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FJ80 transfer case and other woes

Discussion in '80-Series Tech' started by kallen123, Nov 9, 2003.

  1. kallen123

    kallen123

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    Ok guys, I need your expertise:

    Because of a bad VC unit, I'm going to bite the bullet and have my transfer case replaced (after much thought and deliberation -- going to put money into my 80 instead of purchasing a used 100).

    Figuring it's going to cost me an arm and a leg (planning to do work through dealer), I want to get everything else up to spec too. Several minor rear differential-related clunks also exist so I am going to try to have everything clunk-free when all is said and done.

    Can you give me some suggestions about what I should have serviced in order provide clunk-free driving? (aside from the standard transmission backlash of course) Is there such a thing as a rear diff overhaul? How bout axle service? Or bearing replacement if needed?

    I'm somewhat mechanically-challenged, so I don't know what I don't know and if I'm going to spend some money to give my LC a few more years, I'd like to do it right.

    Thanks for the help!

    kent allen
    1994 80
    101k mi.
     
  2. Pitbull

    Pitbull

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    Kent they all clunk. Just change all of the fluids to synthetic and drive it. If something breaks fix it. I know 2 people that own 80 series with over 200K miles and have never changed anything other then oil and filter, and they are still going. (I'm not suggesting you not maintain your LC) just an example of how over built these trucks are. Why would you want to pay someone to rebuild a functioning rearend before it needed it???
     
  3. Beowulf

    Beowulf

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    Kent,
    Like Pit says, they all clunk to some extent.

    Refresh our memory on why you have determined you have a bad VC?
    What makes you determine your clunks are abnormal?

    -B-
     
  4. cruiserman

    cruiserman

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    To save a lot of dough, I would source a used unit and install it yourself. There is someone on the forum looking for a bad viscous coupling IIRC.
     
  5. IdahoDoug

    IdahoDoug

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    Kallen,

    What's the deal with your VC being "bad"? At only 101k miles your rig qualifies as a creampuff since by now it should have nearly 50% more miles.

    Doug
     
  6. IdahoDoug

    IdahoDoug

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    Kent,

    I reread the original thread you started on this, and have given the "bad VC" issue some thought due to subsequent dialog with Kurt. I'll make a bet with you. I know you need new tires (you have 58,000 on these) and you're going to keep the 80 for a long time. So, replace the tires before you visit another mechanic or spend another dime - you've got to get them anyway especially with winter on the way.

    Take the truck for a drive and my bet is that the VC will not lock. If it does, you've lost nothing since you needed new tires. If it does not and all is well, you owe me your undying respect and a cup of coffee next time I'm in your area. I'll even go a step further and recommend a specific tire if you're only driving on the road - the Michelin CrossTerrain in stock size 275/70-16.

    I am 99.9% sure your problem is due to differences in circumference from wear causing the VC to heat up. In the other thread you said you were sure that tires were not the issue since you put new tires on it in 1998 (cough, cough) :slap: What do you say?

    Doug
     
  7. kallen123

    kallen123

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    OK here goes:

    Bad VC unit:
    My center diff locks up after an hour of driving or more at hwy speeds. Based on other's experiences here, it seems that it's a bad VC unit, since a replacement VC unit seems to have solved their problem (which was identical to mine).

    Clunks:
    I have noticed some "newer" clunks (somewhere from the rear diff it seems after turning a corner, upon acceleration). Call me crazy, but these things drive me bonkers and I'm willing to pay to make them disappear. The only clunk I CAN live with is the transmission backlash. Is there such a thing as a "rear diff overhaul?"

    Steering tightness:
    The steering seems rather tight at times on short drives (and NOT from the center diff locking).

    Tires:
    Yes, I was going to go for new tires as part of this repair investment. My point in the old thread about new tires in '98 was that they were all the same brand/model -- not mismatched -- and I would assume the same circumference (although my left rear tire needs a little air -- Aha! I'll try it) Believe it or not, with 60k mis. on them, the tires still look like they have life in them and have some tread left. But I see your point IdahoDoug (and yes, I would be forever indebted to you for that tip!)

    As for new tires, the rig stays mostly on road, but I do occasionally put it to the test off-road :).
     
  8. Beowulf

    Beowulf

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    Kent,

    >> since a replacement VC unit seems to have solved their problem <<

    If you are referring to Kurt, I think the jury is still out on exactly what was the cause of his Xfer overheating and locking. To fix, he replaced the complete transfer case. I think he has determined his VC was OK and he is replacing all the bearings in the Xfer and rebuilding it.

    >> (somewhere from the rear diff it seems after turning a corner, upon acceleration). <<

    Have you serviced the rear FF axle? It has bearings that need grease; it has an axle tube seal that isolates the rear diff fluid from the bearings. Several of us have found *no* grease in the bearings when serviced.

    (Later...)
    I'm not suggesting dry or bad wheel bearings will cause a clunk... I'm suggesting that doing this service will get you a good look at the end of the axles; the flange, the axle nut, the pre-load, and the bearings. If you have no grease and no gear oil then the noise *could* be coming from the wheel.

    >> Yes, I was going to go for new tires as part of this repair investment. <<

    I agree with Doug... start here, then look at the rear bearings and do a full service on the rear axle.

    -B-
     
  9. IdahoDoug

    IdahoDoug

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    Many or all of these symptoms can stem from tires not matching. You still seem determined to drop a bunch of $$$ on a "repair investment" and I'm telling you for the last time that it's highly likely to be tires. The clunks, VC overheating - even possibly the steering having a strange feeling. I'll give you a bit of insight into how sensitive the system can be to the tire diameter issue.

    I back out of our driveway and turn 90 degrees, come to a full stop and shift into drive routinely. One day this summer, I got a clunk upon the shift into drive. A couple days later when I next drove it - same thing. Concerned, I pulled it back into the garage and found my LR tire (inside tire on the turn) was 10lbs low vs the others at 45. Filled it, and have never heard the clunk again. My 2.5yo son plays with the valve stem caps (translation: removes them, chews on them and drops them in that great repository in the sky) and had progressed to playing with the valve.

    So relax. Your tires are definitely NOT the same diameter unless you've done an anal job of rotating them (lessee, that would be over 10 rotations during that time). In all likelihood, you're not used to this being an issue like many on this board. It's a very tight tolerance to prevent activation of the VC. My AWD Subaru actually calls out a maximum tire diameter variation of 0.0790" as the threshold of acceptability. It's worth noting that ANY tire variation on your cruiser generates heat in the VC. The greater the difference, the greatere the heat. The greater the vehicle speed, the greater the heat. Add these two effects and what do you have? Why, a VC that locks up after a bit of high speed driving, but acts normally when you first hop in. If it acts up around town also, you've got a very large tire difference - simple.

    The VC is about the simplest and most durable thing on your truck. It has no wires, no sensors, no motors, - nothing. Looking at it as the SOURCE of the problem is simply wrong. It's FAR more likely to be a SYMPTOM of another problem - i.e. a tire diameter problem.

    Whew. I'm having a hard time finding new ways to say this.......

    Doug
     
  10. Riley

    Riley

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    Ok Doug, you've sold me and I don't have any problems with my VC. But now I've something new to think about.

    What's a good interval for tire rotation on the 80?

    And on the standard Michelin LTX tires, should I be rotating to the other side (or are they particular about rotational direction)? Anybody know?
     
  11. IdahoDoug

    IdahoDoug

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    Riley,

    If you really want to wear them down to the wear bars and still have them even, I'd rotate every 7500 miles or so. Obviously, more rotations are better, but this would be a good number to shoot for and coincides with the Schedule A longer oil change interval for convenience. The LTX is a nondirectional tire, so you can do as you please, but I simply rotated them F/R. Somewhere I have heard that once the tread blocks are feathered (run your hands along the tread in both directions to feel it) in one direction, you'll cause faster wear if you rotate them in the other direction as the little high spots on the tread block edges get quickly ground off.

    You don't have to go nuts and I know everyone here is fond of saying "but it's such a heavy vehicle it's hard on tires.." Malarky. If yours is hard on tires, it's because your tires are mismatched and the VC locks up on the freeway and grinds the crap out of the tires until they're even (and costs you MPG) again. In my experience the 80s are easy on tires becase the tire size is relatively large (275) and they're full time 4WD.

    If you spend a lot of time on winding roads, you'll need to shorten the interval as the fronts will grind off in an accelerated way. Keep em properly inflated, too.

    Doug
     
  12. kallen123

    kallen123

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    Ok IdahoDoug, hear you loud and clear. You're reasoning makes perfect sense to me (VC as a sympton, not a problem)

    Here's my plan:

    - New tires
    - Road test
    - Rear axle service (is there a technical name for this service or is that it? And what's a typical cost for this?)

    I'll report back with good news hopefully! Thanks again for the expert insight!
     
  13. IdahoDoug

    IdahoDoug

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    Excellent! And the bonus is that it's time for new skins anyhow. Also, we're assuming your transfer case is properly filled with gear oil, eh? Removing the upper plug, you simply stick your pinky in and should feel the level at or close to the fill hole. It's a half banana 3 minute check and doesn't require the vehicle to be on jacks. Just slide under with a 17mm socket or wrench and a flashlight. Note there's an identical plug below it that is the drain. Both are on the rear face of the transfer case, I believe.

    Let us know about the VC behavior after the tires and we'll pick up at the rear axle stuff. It's way less than the front axle.

    Doug
     
  14. landtank

    landtank SILVER Star

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    Go Get em Doug!!!! In no time you'll almost have everyone rotating their tires ;)
     
  15. IdahoDoug

    IdahoDoug

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    Nah, then you're all gonna blame me for stripping the wheel lugs. :rolleyes:
     
  16. landtoy80

    landtoy80

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    Kent, How hot does your t-case get? Mine would got so hot you could fry a egg on it. The VC would lock up and not release untill it cooled down. This was after a hour or driving at 70mph.

    As for chunk, go to a gravel parking lot and drive in circles and see of you see and hear a chunk from the front wheels. Keep going round and round to see if you can lock the vc. Do the same after you drive on hwy and the VC seems to lock.

    My birfields were worn and when the VC would lock the weakist link in the drive line was the worn birfields, they would pop.
    I don't know how the rear end could pop.
    My front diff bearing didn't need replacing when I put new bearings in it so I haven't rebuilt the rear yet.
     
  17. Beowulf

    Beowulf

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    Kurt,
    Have you decided that your original VC was OK? When you are rebuilding the Xfer, are you replacing the VC, the bearings, or what?
    -B-
     
  18. landtoy80

    landtoy80

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    I am not sure about the VC.
    I will wait for a rebuild kit to rebuild it. There is only one way to see if the VC is ok, when it gets rebuilt, I will find out if its ok.
    I wounder if the lower gear kit for the t-case would be cheaper than regearing the diffs. This way I could use big tires and small tires with just swaping out the t-case.
     
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