Cat 12 Motor Grader Pinion Issue

Hi Russelln,
this usually is how the engage mechanism feels when the pinion is already engaged--usually someone who does not know about these ponies comes along and plays with the levers and engages the pinion.
You then have to struggle to get the pony to turn against the dragging cluch assembly to get it to fire.
You can disengage the pinion by removing the small cover on the upper right side of the main clutch housing--next to the Main Clutch adjusting cover.
From memory if it does not have the small two bolt cover you should be able to gain access thru the main clutch adjust cover. I am unsure only because I do not have a suitable No 12 Parts or Service Book to double check.
You can look in the opening and see if you can view the end of the pinion where the latch adjust screws are .
By turning the pony flywheel you can align the latches to the opening and use a screw driver or similar to push down on the latch at the screw end and it should allow the pinion to spring back to the disengage position.
Hope this helps.
Cheers,
Eddie B.

Thanks Eddie, but I'm thinking my problem is a little more serious than that, See I had the pony running and I would think if the Pinion was engaged that the Diesel would start spinning, It didn't even when I engaged the clutch which makes me think a fork or something else is broken off the Pinion shaft.

But I'm all ears, I'll take any and all advise and try to keep it simple before going major and doing a tear down.

Access to the pinion latch adjustment screws is the pipe plug between the pony motor and the dash. You should be able (barely) to see if the pinion engagement sleeve is moving in response to the engagement lever.

Bad news is if the engagement arm is the problem there is no access without pulling the engine.

Access to the pinion latch adjustment screws is the pipe plug between the pony motor and the dash. You should be able (barely) to see if the pinion engagement sleeve is moving in response to the engagement lever.

Bad news is if the engagement arm is the problem there is no access without pulling the engine.

[quote="Old Magnet"]Access to the pinion latch adjustment screws is the pipe plug between the pony motor and the dash. You should be able (barely) to see if the pinion engagement sleeve is moving in response to the engagement lever.

Bad news is if the engagement arm is the problem there is no access without pulling the engine.[/quote]

I removed the pipe plug and was able to verify that the engagement lever must be broke because it does nothing. So Now Out with with the Engine. I tried removing that pinion assembly and was not able to do that either. I was only able to dis-assemble that assembly up to 2A3623 Plate. It looks like that plate is pressed into the the clutch housing and I was not able to get that housing to come off, It only moved about 1/4 an inch before it stopped. I did not want to force it and create more damage than might already be done. I'm Assuming once I get the engine removed I can take the rest of this assembly out, take it apart, soak it in mineral sprites, clean it up and inspect it. I did notice that I have a cracked disk (2A3616) which I'm sure has no bearing here.

I have the serviceman's reference book which explains pretty well on how to remove this engine, I'm 99% sure I have the tools to do this. The problem is that this grader is on my ranch where there is No electricity, or enclosed working area 70 miles away from me.

The question is: What is the weight of this engine and will a backhoe be sufficient enough to be used as an engine hoist.

My plan is to remove this engine and Mount\place it on me Equipment trailer and take her where I can do the work without fear of forgetting to bring some tool up there with me and I'll have shop air if needed.

Your going to have to remove the pinion clutch housing eventually anyway to check everthing out (requires raising the pony motor). They get hung up on the big "O"-ring along with the usual rust. You're correct in not over doing the prying on the flange as they have been known to break.

Weight given for a D318 5Vxxxx Industrial Engine is 3,100 lbs which should be a pretty close match.

Well it has been a few days since I posted. I was not able to completely remove the Engine as my backhoe does not seem to have enough Umph to do the job, However I was able to move the engine back about 7 inches and have it resting on the transaxle and and the lower radiator supports. This gave me enough room to get in the bell housing to do more inspections. Hopefully this engine is back far enough to do what I need to do,
So far I have found the following:

Broken, snapped in half (3B9235) Bar assembly. The brake is where the Lever Assembly (3B2632) makes contact with it.

I'm still dealing with getting the Clutch\Pinion assembly out. I will be pulling the Pony motor up in the next few days to remove that thing (fingers crossed)

What would cause the Bar Assembly to brake like this? Age over the years?

That break would explain why you can't pull the pinion in.
Kind of unusual to have it break that way but the shaft is about cut in half for the lever to engage so there is a stress riser involved, that and a lot of time and cycles.

The 8T grader uses the same 3B9235 shaft as the D4 6U/7U series so finding a replacement shouldn't be to hard.

Russlln

Sounds like you are making some progress on your grader. Florin Tractor in Sacramento may be able to help with the parts. If you can get the pinion lever fixed and back together then you could re install the engine. The pinion/clutch assembly can be rebuilt in your shop and installed later on.

When you install the engine, you may want a helper to get everything lined up. If you have a second tractor you can pull or push the grader to the engine rather than trying to maneuver the engine it to place with the backhoe. Those D318 engines are heavy, and the added reach to get around the grader frame multiplies the weight on the backhoe. Don't lose the shims that go between the oil pan and the top of the transmission case.

If the pinion clutch and clutch brake were working well before the pinion lever broke, there may be no real reason to rebuild it unless you want to. The cone shaped clutch brake can wear to the point that you cannot get the pinion gear stopped turning to engage into the flywheel.