Yale GLP-050RENUAF089:
Need Help with Yale Forklift Transmission Problems

I purchased a Yale forklift in December for my farm - Model GLP050RENUAF089. It has the Mazda propane engine. When I first start the machine and shift to forward or reverse there is no response - cant feel the clutch packs engaging. If I let is idle for a few minutes eventually I will start to feel a small jerk as the clutches engage when I shift into gear but still not much movement when I push on the accelerator. If I keep shifting back and forth between forward and reverse and rev the engine it will start to move better till eventually after a few more minutes if seems to shift into gear and drive OK. I only used it over the last 3 month for a few small lifts inside my workshop - too cold and snowy to go outside - once I got it moving seemed to work OK for the short time I used it. We have had real nice weather this week so yesterday I used it outside for 20 minutes or so to move some pallets and after running it for that length of time the transmission seemed to start to slip so I put it away.

I am not very knowledgeable on transmissions but it seems to me like the transmission pump isn't providing enough flow or pressure when the machine is first started. I am going to try and check the transmission pressures but so far I haven't located the test port locations - they don't seem to be where they are shown in my manual. Going to give the transmission valve area a good pressure wash this weekend now that it is warmer and see if I can find the pressure test connections.

In the meantime I pulled the 2 transmission oil cooler hoses off of the radiator this afternoon to see if there was oil flow. I started it cold and as usual could not feel the clutches engaging at first and no oil was coming out of the hoses in forward, reverse or neutral. I let it run for 5 minutes and at that point I could feel a slight jerk in the drivetrain when I shifted into gear but still no oil out of the hoses. I tried revving up the engine and I did get a little but of movement when shifting into forward or reverse and a small dribble of oil coming out the end of one hose - the end of it was about the same height as the top of the transmission case. When I shifted into neutral the oil level in the end of the hose dropped out of sight even when revving the engine.

I would appreciate if anyone familiar with the transmission operation on this type of machine could comment if the oil flow ( or lack of flow) in the transmission cooler hose sounds normal
  • Posted 25 Mar 2021 10:17
  • Discussion started by Blueacre
  • Ontario, Canada
Showing items 1 - 5 of 5 results.
Good day I am new I need some Info related to hydraulic pump pressure ,
where to adjust ,and how to check priority valve and steering pressure
the problem is hard steering 5FD25-30 S1365B Toyota Forklift.Hydraulic system from pump to priority valve , valve bank. steering and brake master cylinder ,any help will be appreciated ,even a topic over the hydraulic steering. I am in South Africa
  • Posted 23 Mar 2022 22:30
  • Reply by Willem_Botha
  • South Africa
yes those older units did use dextron so your good there
it's been a while since i've worked on one of these but...
as for the sluggishness to engage when its cold and getting better as it gets hot?
i would service it
change the filter (if it has one)
also pull the sump screen and clean it (located at the base of the case, may even be part of the suction line fitting, it should be a mesh screen at the pick up of the suction line). Also pull any plugs out of the valve sections and see if there are any screens in them and clean them out as well.
  • Posted 4 Nov 2021 15:32
  • Reply by swoop223
  • North Carolina, United States
You've been swooped!
swoop223@gmail.com
For me, it looks like a hydraulic problem. This is the first thing which comes to my mind. Mine had the same problem. The transmission will disengage if you use the left pedal. The actuator that performs it is on the tranny, and it has a strange balancing beam configuration that allows it to work in both directions. It took me about an hour to find out how it should have been altered and make the necessary changes. With a handbook, it would have been a lot easier. I decided to gift it to my brother after repairing it, and bought a new one from https://www.machinerydealer.co.uk/, now there are no problems at all.
  • Posted 3 Nov 2021 18:03
  • Modified 11 Nov 2021 09:26 by poster
  • Reply by Roby_Sul
  • United Kingdom
thanks for your reply - My service manual says to use Dexron ll for Yale automatic transmissions/torque converter and Allison Type C-3 if it is an Allison transmission/torque converter. I am not sure yet if it is a Yale or Allison transmission but Dexron is normally red and the fluid in the transmission when I got it was red so I stayed with Dexron.

I thought of the inching valve - it is hydraulically actuated internally in the transmission control valve by brake fluid pressure from a line that tees off the main master cylinder brake line so would need to pull the valve apart to see it there is any problem there.

There is also the cold relief valve, anti-plugging valve and pressure sensing valve (sequencing calve) that can all dump hydraulic fluid back to the reservoir if they are leaking or not operating properly.

I got gauges hooked up to the transmission test points yesterday and got the following results. Lots of information but not sure what it all means.

Test port 1 - pump pressure - Installed gauge and started engine - after about 5 seconds gauge climbed quickly to 65 psi and stayed steady there at idle. I revved engine part throttle and pressure went up to about 80 psi - I didnt try full throttle. My manual says specs are 156 to 200 psi

Test port 2 - torque converter - installed gauge and started engine - had zero pressure, revved engine up part throttle but still zero pressure. Shifted transmission into forward and reverse - could feel clutch packs engage and it would move a little if revved up but still zero pressure Specs for converter are 43 to 100 psi.

Test port 3 - clutch pressure - installed gauge and started engine - shifted to reverse and got 65 psi (same as pump pressure). Pressure would climb to about 80psi when I revved part throttle.

Next I hooked up gauges to the pump and converter test points with hoses so I could drive with them both connected. I did my routine of shifting back and forth between forward and reverse and revving the engine and it gradually moved better - the pump pressure climbed to about 80 or 90 psi but still felt like it was slipping a little. I took it out of my shop to the driveway and started to move forward a little faster. I felt a surge like a car shifting gears and when I looked at the pump gauge it had gone up to 175 psi. Forklift was now driving normal with good clutch engagement when shifted and lots of power - I have about an 8% grade in my driveway and I was able to drive up it with no problem other than spinning the tires in the packed gravel in a couple of spots. The torque converter pressure stayed a zero when the machine was stopped or moving slowly but as it sped up with full throttle the converter pressure gradually climbed to about 40 psi at full speed.

I drove it up and down the hill for about 15 minutes to get the oil hot -after that the pump pressure dropped to about 125psi at idle but just revving it slightly above idle it went back to 175psi same as when cold. Converter pressure still at zero when stopped and climbs to 30 psi at full speed.

Next I shut the engine off and restarted it right away - the pump pressure went to about 50 psi at idle and stayed there. I started to slowly rev it up - it climbed to about 80 psi and then suddenly shot up to 175 psi and when I went back to idle it was at 125psi - same as it had been at idle before with hot oil. Tried shutting off and restarting several times - same thing every time - approx. 50 psi at idle - rev it up slowly and it slowly climbs to 80 or 90 psi and then suddenly shoots up to 175psi and drops back to steady 125psi at idle.

Pump seems to be OK - meets spec of 156 to 200 psi when cold at idle (175 psi) and when hot at just above idle rpm - the slightly low pressure when hot probably due to its age and pump wear.?

There seems to be something that is causing low pump pressure for an extended period of time when the machine is cold and for a very short time when restarted after it is hot until the engine is revved up - could it be a sticking pressure valve or something else in the transmission control valve that is bypassing oil flow all the time when cold but then closes when it heats up and the engine is revved ????

Not sure what to make of the torque converter pressure being zero most of the time and the pressure only going up when the machine is moving faster ???

Hopefully someone with more transmission knowledge than me can make sense of the pressure readings.
  • Posted 26 Mar 2021 23:46
  • Reply by Blueacre
  • Ontario, Canada
Check to make sure your inch/clutch pedal cable is fully releasing. It operates as you press the single pedal down to disengage the drive then brake. MAke sure also the fluid in the trans is proper. Should be a hy-Tran universal fluid. Hydraulic or trans. Not red in color.
  • Posted 26 Mar 2021 14:16
  • Reply by ron_k
  • North Dakota, United States
4kliftman

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