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Discussion Starter #1 (Edited)
This is my first post here. I tried searching for the info in the forum, but can't find the information specific to my tractor. My apologies if I missed something obvious.

I have a 2014 x738, A couple years ago I installed a CTC FEL. However, it can't lift much more than 400 lbs at the moment.

I would like to shim the implement relief valve, can someone please tell what is the maximum safe pressure I should target?

Thanks all,
Luis
 

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I believe the max is 1500 psi. Not too many people are comfortable pushing it that far considering stock is 950-1000 psi. I have set mine up at 1200-1250 psi and it is much more capable than stock, and I can still sleep at night not worrying about grenading the pump.
 

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The max pressure stated on a hydraulic schematic for that hydro that was posted some time ago was 1502 psi.

Note that there is a minimum pressure required to raise the arms and bucket with no payload involved. Pressure above that minimum mostly goes to raising payload. A small portion will be required to overcome the additional friction on the pins due to the added weight of the payload.
 

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If youve read the post in the simplicity forum for the legacy xl's and older john deere x series its about the same process for yours. Test before and after just to make sure your not too high. I have mine alittle over 1300psi. How much are you wanting to lift?
 
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Discussion Starter #5 (Edited)
Excellent information. I will target something between 1200 and 1300 PSI.

How much do I want to lift? I don't know. More than 400 pounds.😁

Frankly, I was surprised by how few patio pavers I could lift with the bucket. 800 lbs would probably be a good guess, based on my foggy memory of my successes and failures. Obviously I wouldn't want this much weight up high when moving. (Almost learned the hard way.)

Slight tangent to the above:
In a former life, I worked on automatic transmission hydraulic controls, so naturally I was studying the hydraulic schematic for the K92 (same as K90 controls, I think) while trying to understand the shimming and the Implement relief valve upgrade. (Thanks for the link to the Hydraulic forum, Tudor). Looking at my tractor, and the schematic (attached), I am guessing that forward and reverse rod, that connects the pedals to the transaxle, is acting on (2) Relief/Check/Tow Valve (Forward) and (3) Check/ Tow Valve (Reverse); is that correct? If so, does that mean that Forward has more available hydraulic pressure than Reverse?

Thanks all,
Luis
 

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Item 1 is the implement relief valve (factory set at 995 +/- psi) that you have to deal with. Items 2 & 3 that you have circled are the relatively low pressure charge check/relief valves to ensure that the hydro has adequate fluid for operation.

Item 5 is the charge system pressure testing port which states the maximum pressure rating of 1502 psi.
 

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There isnt a relief valve for the forward or reverse check valves, also both have the same power available. There mostly used for towing and bleeding air from the system. Now if you ad a 45 loader witch jd stopped making in 2013 then forward valve would be replaced with a relief one.
 

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Discussion Starter #8 (Edited)
Tudor, Badgerland01, Summers5, Thanks. I shimmed the relief valve yesterday with an additional 1mm washer. It resulted in a pressure of 1325-1350psi. I tried sanding a washer down, but I found out that it was harder to do than expected because there is nothing to hold onto. I will order washers from McMaster-Carr to bring it down to 1300 or below. (Once I find the PNs buried in one of the threads I read).

Summers5, Thanks to you as well. I did add a CTC loader a couple years ago... just now got around to shimming, installing the relief valve, and revised lever. (Glad I didn't break anything in the meantime)

Back to my question, I am embarrassed to say that I cannot figure out where in the hydraulic schematic the Forward/Reverse pedals tie in to make the silly thing move. I obviously don't know as much about hydro-static transmissions as I do automotive transmissions. Can anyone point me to a K90/92 theory of operation for dummies? :rolleyes:

I really appreciate the help. This is a great forum with very knowledgeable people.

Luis
 

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The forward/reverse pedals are mechanical, not hydraulic. The are linked to the swash plate inside the hydro which changes the displacement of the pump. (Red ball lever in the video.)

 
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Discussion Starter #10
Great video. That makes perfect sense & fits with what I understood from the hydraulic schematic.

Thanks!
Luis
 

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Powertrain, theres a member on here whos done a few videos on the k91 which is about the same as the k90 in yours. Search for mrbeef on mtf or on youtube under mmrbeef alot of good info there.
From my understanding(basic) the forward and reverse pedals are connected to a lever that controls a swashplate which directs the flow of oil to the pistons in the motor unit. that then is connected by gears to the drive gears.
The oil is pressurized in a charge pump first then pump(pistons motor unit) to get the required psi for the drive system and then the steering and implement ports.
 

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I just saw Tudor posted before i did, should give you a basic understanding.
 

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Discussion Starter #13
Summers5, thanks for the tip. I definitely will look for the videos. I still have plenty of questions...

Thanks
Luis
 

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Discussion Starter #14
Follow up post.

I finally got around to testing my loader capacity since shimming the relief valve on my x738 a couple months ago.

Previously, I could lift a very limited number of pavers on my loader. I don't recall the count. Probably around 16-20. At 18 pounds each, that would be 288-360 lbs. (if it was more, I don't recall. But surely not more than 400 lbs)

With the relief valve now shimmed to 1350psi, I retested the lifting capacity. My loader will now lift 32 pavers or 576 lbs to a height of 2-3 feet. (See 1st picture)

With an additional 2 pavers (34 total) @ 612 lbs. It will lift them to 6-12". Slowly. (2nd picture)

FWIW, In order to add some stability, I have a weight bar that I modified to hold 12 weights (504 lbs). (3rd picture). I also installed 1" wheel spacers; the practical maximum with the 60" deck still in place.

While I would love to be able to lift more than 600lbs, it should suffice for most loader jobs. Where I would want more lifting capacity would be when I am using a set of clamp-on 43" forks. (See pic 4. Real forks are not an option with the CTC loader). The lifting capacity with them will of course be reduced. Hopefully it will be enough to be useful. I was able to lift the back of a 5'x8' utility trailer with the tips. So roughly 200 lbs? I will get a more accurate measurement with them later.

Overall, I am happy with the higher lifting capacity

Thanks all for your help!
 

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Good to hear! Always nice to see a follow up with pos results.
 

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I have actually replaced the lift cylinders on my CTC loader with 1-3/4" bore units (stock is 1-1/2"), and lift capacity is probably in the 700-800+ pound range (do not have a convenient way to measure). Doing this is a bit tricky as there are limited 1.75 cylinders out there and I had to modify a longer pair to fit. With 420# of ballast I am able to lift enough to make the rear end very light and bouncy. I am shimmed to around 1250 psi.

I am not sure if 2" cylinders will physically fit in the loader frame, but they are certainly much more popular and come in many more sizes.

At some point I will be doing the same (1.75 conversion) for the curl cylinders, which now feels "weak" to me.
 

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Discussion Starter #17
Some good thoughts, TractorPete. I thought about going to bigger cylinders. What sort of work was involved in shortening the 1.75" cylinders?

I will investigate the 2" cylinder option, but I think (guess) it might be a bit slow at that point to raise and lower.

As for ballast. My next step move would be to buy 70lb weights as I would rather avoid wheel weights and loaded tires. Though, my next concern would be the strength of the weight bracket and the quality of the (my) welds, if I went much higher.
 

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There is a fair bit of work involved in modifying the cylinders. If you have a lathe and can weld reasonably well it is an option. Baileys and Surplus Center have some 1.72 cylinder options.

Steps involved:
Disassemble.
Setup on lathe/steady reset and cut fixed end off (shorten to get the desired stroke).
Cut existing hydraulic ports off as wrong size/configuration. Drill and weld in new "bungs".
Fab and weld on new end cap and "eye" to cylinder end
1.75cyl_mods.JPG
1.75cyl_big_rock1.JPG
.
Cut rod (to get desired open/closed lengths) and fab/weld new eye.
Reassemble and install!
 

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Discussion Starter #19
I was out at Lathe. :-/ I am going to look for something closer to a drop in.

So... Did you make/adapt that rig to swap between buckets and fork lift? I didn't see it at the CTC site. (I know they are available for 1 series JD)
 

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There are a few threads on various JDQA ("Quick Attach") conversions, mine is here:

It is definitely a worthwhile project if you have more than one attachment, as you can change within a minute. I probably use the forks almost as much as the bucket, for moving stuff around.
 
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