Case 580E weak in reverse until warm – need advice

[kukubesi]

Hey guys, I need some advice on my Case 580E backhoe.
About a week ago I was pushing dirt and noticed the machine started losing power when going in reverse. Forward works fine — even with a heavy load, it’s strong.
Checked all fluid levels — everything is normal. Three days ago I pulled the powershuttle, installed a full service kit, replaced all the clutch packs inside the shuttle, and put it back together. Still the same problem: reverse feels weak.
I also modified the FNR solenoid (the original one wasn’t working at all). After reinstalling, reverse got a little stronger. But here’s the strange part: after running for about 20 minutes, once the engine gets warm, reverse power comes back and it works fine.
For now, I don’t suspect the torque converter or the charging pump — I haven’t replaced those yet, but I don’t feel like they’re the issue.
Has anyone here run into this issue before? Should I be looking closer at the FNR valve/shaft, or is there something else I’m missing?
Any help is appreciated — thanks in advance!

 

[TractorTech]

Welcome to TBN!

It is not the torque converter or charge pump. It sounds like leakage of an oring on the reverse clutch pack or wear on the surface a sealing ring goes. If you installed new seals, which it sounds like you did, the new seal warms up and seals the area better that the old seal.

 

[kukubesi]

Reverse clutch pack has new seals, but it only improves when hot → feels like leakage at the O-rings or maybe piston wear.

ok thanks for u suggestion“Here’s something else worth mentioning”
Before I modified the FNR CUTOUT SOLENOID machine had no power at all (same as before I serviced the shuttle).
I then added a manual adjuster to push the PLUNGER inside the FNR control valve about 12mm" deeper. With that, it gained a little more power, but only when hot.
Using the stock CLUTCH CUT OUT SOLENOID = no difference.
Question: Is the weak power more likely caused by the FNR control valve PLUNGER travel not being enough, or should I be looking at the reverse clutch piston wear again?
Thanks.

 

[TractorTech]

The plunger travel would make a difference right away in both directions, not after oil is hot. That is why I would be leaning towards physical wear in an area a sealing ring or piston seal rides on the reverse pack as a possible culprit. Again, the old sealing material was worn or not very pliable, but now the new seal is more pliable and expands slightly when warmed up. I'm thinking this way as it has to be something that when hotter, it changes physically.
That's my theory, take it for what it's worth.

 

[kukubesi]

Thanks a lot for your input, really appreciate it!
What you explained about the plunger travel and the sealing ring/piston seal on the reverse pack makes a lot of sense. That’s valuable knowledge for me, and I’m grateful you shared it.
I’ll definitely check this area and try it out. Once again, thank you for pointing me in the right direction — this really helps!