Well my dad had is 98 Chevy 3500 Diesel *junk 6.5* dually for almost 10 years.
Let it run on ebay NR
Chevrolet : C/K Pickup 3500:eBay Motors (item 280439415991 end time Dec-17-09 14:45:43 PST)
Sold it private for 9k
Just went up to Oshkosh Wisconsin and bought a 2000 F350 Dually 4x4 CC LB PS
Runs great but the issue I ran into up there looking at it was that the shift on the fly 4x4 definelty engages you can hear the clunk especially in low but the fronts are spinning. The hubs turn freely and lock but somethings up. What could this be?

 

If I understand, the transfer case is engaging but the front wheels don't pull automaticly? Do the front wheels pull if you engage the hubs manually? The ESOF works on vacuum. It is a common issue for the vacuum lines to develop leaks and then the hubs can't engage automaticly. A quick test for this is put your heater to blow in the A/C ducts. Engage the ESOF and wait for 30-45 seconds and see if the air starts blowing through the defroster with out you doing anything. If it does, then you have a vacuum leak. Do a search on here and there is reams of information on how/where to check.

Jim

 

You could have a vacuum leak, a bad vacuum pump, or a bad valve for the reservoir.

 

Is the 2000 ESOF? I thought they were still manual...

Edit: btw, congrats to your dad for getting the F350 over a chebby!

 

ESOF was an option on all the SD's, my early 99 is ESOF.

 

Would that not matter since I locked the hubs manually?

 

Your father ran that 6.5L diesel for ten years, sold it for nine grand and you label it as junk because???

My 2000 XLT is ESOF.

 

If you locked them manually and still nothing, then you have a bad shift motor on the transfer case or something wrong internally.

 

It engages into 4 low but same thing fronts don't spin just rear.

 

may sound a little crazy, but is the front drive shaft in there? Maybe someone blew a ujoint and never put the shaft back?

 

If you engage the hubs manually try and turn the front drive shaft. If it won't turn your good there and it's in your transfer case. Probably the shift motor. Hard to distinguish between the shift motor and locking hubs from in the cab. A Curtis

 

Ds is there. The clunk is coming from the transfer case you can hear it right under you when you turn it to 4x4 low

 

Figure out if your front drive shaft is indeed being driven by your transfer case or not when in four wheel drive. If it's being driven by your transfer case, the problem is in your front end or vacuum for the hubs. If it's not being driven by your transfer case, the problem is on the transfer case end.

Edit: Just saw what andrewc53 said!

 

When the truck is in park and stopped then you throw it in neutral then kick it it in 4x4 low you feel it right under you. Ill definitely check the Driveshaft here in a bit.

 

Ok driveshafts locked so it must be the vaccum line is cracked on the one side. Im going to replace them, anyone know off hand what size the line is and where do the lines run too?