Advice needed: '94 fj80 involuntary ctr diff lock (3 Viewers)

[landtoy80]

Yes, this is the same problem I had.
I wounder how many VC t-cases Toyota sells a year???
When I ordered the second and third t-case from Toyota, they were almost out of stock.
This makes three people that has had the VC problem. I hope it is from PO neglect.
kurt

 

[IdahoDoug]

Is the issue here that your center diff assembly is getting so hot that it causes the fluid in the VC to remain in the thickened state at freeway speeds? If so, I'd be curious if you have a heat issue period. In other words, I'm saying what if the VC action is a symptom that an exhaust pipe is too close, or a better grade of gear oil should be used. I know a bit about the way VC's work, and generally it's within a narrow temp range so they activate quickly. If so, you might cure this with only a few degrees colder operating temp for the unit. This might be as easy as using synthetic gear oil and fashioning a sheetmetal duct to pull more air past the unit. Or it might be as expensive as rerouting a cat or exhaust pipe, and tapping the diff case for cooling lines. Either way would be FAR cheaper than replacement in my book.

IdahoDoug
(edit - just thought of this. It would be easy to get a few data points by those with infrared temp guns taking a reading on the casing of the unit at the end of an exit after a long freeway drive. If yours is 15-40 degrees higher, then we've got important information) Also, could it be that at PO has oil that is too thick in there - major heat source??

 

[landtoy80]

I used M1 gear oil.
If it was from exhaust, the new case would do the same, right???
The 80 I got had 4 used tires that the PO had just put on. Who knows what tire combo he had on before that. I see so many 4x4/awd vehicles with different size/brand tires. Thats a NO NO for the VC.
I should of tried new tires before I tried a new t-case. The used ones were worn on the out side lugs. The bearing were showing ware but not burnt. It is not cost effective to rebuild as the VC is $700


Kallen, are all your tires the size,brand,diameter??

 

[kallen123]

Yes, tires do not seem to be an issue since I've had it. I purchased the 1994 truck in 1998 from a rather suburban lady who used it to cart her kids to soccer and back. 42k miles when I purchased it and set of brand new tires -- I forget the brand, but they were top of the line at that time. At 100k today, I still have the same tires on the truck and the wear is even (almost due for a new set).

I sometimes wonder if there is some other issue in the driveline heating up the transfer case -- I've had some rear differential clunks (slack maybe?) Maybe something else is worn/out of line and is producing heat from bad contact which gets exaggerated at high speeds/long drives?

Kurt, did the new transfer case COMPLETELY fix your problem? I'd sure hate to pour that money in and find out it still heats up.

 

[landtoy80]

Yes.
I also replaced the birfields as they were worn (200,000 mi)
I can't see anythink that could make the driveline spin at different speeds other than wrong tires.
I wounder if a bad bearing/s could cause the heat?
None of the bearing are burnt but are worn.
At 100f temp 80+ mph for 1000 mi, the new t-case didn't lock up till I pushed the center diff lock switch.
kurt

 

[landtoy80]

The heat issue that locks the VC up is when I drive 65+mph. If I drive less than 60 the VC didn't lock up.
I removed the front driveshaft and drove on HWY at 70+mph and the VC still locked up.
Could a bearing heat up but not be brunt when you inspect it?