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Thread: Old TCM forklift transmission

  1. #1
    Join Date
    Sep 2008
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    Old TCM forklift transmission

    Wondering if anyone here knows forklifts.

    I've got an circa 1990 TCM 1.8T gas forklift - FG18N16 model - that I bought cheap recently with the intention of giving it some love for use around home.
    Old Nissan 1.5L engine, runs perfectly and apart from replacing a couple of hydraulic hoses its almost ready to go.

    It had been sitting for a while and although supposedly running OK when parked up, it now won't drive either FWD or REV.

    I've done the usual things - checked fluid, changed the filter (external spin-on type) and confirmed that its actually pumping by giving it a quick start with the filter off. Very messy - so yes its pumping OK! Not sure how to check pressures.
    Have removed the inching valve, confirmed its not sticking/siezed.
    Pulled the valve body off the top of the trans and worked out which ports go to the clutch packs (single speed - just 2 packs FWD/REV).



    There seems to be about 3mm play in each clutch pack which I think is probably more than what there should be.
    Not much online about these old machines, but its looking to me like the packs might just be worn out (and it likely was stuffed before it was parked up).

    Any help/suggestions appreciated

    Steve
    1985 County - Isuzu 4bd1 with HX30W turbo, LT95, 255/85-16 KM2's
    1988 120 with rust and potential
    1999 300tdi 130 single cab - "stock as bro"
    2003 D2a Td5 - the boss's daily drive

  2. #2
    Join Date
    Apr 2011
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    Dungowan
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    836
    Quote Originally Posted by steveG View Post
    Wondering if anyone here knows forklifts.

    I've got an circa 1990 TCM 1.8T gas forklift - FG18N16 model - that I bought cheap recently with the intention of giving it some love for use around home.
    Old Nissan 1.5L engine, runs perfectly and apart from replacing a couple of hydraulic hoses its almost ready to go.

    It had been sitting for a while and although supposedly running OK when parked up, it now won't drive either FWD or REV.

    I've done the usual things - checked fluid, changed the filter (external spin-on type) and confirmed that its actually pumping by giving it a quick start with the filter off. Very messy - so yes its pumping OK! Not sure how to check pressures.
    Have removed the inching valve, confirmed its not sticking/siezed.
    Pulled the valve body off the top of the trans and worked out which ports go to the clutch packs (single speed - just 2 packs FWD/REV).



    There seems to be about 3mm play in each clutch pack which I think is probably more than what there should be.
    Not much online about these old machines, but its looking to me like the packs might just be worn out (and it likely was stuffed before it was parked up).

    Any help/suggestions appreciated

    Steve
    Put lid back on and check pressures. From my time playin with forklifts, was usually an inching valve issue.
    From fuzzy memory, had one blow a seal on the main shaft, pressure feed through shaft to feed clutch packs.
    Had another chew the tang drive off the torque converter, so no oil pump drive. Sounds like you ruled that out tho.
    Metal in a valve??? Jack up, even with dodgy clutch packs it should drive a bit, and prob only really lose one direction.
    '93 D1 V8 auto
    '93 D1 200Tdi 2-door, ARB's, MD transfer, sill tanks, winch, 2"lift.......
    '95 D1 V8 auto......gone
    '86 V8 RRC.....gone

  3. #3
    Join Date
    Sep 2008
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    Geelong, VIC
    Posts
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    Thanks Rick.

    The only other thing I forgot to mention was that when I put a bit of compressed air in the gallery that goes to the clutch it definitely came out quite freely as a big bubble/bloop in the oil.
    How do the clutch packs normally work from an actuation perspective. Are they some sort of a piston with a seal arrangement?
    If so, I wouldn't expect the air to escape.

    I've identified which port is which so I can test pressures, but which should I be checking? The pressure going to the clutch packs or is it the pressure coming from the pump?

    Steve
    1985 County - Isuzu 4bd1 with HX30W turbo, LT95, 255/85-16 KM2's
    1988 120 with rust and potential
    1999 300tdi 130 single cab - "stock as bro"
    2003 D2a Td5 - the boss's daily drive

  4. #4
    Join Date
    Apr 2011
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    Posts
    836
    Yeah, usually a piston to lock pack up.
    Not sure exact location of test ports on the tcm trans, but there is usually test port for pump, forward and reverse packs.
    Should be able to work out the pump test port. Can't remember exact pressures, but obviously is there is only 20-30 psi, something is amiss. Would think a couple hundred, and should dip a bit and rise again as f/r is selected. If hi and no drive, may have to work out where pack pressure ports are.
    Have a mate that still works with forklifts ( Iiv not played with them or 15 yrs), could see what info he has if you have a model/ serial.
    Single speed forklift trans are pretty basic really, so don't be afraid of pulling it and opening it up. Parts for an older tcm mite be the biggest struggle.
    '93 D1 V8 auto
    '93 D1 200Tdi 2-door, ARB's, MD transfer, sill tanks, winch, 2"lift.......
    '95 D1 V8 auto......gone
    '86 V8 RRC.....gone

  5. #5
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    Melbourn(ish)
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    25,716
    failing fwd/rev divertor valve or a blown out center seal on the clutch packs for fwd/rev
    Dave

    "In a Landrover the other vehicle is your crumple zone."

    For spelling call Rogets, for mechanicing call me.

    Fozzy, 2.25D SIII Ex DCA Ute
    TDI D1(parting/ed)
    Tdi autoManual d1 (Kept it for the girlfriend)
    Archaeopteryx 1990 6x6 dual cab(This things staying)


    If you've benefited from one or more of my posts please remember, your taxes paid for my skill sets, I'm just trying to make sure you get your monies worth.
    If you think you're in front on the deal, pay it forwards.

  6. #6
    Join Date
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    Compressed air nozzle to forward or reverse clutch pack port with valve body removed will tell if seals for clutch pistons are OK as you will see clutch plates move and lock the drive.
    If seals for pistons or clutch pack shafts leaking excessively you will be able to hear it.
    Unit jacked up and turning things by hand will confirm this.
    With valve body fitted to top of transmission find port for pump pressure test...Ö...should be getting something like 70 psi with engine idling.
    inch valve problem will cause lost of drive in both directions.
    with valve body fitted to top of transmission should be able to read separately 70 psi or more though forward or reverse test ports when forward or reverse is selected.
    If oil was black Ö...indicates drive plates been slipping excessively for some time.
    If oil had pinky or creamy colour......ie water in the oil...Ö.leaking radiator cooler...Ö.in time fiction material on drive plates peels off.
    The TCM transmission in that model is normally very reliable and gave little trouble.
    I would be looking for some thing simple...Ö..inching valve not working to its full stroke.
    Is the diff OK ??????
    this transmission is much copied by Chinese forklift manufactures.
    Parts are readily available.

  7. #7
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    Sep 2008
    Location
    Geelong, VIC
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    Old TCM forklift transmission

    Thanks guys - that's really useful info.

    When I put the air nozzle in either of the fwd or rev ports with the lid off it takes a decent volume of air to get any movement of either pack, and its definitely bubbling out in the center of the pack - slightly towards the side that is being applied which makes sense.

    Maybe the center seal you referred to Dave?.

    Inching valve I've had out and made sure its free, no foreign objects in it and its moving full stroke.
    Fluid is nice and clean, original filter was spotless when I cut it open.

    Ron - good tip on the trans being widely copied and good to know that parts are readily available.
    I found this manual online and it looks VERY similar to the one in mine. The look of the diagrams and old style hand numbering makes me think its got a historical source: https://www.forklift.ee/wp-content/u...c_5320_469.pdf

    Page 25, Fig 2-7 items 3 and 17 look like they might be the culprits. Or maybe the pack is so worn that the piston has got to the edge of the sealing surface.

    Forklift Clutch.JPG

    I've just ordered a cheap transmission pressure gauge kit from ebay for $40 so I can check the clutch line pressures, but in the meantime I found an gauge and a fitting so I could connect it to the pump port. There's a lot of needle flutter but its around 160-180psi at idle. Could be a bit higher as its slightly off scale.
    I've still got the pedals out for access, but if I pull on the inching valve rod by hand the pressure definitely drops about 30psi. I'm sure it would drop much more if I could put more force on it.

    I haven't been able to jack it up to get a wheel off the ground as I don't have a jack short enough to get under it, but just realised that I've got a 100mm 10T porta-power cylinder
    Jacked a drive wheel clear of the ground, ran the engine and shifted fwd/rev but absolutely no movement at the wheel.
    Pulled the axle - its still in once piece, but when I put it back in to see if I could feel any diff nastiness it felt way too free. Like there was no center in the diff....
    Poked an eyeball inside the tube and found this (hard to get a light and my phone in there at the same time so apologies for the photo quality):



    That splined collar inside definitely doesn't belong where it is.....

    Steve
    1985 County - Isuzu 4bd1 with HX30W turbo, LT95, 255/85-16 KM2's
    1988 120 with rust and potential
    1999 300tdi 130 single cab - "stock as bro"
    2003 D2a Td5 - the boss's daily drive

  8. #8
    Join Date
    Jan 2008
    Location
    Nowra NSW
    Posts
    3,828
    Without seeing it in person its hard to figure out what's going on.
    A poor man's forklift jack is to tilt the mast all the way back.
    Then get two pieces of wood and fit snuggly between floor and outer mast channels.
    Then tilt forward and the machine will lift itself off the floor.
    Transmission very reliable on that model.
    Some air leakage could be OK
    But is it same forward/ reverse.
    If seals are shot.........you would need to strip transmission which is labour intensive and not worth it on a old forklift.

    Check the diff.

  9. #9
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    Nowra NSW
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    Note
    Most but not all TCMs use a double gear reduction in the diff housing .

  10. #10
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    Thanks Ron.
    Yes, itís the same both forward and reverse.

    I didnít get a chance today to look at it any further, but that splined collar in the diff housing that I tried to take a photo of definitely isnít right.
    Iíll pull the other axle tomorrow and see what it looks like from that side.

    Good tip on the poor mans jack. Iíll keep that up my sleeve.

    I think the double reduction in the diff that youíre referring to is what that Chinese manual has in it. It comprises an initial reduction using a screw bevel gear and the the second reduction being a normal crown wheel and pinion.
    Does that sound right?

    To pull the diff housing out it looks like you need to remove the mast first??

    Steve
    1985 County - Isuzu 4bd1 with HX30W turbo, LT95, 255/85-16 KM2's
    1988 120 with rust and potential
    1999 300tdi 130 single cab - "stock as bro"
    2003 D2a Td5 - the boss's daily drive

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