front differential stays locked

[stukreit]

1997 GM C K2500 4x4 with 6.5td, 160k miles

Over on another thread I've been dealing with various leaking seals. Can't explain this one. Have the front driveshaft off, the diff is definitely
engaged. I removed the actuator (upgraded from heated to motor drive). It stayed locked for a while, then with messing on it heard a Click and it
let go. re-installed the actuator, which was difficult because it was pressing against the rod in there, and it engaged again! I've looked around the
internet and haven't yet found an explanation or disassembly of the actuating internals. Really not looking forward to dropping the diff. It would
be nice if there was something to try on it in-place, like shove a screwdriver on the rod.

I suppose I'll drive it around a bit, warm up the oil, drain it and see if there's metal shavings..

 

[ak diesel driver]

Should be able to reach in there with something and push on it. There might be a Burr on the sliding part making it sticky. Also the spring could be weak or broke.
On mine there was a washer in there that was broken.

 

[FellowTraveler]

Sounds like there is a damaged/broken engagement fork and or other parts inside the p/s engagement housing.

 

[stukreit]

No apparent damage to the fork mechanism. Also, the fluid drained out with no residue other than the general gross
old appearance.

 

[FellowTraveler]

Consider this!

Chevy/GMC K-Series 4WD Axel Engagement Actuator Bypass | 4x4 Posi-Lok

4WD Axel Engagement Thermal Linear Actuator Bypass for the 1988-1998 Chevrolet/GMC K Series Suburban, Tahoe, Yukon 6 Lug and 8 Lug 4WD

4x4posi-lok.com

 

[ak diesel driver]

I'd polish up everything that slides and put it back together

 

[stukreit]

This.
This spacer is for the thermal actuator.
I bought the truck around 2004 with 60k miles. Couldn't engage 4wd so a local shop debugged and fixed or converted it to
motor actuator. He complained that the wiring was yutzed up and it cost him overtime to straighten it out.
The enclosed picture is from a youtube vid on converting from thermal to electrical and finally proves that the spacer should be gone. So how in the world did this truck run fine for the past 15 years, including (a very few) shifts into 4wd?

I'm hoping tomorrow's test drive will be excellent and possibly even see a bump in mpg.

 

[stukreit]

previous post wasn't 100% clear. The thermal-actuator-spacer was installed with an updated-electrical-actuator, so the selector fork was not sitting right. Operating the actuator with the axle tube off of the diff showed that the spacer put the fork out even in retracted mode. Note the wear and galling all over the spacer. Not at all clear how it drove 100k miles in this condition. Sweet mysteries of life...