diagnose 4x4 problem (1 Viewer)

[GaryN]

Hi All,
I'm the new owner of a very nice series 80.. and need help diagnosing a problem with the 4x4.
I took the basic 4x4 course from Tom in Hungry Valley CA last weekend, only to discover the 4wd wasn't kicking in. We took it home, jacked all 4 wheels off the ground and verified that the locking hub are operating, that both front wheels move when in 4hi and 4lo, and that both wheels move together when the front diff lock is engaged. It "appears" that 4wd is working, however it clearly wasn't during the class - the vehicle fishtailed (spinning back tires) up the same hill other vehicles cruised up. Both instructors were unable to get the front tires engaged.
My guess, at this point, is that one of the hubs is failing when under stress. Does anyone have other ideas of tests I could perform?
I'll be uploading a picture and stats into the "vehicle registry" next.
Thank you!
-Gary

 

[jonheld]

It would be helpful to know the year and country of origin.
US spec 80s don't have locking hubs and are full time 4WD with a lockable center differential.
Other countries got locking hubs and part time 4WD as well as some other goodies, like manual transmissions.

 

[Frankencruiser]

So you have diff locks? The lights come on in the dash? Does it make a loud banging noise when the "slipping" is happening? Do you have front locking hubs or just diff locks? Locking hubs are aftermarket on a U.S. 80 series.

 

[GaryN]

Thank you for the help folks,
Its a 1994 FZJ80 with
- factory locking differentials front and rear
- 700r4/split transfer case
- front locking hubs

I don't know the country of origin, its definitely part-time 4wd.
The diff lights come on when enabled, and we verified that the wheels move in tandem when the vehicle was completely off the ground. When the front diff lock is off, the front wheels do not move in tandem. There is no loud banging noise, though the engine is quite loud (cummins). During the class, going up the slope, the back tires were spinning and the instructor on the ground saw no power going to the front. I need to find a slope to test out the 4wd. Any other tests I could perform, with the vehicle off the ground? I can't think of another test, that wouldn't involve the vehicle jumping off the jacks.
-Gary

 

[GaryN]

BTW, I "registered" the vehicle here https://forum.ih8mud.com/80-series-tech/218093-80-series-registry-57.html#post7701132

 

[jonheld]

If the front diff was locked, and assuming at least 1 hub was functioning, you should have gotten drive to at least 1 front wheel. I suppose it's possible you weren't fully engaged on the transfer case.

Hard to say without further diagnosis. You need to determine if the front drive shaft is spinning under the same conditions you experienced the problem. If the front drive shaft isn't spinning, the problem is in the transfer case. If it is spinning, there is a disconnect to the wheels. Could be bad hubs, or broken internal bits. In that case, a clear sound would indicate the problem area.

 

[GaryN]

Hi Jon,
Thank you for the help. The drive shaft spins as excepted. Its conceivable that the cabling to the t-case fails intermittently. I DID notice that the hub locks were somewhat intermittent - I'd flip to 4x4 and it wouldn't engage till I rotated backwards.. or I'd flip to 4x2 and it was still locked for a while. No obvious sounds though. I'll need to ask local club folks where I can find a hill to try climb.
-Gary

 

[badmuthatrucka]

If it has factory lockers front and rear, then it does not have part time 4wd unless you have locking hubs. If you have locking hubs, then you have to get out of the vehicle and lock them, not just flip the switch.

I'm confused about what is going on here. Could you walk us through what you do to engage 4wd, bring very detailed? Do you put the transfer case into 4low to get the center diff light to come on, or have you done the 7-pin mod with the center diff-lock button? Do you have to get out of the vehicle to manually turn the selector on the hubs to "lock"?

The answers to these questions will make it far more easy to help get this figured out.

 

[ToyotaDon]

This is a modified drivetrain with a Cummins engine and GM 700R4 transmission. Unknown transfer case, likely GM, and sounds like stock axles with locking hubs added in place of the drive plates.

The common Toyota issues may not be what's causing this problem, unless it's in the axles themselves. Could be ring and pinion or even Birfield failure and the noise of it might not be heard above the clattering diesel. Kind of reminds me of Robby's column in the latest Toyota Trails.

 

[Funner]

I don't know, this thing is so beyond stock that I am not sure where to begin. I know some warn hub kits have a fusible link that is designed to fail before you lose a u-joint or break an axle. I have no idea if the locking hubs on this rig have such a link, but it could be something to look at.
Also, anyone think the electronics could be lighting up the dash indicating the diffs are lcoked, but they are not actually engaging?

 

[86tuning]

if the front propshaft is spinning when you experience this problem, there is an issue with the front driveline.

hubs, birfs/axles, r&p could have failed.

I would check the hubs first, they're easiest to reach. What brand hubs are they? Can you get some spare drive plates to swap them in?

 

[GaryN]

Hi Folks,
Thank you for the help. Yes, the drivetrain is far from stock. Like ToyotaDon said, its a rebuilt Chevy 700r4 , with a series 60 transfer case with a simple (but very stiff) lever shift. The transfer case lever operates in an "L", with the top of the L being 4x2, the bottom 4x4hi, the right lower end is 4x4lo. When in 4x4lo, the vehicle moves much slower.

To engage the 4wd
- hop out and move both SuperWinch hubs to 4x4 flicker photo
- hop back in and start up engine
- on a slight hill, with brake lever depressed - shift into neutral
- as you let off the brake slightly, and the vehicle moves - use the transfer case lever (to the right of the transmission lever) to shift from 4x2 to 4x4hi. It is a very stiff lever - all mechanical.
- at this point, you should be in 4wd
- to shift to 4x4lo - shift to neutral and move transfer case lever to the right.

As for the differential locks, they are factory installed and we verified that they work when the vehicle was completely jacked up. A picture of the lever is here on flickr

The front and rear differentials are stock - here is a picture showing the front drive shaft going into the differential. We could see this spinning when the transfer case was in 4x4hi/lo

The SuperWinch hubs sounds like the likely culprit. A local 4wd enthusiast poo-pooed the SuperWinch brand. When flipping the hubs from 4x2 to 4x4, should the effect be immediate? With the front jacked up, I noticed a distinct delay - I had to spin the wheel a half turn before I saw the front drive shaft spinning. Once it never engaged - I had to flip the hubs back to 4x2 to 4x4 in order for it to engage.

Could I learn something by taking the locking hubs apart, or should I simply get them replaced?

thank you,
Gary

 

[Roadhouse78]

Replace the hubs, they are defiantly not engaging . Get a set of aisins from a 79-85 Toyota pickup or 4 runner.

 

[GaryN]

Thank you Roadhouse78,
I'll whip out the factory manual and see if its a job I can do myself.
Gary

 

[NorCalDoug]

Hi Folks,
Thank you for the help. Yes, the drivetrain is far from stock. Like ToyotaDon said, its a rebuilt Chevy 700r4 , with a series 60 transfer case with a simple (but very stiff) lever shift. The transfer case lever operates in an "L", with the top of the L being 4x2, the bottom 4x4hi, the right lower end is 4x4lo. When in 4x4lo, the vehicle moves much slower.

To engage the 4wd
- hop out and move both SuperWinch hubs to 4x4 flicker photo
- hop back in and start up engine
- on a slight hill, with brake lever depressed - shift into neutral
- as you let off the brake slightly, and the vehicle moves - use the transfer case lever (to the right of the transmission lever) to shift from 4x2 to 4x4hi. It is a very stiff lever - all mechanical.
- at this point, you should be in 4wd
- to shift to 4x4lo - shift to neutral and move transfer case lever to the right.

As for the differential locks, they are factory installed and we verified that they work when the vehicle was completely jacked up. A picture of the lever is here on flickr

The front and rear differentials are stock - here is a picture showing the front drive shaft going into the differential. We could see this spinning when the transfer case was in 4x4hi/lo

The SuperWinch hubs sounds like the likely culprit. A local 4wd enthusiast poo-pooed the SuperWinch brand. When flipping the hubs from 4x2 to 4x4, should the effect be immediate? With the front jacked up, I noticed a distinct delay - I had to spin the wheel a half turn before I saw the front drive shaft spinning. Once it never engaged - I had to flip the hubs back to 4x2 to 4x4 in order for it to engage.

Could I learn something by taking the locking hubs apart, or should I simply get them replaced?

thank you,
Gary

lol...all this information would've been very helpful had it been provided on the first post.

 

[86tuning]

If you cannot find Aisin hubs for a reasonable price, you can buy drive flanges and not bother with hubs any more. You'll use a weee bit more fuel spinning up the front driveline all the time, but not a significant amount. Best part is that they stick out less than locking hubs.

Stock 80 series in north america are all full-time 4wd and use drive flanges. They're mounted with cone washers, so it depends on whether your locking hubs are mounted with them or not. You will want 6 cone washers per side, with 6 lock washers and nuts. Also the dust cap.

 

[CycloSteve]

Hi Gary,

Happy to help diagnose in person this week if you want...have a few acres of dirt and a decent hill to test the lockers and t-case on. Let my know if/when you want to stop by.



Steve

 

[GaryN]

Thanks for the offer Steve!

Brian, thank you for the help

NorCalDoug, yep - newbie mistake.. next time I'll add the meat.