JD 855 Compact tractor

[sailing131]

I have a question about my 855 tractor engine, I am in the middle of an engine overhaul of my 3TN75RJ engine a direct injection diesel, when i got it apart I discovered that it does not have Pistons that match the John deere workshop manual. The parts supplier I contacted said there are two different pistons one for direct injection and one for indirect injection. This seems to contradict the JD manual. I have the One with the recess in the middle and the JD parts website lists piston AM877822 with the valve cutouts on top. Can anyone shed some light on this problem?
Is there any way to tell from the engine serial number which one i am supposed to have?

 

[jyoutz]

I have a question about my 855 tractor engine, I am in the middle of an engine overhaul of my 3TN75RJ engine a direct injection diesel, when i got it apart I discovered that it does not have Pistons that match the John deere workshop manual. The parts supplier I contacted said there are two different pistons one for direct injection and one for indirect injection. This seems to contradict the JD manual. I have the One with the recess in the middle and the JD parts website lists piston AM877822 with the valve cutouts on top. Can anyone shed some light on this problem?
Is there any way to tell from the engine serial number which one i am supposed to have?

Can you call the dealer to check with your serial number on the motor?

 

[gstrom99]

What's the reason for the teardown/overhaul? If new pistons are needed, I'd put the same style (they're all the same, I assume) back in, that you take out (unless the valves have been smacking the piston). 3TN75 should have the valve cutouts. New rod bolts are called for, also. I have the same motor in my tractor and shop manual (in pdf), which covers several models. Got a pic of the serial/model number plate riveted to the valve cover and the problem piston(s)?

 

[sailing131]

I spent an hour with the parts Guy and a mechanic at the dealer this morning the part number for the pistons is AM875318 he could not tell me what the piston looks like only what was shown on the computer which matched the manual, the mechanic told me that what shows in the parts diagram is not always accurate. Attached is what the pistons looks like when i pulled the head.
Gstrom99- Hard starting lots of blow-by out or the valve cover breather. #2 cylinder worn below the wear limit Pistons worn about .006 below the wear limit.

 

[gstrom99]

I spent an hour with the parts Guy and a mechanic at the dealer this morning the part number for the pistons is AM875318 he could not tell me what the piston looks like only what was shown on the computer which matched the manual, the mechanic told me that what shows in the parts diagram is not always accurate. Attached is what the pistons looks like when i pulled the head.
Gstrom99- Hard starting lots of blow-by out or the valve cover breather. #2 cylinder worn below the wear limit Pistons worn about .006 below the wear limit.

Dang, I don't have an answer... I see your issue/dilema - the manual may very well be printed with a typo - with the model #'s switched. Is the bore worn? Are oversize pistons even available?

I spent some online time looking for pics of that part number. Only one I found was for a used one, and that had the same dish as yours.

Any Yanmar, or industrial engine shops available to you locally? Short of asking them, I'd go ahead and order it, and see.

I've never had mine apart, except to replace the water pump...

 

[sailing131]

Problem solved, I have the right pistons Indirect Injection Vs. Direct Injection Engines | Big Bear Engine Company

You just don't know what you just don't know

 

[gstrom99]

Great! So, does our manual have the pictures/descriptions wrong, or what?