi-lo yielding basically four transmission speeds. Hyd hi-lo yields 16 forward speeds on most JD utility tractors


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## pogobill (Jan 31, 2012)

Tx Jim said:


> I disagree about hyd hi-lo yielding basically four transmission speeds. Hyd hi-lo yields 16 forward speeds on most JD utility tractors


I agree, but I was just commenting that it was possibly a high-low function, as on my tractor, (not a John Deere). Mine is a two speed hydro with the hi-low button.


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## Bigtubz (Jul 1, 2021)

Tx Jim said:


> Welcome to TF
> Proper name is hyd hi-lo. Sounds as if supply tube or seal has failed not allowing hyd pressure to engage clutch. One test is remove cab floor then remove shift cover & blow compressed air into tubes & listen for escaping air. One can also check hyd trans pump pressure on RH side of shift cover. Trans pump pressure should be around 155 psi. The person that stated that lever you encircled in red controls speed of hyd SCV is incorrect. Handle(see photo below) circled in green controls scv speed.
> HTH's Jim( PS: I served as a JD dealer service manager from '74-'87)
> 
> ...





Tx Jim said:


> Welcome to TF
> Proper name is hyd hi-lo. Sounds as if supply tube or seal has failed not allowing hyd pressure to engage clutch. One test is remove cab floor then remove shift cover & blow compressed air into tubes & listen for escaping air. One can also check hyd trans pump pressure on RH side of shift cover. Trans pump pressure should be around 155 psi. The person that stated that lever you encircled in red controls speed of hyd SCV is incorrect. Handle(see photo below) circled in green controls scv speed.
> HTH's Jim( PS: I served as a JD dealer service manager from '74-'87)
> 
> ...


Thank you, and thanks for the attachments as I now have a place to start instead of scratching my head.


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## Fedup (Feb 25, 2014)

In what way have you "lost function?" Be aware that only the rabbit mode is dependent on hydraulics on the 55 series tractors. The turtle mode is spring applied, and with loss of hydraulic pressure the clutch pack will default to lo range. Without hydraulic pressure the tractor will operate in low, won't shift into high, and the lever won't stay in the rabbit position. Is that your condition, or is it something else? Do the PTO and PTO brake operate properly? Those functions are closely related to the hi/lo.


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## Bigtubz (Jul 1, 2021)

Fedup said:


> In what way have you "lost function?" Be aware that only the rabbit mode is dependent on hydraulics on the 55 series tractors. The turtle mode is spring applied, and with loss of hydraulic pressure the clutch pack will default to lo range. Without hydraulic pressure the tractor will operate in low, won't shift into high, and the lever won't stay in the rabbit position. Is that your condition, or is it something else? Do the PTO and PTO brake operate properly? Those functions are closely related to the hi/lo.


The PTO and its functions work correctly, and the tractor operates in low and High Range fine. Have lost the ability to add the " extra boost " it used to have when the rabbit mode is used. Is there anything electrical on the rabbit control?
Thanks for your reply


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## Tx Jim (Jul 28, 2020)

High speed(rabbit) has no electronical control device IE control is all manual by shifting a hyd valve. Do hyd's operate correctly when control valve is in "high position"?


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## Fedup (Feb 25, 2014)

Can you feel some resistance on the lever and does it stay in rabbit when put there? The valve is spring loaded to turtle range. It has a hydraulic detent that should hold the lever in rabbit until it's pulled back into turtle or the engine is shut off. Does that seem to work?


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## Bigtubz (Jul 1, 2021)

Tx Jim said:


> High speed(rabbit) has no electronical control device IE control is all manual by shifting a hyd valve. Do hyd's operate correctly when control valve is in "high position"?


Yes Hyd's work fine in high position.


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## Bigtubz (Jul 1, 2021)

Fedup said:


> Can you feel some resistance on the lever and does it stay in rabbit when put there? The valve is spring loaded to turtle range. It has a hydraulic detent that should hold the lever in rabbit until it's pulled back into turtle or the engine is shut off. Does that seem to work?


There is resistance on lever but no response and rabbit will not stay in place when pushed forward.


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## Fedup (Feb 25, 2014)

Then you need to perform some pressure checks on that portion of the system. The resistance tells you the lever is most likely moving the valve spool, but the lack of response says that pressure in the high range clutch pack is not building to where it should be, and an internal leak in that area is likely. If EVERYTHING else (hydraulic that is) operates as it should and does so even after working a few hours, then it's quite possible you can get by for some time yet operating in turtle mode without doing much (if any) more damage. Still, I would think some pressure checks would be in order.


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## Bigtubz (Jul 1, 2021)

Fedup said:


> Then you need to perform some pressure checks on that portion of the system. The resistance tells you the lever is most likely moving the valve spool, but the lack of response says that pressure in the high range clutch pack is not building to where it should be, and an internal leak in that area is likely. If EVERYTHING else (hydraulic that is) operates as it should and does so even after working a few hours, then it's quite possible you can get by for some time yet operating in turtle mode without doing much (if any) more damage. Still, I would think some pressure checks would be in order.


Thank you


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## Bigtubz (Jul 1, 2021)

I want to thank everyone who has replied, your insight has been most helpful.


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