I'm very good at the old manual locking hubs, But how does the dial-on-the-dash work.
Seems to me the front shaft has to rotate at road speed in order to engage at road speed, yet while having the front end up in the air, and spinning the tires by hand, While the front axle shafts rotate with the respective tire, neither front tire rotates the front shaft. Whats the deal? Are the tires supposed to be locked to the axle shafts all the time?

Thanks in advance

Reamer

'97 Flareside 4x4
40K miles
Pacific Green Regular cab

 

hey reamer: not sure of all the details but the gud 'ol days of hubs are gone. ford has gone to a center shaft disconnect system. what that means is that out of 4 wheel drive your tires don't rotate with the motor but the axle does. look in this months 4 wheel and offroad for a good explanation of this system. seems many compoanies are going to this. funny they don't mention ford in their article only dodge and jeep. but we've got it too.
this system is probably the reason why you can switch into 4x4 on the fly. not like the old days. stop truck, put into neutral, back up a little, ok think it's in. and getting it back to 2wd a treat. still prefer the old system myself.

 

I've put a fair # of miles on my 4x system. I don't like waiting for the system to engage.
I would rather have the hubs manualy locked and ready when I'm out, then pull the transfer case. I'd rather not fully depend on a bunch of electronic solenoids.

 

There are soooo many solenoids that we depend on already, what's one more?

 

The old system could be shifted on the fly into 4HI and out of 4HI. Only needed to back up after shifting from 4HI to 2WD to unlock the front hubs, or, if you prefer, leave them locked and have the front wheels turn the front diff and front driveshaft, until the next time you backed up.

New system has two solenoids, that apply vacuum to lock/unlock right axle shaft to the front diff. The shifter fork and lock is inside the diff, but the vac motor that does the shifting is mounted outside of it. When driving in 2WD, left front wheel turns left shaft and left side gear in diff, which drives the two bevel gears that spin inside the carrier, which spin the right side's side gear backwards. The carrier itself does not spin in this instance. The right side's side gear is disconnected from the actual right axle shaft. The ring gear doesn't turn (its connected to the carrier), so the front driveshaft isn't driven by road speed (remember, its also disconnected in the T-case in 2WD).

When 4HI is engaged, the T-case locks the chain sprocket, driving the front shaft. Front shaft now turns, spinning ring gear and carrier, and right internal side gear, up to road speed. Then power is applied to work the vac solenoids properly, so vac motor works shifter fork, locking the right shaft to the right side internals.

That concludes class for today. There may be a quiz tomorrow!

 

And it gives you the fantastic opportunity to replace the vac pump for $275! Thanks Ford! Thanks for designing a system that can't handle any real off roading or demand on the 4x4! You guys are swell!

Scot


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97 F150 ORP
Towing/trailer package, 3.55LS
34" Mickey Thompson Baja Belteds, Requisite K&N Airfilter
JVC Kamelon CD Player, CB, bug shield, window shields, and other goodies




[This message has been edited by MrScot (edited 09-08-2000).]

 

MrScot
Have had mine for 3yrs, do all the service myself, & have seen no sign or mention of a vacum pump. Where is it?? It has worked great every time I need it--about 20 to 30 days per winter + the occasional deep mud.

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97 Lariet-sc-4.6-4x off road-auto-3.55 LS-
superchip-K&N-3"
pvc air box mod-Granetelli MAF

 

I'm not really sure as to the location. I tried to find it to do myself, but ran out of patience and took it to the dealer. Mine died when I was pulling a felled tree up a hill. I remember it well.....

 

turn the switch or shift the lever, signal is sent to the gem module which ativates a magnetic clutch inside the transfercase which spins up the front drive shaft, then when it equalizes speed the lockup coller ( spring loaded, inside tcase ) locks the chain to the front drivshaft, then the gem signals the vac solonides to energized the axle shift vac motor, it moves a shift fork which slides the axle lockup coller to lock the front (pass) side axle togther. Thus as in the owners manual dont shify in at highway speeds ( about 75k max, in owneres maual ) or you can gernade the magnetic clutch ( inside the tcase)