This 4x4 system is driving me nuts. Its been doing odd things since I bought the truck (like not working when i need it) and I finally got it up on 4 blocks today so that I could put this puzzle together and see where the missing/weak pieces are. Or at least have something intelligent to post here to help me narrow the search. Unfortunately I'm more confused than before.

The system doesn't seem that complicated to me when I read the countless threads here. Here's a few observations / questions...

- I have 2 Lock/Auto hubs and a Lock/Free hub that is great for troubleshooting. I need the Auto system to work because of where I live so another Lock/Free is not an option
-when I have been successful getting the system to engage when I'm out driving in the snow I get a grinding sound and vibration under the floor. Pretty bad.
-I believe that both Lock/Free hubs work reasonable well. Sometimes lag when switching from Lock to Auto. Planning to do the Guzzle hub service asap regardless.

-Transfer case is definitely not engaging / disengaging every time when I make selections in the truck. I can hear the click when it happens. ARE THESE PRONE TO BECOMING INTERMITTENT? I checked the 2 electrical connections going into the transfer case and they both look like new. Squeaky clean.
- I changed the oil in both the transfer case and the Fwd Diff a while back and both fluids were clean. No metal in either unit. Ring and pinion looked good from what I could see.
- with transfer case engaged and fwd drive shaft spinning and hubs positively locked, is it possible for wheels not to spin, cuz mine don't always? If they do turn I can sometimes stop them with my hands.
- with hubs locked, engine off, I can spin either wheel and the opposite when spins backwards (pretty sure that's right) but SHOULDN'T DRIVE SHAFT ALSO TURN?
-IN GENERAL, IS IT SMART TO TRY TROUBLESHOOTING THIS SYSTEM WITH THE TRUCK ON BLOCKS, OR DO FRONT TIRES NEED TO BE TURNING TO ASSIST TRANSFER CASE/HUBS SELECTIONS?
- when I pulled it into the garage I had 4x4 Lo selected (light on) but hubs were not locked. Heater controls worked normally. Took much switching back and forth to get back to 2 wheel drive and after half an hour of fiddling with hubs and the electrical switch inside, I now have an ABS light on and my heater only blows defrost (indicating vacuum problem).
Seems to me that i have a vacuum problem, and transfer case problem and a diff problem!! Hoping ABS was just confused by being on blocks... and that I can reset with ScanGuageII. Any help to make sense of this would be soo appreciated. Truck is still on blocks.

Oh, maybe this is relevant too ... when I flushed the tranny some months back the filter (the one in the tranny) that the parts store gave me was the wrong shape. When I took them the old one to match up a new one they said my tranny is from a different year truck. Mine's an '03. I marked the SN down from mine when I had the cover off. 065S1083 Any chance my tranny not matching up properly with my transfer case?

 

Take the shift motor off and see if it actuates reliably when the switch is activated. If so, try to manually shift the transfer case with a wrench (you will see the shaft when the shift motor is removed) and see if it engages. Follow the vac lines from each hub and check for leaks. To engage a ESOF hub, vac is applied for a short period of time to engage and again applied to disengage (like a ball point pen).

 

Whoa, my initial post didn't look that long when I typed it last night. Thx for reply 78. I'll pull that shifter this morning, and try tracing the vac lines tho I think that is much easier said than done.

In short, I need to understand the Diff. When I suspend both front tires, lock both hubs and spin one wheel by hand, the other wheel turns in reverse but shouldn't the drive shaft also turn?

 

SOunds like a VAC Problem and it will make a grinding sound and Clunk with Low Vac pressure

Low VAC Pressure inhibits a fast Hub engaugement what will cause a Grinding sound then Hard Clunk when it does catch
The condition must be right for the Clunk ie..the rear wheels spinning when front tries to engauge

Sit truck on ground

Switch to 4x4 and roll truck few feet to engauge then Grab the Axel and Spin by hand (If it Locked in Axel wont spin each side)

Switch to 2x4 and roll few feet Axel should spin free each side



With your description of the problem I believe whats happening is a Slow Vac leak

Meaning when you SHift in 4X4 it will Lock in Fine but after a few seconds or so the Vac press bleeds off and it comes Out of Lock and out 4X4 then it tries to shift again and repeats this process over and over Grinding and clunking etc............

I would start by Testing the Vac Lines with a Vac pump to each Wheel needs to hold Vac

If the Lines to the wheels hold vac then test the vac Control silinoid

My truck does this and I have chased it to a Leaky Vac control silinoid and that seems to be fairly common for this problem

If the Vac System is GOOD then we can trouble shoot more

 

I have nevr tried this

I would think the drive shaft would spin With the Hubs in LOCK but IDK Was the Switch in the Cab on 4x4 at this time???

When you manually Lock the Hubs and then SHift into 4X4 do you have 4X4??

 

Here is a site that talks about vac leak in the hubs. Welcome to guzzle's 4x4 Needle Bearing Maintenance Web Page

I would like to find an answer on conflicting points of view.
78 Fordman said vac applied each time switches on and off like a ball point pen.
and Blade35 says vac leaks down and releases the 4 wheel drive.
I think its a vac which hold 4 wheel in place, but now I'm not too sure.

 

That's how mine does leaks Vac and comes unlocked right or wrong

But I think technicaly it supposed to use Vac to Lock and again to Unlock

I will have to reread it again

Mine leaks at the Silinoid so I just lock the hubs manualy when I need to

 

Ok. Tried to pull the little motor on the Transfer Case, and my torx t-20 ain't skinny enough to get on the last bolt. There's always something!

So decided to rebuild the hubs from the Guzzle Bob site instead. They good as new now. Having dissected them, I have to agree with 78fordman that they operate similar to a ball point pen. Once they are locked, it would take suction again to unlock them. Suck on, no pressure needed to remain on, then suck off.

Fired the truck back up to see if re-lubed hubs would make a difference. This time, the transfer case seemed to make a nice CLICK every time I made a selection inside the truck. Was able to verify fwd drive shaft spinning each time too so I'm relative happy now that the transfer case is doing its job. Maybe having unplugged it again fixed the connection.

The hubs on the other hand never worked in Auto at all. When I selected Lock, they would spin intermittently (pretending to be in 4wd, and giving me hope) but never with enough force that I couldn't stop them with my hand. This makes no sense to me. I know that some magic happens in the diff, but I'd love for someone to enlighten me just a little.

So switched focus then to vacuum, per Benny's recommendation. (finally have a vac gauge now) I think there are definitely problems here. The vacuum pump does NOT cycle on and off which indicates to me that there are no leaks. Tested vacuum coming out of the pump and it will hold 16.5"Hg. When I let it leak a little, it drops to 12.5"Hg before cycling back up to 16.5. Is that right????

Didn't have time to trace whole system tonight so just tested vac pressure as it arrives at each wheel well. Rt side pulses to 2.5"Hg when 4x4 selected, then bleeds off right away. I suspect that is way too low. No pressure indicates on left side at all. Maybe line pinched somewhere. Still suspect solenoid Benny?

Anyone have a vac schematic to help me trace? Might just leave old lines there and string new lines throughout. Hopefully I can find some hose that works with existing junctions.

 

Could it be in the Knuckle seal or in the hubs itself?

 

Sure, that's possible. Thanks. but I'm not going to tear apart each knuckle to replace that seal, (at least a days work for me) before i see if it works with proper vacuum pressure.
Can anyone say what vac pressure I'm looking for at each wheel well?

 

Yes Hubs work like a Pen High Vac to Engauge and Lower Vac to Disengauge But Vac pressure does it Both

My slow leak would Bleed off and disengauge I just did Ball joints and put all new seals in the hubs/knuckles it hold vac all day at my wheels




When you hooked up the Vac Gauge at the Wheels that was a Test of Everything Both wheel the res the silinoid etc.....

it depends how/where the Gauge was Hooked Up And you really should start testing from the Pump and work your way to the Wheels

See it starts at the Pump then goes to reservoir then Splits with one to heater and other to 4X4 Silionoid then line comes out silinoid agoes aways and then Splits to each wheel



Its very important where you install the Vac Gauge cause that will determine what Part you are testing






I have a PDF with a Vac Diagram and theory of Operation it will be easy once you see it and has all the specs your looking for

It wont let me post it PM me your Email and I will send a Copy to you

Be a piece of cake when you read thru that though

Oh and one of those MityVac hand pumps with the Gauge is almost a Must to test

You can probably do without it but you will have to Plug lines where it splits to other parts cause you need to test each part on its own really

I hope its a Line but most don't get off that easy or cheap

 

The front differential is an open differential. If you spin one side, the other will turn in reverse. If you are trying to spin the wheels under power in 4*4 you will only really get 3 wheel drive unless you have a locking or limited slip device in the front axle. Two wheel drive if you don't have limited slip in the be rear.

When you start the truck, does your vacuum compressor eventually stop, when it fills the canister?
When you try to flip to 4*4 does the vacuum pump run for a long time or does it stop and your heater stays on setting or goes to defrost?

Check at the compressor, then check at the tank, if those work plug the line going to the ESOF switch which send the vacuum pulse.

This is how you rule out the vacuum pump, the ESOF valve, and the lines to the HVAC controls and the hubs. It is a pain, but if you made it through packing hubs, you can do this.

I am currently running with hubs locked position and switching in and out with the dash ESOF dial. I have the hub seal kits ready to go but it's -20 tonight C.

 

I just went through the same type of deal. Ended up being the hub seal on the left hand side was bad, and yes they are a pain in the *** the change but very easy to diagnose. Just pull the vacuum line off the top of the hub and connect your vacuum pump to the hub or you can do like me and hook up a clean piece of vacuum hose and and just pull the vacuum the old fashion way (your mouth). If the hub doesnt hold vacuum, the hub seal is bad. They are like 60.00 each and you need to fab a seal diver to replace them.

Dave

 

Awesome advice here. Thanks guys. Ended up swinging by mechanics place this morning who was happy to take his mityvac to it and show me what's what. Would have loved to keep at this on my own, but I just don't have the time. He performed very much like you guys are recommending here. Both knuckles held good pressure and we determined that the vacuum pump is fine. He claimed, like Benny, that the solenoid is usually the weak link in the system, so we just changed it. Peace of mind. Seemed to work because the hubs were now locking and unlocking as they were supposed to, on the hoist.
Driving away I selected 4x4 and still felt the significant vibration. Turned out to be a sloppy universal joint at the aft end of the forward driveshaft. (Shame on me for not finding that sooner – had the same problem on a 4runner years ago.) I swapped it with a used but tight one this afternoon and while I haven't had a chance to test drive, I'm optimistic that this is finally fixed. Will report again when I've driven it. Thx again.

 

Hey do you have a Part# for that Silinoid?