Cat 143H. Transmission problem

[MR.ROGERS]

Cat 143H transmission, after 1 hr of operation,4-6 reverse won’t engage, after using it for 30 minutes reverse 2-6 won’t engage, raise rpm then reverse gears engage, Oil,filter and screen clean

 

[Nige]

Can you explain the symptoms a bit more clearly please. You start by saying “after 1 hour” then go on to say “after 30 mins”. Which problem comes first.?

Does the oil appear dark & cloudy or clear & bright.? Does it smell burned.?

Have you tested any pressures yet.?

Also please post a Serial Number.

 

[MR.ROGERS]

Can you explain the symptoms a bit more clearly please. You start by saying “after 1 hour” then go on to say “after 30 mins”. Which problem comes first.?

Does the oil appear dark & cloudy or clear & bright.? Does it smell burned.?

Have you tested any pressures yet.?

Also please post a Serial Number.

Serial# 1AL000097 the tractor is great for 1st hour of operation, every gear engages, then 4th reverse has a pause before engaging, after 2 or 3 times, it stops engaging,from that point using machine continuous,Foward gears start not engaging when changing direction, after another 30 minutes of use, at one point engine Rpms had to be raised before any gear would engage, All of the oil, filter have been changed,using Cat TO 4 oil along with checking screen the system is clean, oil is clear, including the oil that was drained, Thank You for your Help. I’ve changed Gear Selector, trans was rebuilt by caterpillar just over a year and half ago

 

[Nige]

Serial# 1AL000097

OK, so that is a VERY early 1AL machine.

You say Cat rebuilt the transmission 18 months ago. How many hours has the machine worked since then.? Did Cat also rebuild the control valve and, most importantly, if they rebuilt it did they update the valve to the latest specification.?

This was the reason I asked for the machine Serial Number to know if it was built before or after the control valve update.

Do you have one or more 500psi pressure gauges available.?
Three gauges would be ideal. Although the tests can be done with one gauge at a pinch it’s just a whole lot more fiddly to do because the gauge is being constantly switched from one test point to another.

 

[MR.ROGERS]

The control valve was changed 2.5 years ago,and no it’s the original style along with the shifter, I can get pressure gauges!!! I would like to say Thank you, your knowledge is priceless!!! I was having trans problems a year and half ago, took the cat,they informed me that I was about to have Tandem bearings failure and Trunion seal, advised me have repaired! Which.

 

[MR.ROGERS]

Which was done by them All total the bill came to $63000.00

 

[Nige]

The control valve was changed 2.5 years ago,and no it’s the original style

Unfortuately that doesn't completely answer the question. The modifications are in the "guts" of the control valve, not the complete valve assembly which retains the same Part Number as the older style. We'll park that for now but may have to circle back to it later because to check what it has is going to require the valve to be opened up to check some internal parts.

EDIT: When you say the valve "was changed" 2.5 years ago do you mean it was replaced with another complete (new I assume?) valve or simply that the old valve was overhauled.?

 

[Nige]

I can get pressure gauges

A good start. You're going to need three pressure gauges (preferably identical if you can get them) with a maximum reading somewhere in the 5-600psi range.

We're gonna have to invent a testing procedure because the manual calls for all machine systems to be at normal operating temperature before testing pressures. Unfortunately that's when your machine goes t1ts-up so we'll have to do it starting from cold and this means the pressure specs quoted in the manual are not going to be all that much use.

Because the first thing you lose is speeds 4 thru 6 in reverse that points the finger at the High Range #8 clutch. The same clutch is also used for speeds 5 thru 8 in the forward direction. Question: When 4 thru 6 in REV start to act up does the same thing happen with 5 thru 8 in FWD.?

What I'm going to suggest is to put pressure gauges on the test points for both the Low and the High Range clutches and run the test lines from the transmission to the cab. That way you can observe the pressure all the time from the first cold startup to the point where the transmission starts acting up. I'm not too concerned about how they compare to the test specifications at this stage, simply to know how they behave as the transmission warms up from cold.

See the attachment. Hook up a couple of gauges to Test Points D (Clutch #8 - High Range) & H (Clutch #7 - Low Range) and carefully observe what happens both to the maximum registered pressure, and how fast the pressure rises when the clutch engages, when the machine is cold. Check if either the max pressure or the rate of pressure rise changes as the transmission warms up.

Clutch #7 (Low Range) will be pressurized in speeds 1 thru 4 in FWD and 1 thru 3 in REV.
Clutch #8 (High Range) will be pressurized in speeds 5 thru 8 in FWD and 4 thru 6 in REV.

 

[Nige]

You said you were using TO-4 oil. What viscosity.?

 

[Nige]

After having slept on it I'm going to suggest something to do before you start hooking up gauges. It should be relatively simple to do and hopefully will eliminate the possibility of a transmission solenoid valve issue. I suggest that you swap the complete solenoid valves between Low & high Range. To do this you wil first have to remove the nut #3 on the end of the spindle of each valve and slide the solenoid coil off. That will give you access to the hexagon on the valve body itself to remove it. Don't just swap the solenoid coils, swap the valve body as well. You also have to swap the electrical connections.

If the problem moves from the High Range to the Low Range clutch when the transmission gets hot then the cause is obvious.

 

[MR.ROGERS]

Why is it working perfectly in All Gears when it’s cool? Yesterday I operated machine, heavily for 1 hour and 17 minutes before I started having issues, finished the day in 3rd forward and 3rd reverse, as long as I stayed in these gears every worked

 

[Vetech63]

Those electrical solenoids can fail when they get hot. Its a common problem. Nige wants to eliminate that as a possibility before you get into the hydraulic side

 

[Nige]

Those electrical solenoids can fail when they get hot. Its a common problem.

Exactamundo. Either the spool can seize or the solenoid coil can break down electrically when the valve gets hot. That's why interchanging both parts (spool & coil) from the suspect clutch to another clutch station is key. Many people think that all you have to do is move the coil from one cltuch station to another which is incorrect.

 

[MR.ROGERS]

Ok That’s sounding better and better!!! Thank you so much, I think I’ll change these out and see what happens next... I really Appreciate your Wisdom. Thanks again

 

[Nige]

Still pending some answers to earlier questions:-

1. What weight of oil are you using in the transmission.?

2. When you lose speeds 4 thru 6 in reverse at the same time do you also lose 5 thru 8 in forward.?

Another question that came up while I was thinking about this. When you had the transmission overhauled was a new transmission pump and a new cooler fitted at the same time.?

 

[MR.ROGERS]

Cat recommended using 30# T04 that’s what is in there now, When I lose gears it’s All of them except the the ones I was using , which is 3rd forward and reverse.after stopping machine for lunch, Starting back up, All the gears work as they should, As for which parts got replaced, I waiting on print out from dealer

 

[Nige]

Cat recommended using 30# T04 that’s what is in there now,

And that's the correct oil.

When I lose gears it’s All of them except the the ones I was using , which is 3rd forward and reverse.

Sorry to keep banging on regarding this issue. Originally you said you lost 4-6 reverse after 1 hour of operation. Now you are losing all gears except the one you are in at the time. It sounds as though the more the machine has been worked since the problem started the more gears you are losing. Is that a fair description.?