JD 6920 transmission calibration

[thebomberD]

Ive tried again a couple of times, and I see now that tCAL must stand for trans calibration, and that what's actually happening is that the jerking forward is causing the SPD fault and instantly taking me out of the calibration. Is there anyway to eliminate or minimize that jerking,?

 

[Timbo]

Ive tried again a couple of times, and I see now that tCAL must stand for trans calibration, and that what's actually happening is that the jerking forward is causing the SPD fault and instantly taking me out of the calibration. Is there anyway to eliminate or minimize that jerking,?

Stop trying the calibration and fix the underlying broken shuttle valve springs or warped plates .

 

[Phil P]

Stop trying the calibration and fix the underlying broken shuttle valve springs or warped plates .

If you read back he’s just had the transmission rebuilt and new plates so provide they have been installed correctly that shouldn’t be the problem.

Ive tried again a couple of times, and I see now that tCAL must stand for trans calibration, and that what's actually happening is that the jerking forward is causing the SPD fault and instantly taking me out of the calibration. Is there anyway to eliminate or minimize that jerking,?

I’m taking it your parked on level ground? SPD means the control is seeing too much forward or reverse motion. You will feel it trying to move very slightly during the calibration as it uses this to see when the clutch is starting too engage but too much motion and it thinks the tractor is rolling away and stops.
If the previous calibration was a mile different (ie the clutch fill times have changed dramatically) it can take a few attempts to get it to calibrate.

When the transmission was rebuilt where the clutch cooling valve springs inspected/replaced? These are usually the cause of a clutch failure and can cause poor forward/reverse modulation.

Another issue could be the clutch modulation (femeur) valve has got a week spring or scored valve. They can start to get a bit jumpy around 8k hours

 

[thebomberD]

The mech changed the fwd/rev pack, it consisted of 3 thin friction plates and two plates around 6mm thick. He also changed 2 valves, but I'd be lying if I told you I knew what they were. The friction plates that came out were almost completely stripped of their coating so I presume there would be a massive difference in the bite between new and old. I only have the tractor 2 years, so maybe as the plates wore the previous owner had carried out calibration to compensate. The prob I have is I cant get though the calibration process, I wouldn't mind doing it 10 more times If I thought the prob would be solved. I parked on a level yard, then on grass to minimise the rolling, then in the yard again with 4*2 blocks in front of wheels(even though I'm sure that was the wrong thing I wanted to keep trying)

 

[Phil P]

The mech changed the fwd/rev pack, it consisted of 3 thin friction plates and two plates around 6mm thick. He also changed 2 valves, but I'd be lying if I told you I knew what they were. The friction plates that came out were almost completely stripped of their coating so I presume there would be a massive difference in the bite between new and old. I only have the tractor 2 years, so maybe as the plates wore the previous owner had carried out calibration to compensate. The prob I have is I cant get though the calibration process, I wouldn't mind doing it 10 more times If I thought the prob would be solved. I parked on a level yard, then on grass to minimise the rolling, then in the yard again with 4*2 blocks in front of wheels(even though I'm sure that was the wrong thing I wanted to keep trying)

When you say the forward/reverse pack your do know they are separate clutches/brake packs? Where they both inspected?
The reverse brake would have to be removed to get tho the forward clutch drum which sits inside a planetary gear set.
Is there still any sign of dragging, select A range then rev the engine, does it try to creep forward/reverse?

 

[thebomberD]

No nothing like that, no creep when the shuttle is off, it operates pretty much as normal. If I start off without using the clutch the takeoff is much smoother. Even if I use the clutch taking off in c1 or d1, it's very jumpy but it's bearable. The real prob is inching in on loader implements or rear implements or hooking a trailer. I find myself in A1 as it's the only way to have any control. I have a pic of the old discs I'll send later.

 

[Phil P]

No nothing like that, no creep when the shuttle is off, it operates pretty much as normal. If I start off without using the clutch the takeoff is much smoother. Even if I use the clutch taking off in c1 or d1, it's very jumpy but it's bearable. The real prob is inching in on loader implements or rear implements or hooking a trailer. I find myself in A1 as it's the only way to have any control. I have a pic of the old discs I'll send later.

How many hours?

 

[thebomberD]

7200, 6350 when I bought it

 

[Phil P]

7200, 6350 when I bought it

I wouldn’t be surprised if the clutch valve isn’t getting tired at the hours on a loader tractor. Trouble is a valve is a bit on the expensive side to just throw in and try it! Could be worth getting the dealer to do a few diagnostics first.

 

[thebomberD]

I wouldn’t be surprised if the clutch valve isn’t getting tired at the hours on a loader tractor. Trouble is a valve is a bit on the expensive side to just throw in and try it! Could be worth getting the dealer to do a few diagnostics first.

I've tried a few times since, no go. I called a new guy, hopefully he'll come up with the solution. He did mention it sounded like it was something internal, so might end up being the clutch valve. Thanks for the help. I'll post when I get it sorted

 

[Paul croxson]

No problem, bills in the post

Hi phil. Got a similar issue.
when the calibration is being done, is it the valve you are calibrating, or the tractor?
Cheers
Paul

 

[Paul croxson]

No problem, bills in the post

Hi phil. Got a similar issue.
when the calibration is being done, is it the valve you are calibrating, or the tractor?
Cheers
Paul

 

[Timbo]

Hi phil. Got a similar issue.
when the calibration is being done, is it the valve you are calibrating, or the tractor?
Cheers
Paul

You are calibrating the fill times of the various clutches til they reach a predetermined bite

 

[Paul croxson]

You are calibrating the fill times of the various clutches til they reach a predetermined bite

Thanks timbo . Got a 6115r and a 6430. One valve shat itself, the one that didn’t works perfect in both tractors. Got a new one that is still snappy in both tractors. Was wondering whether it’s a dud valve, or that is what needs calibrating?
Thanks again
Paul

 

[Phil P]

Thanks timbo . Got a 6115r and a 6430. One valve shat itself, the one that didn’t works perfect in both tractors. Got a new one that is still snappy in both tractors. Was wondering whether it’s a dud valve, or that is what needs calibrating?
Thanks again
Paul

As Timbo says, when you do a calibration the controller is learning how fast to open the valve to engage the clutch packs. If you replace the valve it will have a different spring value to the old one so will open/close faster/slower for a given voltage. This means the controller will need to re-learn the clutch time/pressure values. This is also why over time they need calibrating again as the valve spring weakens with age and use.

 

[Paul croxson]

As Timbo says, when you do a calibration the controller is learning how fast to open the valve to engage the clutch packs. If you replace the valve it will have a different spring value to the old one so will open/close faster/slower for a given voltage. This means the controller will need to re-learn the clutch time/pressure values. This is also why over time they need calibrating again as the valve spring weakens with age and use.

Thanks phil, and timbo, which comes out as tomboy with auto correct, lucky I checked.
can you set a valve with a 6115r? Or is it a JD tech job?
thanks again for your time
paul