68RFE just quit working

[TSandner]

It started with erattic shifting when trying to go to fifth or sixth. It would hunt for a gear and feel like it was slipping a little. It would go into limp home where it would start in first go direct to forth. It did record a P0868 code, low line pressure. Hoping for a cracked or loose filter I had a fluid and filter change and the code cleared. It did not fix the problem. I discovered that if I manually selected the 4 position so it would not try for 5th or 6th it worked fine. It never did record another code. The shop was on a test drive with the scanner plugged in and it quit pulling completely. Would not go forward or backwards. Had to tow it back to the shop. Any ideas?

2008, 2500, 4X4, 6.7, No power train mods or programmer. Edge Insight CTS, ARE Topper, Rino spray in bed liner.

 

[transe]

Have 'em hook their scanner back up, and check Line Pressure and Desired Line Pressure (in Park, at ~1200 engine RPM). LP should match DLP (within a couple psi). If not, then likely either a bad filter (loose, dislodged, cracked, split open, etc.) or (if filters are OK) a stuck main regulator valve (in the pump, which requires trans removal to inspect / repair). If LP is OK, then check Engine Speed, Turbine Speed, and Output Speed, while idling at a stop in Drive (or Reverse). If all three are greater than zero, problem is not in the trans. Either transfer case is in Neutral, or rear driveshaft / rear axle has failed. If turbine is greater than zero but output is zero, then trans is indeed slipping. You will need to pull the trans and tear it down to inspect the clutches and repair as needed. If turbine and output speed are both zero, then pull trans and check for broken input shaft, failed torque converter, broken flexplate, or missing converter bolts.

 

[TSandner]

This is just a follow up for anyone curious about the outcome. When the shop pulled the pan they found the pressure had built up to the point it blew the spin-on filter off the threads, stripping the threads in the process. There was also significant clutch material in the pan. I guess when the filter blew it let the clutches slip and wear off the material. With the amount of material in the pan I would no longer have confidence in the transmission if the pressure problem was found so they replaced the entire transmission with a jasper unit. The good part is 3yr/100,000mi warranty. The bad part is the just under $4,000.00 bill. All this leads me to believe the main regulator valve TransEngineer suggested was a high probability. I'm sure if we could have gotten that far with troubleshooting it would have been a much less expensive fix.

 

[transe]

The spin-on filter does not see line pressure. It only sees the pressure in the cooler return line. The filter was the problem. Sounds like either it was tightened too much when originally installed, or was not tightened enough (causing it to loosen up and fall off), or you got your torque converter so hot that the oil (even after the cooler!) was hot enough to melt/weaken the plastic snout.

 

[JConquest]

68RFE_ Just went through similar issues including replacing filters with no resolution. Just picked up the truck last evening from the local TRANCO shop. The culprit was one of the seals had failed allowing transmission fluid to freely flow through the transmission. Result was damaged clutch packs serviced by the culprit valve about the size of a quarter. Nearly 4 G later, it seems to be working fine. Upgraded components were installed.