John deere 655 engine swap???

[coyote556]

Hello,

I have a john deere 655 with a bad engine. there is no compression. if it would fit, I had considered switching the engine to a yanmar out of a 755 becuase of the additional horsepower, instead of repairing my engine or replacing it with the same yanmar. Does anyone know if this will work? My 655 has a yanmar 3TN66UJ engine. thanks for the help

 

[sixdogs]

I can tell you how to find out.
Go to the John Deere website and go to the "lookup parts" section. By fooling around with the two model numbers and seeing what numbers fit where, you can determine the fit. I had a JD 900 and found out a lot of others would have fit. I'll bet your experience will be similar.

 

[coyote556]

I had done that prior to posting on here, but the only engines it showed for a swap were the same model yanmar, from different tractors. I was wondering if there were any yanmar experts who could tell me a similar model engine, with a little more power, I could swap out that would still fit? thanks

 

[sixdogs]

I had done that prior to posting on here, but the only engines it showed for a swap were the same model yanmar, from different tractors. I was wondering if there were any yanmar experts who could tell me a similar model engine, with a little more power, I could swap out that would still fit? thanks

I compared the crankshafts, clutches and transmission parts among others. It gave me a general guideline that suggested it would fit. I sold the tractor so I never got to finish but would have tried to find the swap tractor and measure from that.Maybe you could find one in a junkyard?

 

[coyote556]

i didnt think of checking crankshafts. that is a good idea. I just checked shortblocks. thanks

 

[sixdogs]

There is also a "where used" function of JD parts that tells you where a certain part will fit and in which tractor models used. That was very helpful. I'll bet your engine is one with a hard-to-check oil dipstick that ran low on oil and burned the bearings. Mine was. If so, check the oil pressure with a gauge on the new one.
I looked and the 655 and 755 were made over the same time frame and both had hydros available. I would check overall length of both tractors and compare as well as what type of hydro available. Also compare hoods to see if interchangable. Yanmar/JD made that whole class of tractors somewhat similar and share design similarities. I'll bet it fits.
I can't find it right now but I actually have a sales booklet on either that line or the 650/750 group from the 1980's.
After I weighed all my options I decided to sell the old and replace with a different tractor.

 

[coyote556]

Well, it does not look good. The valve cover is different, as is the crankshaft and hood. I noticed the 755 holds more fuel, so i thought the tank maybe bigger, resulting in a longer hood, but who knows. The valve cover and crank being different really discouraged me.

 

[sixdogs]

Not done yet. Call a tractor junkyard such as one of the big ones in Ohio. Search the net for names and ask if they have any info on your question.. Some will list what they have for models. most have a book of cross-reference that might help.
You could also stop in a JD delership Dervice dept and try to find an older guy that might have an idea. Ditto to call one of the big Yanmar dealers--there is one is sourthern Tenn--maybe Wincester or close by.
Remember to check overall length of tractors and see if close. Back out tire diff and see what you have

 

[1stJDOwner]

Coyote - I've got a 655 myself. It starts like a bear. How did you finally realize it had bad compression? I should find out once the weather finally breaks. New to all some this myself. Thanks for the info.

 

[coyote556]

I actually bought it that way. I planned on trying to get it going. They guy I bought it from took it to the local deere dealer and they told him it had little to no compression. I plan on testing the compression for myself to be sure. I know one thing, it definately will not start.

 

[yankeerider]

My JD manual says the 755 uses a Yanmar 3TNA72UJ and the 855 a 3TN75 RJ engine. Maybe you can find dimension specs based on that?

 

[MeanGreenAZ]

I know this thread is a bit old (over 5 years) but in case someone comes looking for information I just swapped the 3TN66UJ out in my 655 for a 3TNE68. It was as straight forward as it could possibly be. I had to swap the water pump and alternator from the 3TN66 but other than that everything bolted right up. Went from the 16hp 3TN66 to a 20hp 3TNE68. Gain of 4hp and now it starts on the first attempt.

 

[kebo]

My JD manual says the 755 uses a Yanmar 3TNA72UJ and the 855 a 3TN75 RJ engine. Maybe you can find dimension specs based on that?

I know the 750 is a 3cyl (I had two of them), and I am pretty sure the 650 is a 2cyl. I am "guessing" that the 655 and 755 are similar in that respect?? If so, that alone would probably make for some significant differences. Still, they may bolt up the same??

 

[Mechanos]

Research the engine itself. Many of the 3TN series share the same block with same stroke... different bores size for different displacements. If you find a 3TN with the same stroke as your original engine, but with a bigger bore... it will more than likely be a straight bolt in. That was the case with my 955. The original engine was a 3TN84, but I have a 3TNE88 installed in place of the original. The 84 and the 88 have the same stroke.

 

[coyote556]

Research the engine itself. Many of the 3TN series share the same block with same stroke... different bores size for different displacements. If you find a 3TN with the same stroke as your original engine, but with a bigger bore... it will more than likely be a straight bolt in. That was the case with my 955. The original engine was a 3TN84, but I have a 3TNE88 installed in place of the original. The 84 and the 88 have the same stroke.

Thanks for posting. I sold my 655, but would like to find another one someday. I will keep this engine swap in mind for sure. Thanks again