D4H transmission

What can be done about the millisecond that it stays in neutral when down shifting from second to first with a blade full of dirt? The trans was removed under warranty for some shifting problem, and when we got it back it had "polished" (whatever that means) hand-stamped on the transmission rear cover. But for the last 6000 hrs., it has always done this. The hotter it gets, the wider the gap seems. The thing I don't like is when it finally gets around to completing the shift, (at full engine revolution) it slams into first. Any ideas appreciated. thanks, Fritz

The best thing you can do is be gratefull that it goes into gear... Mine is an early serial number 4H and it needed valve updates and fought this problem for a couple years when it was new... It was bad enough that it would sit there and NOT go in gear. It was always worse when it was hot. It gets kinda hairy when you're poking fire with it and you drive into the fire and can't back out...
IIRC, they played with the springs in the valve spool and mabey did some polishing on the spools too. Lately it hasn't been bad... This one is somewhere around 5K hours now I think.
I dunno how you push anything with it in second gear anyway...

Rod

Fritz,
I assume the Shift Hesitation /Slamming into Gear has gotten worse lately?

Does the Powertraing get overheated quickly/easily now as compared to when new?

Presume you have changed Trans Filters, use the correct viscosity oil for the teamperature range you operate in, checked screens on Powertrain sump, and checked the flex hose going to powertrain pump for collapsing/restriction?

If so, I'd suggest getting someone very familiar with a D4H to do an overall pressure test on the Powertrain Hydraulic System. Its covered pretty well in the Service manual which also has the Specified Pressure levels, but a few memories below:

The slamming into gear indicates a non-modulated shift - -the trans valve spools were probably polished trying to remove burrs.

There is a slight bit of time in a trans shift as one speed is dropped out and another is engaged - -it should not get worse as Temperature gets hotter - - that situation indicates a Leak somewhere in the system, which gets more apparent as oil heats up and gets thinner (reduced viscosity).

In the D4H, the Steering Clutches and Brakes get Priority on Oil pressure & Flow, then Trans P1 (Speed Clutch) and P2 (Trans Directional) Clutch.

The LH & RH Steer Clutches are Pressure Applied, and LH & RH Brakes are Pressure Released / Spring Applied, thus when you are dozing, all 4 are pressurized all the time.

In a Transmission shift, either to change Speed or Direction:
1) The Steering clutches and Brakes always stay applied and get their Oil First!
2) The Trans P1 Speed Clutch fills first, then
3) The Trans P2 Direction Clutch fills.

IF ANY CLUTCH or BRAKE Piston Seals, or the Parking Brake Valve (Which dumps Brake supply oil to both spring applied brakes to engage them) are leaking, the trans engagement will be delayed. It will get worse as oil temp rises.


Fritz, the best way to Find a Leak is by a pressure test done at Engine Low Idle (NOT HIGH IDLE!!)speed with Warmed-up Powertrain oil.

Install gages on all 5 steer valve ports (Supply, LH Clutch, LH Brake, RH Brake, RH Clucth), Trans P1 & P2, and the Pump Port (I think its also on rear of trans cover).

With Machine parked in an open area away from all people and machines, Powertrain Oil Warmed up, and Engine at Low Idle, Watch all gages as as the following steps are done - -you are essentially "cutting off" functions one-by-one so that the Leak is cut off - -which will show itself by the remaining gages going UP in pressure.

1) move the Parking Brake lever from Parked to the Run position and back - - gages may flicker as Park Lever moved but should not change high level.

2) Watch Trans P1 as you slowly move each Steer Lever back through Clutch, then Brake - -you are shutting off flow to each clutch/brake piston as you do this - -and IF P1 Goes up, you have just shut off the leak and need to fix that component.

3) At Engine Low Idle, with Park Brake Released, and foot applied Servine Brake APPLIED, shift trans through and pause for a few seconds in 1F, 2F, 3F, Neutral, 1R,2R, 3R - -again, if Trans P2 varies more than 10-20 psi in any of these gears, it indicates a leak in a Trans Speed or Direction Clutch.

If a "leaker" is found, fix that component.

If Pump Pressure is low and stays low, it may indicate a worn pump or a partially blocked oil sump hose/tube.

And, at 6000 hours, it simply may be time for a trans/torque convertor overhaul.

Best Wishes!
John

V
VERY GOOD EXPLANATION OF WHAT NEEDS TO BE DONE.
NOT MANY FOLKS CAN EXPLAIN IT THAT GOOD.

Power shift (Modulation)the time from shifting untill clutch is engaged is controled by an orifice that controls the oil flow in behind the load piston. On these valves the orifice is plastic and has a screen. They are different sizes and different colours. Replace it first.
Later Bob