Dodge Cummins Diesel Forum banner

1 - 5 of 5 Posts

·
Registered
Joined
·
9 Posts
Discussion Starter #1
I'm having slow response out of my 4WD unit (takes awhile to engage) and dealer suggested rebuilding the vac pump - before I do that, I decided to check those cheesy vac lines for leaks.

Starting right out of the pump - I pull about 24/25 mmHg
At the firewall - same
Coming into actuator - 19
So, is that enough of a drop to be causing my problems?

Also, is 25 sufficient pump vac?

BTW - this is on a 2000 Ram 2500 4x4 w/ 165,000 miles on it.

Cruise and HVAC work fine.
 

·
Banned
Joined
·
432 Posts
That should be more than enough to operate it. I'd suspect the actuator first....they are far more problematic than the vacuum pumps.
 

·
Premium Member
Joined
·
12,068 Posts
Vacuum good.
 
  • Like
Reactions: bunchgrass

·
Registered
Joined
·
9 Posts
Discussion Starter #4
That whole actuator setup is pretty vulnerable as it sits. Not a lot of protection from "stuff" hitting it and the associated switch wires/vac lines etc. If you get into some deep snow/mud etc .....

Anyway, my problem was with a slow actuation of 4wd after shifting. Found this out the hard way while pulling a loaded trailer up an icy hill. Dropped it into 4H as my rears started to slip - no go. Pretty quickly I was starting to slide backwards (and jack knife the trailer) so moved it into 4L and everything was honky-dory. It was a little cold, maybe about 5F but the pickup was had been driven for a couple of hours and was undoubtedly warmed up transfer case fluids.

After screwing around with all the vac crap it seems that the problem has disappeared - I hate when that happens!
 

·
Registered
Joined
·
5,650 Posts
19 should be enough, but you could have leaks any where along the line, or even a faulty switch (on top of TC) that leaks or does not operate properly.

get a hand operated vacuum pump and hook it to the diff actuator and see if it will hold a vacuum, if it does not that will be the reason for slow 4x4 engaugement
 
  • Like
Reactions: bunchgrass
1 - 5 of 5 Posts
Top