Hey all. I have a 4000-ish hour 742 that sat abandoned for 25 years before I bought and re-powered with a v2203DI. Wonderful machine except for one issue. Slow pivots with just a little bit of forward left and no right or just a tiny bit back right is super jerky. But only when I am stopped or slow back on right drive. Forward slow is fine. Slow back is fine. Slow left hand pivot is fine. Only when I try to feed in a bit of forward left when right drive is stopped or slow back to I get jerky motion. It worked fine all winter with chains and snow, but now seeing on dry terrain. How can I further isolate?
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They should have a hydraulic motor on each side (right and left sides). The drive motors are controlled with servo valves. Lift the unit and try checking the adjustment from the left side and the right side. They should be synced with each other. Sometimes strange things happen when a drive motor starts to fail. Research information on YouTube. One of the channels I follow did a drive motor replacement. I found it interesting because he talked about the symptoms before the drive motor completely failed. One side would drag behind slightly and it would creep while sitting. I thought it was interesting. Check out my page and view my subscriptions. I am subscribed to Andrew Caramata. He works on a lot of different pieces of equipment. I will be tracking/documenting some work on my 843 in the upcoming weeks. By the way the controls look I will have to adjust my servo valves. Hopefully my drive motors are in good shape. Check out my channel Flat Thunder Channel
The 743 series do not run servos like the 743s did, they have direct connections to the drive pump.
What sort of ground are you turning on? sticky surfaces like concrete and asphalt grab the tyres and make movements jerky at slower speeds.
You can always try swapping motors from side to side and see if the issue moves.
They are very good machines
Thanks for the correction. I thought the controls were similar. Do you know what other models are similar / match the 843? Swapping the motors sounds like a good test to see if the symptoms follow the motor.
I actually thought the 854 was the only hydraulic servo controlled machine, possibly the 9x series might too. The only other servo based machines would the SJC ones that use electric servos, not hydraulic/
How do you find the hydraulic servos for response time? I thought there was a short delay vs instant for direct connected drive systems.
I took screen grab the service manual, but then I remembered I could not post pictures without a host. If you look in the manual it will outline the procedure. Lift the unit so the tires are raised off the ground, with the levers in neutral check for creep forward or backwards. Then using a rpm gage adjust the forward and reverse to obtain the same rpms on both sides (full forward lever movement / max travel speed). It is just a valve body as far as I can tell. If the internals are intact and the linkages are adjusted for neutral and full flow synchronization between both sides then all the mid lever positions should follow suite (its a servo control, but via mechanical linkage). Maybe this linkage has damaged components and or lost it's adjustment. If it isn't this issue then I would anticipate a failing drive motor. Note my 843 has some redneck modifications that were installed on these linkages. Once my engine is re-installed I will address this linkage repair and adjustment in an upcoming video. I guess I just cant help but be entertained fixing other peoples scrap! Saving old worn out stuff one piece at a time.
. Check out my channel Flat Thunder Channel Thanks Tazza. It is less noticeable on dirt than concrete, but still an issue. I need to do a bit more messing with the linkage and centering bar, and then look to swap drive motors
