426 cat stops moveing

[gusbratz]

i have a 1987 2wd 426 cat wit 2400 hours on it. it has developed a problem, about 5 months ago i was digging stumps and i went to reposition and the machine wouldn't move fwd or rev. i took the floor pans up and tapped on the neutralizer selonoid and then it worked. i have put about 200 hours on it since then. i drove down to the neighbors house 3miles away and loaded rocks into my dump truck for 8 hours. then on fri roaded the backhoe home. today i started it to start doing the latest project and it did it again. i shut it down and tapped on the neutralizer sel. nothieng. fluid level is good and the trans filter was replace about a year ago. i can hear the selonoid click when i push the button on the shifter and on the loader bucket so i would thing it was working. i shut it off and came back in about 2 min and it moved about 80' then just stopped moveing again. let it sit a couple min and started it and it worked. put it in rev and drove back to the garage . and when i put it in neutral then fwd it was dead again. sounds reminiscent of this thread https://www.heavyequipmentforums.com/showthread.php?15951-cat-426-drive-electric-solenoid/page2& but with only 2400 hours i would be surprised if it had a bad transmission. any advice is welcome i am not sure where to start.

 

[gusbratz]

so I drained the oil and took out the suction strainer under the little oval cap on the bottom of the transmission and it was choked with bits of black hard plastic a couple were as big as a quarter. with a few bits of aluminium in the mix. I cleaned it off and put it back together and it worked for about 8 hours then I lost fwd totally and reverse only works for about 20 seconds after I start the machine. so I guess the clutch packs must be bad. hard to believe after only 2200 hours the transmission would go out but it is almost 30 years old. unless there is a hose coming apart and shedding liner into the system or there is a piece of something plastic somewhere in the trans I guess the fact is it needs to come out and get torn down.

 

[Nige]

Have you still got all the material from the strainer..? Post some good photos.

 

[gusbratz]

the stuff and the bits and my precious paw

 

[Nige]

Those black bits look like the inside of a hydraulic hose to me. Not sure what others might think.

Did you find anything that looked like fried bits of clutch material..? It's difficult to identify what the smaller "slimy" stuff is on the suction screen.

 

[Bob/Ont]

Looks like clutch plate material to me.
Later Bob

 

[gusbratz]

I drained the fluid and cleaned the suction screen again. then i filled it with cheap 303 transmission oil from tractor supply. 27$ for 5 gallons so it must be quality stuff. i only have a little run time before the suction strainer clogs up again so the best i could do was take some pump pressure readings with the oil cold. when doing the converter stall test i could hear grinding when in forward. here are the pressures, they don't match up with the book but maybe you could help me trouble shoot what i should be looking for when i get the transmission out.

pump pressure in N at low idle 50#
pump pressure fwd at low idle 105#
pump pressure fwd high idle 105#
pump pressure rev low idle 160#
pump pressure rev high idle 160#

Torque convertor supply pressure at low idle in neutral 25#
torque convertor supply pressure in neutral at 1900 rpm 50#
torque convertor supply pressure in fwd 4th gear at 1900 rpm 65#
torque convertor supply pressure in rev 4th gear at 1900 rpm 74#

fwd clutch pack pressure low idle in fwd 40#
fwd clutch pack pressure low idle in rev 0#

rev clutch pack pressure low idle in rev 130#
rev clutch pack pressure low idle in fwd 0#

lube pressure was 6# in neutral at idle, 6.5# when in fwd or rev.

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[Bob/Ont]

Forward clutch is leaking oil and the plates are ground up. Take trans out and rebuild it. Be sure to clean cooler and hoses.
Later Bob

 

[gusbratz]

well I got it out after work last night, pretty tight squeeze. I really struggled to get the flexplate on the torque convertor to separate from the flywheel. I thought I must have missed a bolt so I slid the transmission back forward and checked them. they were all out but it seemed to be hanging up on the pilot stub going into the flywheel. I was about to come ask if there was something I was missing but a big pry-bar got it out. took a lot more force than It should have for something that should just slide in and out. to top It all off we got our first little spit of snow while I was doing this out in the driveway as it's getting dark. yeah. At least it's in my garage now and i can have the stove going while i tear it apart after work tonight.

 

[gusbratz]

I got the transmission apart last night, the clutches are just plain old worn out. the material appears to be bonded to a metal backing and it is just paper thin and worn off in places. why has this happened? could it be the pump pressure is too low and allowing the clutch pack to slip instead of letting the torque convertor do the slipping like it should? should I rebuild the pump? I mean once the forward or reverse is engaged it should be locked up and not wearing out like this with only 2400 hours on the machine. the only thing that looked weird to me was the output shaft shim pack under the rear cover looked like the bearing race was spinning against that shim pack and had worn the shim away. I guess I will replace that shim with a .007 one to tighten the bearing up a little. I don't really want to dump a bunch of money into this and want to do the bare minimum. I am thinking just friction plates and gaskets to put it together.

 

[Nige]

I don't think that's all necessarily down to wear. The way the friction material has spalled off could indicate some sort of interaction with the oil in the transmission. What oil are you using..?

Also at least some of the metal separator plates are visibly scored and should be replaced. Any that are blue from heat should also be replaced. You'll probably find very few of them are in a condition to go again if the friction plates are all as bad as what's in the photos.

With all that material flying around it's quite likely the pump will be toast and not rebuildable, but yes in answer to your question the pump should be rebuilt.
Plus every hydraulic line in the power train oil system will need cleaning out, plus the transmission cooler if it has one.

 

[Bob/Ont]

Check pump drive tangs on the torque converter. If worn will damage the new pump.
Later Bob

 

[gusbratz]

do you guys think I should replace the pump? the drive tangs looked fine at a glance.

 

[Bob/Ont]

Open it up and inspect it.
Later Bob

 

[gusbratz]

ordered a new pump, gasket kit and a clutch kit from joseph industries. i started to finish tearing apart the clutch assembly last night and look what i found. looks like the springs broke and got into the piston and bitched every thing up. not sure if this is the cause of the problem or if all the clutch material delaminating caused the pack to be so thin that hyd pressure smashed the piston into the springs. it looks to me like this spring has been broken a long time. every imprint must be a forward reverse shift taking pressure off the bits and letting them move and get smashed again. so i ordered new springs and 1 piston off ebay last night because it is friday and everything is closed. i am experiencing buyers remorse about the ebay purchase. hoping the quality is not poor. the seller is obviously chinese.

 

[Bob/Ont]

Worn clutch linings = longer piston stroke = more spring compression = broken springs Get everything cleaned out good.
Later Bob