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Mid 90s Cat DP70

Discussion in 'Forklifts/Telehandlers' started by tbsalvagefab, Jun 30, 2022.

  1. tbsalvagefab

    tbsalvagefab Member

    Joined:
    Jun 16, 2022
    Messages:
    6
    Location:
    North West NC
    This is a mid 90s Cat Dp70 Forklift
    SN T20C603002
    6cy Mitsubishi na, 2 speed fwd-rev automatic, 15000lb capacity
    Machine has 21,000 hrs- engine appears to have been "rebuilt" as there is a tag from EPS on the engine

    I have been chasing a low power issue in this lift in my spare time. Typical struggling to traverse bumps, and going up hills is a fools errand. Machine will easily lift 15k, engine starts instantly, and it does go forwards and backwards. I do see a little white smoke when you leave it floored. Machine did not have any transmission oil on dipstick when I got it. Only history I know is that it was out of a blockyard with 3 other machines, no idea on circumstances. I also own a 8k hyster from that group of machines and it only needed a few seals and some engine oil to be a regular worker.

    I have the manuals for this machine and have pulled pressures off the transmission

    • TC Inlet 62psi within the 7- 70psi
    • Clutch pressures Low gear fwd and rev, 178ish after shifting(drops to 100 during a shift then immediately regains 178), within 150-230psi
    • Main pressure is 178 within 150-198
    • Can't test speed clutch as machine will not go fast enough
    • Stall test 1700 rpm checked with optical tach off crank pulley, supposed to be 2050 +-100

    What I have done

    • Replaced transmission, fuel filters, and transmission oil. Have not found any glitter or chunks in filters/pans (cut apart and looked)
    • Pulled and inspected clutch packs, frictions and steels measured new, resealed clutch pistons while I was in there.
    • Pulled and inspected TC, Stator sprag clutch works, can't see any cracks in the pump or turbine. Can still see original machine marks and cast surfaces.
    • Replaced head gasket because it was pressurizing coolant tank

    Remarks
    A low stall is either the TC or engine, and with it running as well as it does, I can't see how it is the engine.
    I'm going to ask around locally and see if its' worth tossing it on a dyno just to rule the engine out entirely.

    No visible carnage in TC, so at a loss there


    When i first drained the machine i got about 5 gal out of it(didn't overfill a bucket). I'm pretty sure I added 6 gal of new ATF to the machine after changing filters/fluids (I didn't keep the receipt and its been several months), and now when I pulled the engine/trans I only got about 4.25 back out the pan. Is that a big enough difference from the needed 5.8 to possibly be the issue?

    Been off and on this machine so my diagnosing and process is terrible. I just don't want to put it back together, overfill it, and pull it again. Even though that's probably what's going to happen. I just don't have any experience with automatics. Will try to post some pictures of TC bits

     
  2. Chrisso

    Chrisso Well-Known Member

    Joined:
    Apr 6, 2021
    Messages:
    227
    Occupation:
    Diesel Mechanic
    Location:
    Australia
    In those manuals you have, are there any specs for operational tests, such as cycle times for the mast, any other performance checks that could isolate the engine?

    Since you have the manuals you probably have more info than most people here.
     
  3. tbsalvagefab

    tbsalvagefab Member

    Joined:
    Jun 16, 2022
    Messages:
    6
    Location:
    North West NC
    That's an idea, Spec in the book is 86 feet per minute max load and 92.5 fpm, raising unloaded at max rpm. Something else to test when it goes back together. Pump runs right off engine, so doesn't use tc.

    I was looking for the obvious smoking gun and it seems that it's allot more subtle than that. I don't have the knowledge of how to call a tc bad or good though. Can anyone chime in and describe what does a "bad" TC look like inside? What does wear look like? Is it something visible by eye? I would figure you would treat it like a water pump and look at the vanes, but the book doesn't give specs beyond visual inspection.

    I'll get the engine tested, toss it all back together one more time, overfill the transmission, and if it's still broke then i'll pursue a replacement/repaired/used TC, $$$$
     
  4. Chrisso

    Chrisso Well-Known Member

    Joined:
    Apr 6, 2021
    Messages:
    227
    Occupation:
    Diesel Mechanic
    Location:
    Australia
    Since you've had the TC apart and inspected it, I think you would've noticed a smoking gun if there was one. Impellor, stator, turbine vanes can become razor sharp and/or cracks appear on or around the vanes. Any contact between impellor, stator and turbine is also very noticeable, and is a bad thing. No experience with forklift TC's but the larger ones have cast metal ring seals on the shafts that direct oil through the TC. These can also fail and cause drive loss.

    I've seen sprag clutch fail and loose drive at low engine speed intermittently initially, eventually losing all drive. Again if you've has this apart I reckon you would know if it is bad.

    If it was a left pedal issue (trans neutralizing valve or TC impellor clutch) I'd expect the stall RPMs to be higher, not lower. Hoping someone else w/ more experience on lift trucks will chime in.
     
  5. tbsalvagefab

    tbsalvagefab Member

    Joined:
    Jun 16, 2022
    Messages:
    6
    Location:
    North West NC
    Really appreciate the clarification Chris. The knowledge available on this site is always worth the time.

    ….. so I put it back all back together and dumped 6.5~ gallons into the transmission.
    Wow... put enough fluid in it and you get the right stall speed, 2100rpm. I'm so stupid. 0/10
    Maybe the intake has a suction leak somewhere? idk if it's enough to investigate further.

    Got a bunch of small things left to go over and check/fix but it will now climb steep hills gradually and accelerate better. Definitely not designed to live on a mountain though.

    Should have triple checked that, though at least I got the "experience".

    I think every machine from that yard was short one fluid or another. One of the machines I passed on had 1/8 of rock dust inside the intake manifold, and the other looked like someone filled the engine bay completely full of oily dust, must have been 5-7 inches or more in spots.
     
  6. TD24

    TD24 Senior Member

    Joined:
    Jan 3, 2011
    Messages:
    271
    Occupation:
    RETIRED (Mostly)
    Location:
    MS
    Not familiar with your truck, nor its transmission neutralizing/inching controls...
    BUT...If it was a Clark or Hyster. I would examine the inching system. Lots of times, the pedal does not return all way up freely, due to a weak, broken or missing return spring. Possibly some debris jammed under floorboard.
    If there is a pedal; and linkage downward to the transmission control valve. Try to lift/pull the actual spool outward. If practical, connect a piece of tie wire to the last joint before entry to valve, crank, mount and drive, applying upward pressure on wire to keep everything in its (supposedly)return position.
    This is fairly common on the Clarks and Hyster's of yesteryears. The spool gets gummy inside the valve body and
    tends to stick partially unless all linkage it fitted and return spring is strong. Worn pins, ball joints and wallowed out
    holes in linkage can contribute enough to cause this.
    A pic of the control valve linkage on the transmission would/maybe helpful.
     
  7. tbsalvagefab

    tbsalvagefab Member

    Joined:
    Jun 16, 2022
    Messages:
    6
    Location:
    North West NC
    Coming back with issue resolved for sure this time,

    So on the Cat DP70 and DP60 they have a High/Low solenoid on the transmission. Ecu uses a pulse generator off the driveshaft to change gears when in 2speed mode.

    There is no ecu on this machine... just an empty mounting place under the dash where it should have been.

    Also this transmission defaults to 2ND GEAR in the unpowered state. You need to energize the H/L solenoid to shift to 1st

    Rewired the 2 speed switch on the dash to power the solenoid, and tada! Climbs hills like it's nothing even loaded to the gills.
    Still a case of terrible troubleshooting, but it's fixed for good now
     
    TD24 likes this.
  8. TD24

    TD24 Senior Member

    Joined:
    Jan 3, 2011
    Messages:
    271
    Occupation:
    RETIRED (Mostly)
    Location:
    MS
    Love it when a plan comes together.. Even spontaneously!