Reversing in 4X4

I am restoring a 86 4x4 and had a professional shop install redo the transmission. When I left the shop, the 4x4 function worked great at the coast in the sand.

Around Xmas went to the mountain and upon reversing I heard a pop in the front end. It only happens when you I back up in 4x4. The pop is unnatural to any 4x4 I have ever owned.

It has manual locking hubs, whats interesting is that prior to making that bob it was really hard to engage the locking hubs. After the pop they are really easy to engage.

A few things I wanted to clarify. I know with every 4x4 I have owned its recommended to run it in 4x4 every once in a while to get all the oil flowing to the right places. I read somewhere (dont remember where) that you should never do that with those toyota vans and not on dry pavement? Is that true?

My other question is when locking hubs are locked can you drive it and shift on the fly with no problem... I know you cant be going more then 50 miles an hour.

Any advise / tips would be most appreciated.

M.

There should not be popping sounds in reverse.

The fact that the hubs were hard to turn before but now are not, after the noise occurred, would lead me down the road of inspecting/overhauling the hubs.
They do need to be serviced from time to time.

As to the other questions, never use 4WD on dry surfaces, there is no central diff to absorb different speeds of the wheels (think cornering).
It will tear itself to pieces if you do use it on high traction surfaces.

Once the hubs are locked (and working correctly) you can shift on the fly.
Don't know about the 50mph thing but I DO know I have successfully engaged at speeds of up to 120Kph (~70mph) without incident, just make sure the fr wheels are pointed straight ahead.

Thank you much appreciated. So wet pavment as your leaving a a ski area let's say ( untill your able to switch to 2x4) is ok right?

Thanks again!

Short distances with minimal steering input are acceptable.
Leaving the hills, you're probably okay but once you're past the ice/snow/loose gravel you'll want to have it in 2WD.
It's easy enough to shift, so there is little reason not to.
I'm in the snow belt and the conditions are variable at best, I am constantly mowing between 2Hi & 4Hi in the winter.
I've also been known to slide over a little to put 1 side into the snow just outside of the worn dry part, all just depends on the conditions.
Generally speaking, I wouldn't use it for rain, unless the roads were like rivers.

You'll want to limit "dry" use as much as possible, within reason, you'll get the feel for it soon enough if you pay attention.
Backing with steering input is the most noticeable, it will jump and squirm and bind if you try it.
(it winds up the drivetrain till something breaks free and releases the tension, hopefully that's the tire losing traction and not a U-joint, etc.,)
If you have trouble shifting from 4Hi-2Hi that is also an indication that things are winding up.

You'll wanna inspect those hubs before doing much driving though, if they aren't functioning properly, that could do some nasty damage, in short order too.
BB

Noted and I will get those hubs checked out. Thank you again :-)

Does the dry pavement problem mean that 4wd differentials are locking and can't handle stress of regular surfaces? Sorry but of a noob here but why would dry pavement cause this? Is this true for manuals hi lo and automatic? Thanks in advance.

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Originally Posted by Burntboot

Short distances with minimal steering input are acceptable.
Leaving the hills, you're probably okay but once you're past the ice/snow/loose gravel you'll want to have it in 2WD.
It's easy enough to shift, so there is little reason not to.
I'm in the snow belt and the conditions are variable at best, I am constantly mowing between 2Hi & 4Hi in the winter.
I've also been known to slide over a little to put 1 side into the snow just outside of the worn dry part, all just depends on the conditions.
Generally speaking, I wouldn't use it for rain, unless the roads were like rivers.

You'll want to limit "dry" use as much as possible, within reason, you'll get the feel for it soon enough if you pay attention.
Backing with steering input is the most noticeable, it will jump and squirm and bind if you try it.
(it winds up the drivetrain till something breaks free and releases the tension, hopefully that's the tire losing traction and not a U-joint, etc.,)
If you have trouble shifting from 4Hi-2Hi that is also an indication that things are winding up.

You'll wanna inspect those hubs before doing much driving though, if they aren't functioning properly, that could do some nasty damage, in short order too.
BB

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I have had toyotas all my life. Especially 4x4's, I live in snow country.

It's NEVER recommended to drive on dry pavement with the hubs locked in 4 hi, and especially low. Theres a huge potential for binding in the hubs and transfer case... on dirt, snow and really any other surface that offers limited traction, theres room for play in the system, ergo no binding... Just a good rule of thumb.

And after having taken apert and rebuilding various types of locking hubs from Asin's (auto and manual), ford, warn, superwinch and on and on... all I can recommend from the symptoms you gave is to pull the locking hubs and have a look... I have run into a few instances on Toy's that had some pretty bad neglect and needed to really just be cleaned and regreased so the spring and gears inside were able to move freely and engage. Then I have had other scenarios that had cracked gears/ broken springs/ internal parts that needed to be replaced. From playing with these, they appear to be any standard locking hub from 85-95 toyota ifs 4x4's.

Should be part # Aisin FHT018

Hope that helped.

It would be a good idea to disassemble and inspect the locking hubs but, if I understood your original post, it only popped once and hasn't done it since, it's probably ok.

My van, MasterAce Surf 4WD with auto transmission, says specifically to stop and put in neutral before you engage the 4WD. I didn't once, left it in drive while coasting. The 4WD did engage but I heard and felt bumping sounds. I believe the 4WD did not fully engage, I'm really glad I didn't put any real stress on it. Ever since, I've always put in neutral and no issues.

Grant - It has nothing to do with the strength of the units.

When 2 wheels on one axle go thru a corner, the outside wheel has to travel further than the inside wheel.
On loose surfaces this doesn't pose a problem as one wheel will slip and accommodate the speed differential but on dry pavement, traction is high, the tires don't want to let go of the road and the forces are transferred into the drivetrain until something lets go, hopefully a wheel slips but it can cause breakage of hard metal parts too.
Your axles (both front and rear) have a "differential" to accommodate this action, but linking the fr and rear axle together, recreates the same situation.

There are 2 ways of solving this problem
1) have the driver shift out of 4WD
2) add yet another differential to the centre of the vehicle, adding complexity and weight, increasing fuel consumption, maintenance requirements and driveline power loses

"Modern" AWD's employ the 2nd method


As far as shifting on the fly, don't know about that JDM stuff, but NA 4WD vans are considered SoF and I have done so for many years without issue.