Clark HR28000 series transmission

[Ky Logger]

It will barely move in reverse about a inch but has all forward gears, tough to narrow down the problem. It does have a declutch , first can I take the declutch out and plug it ?
I know it could have a declutch for forward/reverse for just forward for just reverse, the pressure from the control valve seems to be close to the same, second where is the modulator regulator spool , I can plug it and narrow done whether it's the control valve that's messed up or the clutch pack, if I knew where mod reg spool is at .

[mike_belben]

I dont know this transmission, but in general its good to check the basics before you get in too deep.  Fluid level, good filter(s) and or sump strainer clear are a given.  

Pull whatever panels necessary to access the connection between your cables or rods and the actually fwd/rev spool.  The spool needs to plunge in and out a metered amount.  First thing is to be sure that slop from worn out pins or bell cranks or clevises isnt your issue.  Dig deeper after that all checks out.  Id personally disconnect the cable etc and try to move the spool manually to see if it still has reverse.   Control valves direct fluid pressure to various planetary circuits so if they have sufficient cross leakage or whatever you dont get the gear you were after.

[Ky Logger]

Thanks for the reply, I haven't checked the value spool manually but have looked to see if it's going in I'll take shift lever loose and do it by hand to see if it's binding

[mike_belben]

Its not so much a matter of binding, but when you have say three 1/4" pins that wear half way through youll have a stackup of over a 1/4" slop across the trio so the valve doesnt move the right amount. Thats what happened with my dozer anyway. 

[kiko]

What is the application of this transmission, Clark or Timberjack maybe.  After you have verified the shift valve travel then you need to measure transmission pressure. You already know it is within range because forward works, what you will be looking for is pressure drop when reverse is activated.
Just for safety's sake, I personally knew somebody who was sitting on the tire of a 450c TJ messing with the shift valves, he engaged the transmission and he is no longer with us.  

[Ky Logger]

It's a timberjack, it's got another problem to, no hydraulics will work in the mornings until you move the blade a little with fortlift,
It's going into the right position on the control valve, I guess it's possible to be leaking internally on the reverse clutch. I'm going to pull it out and open it up after I do a few pressure checks on the pump and the clutches  again, where else to you check pressure at besides the control Valve Any ideas on transmission or hydraulics

[kiko]

What model TJ do you have?

[Ky Logger]

Could there be something inside the valve blocking the pressure line going to reverse clutch, it will move just a little , or a hole in the pressure line going to reverse.

[Ky Logger]

1988 450B

[kiko]

Ok.  Where the hoses come out of the transmission pump to the transmission filter , in one if the fittings there is a port that is for the transmission gauge that is or once was on the dash. The pressure adaptor that is for the dash gauge has an orifice in it. Remove it and replace with a fitting that will fit your gauge set up. Should be about 270 psi.
As for the hydraulics, sitting in the seat on left hand side is the suction pipe for the hydraulic pump suction.  Starting at the hydraulic pump is a metal line that goes down. There is a coupler there that connects to another pipe that runs on the bottom of the engine compartment towards the hydraulic pump and another coupler that connect it to the tank. Something is leaking in your suction line causing the pump to loose prime.  It could be one of the couplers or the pipe. I have seen the pipe that runs the engine compartment wear thru from laying and vibrating in the dirt. Even a small hole will cause this issue.

[Ky Logger]

It's leaking where the hose connects to the pump, I've cleaned the whole Skidder up with high pressure water I can find most of the leaks, I seen the oil coming out right there today I'll double check but I'm pretty sure it the line your talking about, I have a transmission pressure gauge , it's showing good pressure in all gears

[Ky Logger]

If I move the grapple the hydraulics will not start working it has to be the blade, that seems odd. I will get that leak fixed!

[Ky Logger]

Ok I see now your saying take dash guage out and check with another gauge ? Is that correct? I believe the dash gauge is Top of the big line coming out of pump, ,

[Ky Logger]

I have all the sheet metal off I can see and get to everything, is that how I check clutch pressure in the orfice between the transmission pump and the bell housing? Isn't that what's called a regulator valve, there's a orfice in the top of it 

[kiko]

Yes, where the dash gauge connects to the fitting in the transmission pump. If your dash gauge works then that should be enough to diagnose .  If pressure drops when in reverse and stays low, you have seal leakage internal. If it remains the same the clutches could be worn excessively. The regulator valve is sandwiched between the trans pump and torque converter housing. All the piping to the reverse clutch is internal piping, an issue with the internal piping would also show low pressure when in reverse.  I have rarely seen issue with the internal piping.  There is a plug in the middle top of regulator I seem to recall but can't say for sure it is a pressure tap, I have never used it.  That hydraulic pump suction may not show leak when running. Now that it is clean ,  get the hydraulics moving and then shut down then look for the leak. It may take over night to see it.  The hydraulic flow on the jack goes as such, suction line to hydraulic pump on transmission to grapple/boom valve, to hydraulic filter under engine to blade steer pump on engine to blade/ steer valve on dash.  Working  the blade up and down just charges the system enough to get the oil in the pumps.

[Ky Logger]

Ok I can see the leak at the hydraulic pump, it's where the line connects to the pump, not actually the line the leak is in the fitting that comes out of pump that the line connects to I'll address that and look for other leaks on the suction line, I'll just have to tear transmission down and rebuild maybe a soft rebuild gasket seals clutches, maybe no bearing or hubs the clutches sit in are bad , thanks I'll post the pressure readings tomorrow if I get to take them 

[Ky Logger]

Where is the best place to get the transmission parts?