D4D powershift

[Dave Neubert]

Well if it is low your converter is bypassing and needs rebuilt

 

[BradleySherrell]

The pressure was low on the inlet to the TC compared to the manuals specs. In neutral, 40 psi, 1st fwd 50 psi, 2nd fwd 50 psi, 3rd fwd 75 psi, 1st rev 50 psi, 2nd rev 50 psi, 3rd rev 75 psi. None was as high as the specs, (110 +/-10 psi)

 

[Nige]

Those pressures you mention, was the complete machine up to operating temp and the throttle wide open..? The only value you need to take note of is the one in 3rd speed converter stall. Your measurement of 75psi is 25psi below the floor of the specification tolerance (100psi).

Maybe I missed it, but what was your measured converter outlet pressure..?

Now might also be a time to measure Pump Pressure just to get an idea of how much hydraulic grunt it's supplying

 

[Mark250]

The pressure was low on the inlet to the TC compared to the manuals specs. In neutral, 40 psi, 1st fwd 50 psi, 2nd fwd 50 psi, 3rd fwd 75 psi, 1st rev 50 psi, 2nd rev 50 psi, 3rd rev 75 psi. None was as high as the specs, (110 +/-10 psi)

Hi, the inlet convertor spec is the maximum oil pressure allowed for the convertor
by design. It is a safety valve. the only time you will see that kind of pressure is with very cold or wrong viscosity oil or there is some problem with oil flow within the convertor.
the working pressure within the convertor is controlled by the outlet relief valve which in this case is a fixed orifice (welsh plug with a hole in it) in the outlet of the convertor
the spec is idle 4 psi min and high idle 40psi +/_ 10 psi
this is checked with machine in a stalled condition in third gear

Mark

 

[Nige]

Good catch Mark. You just reminded me that the converter inlet pressure is the ONLY powertrain pressure test that is done with cold oil. In fact looking at a couple of other models the TC Inlet pressure spec is listed as "Xpsi maximum with cold oil".

 

[Bluox]

Good catch Mark. You just reminded me that the converter inlet pressure is the ONLY powertrain pressure test that is done with cold oil. In fact looking at a couple of other models the TC Inlet pressure spec is listed as "Xpsi maximum with cold oil".

Actually all the pressure checks are done with oil at normal operating temperature .
Bob

 

[BradleySherrell]

Hello guys, sorry I haven’t been on her in a bit, been busy lately. But today I got the dozer up to operating temperature, checked the pump pressure on the filter housing and it was (300psi in 1st fwd) (2nd fwd 110psi) (300psi fwd 3rd) (300 psi 1st rev) (90psi rev 2nd) (300 rev 3rd), so I’m assuming the fluid is bypassing somewhere in second gear. I took the control valves off the top of he transmission to inspect and everything was really clean all springs seemed to be good there. O rings between the directional control and the transmission Were a little flat but wasn’t broke up at all. Any ideas on where the fluid is bypassing?

 

[Dave Neubert]

Clutch pack seals

 

[Nige]

Agree with Dave. Piston seal failure in the 2nd speed clutch (#4 clutch). Indicated by the red area in the diagram below. The transmission would need to be removed and disassembled to fix it. Attached is the Service Manual for the job.

 

[BradleySherrell]

Got the transmission out of the dozer (was a job) got it all apart un stacked all the clutch packs and started rebuilding the clutch packs from the bottom up, got to the 4th clutch pack and sure enough the inner piston seal was completely gone, nothing left, so that’s my second gear problem. Thanks for leading me in the right direction got it all assembled back together today and going to try to get it back in tomorrow. I’ll let you guys know how it goes when I get it back together

 

[Dave Neubert]

Did you check clutch pack operation with air?

 

[BradleySherrell]

I did not check them, really don’t have the means to do that. I guess I’ll just have to hope everything’s good, everything was clean as new inside and my clutches were like new and everything went back together great so I think everything will be fine

 

[Dave Neubert]

Its just extra insurance. I guilt a Cat skidder trans once it took 30 hrs to get it outso I paid Cat 1100 bucks to dyno it they took my 1100 and did not bother to tell me that 2nd gear was not working I guess since I was considered competition they hung me out to dry

 

[Nige]

Did you replace the piston seals on all the clutches..? It would be a shame for you to get it back in the tractor and then have the seals on one of the other clutch pistons fail in short order.

 

[BradleySherrell]

Nige, yes we replaced all clutch pack seals, and all seals in the transmission, every o-ring or seal we could find we replaced it. Got everything put back together today and put her to work, worked it hard for 2 hours and it worked flawlessly. Usually within 30 minutes of working it wouldn’t pull itself in second gear. So I think everything is Good, I also put new oil filter and got some Caterpiller transtorq TO-4 oil to put back in it.

 

[BradleySherrell]

Hello guys Ran the dozer for about a week and had no issues whatsoever second gear worked perfect, transmission never got above half way on the temp gauge, everything worked great. Today I was pushing clay up to build up a pond dam and second gear started to act up again(trans temp not even half way), thought maybe the fluid was low, pulled the stick And the fluid was full of bubbles, and second works sometimes and sometimes it don’t now, but still doesn’t have the track power as it did earlier this week. Really stumped don’t know what’s wrong with it now.

 

[Bluox]

If you are working on a steep slope put two more gallons of oil in it and try it.
Bob

 

[BradleySherrell]

How much movement are you suppsed to have when you check the clutch packs with air?

 

[BradleySherrell]

I found a piece of the piston seal ring sticking out of the top of the #4 clutch pack today, I guess it’s blew the seal ring out again. Not sure what’s causing this, didn’t see anything else wrong with the transmission when I had it apart. I thought maybe the clutches were wore too much and the piston was sliding out too far to engage, but the clutches looked good so im not sure what’s going on, something not right somewhere, any ideas on what’s going on would be greatly appreciated. Thanks in advance

 

[Bluox]

Did you measure your clutch pack height ?
Bob