4WD Won't Engage

[DancesWithKnives]

I've got a '93 Chevy K2500 with about 130,000 on it. I recently tried to shift the transfer case into 4WD but the 4WD indicator light didn't illuminate and I could not get the front drive to engage (in either high or low range). No other indications of any problem and it still works fine in 2H. Anyone had this happen or have any thoughts on whether it can be resolved by a backyard mechanic like me?

DWK

[LampLighter]

If it is electric shift, as opposed to the old floor manual shift, I might know what to do. My Ranger was doing that alot until I resolved it.

Crawl under truck. Look at transfer case area. Find electric harness. Should be a plug in the harness with up to 7 pins in it. I Know that plug is sealed and has factory grease on the pins. So what. That was my problem. Pull plug apart, and clean the male pins one at a time with a piece of rolled up emory cloth. Put it back together and try. I never had that problem again after that.

[Sidekick]

I had a 92 GMC. I'd check fuses first and then look at the wiring that runs to the transfer case and the front hubs and make sure everything is plugged in and not pulled loose. I doubt it's anything serious.

[LampLighter]

Yeah, the fuses are so common sense, I just assumed he was beyond that already.

[DancesWithKnives]

Gentlemen---thanks for the advice! I assumed the problem is probably electrical because there was never any performance problem with the transfer case. I think it would be a good idea to polish up those electrical pins.

Much appreciated,

DWK

[Sidekick]

Dielectric grease on any connections is a good idea.

[LampLighter]

That grease is popular when joining aluminum to copper. I blasted the grease out with carberator cleaner then sandpapered the pins.

[DancesWithKnives]

Good idea. I've got some of that grease for my battery terminals.

Thanks again,

DWK

[greenjeans]

Sounds more like the 4X4 actuator to me. Take a look at this link here http://www.chevytalk.org/fusionbb/showtopic.php?tid/214569/

[DancesWithKnives]

I'm also very grateful for this link. In addition to the other ideas, I've been meaning to check a Chevy truck website and post the question.

Thanks a lot for that lead,

DWK

[LampLighter]

Stick around. In about a month we will have done rebuilt your truck. :D

[Lumox]

Probably the heat actuated thing on the axle. My 94 went out on me on a cold snowy day leaving hunting camp. The heat actuated things don't like to work in the cold, who would have thought to put a 4x4 actuator on a truck that didn't like to work in the cold???? I replaced it with an aftermarket manual device, called posi lok. It is a cable that mounts on the bottom of the dash and you just pull it out when you want 4x4, kind of like an old style choke cable. Installation was not too tough and you will never be without 4x4 again.

[Bushman]

This is exactly the reason that I am reluctant to give up my old 4x4 with the lock out hubs and that big lever through the floor. When all the 1/2 tons were coming out with the push button actuators and the automatic hubs, the 3/4 and 1 tons still had the lockouts and the levers. That told me that what I had was worth keeping. That low range without the front hubs locked in is terrific for slow controlled backing with a manual transmission. I've used it repeatedly will no problem what so ever.

[DancesWithKnives]

Lumox: Thanks for the modification tip. And yes, I had it up in Montana hunting in some ten below weather.

Bushman: My '75 Bronco has the traditional 4WD setup and it works well. However, it doesn't have the room and highway comfort of the bigger chevy truck.

Thanks again,

DWK

[BILL K]

I've got a '93 Chevy K2500 with about 130,000 on it. I recently tried to shift the transfer case into 4WD but the 4WD indicator light didn't illuminate and I could not get the front drive to engage (in either high or low range). No other indications of any problem and it still works fine in 2H. Anyone had this happen or have any thoughts on whether it can be resolved by a backyard mechanic like me?

DWK

My Honey's vintage "Jimmy" had the same problem at the beginning of this past winter.
Believe it or not, the simplest fix did the trick and the FWD now works fine.
Check fluids.

[Rock Chuck]

I'm coming in late on this and by the now the problems likely fixed, but I highly recommend the manual Posi-loc kit that replaces the thermal actuator with a cable setup. I put one in my '91 last fall before hunting season. It solved a lot of problems with the stock actuator. It's WAY overpriced for what it is, but it's worth the money to get rid of that monstrosity that GM came up with.

The stock actuator uses electricity to heat up. As it heats, it moves a shifter inside the axle to lock the 2 sides together. The colder it is, the longer it takes to shift. If you happen to be sitting in a creek, it might not be able to get hot enough to shift at all, even if the electric contacts don't short out.

The Posi-loc simply uses a cable to move the shifter. That's all there is to it. You have a button in the cab that you pull out to shift it, then use the floor shift to lock the t-case in or out. I find that it's easier to shift the t-case to 4H, then pull the knob to lock the axle, but it can be done either way. It just seems to shift more smoothly this way. Once it's locked, shift the t-case as needed.

[DancesWithKnives]

Thanks! Actually, I got involved in a project with another vehicle and have let the truck mellow, since I won't be using it for awhile. I will look in to your suggestion along with all the other great advice I received.

Much appreciated,

DWK

[Rock Chuck]

If you install one, read the instructions carefully as to where to drill the hole through the firewall. They've picked a good spot, but it's a little hard to understand on paper. Also, take care where the end of the cable housing attaches to the axle. That's a high stress point and it's hard to get it tight enough to hold when the cable is being forced through it. When shifting, don't force it or the housing will come loose. If the 2 axles aren't lined up, it won't shift instantly. You need to keep some gentle pressure on it until it moves.

[DancesWithKnives]

Thanks for the special tips!

DWK

[Tanstaafl]

If electric shift, many people do not engage the 4wd for months, or even years, then doesn't work. I make sure to exercise my Ford Explorer 4wd controls at least once a month, Never have had a problem, unlike some other Explorer owners I have read about.

[DancesWithKnives]

No Free Lunch,

Good point. I actuate the 4WD every couple months---sometimes more frequently. In addition to keeping the electric actuator working, I like to spin the lubricant around in the front end periodically.

DWK

[DancesWithKnives]

Well, I got done with my other auto project and finally turned back to the truck---since I need 4WD for a trip in a couple weeks.

It turns out that there is a GM service bulletin on this subject: #76-43-01A (9/18/1998). The good news is that it is possible to replace the heat-operated 4WD actuator with one that operates off a small electric motor (OEM part in later model trucks). You simply need to splice an additional wire and seal the connection. The bad news is that the motor housing protrudes out of the threaded cavity into which the old unit fit and its body is PLASTIC. Although it is not in the most vulnerable spot, branches, etc. could certainly whack it.

The old unit has a solid metal body that fits largely within the threaded cavity, it lasted 17 years, and a replacement can be had for $60 (including tax and shipping). Since I'm busy with a lot of things, I'm just going to replace the old unit with another heat-actuated part and see how many years I can get out of it. It's a 5-10 min. job, tops. If it fails relatively quickly, I'm going to do the somewhat more expensive and time consuming cable conversion that previous posters were kind enough to mention.

Thanks again for the advice!

DWK