Be advised to be careful when shimming your Machine to Get More Lift Because You Can Kill Your K92. It Just Happened to a X748 at a JD dealer where My Brother Runs the service Department and the trans is not covered Because it was shimmed so the warranty was Voided On the trans only. The Machine was only Purchase a year ago The Owner is Looking at $2,000 Plus In Part’s and Labor I guess the Guy Managed to crack the Case or something along that line:thThumbsU
So the actual damage to the K92 was a cracked case? Couldn't that be repaired? The price tag on the K92 replacement is an issue (to me) with the old X7XX's.
They make the shim kit for a reason, and that's because the pressure varies from machine to machine, and even on the same machine over time as things wear, and you must vary the shims to bring the pressure to within the manufacturers specifications. If the trans no longer functions, how could they tell that it was shimmed to the point where the pressure was out of spec?
Did the owner shim it himself, or did the dealer do it for him? If the dealer did the shimming, then I would think that the dealership should at least share the cost even if Deere won't cover it under the warranty.
Shimming means there was a thin piece of metal "shim" that was put in a relief valve to force the relief to not open untill a higher pressure is reached. Not done properly something will give/break. So instead of lifting 500lbs he may have shimed to lift 800 lbs as just random numbers. It wouldn't be added height-it would be added power to lift something heavier.
They make the shim kit for a reason, and that's because the pressure varies from machine to machine, and even on the same machine over time as things wear, and you must vary the shims to bring the pressure to within the manufacturers specifications. If the trans no longer functions, how could they tell that it was shimmed to the point where the pressure was out of spec?
Did the owner shim it himself, or did the dealer do it for him? If the dealer did the shimming, then I would think that the dealership should at least share the cost even if Deere won't cover it under the warranty.
Owner shimmed it himself way Beyond design specs(shop New about it) I don't Know all the details( one of the Mechanics In the shop said the Case was Cracked I didn't Close enough to see) But I was at the dealership where it was yesterday I Know two of My friends from Deere Corporate know about it and will be out soon to look at it. I Guess the Guy was Picking up something really Heavy with the Loader and did something I didn't Get Up close to the tractor But I saw the Mess it Left from the trailer to the shop He also Damaged the Hydraulic cylinders On the 45 Loader and the darn tractor was covered In Low Vis
As of when I Left the dealership I was told Deere will not stand Behind the cost of Repairs for the transmission because it was shimmed But there Might Be other Factors as well I'm Guessing owner abuse Because the Loader was Messed Up as wel Thats why I said Be carefull when shimmingl:thThumbsU
That just took the level of concern about my loader/hydro from low back to nearly non-existent. If somebody abused the thing bad enough to damage the loader, they deserve what they got; those things are built like tanks.
Boy, I'd sure like some details! I have a 455 with the IRV shimmed to about 1250psi. The factory forward relief valve is set at about 3900 I think. So, I have a hard time believing that an implement valve setting of 1250 would hurt the transaxle. Now, the loader itself, I'm sure one could damage it badly with overloading. I wonder if he had the proper forward relief and/or was it what he shimmed???
Maybe he shimmed both relief valves instead of just the Implement Relief Valve? Or he didn't stick a gauge on it and thought of .005 will help then .020 will really help! :sidelaugh
Boy, I'd sure like some details! I have a 455 with the IRV shimmed to about 1250psi. The factory forward relief valve is set at about 3900 I think. So, I have a hard time believing that an implement valve setting of 1250 would hurt the transaxle. Now, the loader itself, I'm sure one could damage it badly with overloading. I wonder if he had the proper forward relief and/or was it what he shimmed???
Part of the charge pump housing is the case with enough thickness to deal with the designed max pressure of 1502 psi. The pump and motor cartridges and the valve plates are iron and steel and the associated internal passages are througn much thicker sections of the case designed to handle the higher pressures.
It was the case that failed, not the transaxle as such.
It must have had a car on the back for a counter weight. How could you lift that much to damage the loader and crack the case without tipping the tractor over or putting it on its nose. I have a weight box on mine with concrete wall blocks in it. Figure it weighs around 400#s plus my 275#s. What could you be trying to lift that would do that much damage, crazy. I can pick up a full scoop of wet topsoil or even stone and it handle it fine, just have to keep the load low, and take wider turns. People must see a front end loader and just assume they can move the world with it.
It makes me wonder if guys are asking for problems when putting loaders on these GT's. LIfting 400-500 lbs seems like a big strain on a little machine, especially when it sits out front 2-3 feet.
It makes me wonder if guys are asking for problems when putting loaders on these GT's. LIfting 400-500 lbs seems like a big strain on a little machine, especially when it sits out front 2-3 feet.
Sounds like a combo of things...and mostly abuse. Shimming to spec or the top end of the spec is perfectly fine. Going over spec and the beating the **** out of it is another matter.
Plus, the hydro drive relief valve just cuts out spikes, it won't prevent overloading of the trans. In other words, it won't "stall" the hydro like the valve on a CUT or SCUT will. So, on an X7 you can keep on pushing and spinning beyond a safe limit. Eventually something will POP!
I'm trying to find Out what the Guy was doing when all heck Broke Loose I'm sure I'll Hear in a Few Days from my Brother. They told me the Guy that owns the X748 did something Similar In the Past with a Kubota Sub Compact Killing the trans and Damaging the Loader and He doesn't Maintain his equipment Very Well Because I Guess they go out to His Place to work on a Lot of AG tractors as well for stupid Damage That anyone with common since would Not Do:thThumbsU
What I don't Get Is If You Have Bigger AG & Compacts with a Loader(which I guess the Guy does) Why Bother even shimming a X748 To Get More Lift.
Sometimes Having More is Not always a Good thing. My 45 Loader is at Factory setting sand BTW at Factory I can actually Pick up 600Lbs Of Material High enough To Clear the side of a 4wd Pick Up truck Bed Which Is as High as I go anyways. I Never Have to reach Max Height and to 36inchs By specs it will Lift about 600 to 700 pounds anyways:thThumbsU
Well it has been raining here all day so I did this to keep myself entertained. I recently repaired my 455 hydro and have reread the TM again.
The THRV only protects the FORWARD side of the hydro. It does not protect the Reverse direction. The THRV is installed in the forward closed loop from the hydraulic pump to the hydraulic drive motor. I guess that is why it did not protect the rest of the hydro. Since there were damaged loader cylinders, the IRV did not protect that loop.
My SWAG (Scientific Wild *** Guess) is that the guy picked up an excessive load in the bucket. He lifted it too high and suddenly dropped the bucket. The return fluid to the hydro is SUPPOSED to be "pressure free oil" per the tech manual. By dropping the loader bucket, you create a two cylinder one stroke pump. The return oil is now a high volume high pressure oil flow into the hydro. Apparently, it was high enough to damage something in the hydro. I always wondered why the return lines for some loaders had an in line restrictor on the return side. Now I think I know why.
Why did the loader cylinders fail? I could not find the specs for the cylinders, but the rockshaft cylinder is rated a 2000 psi. Let's just assume the loader cylinders have the same pressure rating. Dropping the loader bucket released the pressure in the cylinders, until the operator returned the SCV to neutral. The operator closed off any path for the oil in the cylinders to go. This happened just before the bucket hit the ground causing the remaining fluid in the cylinders to be pressurized by the falling weight in the bucket to a lot more that normal. This pressure is what damaged the cylinders. The IRV is out of the loop when the SCV is in the neutral position. So, it could not protect the cylinders. I believe you could do similar damage at 1000 psi with the right conditions.
Having said all of that, I cannot blame the shimmed IRV as the reason for the loader failure. Many owners have did this and I have not heard of this type of failure before. I expected it, but I am surprised it is not more common. Was it the cylinders or hydraulic hoses/lines? If the loader cylinders and hoses are rated for 2000 psi, the IRV being increased to 1250 psi should not be a problem. However, higher pressure may cause problems with the charge pump and other functions inside the hydro such as the lube oil and PTO. John Deere would definitely have the right to void the warranty on the hydro.
You ALWAYS want to carry the load in the bucket as low as possible or this could happen to you. :duh: Hills and loaders usually do not mix well. :swow: BTDT and have brown briefs to prove it. mg:
Since this owner had a similar problem with a Kubota, I would say the failure was due to the operator not the equipment.
Nah, the "hydraulic" pressure can't get to the "hydro" section, other than the priming oil provided by the charge pump. Return oil from the loader goes straight to the sump(case).
Also, dropping the load like that puts the cylinder under negative pressure as it's going down since the pump flow can't fill the void fast enough. That might suck in some air through the gland, but it will still be restricted in rate of drop.
Like I said this was just a SWAG. You are correct about the negative pressure on one side, but since this is a dual action cylinder both chambers are closed with the SCV in neutral. Could the combination of the high positive pressure on one side and negative pressure on the other side damage the seals?? I really want to find out what was damaged in the cylinders or hoses.
Would you happen to know the PSI in the 455 hydraulic pump to the motor closed loop?? Seems like I read somewhere it was 1550 PSI. I repaired a hydro and checked the charge pump, but could not test the pump to motor loop. The TM does not address this issue. I know how I can test this pressure and just need to know what to expect.
A perfect vacuum is 0 psi. Atmospheric pressure is 14.7 psi. Negative pressure is betwen those 2 numbers. The seals are designed to withstand 2500 psi. I don't see them failing due to negative pressure.
Hydraulic hoses usually have their pressure rating printed on, or formed into, the abrasion protection (the rubber cover on the outside of the hose). Cylinders will sometimes have their pressure rating stamped into one end of the barrel. For FEL hydraulics, the minimum for both is 2500 psi, even for the old Johnson and KwikWay loaders. Somehow, I don't think that JD would derate their equipment below standards used by companies making loaders for light GTs 40 years ago and that are still in service today.
My guess is the damage to the cylinders came from other than hydraulic pressure. More like something broke from the heavy load and the cylinder rods, barrels, or the cross tubes suffered mechanical damage.
I searched, but couldn't find the necessary specs for the K92 pertaining to the pump/motor pressures, but I suspect that your thoughts are correct at 1550 psi, or at least in close proximity. For a Sundstrand Series 15, the rating for GT service is 1500 psi, and the peak rating is 4500 psi. A hydro capable of surviving even peak pressures of 10,000 psi woud be a very heavy piece of equipment. The traction conditions needed to produce 1500 psi at 3/4 thottle are difficult in the extreme to find for my 2400 lb GT. It usually spins its chained tires at lower pressures.
The only way that I can think of to test the pressures in a hydro in a heavy GT or SCUT involves tire chains, a large tree or other immovable object, and a low throttle setting.
Charge pressure is regulated @300 psi. Anymore and it could try to drive the hydro.
PTO circuit pressures are regulated to @ 175 psi.
Hydro loop pressures can be upwards of 10,000 psi, but I think usually @ 5,000 psi on this trand. I know many CUTS go into relief at 10K. No relief valves on any L&G TUff Troq trans - except for the spike limiter for the X7's with loaders.
Outboard hydraulic pressures are capped at @ 1200 psi.
I don't think there are any high pressure hydro loop test ports on these. There are on CUTS.
There is a test you can do to test the general condition of a hydro though. It is a pump/motor internal leakage (I.e. rotator group wear):
- plumb into charge port. More pressure.
- load hydro by pushing against a pole, tryin to pull something, etc.
- if charge pressure holds or dips only a little, the hydro has little internal leakage and wear.
- if the charge pressure drops considerably, there is wear.
The theory at work here is the more hydro pump or motor wear you have, the more internal leakage, and the more oil the charge pump must provide to keep the system primed.
A poor mans test is do you lose steering or lift when under a hydro load? If so, same thing is happening. All the charge pump oil is going to the hydro loop with little left for the steering or lift.
Sent from the MTF Free App
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Related Threads
?
?
?
?
?
My Tractor Forum
4.3M posts
217.1K members
Since 2005
A family friendly forum community dedicated to all Tractor owners and enthusiasts. Come join the discussion about specifications, modifications, troubleshooting, maintenance, and more!