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Thread: How to solve NV4500 oiling problem

  1. #1
    Wheeler
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    How to solve NV4500 oiling problem

    Last week, I took a somewhat sudden and random road trip in my 6.2L Diesel powered '67 FJ40. My setup is a very worn out 6.2L Diesel, with 6.5L heads & turbo, backed by a GM NV4500 and stock FJ40 tcase. My route took me from NV-UT-CO-WY-MT-WA-OR-CA-NV and totaled a little over 3,300 miles. Up until the last 84 miles, the trip went incredibly smooth! I had ZERO mechanical or electrical issues. Despite the known problems and horrendous state of the engine, it used only 1.5 qts of oil, and averaged about 17 mpg. The new oil recovery can after the CDR worked wonders keeping oil out of the turbo and intake!

    But disaster struck about 20 miles past Susanville, just 84 miles from my driveway. Rolling along at about 70mph in 5th, on flat ground, I felt a sudden drop in power... a "lag." My first thought was I lost fuel pressure, but regardless, considering it hadn't had a SINGLE hickup in over 3,000 miles, I should probably stop. There was a nice place to stop immediately on my right, so I pushed the clutch and slipped it into neutral and braked hard to make the spot. The engine stumbled a few times but stayed running. I went to jump out but it died rather suddenly before I could. I attempted briefly to restart, and but only got a click out of the starter. Not good. I noticed some steam or smoke coming from under the hood, so I popped it, but couldn't really see a cause. Engine was not hot, nothing leaking up top. Looked underneath and saw a massive mess of oil from front to back. I checked the engine oil... almost full. Now I was a bit confused. Oil pressure had been normal (low, but normal for this engine, about 12 psi at idle) before it died. The engine seemed to be locked solid. I rolled the FJ back from the road a bit further and continued looking over it. After a while I tried starting it again, and surprisingly, it fired right up... but with some horrendous metal noises that did NOT resemble rod knock. After a few seconds it abruptly stopped, locked again.

    After getting a ride from a friend and returning with a trailer to bring it home, we went to let it roll onto the trailer and found something unusual. When I pushed the clutch (it was in gear) to let it roll, it did not... but as soon as I took it out of gear it rolled fine (clutch in or out). So I thought why not try starting it with the clutch pressed (I have a horrible habit of starting it in neutral clutch out so I can hold the brake and press the gas as the e-brake is non-existent). Fired right up... let the clutch out, dies... Input shaft on the trans was obviously locked, but why?

    I only have about 25k miles on this setup. But from the beginning I feared that the design of the AA adapter from the trans to the tcase was... poor at best. They use only a sealed bearing to keep fluids separated. So, from the start, I have used the special syncromesh fluid in both the trans and tcase just incase they mixed. For the last year and a half, they have not. Levels in both have always been steady and I've only had to top both off once.

    However, this time, and apparently rather suddenly, ALL of the transmission oil ended up in the tcase. When I popped the drain plugs off at home, this was instantly obvious. Clearly the tcase was shooting oil out of the breather (if not from more places) from have twice as much oil as it should, whilst the trans had less than a half quart left. This must have happened quickly (I'm guessing) because the gears in the trans look ok. I don't see any real damage besides the input shaft bearing, which is easily starved due to its position. Hopefully when I get it apart, all it needs is a new input shaft bearing.

    How in the world can I solve this issue? The fill plug for the trans is a good 3 inches HIGHER than the fill for the tcase.

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  2. #2
    Wheeler
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    I don't have a solution, but that really sucks. I hope you get it figured out and kudos for that kind of road trip in a 40.

    Jack
    1985 4Runner on tons and 40's.
    2007 Chevy 2500hd max/alli/d60 front. 2008 FWC Pop-Up Camper

  3. #3
    I piss excellence.
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    While I can't seeing it making a huge difference, is the breather on the transmission plugged? I could see that pushing some oil but not all of it like that.
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  4. #4
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    So I’ve never played with an nv4500, but this is my best guess. I would assume that sealed bearing the adapter uses is just a regular bearing with a seal behind it in stock configuration, and it must have had something flinging oil directly at it??? The vent must be plugged on the nv4500, and as soon as the sealed bearing lost its seal and started feeding oil to the t-case, the trans must have gotten hotter and hotter as it lost oil, became under a positive pressure which helped to “push” the oil out. That’s the only way I see that happening. As far as fixing it, my best guess would be either a new sealed bearing and try to find a tin slinger to go in front of it, or do some measuring and find a regular bearing and seal that would fit and run a tin slinger between the bearing and seal.

    Or, mount a bilge pump in the t-case, to return oil to the trans... haha
    Last edited by 3rd Petal; January 17th, 2019 at 04:24 AM.

  5. #5
    Web Wheeler
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    Put it back together then pressurize the trans and look in the t case. It might be coming from another source. You can run a hose from t-case filler to trans then fill them up to the trans full level. Vent the t-case to the trans as well. Then they have the same pressures and extra goes back to the trans.

    Then fix the motor so you pay that much attention to enjoying the drive, not watching for the engine to crap the bed on you...
    Some people are as useful as a football bat.

  6. #6
    Wheeler
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    You ever think maybe the oil in the trans was just trying to get as far away from the 6.2 as it could???

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