Brad Clayton Posted April 8, 2012 Share Posted April 8, 2012 This truck (2011 F-250 with 6.7l) came to me with a complaint of the 4x4 not working in cold weather. It actually never worked no matter if it was cold or hot out, the customer just never uses 4x4 unless it snows. A quick verification reveals the transfer case is working correctly and the hubs work fine in manual mode. The problem lies in the vacuum portion or auto hub mode. OASIS reveals nothing special and there is no previous history. There are no codes in the system and visually everything looks ok. There is plenty of available vacuum for the system. The CVH solenoid has power to it….. …and the TCCM is supplying ground to the CVH solenoid when the 4x4 selection switch is shifted to 4x4. The solenoid is allowing plenty of vacuum to pass to the hubs. But there is very little vacuum on the measured point at the left hub. It is a straight shot down from the CVH solenoid to the left hub. I block off the right hub with a golf tee and recheck and now there is even less vacuum. Very strange….. The smoke machine is quite handy for finding vacuum leaks, but nothing is revealed when I load the vacuum harness on the axle with smoke. There are quite a few connection points (leak points) on the harness. I inspect the harness convolute for any abrasions or crushed spots and it looks ok. Starting to narrow things down a bit. Now I am getting somewhere.... .....the problem is obviously in that small section of line going to the right hub. I remove the hose and pull a manual vacuum on it and it holds. ??????????????? I hook it back up to the truck and it doesn’t hold. Now I am getting tickered. An extremely close inspection reveals this, the connection has split where it goes through the bracket. (left side shown, problem was on the right side). Closer look I replaced this and rechecked and all was well. A proper retest drive was performed to verify the fix and now I can start trying to grow hair on my head again to replace what was pulled out. Quote Link to comment Share on other sites More sharing options...
cbriggs Posted April 8, 2012 Share Posted April 8, 2012 I have seen a few of these break off on the 2011's, Altough not a partially broken one like you have. This lovely cvh system does a good job of filling itself full of dirt when a leak develops as well. Quote Link to comment Share on other sites More sharing options...
Bruce Amacker Posted April 8, 2012 Share Posted April 8, 2012 Your case studies with pictures are equal to the best ones I have seen from national level instructors. Quote Link to comment Share on other sites More sharing options...
Aaron Posted April 9, 2012 Share Posted April 9, 2012 B-rad does real good work when it comes to writeups and photos. I especially like the parts list ones, for the engine teardown/buildups. I have most if not all of them printed off in my toolbox. Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted April 9, 2012 Author Share Posted April 9, 2012 Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted April 19, 2012 Share Posted April 19, 2012 Re these trucks predominantly breaking the right side and were the track bar ball joints replaced? I have done a number of those ball joints and I ususally end up removing that vacuum line and getting it out of the way. I can see some guys not doing that and possibly damaging the line/connector. Just thinking out loud here. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.