LJ77 electric to manual hub conversion

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Feb 1, 2017
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Hello,
I just converted my 1991 LJ77 OEM electric hubs to manual AVM hubs from Euro4x4. The conversion mechanically went fine, but 4WD is not engaging (front drive shaft spins when hubs are locked). Prior to conversion the dash push button Hub Lock and 4WD buttons worked fine. Now the Hub Lock light turns on, but 4WD light does not light. Is there anything electrical that needs to be done to allow the 4WD to engage?
Thanks
 

Tapage

Club 4X4 Panamá
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but you said front DS spin free with both hubs locked and both front tires on the ground ..?
 
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Nigeria
Sorry I'm new to the 70 series ownership, but if its an electric engage 4wd in the T case would it be wired so that it needs to see voltage that the hubs are locked before it engages the 4wd?
 

divemedic

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Prior to converting to manual hubs, did 4wd in fact work? Is there a reason you converted to manual, or is it because that's what everyone does? Did you convert as part of a front axel rebuild? Did you kit have spacers or shims, and are they configured correctly?
 
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So prior to the conversion one of the electric hubs was not locking/engaging, so I assumed that is why front wheels did not spin when 4WD was engaged. Once the nonfunctional hub was apart, we got it working, but the two spring-loaded electrodes were worn out. From an electrical standpoint prior to the conversion both the Hub Lock and 4WD lights would come on when I activated them on the dash. Front drive shaft would spin when all 4 wheels were on the ground and truck was rolling with this scenario, but no power getting to front wheels. I think this means that everything mechanical is working in the transfer case, but maybe not?
Converted to manual as this was recommend by people who off-road; I'm new to this obviously.
I did not replace the axle, did re-do several brake components.
Let me clarify my prior post, too. I still have the front up in the air (rear is on the ground) and no tires on as I still have to bleed the brake lines. When I lock the hubs and spin the rotor/hub the front DS spins. If I put it into gear with the hubs locked, shouldn't the front tires NOT spin if the rear tires are on the ground if 4WD is engaged? I think mechanically everything is sound, but Troopie75 might be correct that the T case needs to see voltage from the hubs before engaging. Is there a way to bypass that anyone can tell me?
Thanks
 
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It is not common for the tcase actuator to require some movement before it engages. If you have the truck stationary and just hitting the button and expect the actuator to quick right in, thats your problem. There are gears that need to mesh, put the truck down on the ground and drive it and it should engage. With it engaged jack it up and you should see the driveshaft engaged when you try to spin the wheels by hand.

As far as the voltage bypass for e-hubs, you need to have both the "hub" button and the "4wd" button pressed, pressing the "hub" button will make the actuator think the hubs are engaged. I am sure there is a way to bypass, but i just push both buttons.
 
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It is not common for the tcase actuator to require some movement before it engages. If you have the truck stationary and just hitting the button and expect the actuator to quick right in, thats your problem. There are gears that need to mesh, put the truck down on the ground and drive it and it should engage. With it engaged jack it up and you should see the driveshaft engaged when you try to spin the wheels by hand.

As far as the voltage bypass for e-hubs, you need to have both the "hub" button and the "4wd" button pressed, pressing the "hub" button will make the actuator think the hubs are engaged. I am sure there is a way to bypass, but i just push both buttons.
Thanks, that helps. Maybe I prematurely became concerned. I should have the brake lines bled tomorrow and will take it for a spin and see.
 

kbushnz

 
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Be Aware that the 4x4 engagement in the transfercase is a vacuum diaphragm operated by solenoids. So the engine needs to be running.
Also when in H4 you need to push the 4WD button to make it work. If in 4L it will operate automatically.
Now the old system of lights (and engagement) was controlled via the switches you pushed and a little controller.
Now you have manual hubs when you engage them push on the hubs button. Then when you hit the 4wd button and the actuator moves in the transfer box the 4x4 light on the dash will illuminate. Then you should have the drive shaft locked up...
Make sense ?
 
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Be Aware that the 4x4 engagement in the transfercase is a vacuum diaphragm operated by solenoids. So the engine needs to be running.
Also when in H4 you need to push the 4WD button to make it work. If in 4L it will operate automatically.
Now the old system of lights (and engagement) was controlled via the switches you pushed and a little controller.
Now you have manual hubs when you engage them push on the hubs button. Then when you hit the 4wd button and the actuator moves in the transfer box the 4x4 light on the dash will illuminate. Then you should have the drive shaft locked up...
Make sense ?
Yes, thanks, that makes sense. I bled the brakes today and got the tires back on. As soon as I started it the 4WD engaged and worked perfectly, both in 4H and 4L. I don't have an owner's manual for the truck, and haven't experimented yet, but are you saying I can lock the hubs (now manually) and put it manually into 4L and I don't need to push the dash 4WD button for it to engage? Or does the 4WD button need to be pushed for the manual 4L to engage?

Thanks again
 
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Once the hubs are locked, 4H is push button only, and can be done on the fly. 4L is manual only with the transfer case stick, and must be done when stationary with the transmission in neutral.
 

kbushnz

 
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Once the hubs are locked, 4H is push button only, and can be done on the fly. 4L is manual only with the transfer case stick, and must be done when stationary with the transmission in neutral.
I cannot do the H4 on the fly well maybe walking pace.... will graunch every time....And looking at the gear sets there is no synchro...
When you move the lever to 4L it only activates a switch in the box to activate the solenoid to activate the vac diaphram.
Its not directly connected with rods / levers like the old school crusiers.
 

coldtaco

 
 
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I cannot do the H4 on the fly well maybe walking pace.... will graunch every time....And looking at the gear sets there is no synchro...
When you move the lever to 4L it only activates a switch in the box to activate the solenoid to activate the vac diaphram.
Its not directly connected with rods / levers like the old school crusiers.
You should be able to go to 4H on the fly, that's what it's for. Have you tried it with the hubs locked? Today it was grinding trying to get into 4H and I pulled over to check my hubs and they where unlocked. I locked them back in and now it goes into 4H without any problems.
 

Gun Runner 5

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Sadly there is no dash indication that confirms that the electrically actuated hubs actually engaged or disengaged. One of many issues with these hubs.
 

kbushnz

 
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You should be able to go to 4H on the fly, that's what it's for. Have you tried it with the hubs locked? Today it was grinding trying to get into 4H and I pulled over to check my hubs and they where unlocked. I locked them back in and now it goes into 4H without any problems.
Interesting.... I tried it once early on in my ownership (20 years ago) and it did the big graunch.... And never did it that way again, can't recall if the hubs were locked... Will try it again when back out on the trail, truck is in the last throws of having a major mod / repaint.
 
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I'm having the same or a similar problem. I bought my LJ78 with preexisting locking hubs, and until a few weeks ago, they worked fine. To engage 4wd, I have always followed this rubric: 1) turn hubs to 4x4 2) while stationary, press both the Hub Lock and the 4WD buttons on the dash. 3) expect the 4wd to engage once I start moving in gear. This is all in 4wd high of course.
Now, the Hub Lock light comes on, but the 4WD light does not, and my front wheels do not go into 4WD. 4wd low does not seem to engage the front wheels either, though the low range is definitely working, and the transfer shift lever works properly.

Ideas:

A bad solenoid in the transfer case?
A loss of vacuum pressure in the transfer case?

I can't imagine I've actually broken the transfer case mechanicals. I rarely use 4WD, and don't go rock crawling. Please tell me this is something simple (and cheap!) to fix.
 

kbushnz

 
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I have had the same thing before. turned out the shaft was a bit sticky thru lack of use.
But as you have stated check the following.
Solenoid is working (on firewall little plastic thing in a pair mine are next to brake booster)
Vacuum diaphragm is sound on transfer case.
The system used vacuum pressure from the brake booster.
You can remove the vacuum diaphragm unit off transfercase, but some oil may come out. Then you can manually push and pull the rod.
 
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