Another automatic hub question

I just had a question pop into my head while reading some of the other posts here about automatic hubs. You flip the switch to 4H and drive along a bit. You stop your truck, shut it off, and hop out to load some more stuff in the back. You get back into the truck and start it up and drive off still in 4H. My question is this, when you shut off the truck does it disengage the 4H (even though you didn't move the switch) and then re-engage it when you start the truck back up or does it leave it in 4H? It's not an overly important question, just one that popped into my head and made me go hmmmm. I'm sure there are others out there who wonder the same thing.

Lawrence

Reply to
Lawrence
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The hubs are activated by motion of the front axles. The hubs aren't electric, or anything like that, they just engage when the front axles turn. They stay engaged when you stop the truck, as long as the truck is still in

4WD mode. Most automatic hubs don't work too well after a few years, due to improper maintenance. There are exceptions, though.

Spdloader

Reply to
Spdloader

Spdloader, quick question.

Must the 'wheels' be moving to activate the hubs or just the axles? The question is prompted incase the vehicle is already stuck. Can the 4WD be engaged to get unstuck?

: > Lawrence : >

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Reply to
Mellowed

Huh? Maybe on a chevy. The auto hubs ford uses are vaccuum operated; it works a lot like a ball point pen; first vaccuum locks the hubs, then when you turn the switch again the vaccuum unlocks the hubs.

Reply to
Chris Hill

If they're 'mechanical' hubs like the WARN Lock-O-Matics on my old Willys, when you engage the 4wd ,that engine torque engages the hubs. Let up and they will automatically disengage,or if the road is supplying more torque than the engine. Great hubs,on the truck since '58, minor maintenance(look se once a year,add a little grease). Too bad they don't makem any more !!

Jay

Reply to
j.b. miller

The axles turn, locking in the hubs, which in turn move the wheels. The wheels don't need to be moving beforehand. The best plan is to have the hubs engaged before you get into trouble, then you won't have such a mess getting out. Spdloader

Reply to
Spdloader

On what vehicle. Certainly not on my f350.

Reply to
Chris Hill

Chevrolet and Ford both used hubs made by Dana/Spicer, or Warn, to name a few, until Chevrolet switched to the C/V shaft style front axles in the late '80's. Ford didn't switch until almost 10 years later. The hubs and stub shafts would interchange between Ford and Chevrolet for lots of years before then. When Chevy switched over, they went to a system using vacuum/electric to engage the front axle. Don't believe me? Ask anyone with an older S10 Blazer, or S15Jimmy, those vacuum valves go out so often I used to keep 5 to

10 of them in stock in my shop just for those customers who'd come in complaining about not having 4 wheel drive. Jeep started using an electrically activated solenoid on the front axle, which was another bad idea, in my opinion, but it's there anyway. I've never seen a hub on a light truck engaged or disengaged by vacuum. Only mechanical action. I've never seen a vacuum operated ball point pen either. I ran a four wheel drive specialty shop, and I've repaired, and customized a lot of vehicles, but I don't remember seeing one like you describe. I've got four or five sets of different Ford and Chevy auto hubs here, some new, some not, if you'd like to see, they are just smaller/larger drive cogs, with a spring to hold it out of 4wheel drive when not needed.

Spdloader

Reply to
Spdloader

Are you saying your F350 has hubs that are engaged by vacuum? What year, engine, drivetrain do you have? Spdloader

Reply to
Spdloader

Well, we are talking about Super Dutys here, so I guess you could argue the point of it being a "light truck".......

Matt

99 V-10 Super Duty, Super Cab 4x4 (w/vacuum operated hubs)
Reply to
Matt Mead

Are the hubs vacuum? Or, is the 4WD engaged by vacuum?

Spdloader

(If you can drive it without a CDL, then it's light.) lol

Reply to
Spdloader

99 f350 with psd.
Reply to
Chris Hill

Okay, is it the hub, or the front diff, or the transfer case that is vacuum operated?

Bear in mind, I'm not being a smart a$$, just saying I've never seen what you are describing.

I have a '99 F350 Dually, 4X4, PSD as well. I have the Auto/Manual option hubs. They're not vacuum. They are mechanical. I service them every year.

Spdloader

Reply to
Spdloader

They are vaccuum, follow the lines from the vaccuum pump. The tc is operated by an electric motor.

Reply to
Chris Hill

Thanks, Chris! (and Matt Mead as well)

As I said before, I've never seen vacuum operated hubs, ever. I sold my business in 2000 when my dad passed away, and I went into the grading business. I wasn't aware vacuum hubs were around or an option on the Super Duty. Apparently, it was an option starting in '99, still, the Auto/Lock hubs on my '99 aren't vacuum operated, they are mechanical, from the factory.

However, two points to reiterate here are;

  1. The vacuum pulls the hub "cog" in position until the axle engages it, and...

  1. I've still never seen a vacuum operated ball point pen.

Spdloader

Reply to
Spdloader

For the second time, YES the hubs! (The T-case is electric.)

Matt

99 V-10 Super Duty, Super Cab 4x4
Reply to
Matt Mead

It was a bad idea, yes, but it was a vacuum activated solenoid, not electric, that first appeared on Command-Trac equipped ''84 XJ Cherokees. They stopped using them altogether in the early 90's in Cherokees, but the YJ Wranglers had them from '87 until the TJ was introduced in 1996 (as model year '97). They never appeared on Grand Cherokees, either.

'98 and up Ford Superdutys with the electric shift 4wd system have vacuum-operated front hubs. The hubs have 2-position dials labeled "Auto" and "Lock." In the auto postion, working normally, they will be engaged/disengaged by vacuum. The Lock position can be used to engage if the vacuum system is not working properly. Of course, mine aren't disengaging, and I just had it in to the dealer who replaced the left side under warranty, but the right side is still giving me problems. Once again I get to visit this dealer a second time to fix one problem. (argh).

  • * * Matt Macchiarolo
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Reply to
Matt Macchiarolo

Matt, do you know if they were specific to the Selectrac, or Commandtrac Jeeps? I had two '90 XJ's one was a Laredo, the other a Limited, neither had the solenoid on the axle, and both had Selectrac. Spdloader

"Spdloader"

engaged/disengaged

Reply to
Spdloader

The solenoid axle was specific to Command Trac, the non-full-time Tcase.

  • * * Matt Macchiarolo
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Reply to
Matt Macchiarolo

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