4x4 driving problem

[rsdata]

Sorry for the throughly newbie question here. First problem I have ever had with my '96 Tacoma 4x4. Today I had to put it into 4 wheel, H4 range, to retrieve some firewood in a field. I loaded it down pretty good. When I left the field and hit the pavement I attempted to put it into H2 range from H4. It never indicated on the dash that it left 4x4. I had a 20 mile drive ahead of me, and I stopped and tried to shift into H2 range several times. I finally just drove home with the load of firewood. I was on paved road and went only 35MPH for about 12 miles. I hit a 2 mile stretch of 55MPH and I did do 40-45 on that 2mi stretch. When I pulled off onto a rural road again, I heard some dragging sounds and the Tacoma would not roll easily and had oil smoke and fumes coming from underneath. At that point I was only 3 miles from home, so I hitched a ride home. I returned with some tools. I disconnected the drive line to the front wheels. I was then able to shift to H2 range and drove home fine in 2WD.

My question is... I know I should not have drove in 4WD on paved roads at speed...
1. why could I not shift into H2 from H4 when I have done this many times in the past, and had done it earlier in the day? Did my heavy load of fireqood have anything to do with this?
2. where do I start to look at to determine what is now messed up? I suppose an oil change to the transfer case is necessary.
3. Not sure what else to look for or how to proceed.

Thanks in advance for any help offered...

 

[liljlandon]

Did you reverse and rock the wheels back and forth? How often do you use 4wd?

It sounds like you may have heated up the diff, I'd check the fluid level in it first. The transfer case may not be the culprit. If you shift the lever into 2h, it physically disconnects the front output.

There are a few plugs that go into the actuator that engages/disengages your front end. Are they still connected?

Still a lot of variables currently.

 

[SteveH]

check all your fluids for condition (I would drain and replace and look for metal shavings) and level first, try going in/out of 4WD with no load, and the report back.

 

[Jetboy]

While not recommended, driving in 4h on dry pavement isn't going to cause damage unless something else is wrong. I've done it many many times.

Having smoke is a very unusual situation. I'd look for a burned up actuator or some type of electrical short in the front diff. Beyond that, I would look at the front pinion bearing or possible one of the front differential carrier bearings as a failure point. One first thing you could try is to see if the front driveline can freely be rotated by hand. The more I think about it the more I suspect a front pinion bearing.

 

[rsdata]

thanks for all the information... this gives me something to look at. THis is not my main transportation and I only use the 4WD occasionally, but it has never been a problem. This 96 Tacoma has been a work horse for me forever. I haul 2100# of water in a 250 gal tank all summer as I do not have city water. I occasionally use the 4WD when driving on snow/ice or in a field.

I am currently getting things around home ready for the coming winter, and I will be checking this out in the next week. Can anyone tell me what the fluids are in the front diff?

Again I appreciate the input and knowledge on this forum. My other vehicle is a '97 Land Cruiser... that thing is a tank and I take it all over the place.

 

[john505]

that truck have for old type manual pull handle for the 4x4 or the electric switch in it

 

[Haggis]

I think Jetboy is on to it. I have driven mine in 4wd on dry, paved roads countless times. Hopefully the damage, cost is not too much. They are amazing trucks in regards to their durability/ reliability.

 

[rsdata]

I just got back from a garage that has done work on Toyota 4x4 but is not a specialist. Their diagnosis is that the bearings in the front differential have overheated and are now locked up. The front diff will not turn by hand.

He took the vin number and said he has to determine what the gearing is before he can look for a salvage yard part.

Can anyone tell me if it is likely that I can drop the front axle, open it and maybe replace what is bad in there. Is this a likely candidate for a junk yard diff.

I have used the 4x4 sparingly on occasion maybe 6 times a year, but only for short excursions into nearby fields usualy to get firewood. THis is what I was doing this time when I could not get out of 4H range and proceeded to drive home and cause this mess. Probably the only time I have been in 4x4 for any distance was maybe 55-6 years ago, driving on a snow covered road for about 12 miles.

The mechanic said that sometimes the actuators go bad which is why I might not have been able to get out of 4H. He also said that driving with the front drive whaft off in 2H would not harm the vehicle.

Any insight into this front diff problem and what I might be able to do now would again be appreciated...

 

[Jetboy]

I would look for a replacement. If it's stock gearing, they are going to be much cheaper to find a nice used version than the cost of fixing.

It's likely that you could find the bearing that went south (I'd almost guarantee it's the pinion bearing) and replace it. The problem is that it's somewhat time consuming to repair because you'll probably end up cutting the inner race off and there's a good chance it ruined the carrier housing race seat. Just depends on how bad it is. The one time I burned up a pinion bearing that was the case.

A replacement for an ISF diff is probably $50 or so.

You can check the gear ratio by the paint color on the end of the pinion flange. Toyota color codes them from the factory. That is an easy way to tell what diff gearing you're looking for and whether the one you want to replace it with is a match.

Most likely your diff was low on, or out of fluid, or you had water in it. These are not wear parts and should essentially last the life of the vehicle if maintained. I would suggest once fixed, getting it out and driving around in 4x4 a couple times a year to help keep the bearings lubricated.

Good luck.

Edit: To be clear, I think a used diff can be found for $50, but I would not expect to get it swapped by a mechanic for that price. There's quite a bit of work involved. I don't know what that should cost. I'd take a wild guess at $2-300.