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D6C Transmission Problems

Metalman 55

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Feb 6, 2013
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I recently discovered some tranny issues with my D6C, 10K 6516 dozer . Just as I was wrapping up a job I noticed with I shifted from reverse to forward it started getting noticeably "soft" when the direction change occurred, but otherwise all else seemed normal as far as push power, no noticeable noises etc.. The problem happened instantly too.

Pulled the magnetic screen this morning & found considerable debris, mostly what I believe to be clutch fiber looking stuff & as usual some fine metal fibers stuck to the magnet, but mostly fiber stuff.

We plan to check the pressure on the main filter housing next, then pull the filter out & cut it apart if there is evidence of debris in it.

Transmission Group # is 24980 & the Arrangement number is 8S590. Wonder if parts are still readily available if we choose to go that route, or alternatively are rebuilt tranny's still available anywhere for something of this vintage?

Its been a great machine & Ive put over 900 hrs on it since buying it over 8 years ago, without a lot of trouble. Undercarriage is still 80% or better too.
 

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Metalman 55

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Ok.........checked some pressures. Trans pressure at the filter housing is 290 at a low idle & 315 psi at a high idle. A little low.

Speed tap under the floor is 290 psi.

Direction tap is harder to get at..........stay tuned for that one......
 

kshansen

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Well from what I see on that magnet and strainer it all depends on how long since it was out and nice and clean. I mean if it's been five minutes I would get worried but if it's been five years I would not jump to any conclusions.

Have you checked the screen in the bottom of converter housing?D6 converter screen.jpg
 

Metalman 55

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We didn't check that screen. Just pull the bottom cover of the converter for access to it, shown in your diagram? How much oil will we loose, as we didn't drain things yet?

The reason I suspect trouble is I noticed a subtle sudden change in it when shifting from reverse to forward, when last using the machine. No noise or vibration though.

The last time the magnetic screen was off & cleaned was maybe 300 hrs ago. Most of the stuff on it is fiber type media, not much metal, some minor speckling of brass here & there can be seen too.

The filter & housing up beside the engine was very clean when we inspected it today too.........no evidence of debris in it.
 

kshansen

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We didn't check that screen. Just pull the bottom cover of the converter for access to it, shown in your diagram? How much oil will we loose, as we didn't drain things yet?

Should not be much if any oil there if the scavenging section of the transmission pump is doing it's job. I think that one is mostly to catch the chips off the ring gear or parts of starter drive when it fails!
 

Dave Neubert

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The screen don't look to bad try changing the filter check the directional clutch pressure and see how long it takes it to come up wile shifting parts should be no problem OR and after market I would run it until it gets real bad unless you just want to head it off before spring I have built many of these and have never had any problem getting parts Iron Peddlers in NC has rebuilt ones in stock if you want to go that route
 

Metalman 55

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The screen don't look to bad try changing the filter check the directional clutch pressure and see how long it takes it to come up wile shifting parts should be no problem OR and after market I would run it until it gets real bad unless you just want to head it off before spring I have built many of these and have never had any problem getting parts Iron Peddlers in NC has rebuilt ones in stock if you want to go that route

Plan to check check the directional pressures this morning, thanks. As far as the idea of running it till it gets worse, that oil is common to the torque & bevel gear compartment, so wouldn't it be better to head off any problems sooner than later? As mentioned in an earlier post, the only symptom was an abrupt change in shifting from rev to forward where the shift got "soft"; all else seems normal except the debris in the screen which is mostly fiber mat'l.
 

Metalman 55

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Ok..........directional pressure in both directions is about 240 psi & it takes about a second to come up to that pressure. Engine is at about 1000 rpm (just guessing) when we got those readings.
 

Metalman 55

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Ok........here is the transmission filter cut apart..........not much in it, just somewhat dirty. I checked back & its been about 500 hrs since last changed..........a bit to long, just not sure what is recommended, likely 250 hrs ish?

Some very tiny bits of brass specs in it & the rest is just dirt........seems the mag strainer caught all the big stuff. Again, the biggest chunks in the strainer were about 3/16" the longest way & that was all fibrous lining type material mostly. I would say the chunks were enough to fill two table spoons up. It may have been 500 hrs since the strainer was last checked........not sure.
 

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Old Magnet

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Early 10K's run 310 +/- 10 psi speed clutch pressure with 55 +/- 5 psi less for direction clutches so at 240 psi it's a little low so there is some leakage.
 

Metalman 55

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Ok............got some shims installed to boost the pressure a but & now Speed Tap reads about 340 psi at around 1500 RPM & the Direction Tap is 280 psi. at the same speed.

The forward shift from reverse seems a bit better, so think we will keep a close eye on the mag strainer & resume using the machine.
 
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