Availability of Transmission pump new, rebuilt, or rebuild kit for 75 550?

[Recon-one]

I asked a parts man about the transmission pump. He said no to a new one, no to a rebuilt one and no to a rebuilt kit. The only thing available in his book was a O-ring kit. Can anyone direct me to a source for a replacement pump. I am not sure yet it is the pump but symptoms lead that direction. The gage shows good pressure until the dozer gets to working temperature, then slowly loses pressure until in marginal area on gage. If I increase engine RPM it will move into operational area but will barely keep in the operating range. Does this seem to be a weak pump? Do you know where or how I can buy or rebuild a pump?

[DrLoch]

https://www.brokentractor.com/p/john-de ... -at159747/

[Jim B]

According to the parts catalog that pump is not used in a straight 550. The part number for the transmission pump for a 550 is AT44150, I believe. It shows as available to order (about $2700) on the JD construction Equipment dealer's site I use. Of course some NLA parts still show as available.

Did you have the dealer (Assuming you were talking to a JD dealer's parts man) you use do a system search, to see if someone might have one in inventory somewhere? Have you searched using the part number and called or otherwise contacted places that advertise possibilities?

From your previous posts you had a 1977 550 by the serial number you gave. Is this a different one?

[Recon-one]

Thank you for the quick replys. To DrLoch, the pump displayed is not for my dozer and doing a search on their website they do not have the correct one for my dozer. But, thank you for the suggestion.
To JimB, yes, this is the same dozer I had before. I have a shop manual that came with the dozer that is for a 73 model, somewhere I thought I had a 75 model. Thank you for telling me that the serial number shows a 77 model. That might help me in future times.
I have not done any deep research to find a pump. First; it might not be the pump and I was asking opinions from other members. What else could be the culprit? I think I may have a leak in the steering clutch on the starboard side? Could the transmission relief valve be set wrong or drifted out of correct setting? Any suggestions?
Does anyone know of a hydralic shop repair that is reliable? My shop manual shows the single parts in the pump. Did John Deere ever sell individual pump parts or only complete pumps?
I am really just trying to gather information before I decide what to do. I just use it on the farm some time and I might not do anything. It might do all I need without costly repairs.
Opinions?

[Jim B]

Guessing/listing things it might be is just that - guessing. It could be the pump getting weak, it could be a seal starting to fail, it could be something else. You need to be sure you have the proper technical manual, study it and do the diagnostic steps and pressure checks in it to try to pinpoint the cause. You posted 268254 as your serial number previously. I believe for a straight 550 Dozer: The John Deere Construction and Forestry Bookstore shows Technical Manual TM1108 and Operator's Manual OMT70877 as the current manuals. What manual(s) do you have? According to the JD parts catalog the 550 was built 1975 to 1983, so I am wondering about what your 550 manual, for a 1973 550, is.
Jim

550 introduction and info

550 parts catalog PC1437

[Recon-one]

Thank you, Jim. Somewhere I thought I saw 73 on the book that came with the dozer I bought. After reading your reply I looked at the book, which is in poor condition, pages in wrong place, outer face cover missing, anyway I looked closer, and the book I have is the TM-1108 dated 75 Oct. It seems to have the information that I need if I can locate the right page.
I was looking at the transmission pressure test procedure and saw that a flow meter and pressure gauge was required. I do not have such equipment and probably couldn't afford it. Do any dealers rent such equipment, or are there any work arounds? I am sure I cannot afford the dealership fees for such a test, since I priced the gasket for the transmission filter screen cover, the price was close to $80. I made my own and it works fine. I am afraid what a road trip and mechanic would cost. Before I retired from work, I was a surface (strip) mining reclamation inspector, I was around huge dozers, loaders and haul back equipment. Talking with the mine foremen I heard what the cost of dealer repairs amounted to. It was cheaper to build a shop, employ mechanics and do their own repairs.
I can do some pressure tests, so I will try to isolate the problem. My gauges don't go high pressure, but I might buy some or be able to borrow from some mechanics.
Thank you for your help.

[Jim B]

Just to explain the dates in the manuals. The dates you may find in the manuals do not necessarily relate to the year of a machine. Most of those are printing dates. For example, some info might have been in a 1973 manual and didn't change when they printed a 1975 manual. The pages not being updated will still be dated 73, while pages with new info may have a 75 date. Then there is a date code (usually as a suffix to the manual number), the original JD manuals have, that tells which printing a manual is. That code may appear on aftermarket reprints that copy JD originals. The current TM1108 on the JD bookstore is TM1108_X1(01NOV86) and may have had multiple page changes over the years, from the printing you have, while it may still have some pages with the 73 dating on them.

I doubt a dealer will rent you their test equipment. You can buy liquid filled gauges for testing fairly inexpensively from eBay and other sources. There are some sources for simple flowmeters you can find, that may work for you, but could cost several hundred dollars. Could some of the people you used to work around give you leads on local independent mechanics that might have the test gear needed? They might be less expensive to do the testing for you than the dealer. A contractor operating their own shop might be another source to check with

It has been said many times on these Boards that, "There is no such thing as a cheap crawler." This has been said since people started with the small green ones, you have a newer, larger, more complex crawler and unfortunately it is going to be much more expensive to test and repair when it has problems, than those older green ones. That's just reality. If you get the testing done and the transmission needs to come out and be repaired, do you have the tools and equipment to handle the repair? If you haven't done this, do a web search for "John Deere 750 Crawler Hydrostatic Transmission testing and repair". You can view several related videos to give you some idea of what you are looking at and why the proper diagnosis is going to be critical. Not trying to scare, you just trying to prepare you.
Good luck,
Jim