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John Deere 4840 Powershift Troubles
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mack
Posted 4/28/2021 14:48 (#8977150)
Subject: John Deere 4840 Powershift Troubles


Having troubles with a 4840 JD power shift transmission. Pulled out onto the road and started through the gears. Shifted into 8th (high) gear and started slowing in speed while climbing a slight grade and the transmission light came on in the cab. Shifted down and nothing changed. Tractor will not move now in any gear. Never made any loud noises and no previous issues/indicators to this point. Any ideas on what to look for?
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Mudpie1971
Posted 4/28/2021 14:54 (#8977159 - in reply to #8977150)
Subject: RE: John Deere 4840 Powershift Troubles


Have you tried it again after it sat? Brakes may have come apart and plugged your filter which prevents oil flow. Usually it will work again for a short time after you shut it off and let some of the gunk fall off the filter, then it will plug again. Happened to me on my 4640. Good Luck
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mack
Posted 4/28/2021 14:58 (#8977165 - in reply to #8977159)
Subject: RE: John Deere 4840 Powershift Troubles


Have not tried it yet. Put it in neutral and pulled it a short distance to get it off the road.
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pirlbeck
Posted 4/28/2021 15:01 (#8977169 - in reply to #8977165)
Subject: RE: John Deere 4840 Powershift Troubles


West Central Iowa
mack - 4/28/2021 14:58

Have not tried it yet. Put it in neutral and pulled it a short distance to get it off the road.


If you have to tow it any more be sure to disengage the tow lever on the LH side of the rear end, just forward of where the final drive housing bolts to the rear end housing.
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pirlbeck
Posted 4/28/2021 14:59 (#8977166 - in reply to #8977150)
Subject: RE: John Deere 4840 Powershift Troubles


West Central Iowa		If it is not a plugged sump screen as the other poster mentioned, the torsional damper (drive plate) in the flywheel may have failed.
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tmrand
Posted 4/28/2021 15:06 (#8977179 - in reply to #8977166)
Subject: RE: John Deere 4840 Powershift Troubles



Southeast Colorado		I know you're supposed to be able to just shift up into 8th on the go with no clutch.............but I always hated how our felt doing that. We've got something 17k hours on one and I've been clutching between 7th and 8th from the get go. Just never cared much for that jerk it gives you without doing that.

Good luck to the original poster. I suspect this drive plate pirlbeck mentions is the problem.
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D&M Farms
Posted 4/28/2021 17:18 (#8977273 - in reply to #8977179)
Subject: RE: John Deere 4840 Powershift Troubles


Stoddard Co. SEMO		Torsion dampener. They’re in the P.S. tractors from 20-40 series. If you have one long enough you may have problems. Replaced the ones in both my 4840’s but they have seen a lot of hours in the past, especially on land plane floats.
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JD 9400
Posted 4/28/2021 22:18 (#8977870 - in reply to #8977179)
Subject: RE: John Deere 4840 Powershift Troubles


Southern Pa.
tmrand - 4/28/2021 16:06

I know you're supposed to be able to just shift up into 8th on the go with no clutch.............but I always hated how our felt doing that. We've got something 17k hours on one and I've been clutching between 7th and 8th from the get go. Just never cared much for that jerk it gives you without doing that.

Good luck to the original poster. I suspect this drive plate pirlbeck mentions is the problem.


X2 on using the clutch to shift from 7th to 8th. We've always done that on the 8 speed PS starting way back with the 4020 tractors.
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nw_bearcat
Posted 4/28/2021 17:16 (#8977272 - in reply to #8977150)
Subject: RE: John Deere 4840 Powershift Troubles


Top middle of MO. land of green hills and grass		What kind of oil filters and date of last change?
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ccjersey
Posted 4/28/2021 18:33 (#8977361 - in reply to #8977150)
Subject: RE: John Deere 4840 Powershift Troubles


Faunsdale, AL		Other than the early power-shift 20 series with the disconnect clutch lever, my experience has been the torsional damper in front of an 8 speed powershift is fine until it shears the center out and then suddenly tractor engine will run but NO steering, hydraulics or drive.

The older ones with the disconnect clutch could slip under load. I think usually noticed in high gear first
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Olddeeres4ever
Posted 4/28/2021 20:43 (#8977623 - in reply to #8977361)
Subject: RE: John Deere 4840 Powershift Troubles


1 hour east of ol cheyenne		Bought a 4640 about 30 years ago. It was a ytade in with a new JD crate engine in it. Was traded in with a blown up engine and dealer put a new crate engine in it. It sat on the lot for about 15 months. The new crate engine had a cracked plug in the cam galley allowing engine oil to fill dampener cavity about half full. Took it to the field and the " clutch" started slipping. They fired the engine up on splitting stand to find the oil leak. It had soaked up the disc material on the dampener and caused it to slip under a pull. New disc in there and good to go for 10000 hours and counting. We owned several powershift tractors and never had one just quit but mecknaik said it can happen.

Edited by Olddeeres4ever 4/28/2021 20:44
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edgeman25
Posted 4/29/2021 20:09 (#8979386 - in reply to #8977150)
Subject: RE: John Deere 4840 Powershift Troubles


I have the exact same problem that happened to me on our 4840. I also lost power steer and power brakes. Is there any way to check the torsional damper without splitting the tractor?
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ccjersey
Posted 4/30/2021 05:51 (#8979796 - in reply to #8979386)
Subject: RE: John Deere 4840 Powershift Troubles


Faunsdale, AL		No drive
No pto
No hydraulics
No steering and brakes

Loosen up transmission filter real loose and put a bucket under it so it can drain. Crank engine up and see if you get Lots of additional oil flowing out into your bucket indicating the transmission pump is turning. No more flow, it’s not turning or sump screen is completely plugged. Next step is to drain transmission and check sump screen.

Don't keep running the engine because the front pump will eventually seize from lack of lubrication. It’s not going to suddenly fix itself if you keep running it.
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