Hello, I am helping a friend work on a John Deere 670B Motor grader Sn DW670BX548363 He purchased this machine running but it will not move in any gear forward or reverse. Engine runs great, all hydraulics and brakes work fine but transmission does not respond in any gears. We are waiting for the service manual to come in but i was looking for some pointers to diagnose where the failure might be on this blade. I read another post on here with similar symptoms that ended up being a failed damper drive: HeavyEquipmentForums What is the best way to determine if we have a failed damper drive or issues internally on the transmission?
Update: Parking brake releases and when you drop the machine into gear you can hear it load slightly. You can hear the transmission shifting through all the gears when you upshift and downshift so i am thinking the damper drive and transmission are ok. I pulled the inspection covers on the tandems and everything looks fine in there, no broken chains. Machine will not move with the diff lock engaged either.
Do you have a transmission pressure gauge on the dash panel that works?
I am not sure if it works but there are no active lights on the dash.
I don't know where to tell you to look for it, but some of those had a transmission disconnect. Should be somewhere on the transmission or drop box I think, lever with a spring loaded pin you pull out and turn the lever. Guessing it would be for towing?
I agree with lantraxco^^^. Check to see if your disconnect has been put into tow mode. If it is not then pressure checks are in order.
I located the tow disconnect lever on the right side of the transmission and moved it to all positions with no luck, still wont move. Again when you shift the machine into all gears you can hear it engage and "spool up" components internally in the transmission as if the transmission is functioning just not getting power to the tandems through the axle.
There should be a park brake disc and caliper under the engine , coming out the top of the transmission cover --- Does that park brake disc spin when your shifting through the speeds? I'm wondering if the ring gear retaining bolts sheared off .
When you shift through the gears, does the engine rpm "load down" in each gear? The higher the gear the more the engine should momentarily drop in rpm. If it does then something down stream in the gearing like Johnathan mentioned would most likely be the issue. If the engine really doesn't do anything at every shift then run through the clutch adjustment procedure. The only way for you to lose all gears (assuming the trans pump has good flow and pressure) is the clutch adjustment which controls the C1 and C2 clutch packs. One of those packs are engaged in every gear. Which brings me back to my statement in post #6 - I think regardless of the engine reaction you need to check pressures to isolate the problem.
Ran a few pressure tests per the service manual here are the findings: Transmission Pressure good 180 Psi Lube pressure good 60 psi Interrupter valve pressure check ok did not move at all when shifting from Neutral F to Neutral R Lifted machine up with rippers/blade, you can roll tires and engage diff lock it works good.
Sounds like spider gear issues within the differential??
If the diff lock works and the other side turns when you turn a wheel, everything up to the ring gear *should* be good? I'll put money on the disconnect or something in the drop box.
Update: Pulled the engine today as well as top covers on the trans/diff found the tow disconnect shift fork “tips” broke off. Tow disconnect was in neutral even though the lever was “engaged” from the outside.
That's a bad news/good news deal, bad news: It's broke. Good news: That's probably the absolute cheapest thing in the whole drivetrain to repair?