John Deere 7920 rough ivt

WBContract · Sep 27, 2016

Hi
Just wondering if anyone else has had trouble with a clunky shifting ivt?
I'm presuming that around 10-13kph the ivt changes a range. Mine some times has quite a rough/clunk when shifting mainly under load while at lower revs.
For example if you are pulling a roller at say 1400rpm and 12kph and come to a hill the tractor tries to maintain speed by increasing revs and it does a real rough shift.
Likewise if you are slowing down on the road when it passes through that 10-13kph area it sometimes does a real rough shift.
Almost seems like it's lacking oil pressure or something, I have found that setting the minimum revs around 1800rpm even in very light draft situations helps.
John Deere have calibrated transmission but that didn't help alot.
Any help would be appreciated.

mushnt grummmble · Sep 27, 2016

Sounds like a syncro ring

nick... · Sep 27, 2016

Sounds expensive

Nick...

Kevtherev · Sep 27, 2016

Accumulator @Boothy

chickens and wheat · Sep 27, 2016

our 8345 hire tractor did that last year, apparently the hi lo is a simple gear, it should change seemlessly because the tractor only allows a change when the two sides are speed matched, not sure how the 8345 got fixed but I believe it had to be split.
dealer recalibrated it a couple of times but left saying it needed major surgery

NZ Tech · Sep 27, 2016

Does the machine clunk/clonk when you switch it off... Midway down the machine in the flywheel area?.

Have you checked the driveshaft UJ's aren't wearing out?.

Boothy · Sep 27, 2016

chickens and wheat said:
our 8345 hire tractor did that last year, apparently the hi lo is a simple gear, it should change seemlessly because the tractor only allows a change when the two sides are speed matched, not sure how the 8345 got fixed but I believe it had to be split.
dealer recalibrated it a couple of times but left saying it needed major surgery

It did get split along with an 8360r next to it believe they replaced the hydro unit as well so I was told by our usual mechanic!

BS Farming · Nov 8, 2021

WBContract said:
Hi
Just wondering if anyone else has had trouble with a clunky shifting ivt?
I'm presuming that around 10-13kph the ivt changes a range. Mine some times has quite a rough/clunk when shifting mainly under load while at lower revs.
For example if you are pulling a roller at say 1400rpm and 12kph and come to a hill the tractor tries to maintain speed by increasing revs and it does a real rough shift.
Likewise if you are slowing down on the road when it passes through that 10-13kph area it sometimes does a real rough shift.
Almost seems like it's lacking oil pressure or something, I have found that setting the minimum revs around 1800rpm even in very light draft situations helps.
John Deere have calibrated transmission but that didn't help alot.
Any help would be appreciate

Boothy said:

It did get split along with an 8360r next to it believe they replaced the hydro unit as well so I was told by our usual mechanic!

Click to expand...

Hi WB contract, just wondering if you had any luck with the 7920 with the clunking noise as we have one with a similar issues ?

NZ Tech · Nov 9, 2021

Check system and lube pressures for a start. Get it smoking hot as the trans pump housing wear on these with just use.

They only have high and lo clutches in the trans and pretty sure they shift closer to 20ks phr so probably can't be that.

Start with the first part and make sure pressures are good. I'd still check the shaft and ujs for problems as well. The tow disconnect can be problematic but that will make a noise shuttling forward to reverse.

BS Farming · Nov 9, 2021

WBContract said:
Hi
Just wondering if anyone else has had trouble with a clunky shifting ivt?
I'm presuming that around 10-13kph the ivt changes a range. Mine some times has quite a rough/clunk when shifting mainly under load while at lower revs.
For example if you are pulling a roller at say 1400rpm and 12kph and come to a hill the tractor tries to maintain speed by increasing revs and it does a real rough shift.
Likewise if you are slowing down on the road when it passes through that 10-13kph area it sometimes does a real rough shift.
Almost seems like it's lacking oil pressure or something, I have found that setting the minimum revs around 1800rpm even in very light draft situations helps.
John Deere have calibrated transmission but that didn't help alot.
Any help would be appreciated.

NZ Tech said:
Check system and lube pressures for a start. Get it smoking hot as the trans pump housing wear on these with just use.

They only have high and lo clutches in the trans and pretty sure they shift closer to 20ks phr so probably can't be that.

Start with the first part and make sure pressures are good. I'd still check the shaft and ujs for problems as well. The tow disconnect can be problematic but that will make a noise shuttling forward to reverse.

Sorry mate the rest of my issues didn’t attach, here is what I have done so far,
7920 with around 3000hrs on it, has never had any previous issues. The suction screens have been checked both in the diff housing and the two screens in the front cover and all seems fine. When working it with a light load and with the ivt setting at number 3, so the machine is doing around 1200rpm you’ll be travelling along at 9.6kph and go to slow down under 8.6kph and the machine makes a distinctive clunking/banging noise as though it is dropping into “low range” which has never been noticed before.

I have swapped both hi and low range solenoids around along with the reverse brake solenoid but didn’t really seems to make a difference, also swapped the spool valve and springs, the hydro control solenoid is within the ohms specs and there are no codes, machine calibrates fine aswell. It still seems to happen with the MFWD off and the uni’s on the input shaft have been changed along with the rear engine dampener. Machine doesn’t have TLS. Have checked system and line pressure around 45c and the pressures seem to be within spec, have done the hydro control pressure check along with the element leakage test, hi,low and reverse brake and couldn’t really see any dramas there.

Any help would be greatly appreciated

NZ Tech · Nov 9, 2021

Have you tried removing the mfwd shaft and retesting.

The tow disconnect can cause issues with a loose hi/lo in the trans. I've also seen the pinion output bearing fail on the transmission side but at higher hours.

Try removing the mfwd shaft and see if it's not a lead issue I'm the 4wd for a start.

BS Farming · Nov 9, 2021

NZ Tech said:
Have you tried removing the mfwd shaft and retesting.

The tow disconnect can cause issues with a loose hi/lo in the trans. I've also seen the pinion output bearing fail on the transmission side but at higher hours.

Try removing the mfwd shaft and see if it's not a lead issue I'm the 4wd for a start.

Thanks very much for that info mate, after the MFWD was disconnected it didn’t really seem to make a lot of difference. It may be a case of either letting it develop or remove for internal inspection? Makes it hard when it’s not throwing any DTCs and is calibrating fine though. Can the tow disconnect be adjusted in anyway ?
Thanks again for your help mate

NZ Tech · Nov 10, 2021

Lastly try disconnecting the tow disconnect. Lh rear final drive its a lever above it. Cycle that.

It's probably going to be a let it develope type deal. Best case... Do an oil sample and see if there is any metal in the oil and if not. Run it and see. Sadly.

BS Farming said:
Thanks very much for that info mate, after the MFWD was disconnected it didn’t really seem to make a lot of difference. It may be a case of either letting it develop or remove for internal inspection? Makes it hard when it’s not throwing any DTCs and is calibrating fine though. Can the tow disconnect be adjusted in anyway ?
Thanks again for your help mate

BS Farming · Nov 11, 2021

NZ Tech said:
Lastly try disconnecting the tow disconnect. Lh rear final drive its a lever above it. Cycle that.

It's probably going to be a let it develope type deal. Best case... Do an oil sample and see if there is any metal in the oil and if not. Run it and see. Sadly.

Okay mate will do, thanks again for your help I’ll keep you posted on what happens

WBContract · Nov 28, 2021

Hi BS Farming. Got your message re 7920 trans. That was a few years back but from memory the dealer said that there was a trans software update available which they installed. Made all the difference if I remember right. Felt like a totally different trans, tight and smooth with no clunk in the shift. Back in 2016 when I first asked the question the tractor must have had around 6000 hours.
She's got just on 12000 hours now with no trans issues at all since.

WBContract · Nov 28, 2021

BS Farming · Nov 28, 2021

WBContract said:
Hi BS Farming. Got your message re 7920 trans. That was a few years back but from memory the dealer said that there was a trans software update available which they installed. Made all the difference if I remember right. Felt like a totally different trans, tight and smooth with no clunk in the shift. Back in 2016 when I first asked the question the tractor must have had around 6000 hours.
She's got just on 12000 hours now with no trans issues at all since.

Hi,
Thanks very much for that information, i will see if they can do another update. Hopefully that might be all it is.
Regards

John Deere 7920 rough ivt

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