Did I break it?

[phantom309]

I dug the truck out of a snow bank today here in edmonton,.got it started on its 4 working glow plugs poor thing,.used the 4wd to move in the deep snow, and out on to the road,. drove it about 10 miles in 4wd high at 35-40 mph,.the roads were extremely icy so it was great, stopped at a light, and couldn't get rolling hardly at all and realised then i had no 4wd,.it seems the transfer case works in the hi/lo ranges etc,. but no 4wd?
did i break something? never made any weird or expensive noises at all,.
What model of transfer case would it have? its a 4l80e auto trans, and the transfer case gets its lube from the transmission,.
Its a manual lever on the floor to shift it,.lever is working fine, but no 4wd hi or low,.:confused:

Thanks
Nick

[DmaxMaverick]

Does your '94 have the original front diff, or an later model actuator? It sounds like (absent the "I really broke something" noise) the thermal actuator has gone south. Simple, and relatively inexpensive upgrade, or about the same cost to restore what failed.

[wpdozer]

I installed a manual Posi-lok setup in my friends 92 S10 blazer. It's basicly a PTO type cable that replaced the unreliable vacuum actuator. Posi-lok also has a system that replaces the thermal linear actuator on your truck. Check it out. www.posi-lok.com (http://www.posi-lok.com) Part#800, $159.05.

[JohnC]

Do you have a lighted display near the transfer case lever? when you move the lever to 4WD the front driveshaft should light up. When the front axle engages it should light up. If you only get the driveshaft light, then the diff. actuator is probably TU. If it starts working again when the temperature goes up, it's definitely on its way out. In 4WD there should be 12 volts on the actuator and it should get warm (if it has 3 wires it is not a thermal actuator).

[phantom309]

Thanks for the replies,.
This falls into the category of ,..."I had no idea?!!"
so i,ve been reading about these thermal actuators,. seems like a really poor design, its been cold here -12C and i,ve no shop so i haven't been under it at all,.
My question is ,. why is it there? why does that axle need to be disengaged?


thanks for the 4x4 education,.

nick

[DmaxMaverick]

Actually, the "axle(s)" don't disengage. The diff lock disengages the axles from the propeller shaft and some of the diff rotating mass, but the axles continue with the wheels. This is purely for economy purposes (turning a greater rotating mass requires more fuel energy). Some have said it also helps lengthen service life of the front diff, but I've seen many times more failures after long periods of non-use, compared to frequent or continuous use.

[phantom309]

So the front driveshaft continues to turn at all times?
So again i,m wondering why the 1 axle is disconnected,.purely for economy?
I,m thinking of building a positive engagement and have the axle locked all the time,.enough of this BS no 4wd stuff especially when i need it.http://www.fullsizechevy.com/forum/general-discussion/technical-maintenance/429569-home-made-actuator-build-thread.html
so is thing locking the diff? or one axle?
Thinking back on things i do remember one time it wouldn't engage, last summer,. and i backed the truck up 20 feet or so then it worked,.

nick

[DmaxMaverick]

No. The front propeller (drive) shaft is disengaged from the diff. The axles (half-shafts) remain engaged to the wheels, but disconnected from the front propeller shaft.

However you do it, the end result will be the same. OEM thermal, later model stepper, or mechanical, it will be engaged, or disengaged. You could leave it engaged, but economy takes a hit, and can cause noise and vibration. An advantage to this would be virtually no synchro wear in the TC for on-the-fly engagement (traveling relatively straight, with no traction loss at that time). If you live/drive in climates requiring frequent or full time 4x4, seasonal shifting could be an option. The problem with a mechanical solution, such as in the link you posted, "on the fly" or a convenient shift, should the need arise, would not be possible. Options include: mechanical static (on, or off, as you set it at the diff); mechanical linked (under hood, or in cab mechanical lever/knob); OEM thermal; upgrade to later model stepper.

The solution referenced by wpdozer is unique to the S-10 models. They use a vacuum pod to cable to diff for dis/engagement, with a vacuum valve located on the transfer case.

[phantom309]

So it turns out if you have the 8 bolt hubs and a gvw of 8600,. you can't upgrade to the electrical stepper motor,.
too bad,. i think that would have been a better cure,.
http://www.4x4posi-lok.com/popup/app_chevy-k_how.html
a cable setup seems foolproof when its done,.

Nick

[phantom309]

so after some research mebbe a screw type actuator might work great,.

http://www.servocity.com/html/25_lbs__thrust_linear_actuator.html