pmsmechanic
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- Southern Alberta, Canada
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In school we were taught that 10 psi oil pressure per 1000 rpm was adequate.
John Deere 755 Newbie
- Thread starter Moukie
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Agvg
Elite Member
30w is thicker when cold but thinner warm than 15/40 so it doesn't make sense. But are your bearings worn your crankshaft is probably also worn and needs machining or replacement.
Have you measured the pressure?
Have you measured the pressure?
Thanks for all info. Mechanical pressure gauge measures 10-12 psi at operating temperature and WOT; too low for me to be comfortable, so I will likely tear into at least the bottom end.
As for cylinder leaks, no problem buying the tilt cylinder seals from JD. The ps cylinder - wow, welded together. Time for me to get out my saw and welder to give it a shot. Does anyone happen to have the numbers/count for the seals that go back in? Sure makes it nice to have everything laid out and ready before I take it apart.
Thanks so much. This is going to be fun. Happy Pumpkin Day to All!
David in SC
As for cylinder leaks, no problem buying the tilt cylinder seals from JD. The ps cylinder - wow, welded together. Time for me to get out my saw and welder to give it a shot. Does anyone happen to have the numbers/count for the seals that go back in? Sure makes it nice to have everything laid out and ready before I take it apart.
Thanks so much. This is going to be fun. Happy Pumpkin Day to All!
David in SC
Update on where i am:
1) I have replaced missing glow plug control module. Have not yet tested plugs; but hope to today. Pleased to see the dash light actually came on. No chance of cranking today without glow plugs, as temps will not hit 50.
2) Have re-packed both tilt cylinders. Have not yet put back on, but will soon.
3) Have scrounged metal i need to re-condition bucket
4) Am thinking serious about "siping" the rear tires to give this machine some traction. I can't even hardly maneuver in my backyard without spinning. Don't want to switch to ag tires, as they are too aggressive.
5) Figured out why i have no tach/hour meter. The brass fitting that houses the gear that drives the cable was not seated at all in the base; so the gear was not engaged at all. Housing is all full of crud. Cable inside was actually not broken. I have cleaned it all up and have it ready to put back in. How far in does the brass fitting insert? Hard to tell exactly; there is a ring around the brass fitting; almost like an o-ring groove, but no clearance for an o-ring. It does appear the brass fitting should recess some amount into the base. I can possibly measure and get close. My manual does not show any pics of this.
6) Have sheet metal to fabricate the missing engine cover. Both appear similar, so should be able to do. Just takes time and patience. I have neither, but love to tinker when i can.
7) Went to JD dealer yesterday and bought new fuel filter, hydro oil and filter, and another oil filter......in anticipation of pulling oil pan to measure bearing clearances. Whoa. Dealer quoted me over $300 each for rod bearing inserts! I looked at him like he was an alien and he said "yeah, they are expensive". My plans are now changing. I think i might now just take a chance on it and run the heck out of it and see what happens. No way in the world i will spend $2,000 to replace 6 bearing inserts and a rear seal. That is crazy.
I hate to be cynical, but that is absurd. Couple questions as i seek alternatives:
1) What will likely be my failure for running with low oil pressure? Spun bearing, crank damage?
2) I see the Yanmar engine code of 3TNA72, and i think the UJ at the end only indicates it was used for John Deere applications. If that is true, i would assume the internals of all 3TNA72 engines to be the same. Does that seem reasonable?
3) If that is the case, i see complete engine rebuild kits on ebay for about $500. Yes, they are from China, but what isn't nowadays. Shoot, i can buy a complete rebuild kit for the price of two rod bearing inserts from JD. Any thoughts?
4) Another option is to purchase a donor engine. Again, i can find 3TNA72 engines easier that 3TNA72UJ engines. Is the base engine the same?
Yeah, i am very frustrated with pricing of replacement parts for this machine. But, still moving forward. If i can get comfortable with engine oil pressure, next will be to tackle the non-working front drive axle. That will be exciting.
Thank you again in advance. All feedback is welcomed.
David in sunny, but cold SC
1) I have replaced missing glow plug control module. Have not yet tested plugs; but hope to today. Pleased to see the dash light actually came on. No chance of cranking today without glow plugs, as temps will not hit 50.
2) Have re-packed both tilt cylinders. Have not yet put back on, but will soon.
3) Have scrounged metal i need to re-condition bucket
4) Am thinking serious about "siping" the rear tires to give this machine some traction. I can't even hardly maneuver in my backyard without spinning. Don't want to switch to ag tires, as they are too aggressive.
5) Figured out why i have no tach/hour meter. The brass fitting that houses the gear that drives the cable was not seated at all in the base; so the gear was not engaged at all. Housing is all full of crud. Cable inside was actually not broken. I have cleaned it all up and have it ready to put back in. How far in does the brass fitting insert? Hard to tell exactly; there is a ring around the brass fitting; almost like an o-ring groove, but no clearance for an o-ring. It does appear the brass fitting should recess some amount into the base. I can possibly measure and get close. My manual does not show any pics of this.
6) Have sheet metal to fabricate the missing engine cover. Both appear similar, so should be able to do. Just takes time and patience. I have neither, but love to tinker when i can.
7) Went to JD dealer yesterday and bought new fuel filter, hydro oil and filter, and another oil filter......in anticipation of pulling oil pan to measure bearing clearances. Whoa. Dealer quoted me over $300 each for rod bearing inserts! I looked at him like he was an alien and he said "yeah, they are expensive". My plans are now changing. I think i might now just take a chance on it and run the heck out of it and see what happens. No way in the world i will spend $2,000 to replace 6 bearing inserts and a rear seal. That is crazy.
I hate to be cynical, but that is absurd. Couple questions as i seek alternatives:
1) What will likely be my failure for running with low oil pressure? Spun bearing, crank damage?
2) I see the Yanmar engine code of 3TNA72, and i think the UJ at the end only indicates it was used for John Deere applications. If that is true, i would assume the internals of all 3TNA72 engines to be the same. Does that seem reasonable?
3) If that is the case, i see complete engine rebuild kits on ebay for about $500. Yes, they are from China, but what isn't nowadays. Shoot, i can buy a complete rebuild kit for the price of two rod bearing inserts from JD. Any thoughts?
4) Another option is to purchase a donor engine. Again, i can find 3TNA72 engines easier that 3TNA72UJ engines. Is the base engine the same?
Yeah, i am very frustrated with pricing of replacement parts for this machine. But, still moving forward. If i can get comfortable with engine oil pressure, next will be to tackle the non-working front drive axle. That will be exciting.
Thank you again in advance. All feedback is welcomed.
David in sunny, but cold SC
shooterdon
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- 2019 LS XR4140 HST Cab; 2020 Kawasaki Mule SX; 2021 Bad Boy 54" ZT Elite
I feel your pain and frustration. As a new JD855 owner I have been shocked at the repair/parts costs. Fortunately, I got my tractor at a very reasonable price so it softens the blow a bit. Still....It makes purchasing a used older tractor a crap shoot. I nearly bought a second machine that was only going for $3800 that had no attachments and was in better condition than mine. I thought that was a lot of invest for a backup or parts machine...but maybe I should have got it.
It makes buying new and having a warranty look better all the time. I suppose that is part of the marketing plan....make repairs so expensive that people give up on the older machines.
BTW, I have over $2200 in repairs so far. Still no parking brake and will need to do the FEL cylinders eventually as they have slow leaks. No glow plug light and fuel gauge does not work.
It makes buying new and having a warranty look better all the time. I suppose that is part of the marketing plan....make repairs so expensive that people give up on the older machines.
BTW, I have over $2200 in repairs so far. Still no parking brake and will need to do the FEL cylinders eventually as they have slow leaks. No glow plug light and fuel gauge does not work.
hotrod1016
New member
John Deere outsources a lot of parts. I have invested over 2,000 fixing the 4wd on my 755 and then after 3 1/2 months one of the outsourced beating failed. Cost me another 400 because John Deere only has a 90 day warranty
beenthere
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Went back and read your OP. Hope you are not getting discouraged and won't give up on your project.
Just checking in.....
Great suggestion to check a machine shop for bearings. I will do that.
I am not getting discouraged; just a bit anxious. I just clicked purchase for 3 new glow plugs, as my module appears to work, but all 3 plugs had essentially no resistance. That should be a win, I hope, when they come in. I also got the tach cable gear re-seated properly today, and did a little more cleaning while at it. Good opportunity to remove and check belt and then tension properly.
I am only getting anxious because I am fixing all the little things to make the machine more reliable/useable, but I know the first time I take it out and work it, it may suffer a catastrophic event due to low oil pressure. I refuse to spend the kind of money JD dealer will want for a new JD engine rebuild kit. Shucks, I can buy a complete engine rebuild kit from China for less than the price of two rod bearings from JD dealer.
I would love to hear some feedback on the quality of the rebuild kits I see for around $500 on ebay; especially from someone who has used one. Even if I just used the bearings and threw the rest away, I would come out much better......if the parts are made of good quality.
Anyone have any experience with these kits, and does anyone know if they even work for a JD 755?
Thanks much,
David in chilly SC.
Great suggestion to check a machine shop for bearings. I will do that.
I am not getting discouraged; just a bit anxious. I just clicked purchase for 3 new glow plugs, as my module appears to work, but all 3 plugs had essentially no resistance. That should be a win, I hope, when they come in. I also got the tach cable gear re-seated properly today, and did a little more cleaning while at it. Good opportunity to remove and check belt and then tension properly.
I am only getting anxious because I am fixing all the little things to make the machine more reliable/useable, but I know the first time I take it out and work it, it may suffer a catastrophic event due to low oil pressure. I refuse to spend the kind of money JD dealer will want for a new JD engine rebuild kit. Shucks, I can buy a complete engine rebuild kit from China for less than the price of two rod bearings from JD dealer.
I would love to hear some feedback on the quality of the rebuild kits I see for around $500 on ebay; especially from someone who has used one. Even if I just used the bearings and threw the rest away, I would come out much better......if the parts are made of good quality.
Anyone have any experience with these kits, and does anyone know if they even work for a JD 755?
Thanks much,
David in chilly SC.
