Update...
This weekend I did some more checking and here's what I found...
1. I took the truck for a ride. Again, when in Low, the truck shifted and drove fine
...yet when I shifted to High, it felt like the tranny was gonna drop out :mad: .
2. With truck running and stopped, I shifted from Low to High and observed a slight and momentary increase in engine RPM, then it went back to normal idle. Same thing happened when shifting from High to Low
.
3. With the truck running, in neutral, rear axle in Low and e-brake applied, I crawled underneath and disconnected the Low side vacuum tube at the diaphragm. Yup, I got vacuum
. High side line was dead (no vacuum). Also noted a corresponding slight increase in engine RPM with the line disconnected. Reconnected everything, went to the cab and shifted to High, and then disconnected the High side. Yup, I got vacuum
. Low side was dead (no vacuum). Again noted a corresponding slight increase in engine RPM with the line disconnected.
At this point I felt confident that all vacuum lines/tubes were OK and that the switching mechanism was fine because I had vacuum and that vacuum did switch between the High and Low lines just prior to the diaphragm. I looked at the diaphragm and it looked suspicious. Perhaps it’s me but rather than a sealed assembly, it is an upper and lower housing with a rubber seal or gasket. Click here
Diaphragm to see an image of the diaphragm. (Camera tilted to get best shot of unit). Perhaps it is OK? Don’t know yet… :confused:
No on to the real puzzling issue…when I shift into high (w/ normal connections everywhere), any problems and noises I hear are coming from directly beneath the cab…not the rear-end. While I am still trying to figure out the vacuum system and how everything is interconnected and dependent on each other, I gotta trust my ears
. Sounds and feels like the clutch or perhaps a throw-out bearing? The grinding/clunking noises (like it’s jumping out of gear) are coming directly below me.
So, that’s what I have for the update. Next check is to do as Jolly mentioned, which is to remove the diaphragm and see if I can manually shift from Low to High. That will also give me an opportunity to more closely inspect the diaphragm assembly on the bench.
Thanks folks and please reply with any feedback or addition ideas/comments!!!
Take care and I’ll post again soon…
