12g Transmission

[pedrocar]

Hi 12g sn3wco1360
This grader has 20k on the trans never been apart serviced 200hrs ago very clean ,pushing a heavy load started shuddering barely turning the wheels in 3hrd gear ,went to Cat checked pressures all in spec ,filter clean ,could it be just a case of old o rings cracking/failing leaking under load all other gears are fine

 

[Chrisso]

could it be just a case of old o rings cracking/failing leaking under load all other gears are fine

Possibly... clutches slip due to low hydraulic pressure or too much wear/damage from contaminants, or a combination of both. In theory 6th speed should have similar symptoms...


What grade oil are you using?

 

[Nige]

With 20k on the trans the condition of the piston seals is probably something like glass.

 

[pedrocar]

Possibly... clutches slip due to low hydraulic pressure or too much wear/damage from contaminants, or a combination of both. In theory 6th speed should have similar symptoms...
View attachment 281010

What grade oil are you using?

TDTO 30 Cat

 

[Chrisso]

It sounds like all the bases have been covered, good oil, good pressures, clean filters. No clutch or torque converter to complicate anything. Sounds like a tranny-out fix to me.

Looking at the table above, that #3 clutch is working it's butt off even when the machine's doing nothing.

 

[pedrocar]

The story grader went to Cat they checked the pressures screens ,filter ,suggested a rebuild .
I asked if they checked the modulator cable was told it wont be that ,well got it floated home checked the modulator cable out of adjustment and streched fitted a new one adjusted ,went back to work no more problem

 

[Chrisso]

Thanks for the feedback Pedro. Sounds very strange if it was only faulting in 3rd gear.

 

[pedrocar]

3rd gears what we use so it was the most we experienced it at

 

[Blue-Fox]

3rd gears what we use so it was the most we experienced it at

My 74 12G has suddenly been losing 4th, after you get working it a couple hours. About 28K on it. makes me wonder if it's the same issue. Thanks for the post, I will have a look.