# 1988 chevy k3500 4wheel not working



## terrapro (Oct 21, 2006)

I just bought a 1988 chevy k3500 today. Yesterday I test drove it and the 4wheel worked fine, today the guy dropped it off and we were going through everything and the 4wheel won't engage now. When you put it in 4high you can feel the gears change and the torque increase but the front drive won't work. 

I dug threw old threads and the problems and it seems it is either the actuator or the switch, how do I know which one it is? Or could it be something else?


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## 2COR517 (Oct 23, 2008)

Check for voltage at the actuator when the key is on and the case is in four wheel. There is a fuse for the actuator, check that first.


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## terrapro (Oct 21, 2006)

2COR517;1343482 said:


> Check for voltage at the actuator when the key is on and the case is in four wheel. There is a fuse for the actuator, check that first.


The actuator is on the passenger side facing towards that wheel correct? Surprisingly I have had 4 of these trucks and never had a problem.


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## Chrisxl64 (Dec 10, 2008)

if you feel the transfer case engage, and spin up,,,could it be an auto lock hub problem?


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## Chrisxl64 (Dec 10, 2008)

wow,,,feel like a moron rolled down didnt see anyone had already replied about actuator,lol.


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## terrapro (Oct 21, 2006)

Chrisxl64;1343680 said:


> if you feel the transfer case engage, and spin up,,,could it be an auto lock hub problem?


No, we do not feel the case spin up. I can feel the transfer case engage while moving the lever with someone under and someone over. So I assume the transfer case is engaging but the front wheels will not turn...but if i put it in 4low I can feel the torque almost double, it will bend the truck almost...4:56 gear.


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## terrapro (Oct 21, 2006)

Chrisxl64;1343682 said:


> wow,,,feel like a moron rolled down didnt see anyone had already replied about actuator,lol.


No I feel like a moron! I own three of these trucks and don't know where the actuator is, honestly never had a problem until now.


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## 2COR517 (Oct 23, 2008)

terrapro;1343677 said:


> The actuator is on the passenger side facing towards that wheel correct? Surprisingly I have had 4 of these trucks and never had a problem.


Correct. Looks like this.


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## terrapro (Oct 21, 2006)

2COR517;1343903 said:


> Correct. Looks like this.
> 
> View attachment 102549


thanks 2COR! From what I have found they are around $80?


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## terrapro (Oct 21, 2006)

Nope not it. So next on the list is the transfer case switch. Local store couldn't get it for me until tomorrow but we havn't tested it yet anyway.

BUT in the process of testing for the 4wheel we managed to blow the wheel cylinder in back. I was going to rebuild the back brakes anyway, better sooner than later I guess.


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## 2COR517 (Oct 23, 2008)

terrapro;1343926 said:


> thanks 2COR! From what I have found they are around $80?


That's about the right price. Even though it is currently working, you might consider a couple options. First is to simply put a spacer in axle housing then screw the actuator in. A 3/8 drive socket, about 7/8, works well. A lug nut will work too. The big advantage to the spacer is that you will have instant 4wd when you pull back on the lever. The disadvantage is a slight impact to fuel economy. On a one ton with 4.56 gears it's not going to make much difference.

This is the other/best option..

http://www.4x4posi-lok.com/


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## terrapro (Oct 21, 2006)

Well I have now replaced the acuator and the TC switch and patched some broken wiring but still won't work. My tester is on the fritz so I can't check for voltage yet but I have to assume I have more broken wiring somewhere because I can't think what else it could be.


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## Chrisxl64 (Dec 10, 2008)

2COR517;1344343 said:


> That's about the right price. Even though it is currently working, you might consider a couple options. First is to simply put a spacer in axle housing then screw the actuator in. A 3/8 drive socket, about 7/8, works well. A lug nut will work too. The big advantage to the spacer is that you will have instant 4wd when you pull back on the lever. The disadvantage is a slight impact to fuel economy. On a one ton with 4.56 gears it's not going to make much difference.
> 
> This is the other/best option..
> 
> http://www.4x4posi-lok.com/


Cor Im missing the concept here,,,can you re-explain?


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## mcwlandscaping (Sep 8, 2005)

Chrisxl64;1345736 said:


> Cor Im missing the concept here,,,can you re-explain?


Two things happen when four wheel drive is engaged: The transfer case is shifted and the front differential locks into the driveshaft via the electric actuator mentioned above. If you take the actuator out and put your finger in there, there is a spring loaded plate the the actuator pushes on to do this. What 2COR is saying is to put a spacer in the tube that always keeps that spring plate compressed keeping it locked in all the time so the only thing left to shift to get 4*4 is the T-case.

This is how ive engaged the 4*4 on my 97 for the last couple years as I cannot for the life of me figure out why I can't get power to work in the plug for the actuator (mine is the new style though). I use a lug nut with a valve spring on it ;-)

The other option that ive done before is to take that older style Thermal actuator like 2COR posted a picture of above and wire it into its own switch on the dash. That way you eliminate the possibility of the switch on the T-case failing to send the signal to the front diff actuator on its own.

OR you can get a GM update kit that converts your old style thermal wiring to the new style actuator which is a much faster and reliable system. But if your T-case actuator switch is faulty that would still have to be replaced to be able to do that conversion.


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## Plowtoy (Dec 15, 2001)

mcwlandscaping;1346234 said:


> you can get a GM update kit that converts your old style thermal wiring to the new style actuator which is a much faster and reliable system.


This is the best way to FIX your problem IMO. I did a bunch of these in the late 90s when i was working at the dealership. Its a pretty simple upgrade and not real expensive


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## terrapro (Oct 21, 2006)

Plowtoy;1346557 said:


> This is the best way to FIX your problem IMO. I did a bunch of these in the late 90s when i was working at the dealership. Its a pretty simple upgrade and not real expensive


Unfortunately I have already dropped $100 on trying to fix the problem so I am kinda commited now. I am pretty sure it is a wiring problem, what else could there be?

Anyone know anything about these 88 K3500 camper packages? I just put about 25 miles on it around town and it is a torque monster. Its not the power from the motor but its got to be the gearing. Did they put a different build on the trans because the shift points seem lower and of course being a 3 speed with these gears in the rearend it doesn't like to go faster than 45mph without the motor feeling stressed.


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## 2COR517 (Oct 23, 2008)

Does the truck have a tach?


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## terrapro (Oct 21, 2006)

2COR517;1347706 said:


> Does the truck have a tach?


No tach. It shifts with light throttle from 1-2 at 10-12mph and 2-3 at 22-25mph, heavier maybe almost half throttle 1-2 18mph and 2-3 at around 30mph...seems alittle low to me. But I think the speedo is off as at 45 on the speedo people are usaully just barely passing me in a 55mph zone.


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## Chrisxl64 (Dec 10, 2008)

If your lucky enough to have your build codes, that will tell you what rear gears you have.

Codes for rear ends:
G75 3.70 rear 

G76 3.36 rear axle ratio 

G80 Positraction rear 

G82 4.56 Rear axle 

G84 4.10 Rear axle 

HO5 3.73 Rear Axle


If not,,,you could always pop the cover, and check the gears themselves. Never hurts to change diff fluid anyhow.


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