Topic: 4WD light stays on

[mldave]

On my 86 truck..it snowed yesterday,then melted and was mostly ice this morning heading to the coffee shop.Just a short three block drive home on a combination of light ice and drive pavement.Locked hubs and put in 4Hi for the ride home after coffee for better traction,After parking and shifting back to 2Hi the 4WD light stays on.What gives??

[OOPS]

Switch on t-case may be stuck or fused in closed mode!!!

[BigMike]

The 4WD lamp is grounded by a trigger switch/plug located on the passenger's side of the reduction housing of your transfer case. For your 1986 truck, this is a single wire switch that simply sends a ground signal to the lamp which is powered (whenever the key is in the ON position).

If its related to the weather, than its possible the rubber coating seal of the switch is damaged, and water was able to get inside the switch and short it out (constant ground), or water got inside and slowly rusted its internals and it just needed 1 more cold night before it gave up the ghost.

Otherwise, because it's a simple ground, it's possible it's wire has been shorted somewhere between the switch and the lamp (another way to have a constant ground). Maybe a rock hit it, or it was slowly rubbing against something.

The easiest way to check if it is a faulty switch or a short in the wire somewhere is to simply unplug the switch at the transfer case and check if the lamp turns off (in 2WD & the key in the ON position). If so, then you have a bad switch. If not then you have a short somewhere in the wire leading to the lamp.

The 4WD Lamp Indicator switch / plug in question is this one:


Good luck
BigMike

[mldave [OP]]

Thanks for the replies.Does it hurts anything to drive in 2wd with the light on,hubs unlocked?

[BigMike]

In general, No. However, there may be possible concerns depending on the issue. Without giving this a great deal of thought...

1) Switch is so badly damaged internally that it starts leaking gear oil.
2) Switch is so badly damaged internally that it allows water and other debris to enter into your t/case.
3) Switch is so badly damaged internally that you are no longer able to engage 4WD unless you remove the damaged switch.
4) The short is caused by the wire entangling itself with your front driveline, which could cause further damage to your wiring harness.
5) The short is caused by the wire somehow wrapped around to the exhaust side and may melt on your exhaust.

The 4WD lamp is merely an indicator lamp and nothing more.

BigMike

[mldave [OP]]

Thanks people.....

[mldave [OP]]

BigMike,got the light out.Unlocked the hubs and drove around the block,seemed like it was in 4low.Parked and moved the selector from 2Hi to 4Hi a few times and the light went out.Now if you could only help out with my big problem on this truck,the clutch.A shop put in a Sachs clutch kit and it shifted good for a few weeks and then gradually got harder and harder to shift at times.He bled it again and that lasted another few weeks,bled it again another few weeks and so on.Last trip to the shop he just got a couple of wrenches and adjusted the CMC rod I believe and again it shifted good for a few weeks before the same hard shifting into first and second and reverse.He said the clutch bracket was good.It dosen't leak fluid.Funny thing is when I start out first thing in the morning it's hard to get into first,but coming to the first two nearby stop signs it shifts like butter into gear.After that it's anyones guess as to how it will shift.IF I shift into reverse as soon as it turns over mostly it'll go in with a slight grind.Seems the harder it is to get into gear the tougher/or if at all it is to get into first.I know I should have gotten Aisin parts but had to have the clutch kit put in on borrowed money so I had no choice.MT-90 and the shifter bushing and seat were put in by a friend a year ago.Do you think the CMC could be bad,though not leaking or that little rubber hose is bad?The shop fellow talked about fabricating a longer CMC rod,but when he'll ever get it on his lift is anyone's guess.Could he have damaged a clutch part on installation?..and why does it shift fine once in awhile and mostly dosen't......thanks for reading this long winded post as I'm totally sick over this 4 month ordeal and would trade this nice looking truck for a Honda car if I could.

[OOPS]

Get a flashlight, lay on your back on the DS floor, shine the light on the bracket that holds the clutch pedal, look for cracks in the bracket. Also check the firewall around the where the CMC bolts to for cracks in the firewall.

If there are cracks, the movement does not allow the pedal to depress the MC all the way which in turn does not allow the MC to send enough fluid to the slave cylinder to compelty disengage the clutch causing drag and hard shifting.

It can be fixed, but it is not an easy fix.

[mldave [OP]]

OOPS,the bracket was checked by 2 shop mechanics and also one shade tree mechanic...

[OOPS]

OOPS,the bracket was checked by 2 shop mechanics and also one shade tree mechanic...

How about the firewall, they also crack there.

[mldave [OP]]

That's okay also.....

[helipilot77]

I'm going to guess you have a bad clutch master cylinder. Often times when they leak it doesn't show up because the fluid is leaking past the seal and it just goes into the fluid reservoir. I had the same problem with a Mitsubishi eclipse. One way to find out is to pump the clutch lightly just at the very top of it's travel. If it improves your shifting, you have a bad clutch master cylinder. Which is an easy fix. Hope this helps.

[Rocksurfer]

Yup I was thinking the same thing, you may have a bad master or slave. Sounds like your not getting a complete clutch disconnect since it grinds or is hard to shift at a stand still. The sincro's will put the gears in line while moving and would be why it's not happening there. Also if you changed your gear oil make sure you have a GL4 rating, GL5 is not what you want in there it is a great oil but in an early trans will cause the gears to not align properly. Something about being too slippery and allowing you to shift quicker past the sincro.