Tractor Repair: 5140 case/ih tractor, shade tree mechanic, clutch packs

Question
Good evening Mr.Jossie. I'm a half shade tree mechanic not up to date on these modern tractors. I  have a 5140 case/ih 2wd tractor with a synchromesh forward-reverse transmission. It has about 6,000 hours on it.I have had the tractor about 3 years. Not long i say about 6 months after i bought it it started to stop pulling or barely move after running it for awhile.You can cut it off let it set of about 15 or 20 minutes and it would run fine.But now it seems to do it more often. Also it seems to do it when you shift from forward to reverse. Most of the time it does it in forward but it has done it in reverse. I took it to one local case/ih dealership they said it was the hydraulic pump (cost bout $5,000). On that note i decided to go to another case/ih dealership. There finding was the clutch pack (bout $3,500). As you can see I'm really at a loss of which direction to go. Maybe you can guide me in a more general direction. Thanks for your time and wisdom.

Answer
 If this is not a powershift model, then the only hydraulic clutch packs are for the forward and reverse shuttle.  There is a shuttle control valve on top of the rear end under the seat that directs oil to the forward or reverse clutches, and also provides clutch pedal and diff lock control.  It is most likely a modulation spool that is sticking intermittently in the shuttle valve.  If it was the hydraulic pump, the other hydraulic functions wouldn't work and it wouldn't start working again after you shut it off and let it sit for awhile.  If a clutch pack failed, it wouldn't move in that direction at all and wouldn't start working again either.  The pressures to the forward and reverse clutches can be checked with pressure gauges.  The clutch packs should have about 300 psi when pressurized, and when the problem occurs they probably will only have about 40 psi.