D6T Transmission Issues

[CRR]

Hello all, I have a D6T with some odd transmission issues. (S/N: KJL01024) (7500hrs). Original complaint was no 2nd gear forward. Arrived at unit and found it has NO 2nd or 3rd fwd, and no 1st reverse.
1st forward and 2nd and 3rd reverse DO work. No codes active or stored. Went through and checked all clutch pressures and even made it through a clutch fill cal. All clutch pressures are in spec.
Eventually pulled the transmission filter and found it imploded and absolutely full of clutch material, so immediately thinking with that much clutch material in the filter/oil there has to be a bunt out clutch pack.
I guess my question is why are all of the speed clutches only working in one direction? As in, why does 1st operate in forward but not reverse? And vice versa for the 2nd and 3rd speed clutches.

 

[Nige]

Strange symptoms, and somewhat puzzling because on the face of it the transmission has not lost a signle speed clutch or a single direction clutch. The fact that the filter has imploded does not bode well and could be related to the strange gear selection issues. It makes me wonder what the condition of the suction screen is like.

My first suggestion would be to put a new filter in it, plus remove and clean the suction screen, and see how it goes from there. But be prepared for disappointment, because I think that transmission is coming out sooner rather than later. If the filter has imploded then it is likely that some debris has made it all the way to the modulating valves.

 

[pittsburgh cat man]

I think I would be checking wiring and switches those combinations don't make sense et would be a big help

 

[CRR]

I had ET hooked up and went through a clutch fill calibration and it passed successfully although clutch #5 (1st speed) was at a limit. Other than that no codes, computer is seeing requested speed and direction

 

[pittsburgh cat man]

I seem to remember being able to see clutch engagement with et I had one that would engage 3 clutches at one time. Talk about coming to a screeching halt! It turned out to being a selector switch

 

[Deimos]

Hello all, I have a D6T with some odd transmission issues. (S/N: KJL01024) (7500hrs). Original complaint was no 2nd gear forward. Arrived at unit and found it has NO 2nd or 3rd fwd, and no 1st reverse.
1st forward and 2nd and 3rd reverse DO work. No codes active or stored. Went through and checked all clutch pressures and even made it through a clutch fill cal. All clutch pressures are in spec.
Eventually pulled the transmission filter and found it imploded and absolutely full of clutch material, so immediately thinking with that much clutch material in the filter/oil there has to be a bunt out clutch pack.
I guess my question is why are all of the speed clutches only working in one direction? As in, why does 1st operate in forward but not reverse? And vice versa for the 2nd and 3rd speed clutches.

It looks like the oil passages are clogged with worn material. During calibration, oil is supplied to one clutch, and the pressure is sufficient, but during movement, oil is supplied to two clutches, and the pressure may not be enough to fully engage both clutches.

 

[Mobiltech]

What does the dash show when you’re in the gears that don’t work. Is it indicating the gear you selected . You could also look at et to see what signal the ecm is getting from the shifter.
When you do the manual clutch pressure calibration for each clutch is the pressure setting easy to get to.
If the filter is imploded the modulation valves are probably get contaminated and sticking sometimes.

 

[tctractors]

with D6R and T series Tractors the fast way to find out if you have a rebuild on your hands is to remove the square plate held in place by 4 bolts near the bottom of the back case between the drawbar mounting, behind the plate is a cylindrical screen that loves to catch clutch plate failings, the clutch pressure calibration is best done before the clutch fill calibration, I am a few months off 70 and can turn up on Site and whip those transmissions out in around 4 hours by myself, getting them back together depends on your luck with the last nearside axle shaft, they can be a pain so I always slacken off the Track tension to make thing easier, the smashed filter might cost you a full set of modulating valves, don't rush in to fitting them until you have done a total clean out of the oil case and Torque plus screens, was the filter a CAT item ?

 

[Nige]

was the filter a CAT item ?

Good question. You would think that the spool in the filter head would have moved all the way over to 100% bypass if the element particle loading became too high.
If it was an OEM element what Part number was it.?

 

[CRR]

OEM filter. P/N 328-3665.
Messed around with the unit today and kept shifting through all the speeds and all of a sudden all of the gears came back all at once. At this point I am thinking there has to be a passage that is/was plugged.
When it is acting up, it bogs the engine down to about 1600rpm, but no movement. Watching ET when this is happening the torque converter rpm is 0.
I’m thinking for a total clean out the transmission will be removed and all passages cleaned thoroughly, plus an inspection of all components which I’m sure will lead to a full rebuild. I learned today that since the customer has owned this unit (7 years) the transmission oil and filter have never been replaced. So a combination of poor maintenance and neglect is the likely cause. I once again went through each parameter and reading with Cat ET and confirmed no codes, speed/direction requests are being acknowledged by the ECM, the proper solenoids are being engaged in each gear

 

[Nige]

I’m thinking for a total clean out the transmission will be removed and all passages cleaned thoroughly, plus an inspection of all components which I’m sure will lead to a full rebuild.

Like @tctractors mentioned, on top of all the other parts I think you will be in for 5 new clutch modulating valves. They don't like having that much contamination passing through them.

I learned today that since the customer has owned this unit (7 years) the transmission oil and filter have never been replaced. So a combination of poor maintenance and neglect is the likely cause.

That could be the title of a sitcom - "How to Root a Transmission in 7.5k or Less"........

 

[Mobiltech]

If the torque is stalling when it won’t move that sounds more like you have 3 clutches engaged at once. This probably happens because one modulation valve is sticking and not releasing that clutch when it should.

 

[tctractors]

Is it time to ask about the Brake pressure, asking for a friend.

 

[CRR]

I actually did check brake pressure. Pressures are within spec and are applying/releasing properly