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D6c jumping out of gear

D6c jumping out of gear

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74A6C
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I've got a 74a D6 that's in pretty good overall shape, I bought it from a small construction company about 4 years ago. S/N is around 1300, the plate on the dash is gone and the winch covers the one on the rear. My issue is it is jumping out of forward and reverse. I've found that gear one through three make no difference, as far as staying in the selected direction, never have any use to run 4th, unless I'm walking across the farm. Sometimes the problem is more prevalent than others. I've got a parts manual and a reproduction service manual. I'm guessing start with the interlock, but I'm asking before assuming. Any and all help is appreciated.
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Sun, Apr 12, 2020 7:32 AM
edb
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Hi 74A6C,
welcome to the BB.
From my Specs book we are given a centre to centre distance for the Interlock Linkage Rod as :- 15.22"
This dimension can be correct but lost motion--worn linkage etc.-- can allow the Interlock inner mechanism to be short of its intended position to fully lock the shifter rails in place.
Worn gear shaft bearings within the Trans. can overload the linkage too by allowing the gear teeth to run at angle and so cause end thrust on the gear shifter levers etc.

The Fwd. Rev. mechanism is the most used linkage and so wear is your enemy in high hour poorly maintained units.

Others may be able to contribute more as I do not recall any of these DD units in our area so have no experience of them.

Hope this helps.
Cheers,
Eddie B.
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Sun, Apr 12, 2020 1:22 PM
74A6C
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Reply to edb:
Hi 74A6C,
welcome to the BB.
From my Specs book we are given a centre to centre distance for the Interlock Linkage Rod as :- 15.22"
This dimension can be correct but lost motion--worn linkage etc.-- can allow the Interlock inner mechanism to be short of its intended position to fully lock the shifter rails in place.
Worn gear shaft bearings within the Trans. can overload the linkage too by allowing the gear teeth to run at angle and so cause end thrust on the gear shifter levers etc.

The Fwd. Rev. mechanism is the most used linkage and so wear is your enemy in high hour poorly maintained units.

Others may be able to contribute more as I do not recall any of these DD units in our area so have no experience of them.

Hope this helps.
Cheers,
Eddie B.
Thank you for the reply Eddie. I've measured that and came up with 15.25 and really didn't find any signs of slop in the linkage. The shifter itself makes a pretty solid engagment, but still has a lot of travel back and forth. It will nearly lean back to neutral while in forward.
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Mon, Apr 13, 2020 1:41 AM
Old Magnet
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Reply to 74A6C:
Thank you for the reply Eddie. I've measured that and came up with 15.25 and really didn't find any signs of slop in the linkage. The shifter itself makes a pretty solid engagment, but still has a lot of travel back and forth. It will nearly lean back to neutral while in forward.
You need to get the cover off the interlock plunger compartment and see what's going on. Maybe a broken plunger.
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Mon, Apr 13, 2020 6:11 AM
edb
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Reply to Old Magnet:
You need to get the cover off the interlock plunger compartment and see what's going on. Maybe a broken plunger.
Hi Team,
now you have confirmed the Factory setting OM has covered the next step for you.

The Fwd/Rev lever is usually used more than any of the others so the interlock plunger and slider rod groove that the plunger engages and that the shift fork is mounted to is the next likely area to inspect as OM says.
Cheers,
Eddie B.
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Mon, Apr 13, 2020 7:52 AM
74A6C
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Reply to edb:
Hi Team,
now you have confirmed the Factory setting OM has covered the next step for you.

The Fwd/Rev lever is usually used more than any of the others so the interlock plunger and slider rod groove that the plunger engages and that the shift fork is mounted to is the next likely area to inspect as OM says.
Cheers,
Eddie B.
Thank you for the advice. I'll see what I can find.
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Mon, Apr 13, 2020 9:15 AM
rjh-md
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Reply to 74A6C:
Thank you for the advice. I'll see what I can find.
There must be a problem in the transmission interlock .I have a 74 A and the forward and reverse bar has a lot of slop in the linkage ,and never jumps out of gear when the forward and reverse bar engages the gear
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Mon, Apr 13, 2020 10:25 PM
Old Magnet
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Reply to rjh-md:
There must be a problem in the transmission interlock .I have a 74 A and the forward and reverse bar has a lot of slop in the linkage ,and never jumps out of gear when the forward and reverse bar engages the gear
Interlock can be a touchy adjustment and subject to wear and plungers have been known to fail.
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Mon, Apr 13, 2020 11:15 PM
greghill25
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Reply to 74A6C:
Thank you for the advice. I'll see what I can find.


Good luck and update us on what you found out.
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Tue, Apr 14, 2020 9:27 AM
Ray54
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Reply to greghill25:


Good luck and update us on what you found out.
I had a problem for a time. Pulled the side cover with the interlock plungers,cleaned with solvent and air. Sprayed with lube and it worked without any more trouble. I was surprised as there was nothing I could see or feel. I was expecting a weak spring or rust.


It was one of the mounts of success I generally only dream about. So who knows if it will work for you.
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Wed, Apr 15, 2020 12:47 AM
ccjersey
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I had the problem of the 5 speed shifter popping out of first gear on my D6. I was unconvinced when everyone here told me it was probably because of the slop in the main clutch and linkage to transmission lock mechanism.

So I did a test with the tractor stopped, engine stopped too....

with transmission in first gear (my problem gear), I engaged the clutch and then pulled on the gearshift to try to get it to pop out into neutral......it did not, no tendency to move toward neutral at all. So I knew I had a functioning lock on that shift rail and the problem was elsewhere.

Next, I kept up my hard pull on the gearshift and simultaneously pushed the clutch lever forward. There was a lot of slack in it and about time all the slack was taken up, suddenly the gearshift slipped into neutral. My solution was actually pretty simple, I just adjusted the linkage between clutch lever and lock lever on the side of the transmission. That saved a lot of reworking of the internal clutch release mechanism where most of my slack seemed to be.

When I got it right I knew it was right because I repeated my test and the clutch popped out (released) just befor the transmission unlocked and allowed the shifter to move out of gear.

I would try a similar test before I did much tear down on your transmission. It’s possible the reverser gears on yours have enough wear that they tend to shift under load unless the lock is secure. As I said mine was first gear and while I’m sure it has some wear, once the lock was functioning properly, I never had any more trouble
D2-5J's, D6-9U's, D318 and D333 power units, 12E-99E grader, 922B & 944A wheel loaders, D330C generator set, DW20 water tanker and a bunch of Jersey cows to take care of in my spare time😄
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Wed, Apr 15, 2020 7:00 AM
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