73 450b low pressure in reverse

[Anthony Rivieccio]

anyone know what could cause reverse only to have low pressure on a 1631 hr machine?
thought there might be a pipe tube screen or valve accessible without removing the engine.

seems that the previous owner did some work on this in attempt to make reverse work and part of that work was as he said: cleaned the filter, drained the fluid and filled w new. selector linkage seems fine

[Jim B]

It could be seal failing in the reverse clutch. Have you done all the diagnostic tests in the manual and know the pressure is correct everywhere else?

It is great if you have a 450B with only 1631 hours on it. Were those hours verified by the owners prior to you? My thought the current hourmeter may show 1631, but I expect it has way more than that on it, without having documentation to prove the low hours. It is not uncommon for meters to fail and be replaced.

[Anthony Rivieccio]

Thanks Jim !
not documented hrs but the engine sounds fine and the pins look good and untouched. although the backhoe attachment looks more used the rest of the machine but not all played out. I stow the boom, stick and bucket up so that the pistons are retracted. the boom falls slowly but the lock stops it. the stick and bucket stay put. no external leaks that i notice.

don't know if i did full diagnostics but went through the selections and timed the drop back to pressure again
at idle starts at 185 drops 20 lbs and then up to 180 in about 1.2 sec, 1600 rpm pressure is about 200, drops 20 lbs then up to 195 in about 1.1 sec. in both H and L. R drops 60 lbs and hardly makes a return.
this is the best i can get it, engine off and engine on clutch free travel are about right (will check and update) but the nut on the adjustment rod under the left bell housing rubber plug is about one thread off the rod.
but w that nut turned off the rod two threads selecting R drops about 50 lbs and then up to 150 in about 1.4 sec. enough to move the crawler 6 inches but no more than that. cant keep it that way though bc the timing to H and L are too fast.
wish my manual had more detailed info on the trans circuitry
would like to find more info before pulling the engine.
i assume i have to pull the engine to pull the input shaft so the reverser is free to lift

why would the gauge show such a good response and pressure in L and H ? is there something different about the reverse seal? or maybe a sharp piece of metal got to it ? i took apart a trans which broke an accumulator spring. a spring fragment cut the third gear seal. Maybe this reverser has a passage to reverse which get lose or otherwise can leak?

[Jim B]

From your description it sounds like bad sealing of the reverse clutch circuit, possibly the clutch seals.

TM1033 has a group (25) in the General (10) Section giving separation and installation procedures for the various components. The power train section has a pretty good rundown of the hydraulic circuits in the HLR transmission.

[Anthony Rivieccio]

Thanks again Jim ! i have that manual. it shows a diagram of the circuitry without showing pictures and locations. I'll have to disassemble it to discover that by tracing the path and examining the parts for fluid seal. I also have to assume that the engine must be pulled so the input shaft can be pulled to allow the reverser to be hoisted out. Didn't want to touch it right at the moment if i didn't know for sure that some reverse circuitry which could be the culprit is accessible and serviceable from the under the top cover. you see the input spline might be rusted to the clutch disk which could make it a project for another time as a deciding factor on which machine to work on at the moment. this crawler, disconnect the back hoe and do some work clearing woods, or go in with a dynahoe 190. take longer to level things with a wheel loader / hoe but the hoe is much bigger and could help with the clearing / stump pulling. thinking each machine could knock down the same size tree.
(BTW the JD hoe is for sale on fb marketplace Amsterdam NY)

so bc i'd prefer to start using the crawler, i really needed advice form someone familiar with whether there is a fair chance of a reverse leak accessible w/o removing the engine..

[Jim B]

I admit I don't have all the answers and hopefully someone will have a magic answer for you to use it to fix without getting inside the HLR.

The HLR clutch control unit is mounted inside the Range Change (HLR) compartment (there is a picture in the manual of its location). Drawings show, and it is described how oil to operate all three clutches is ported to them from that control unit. The passages are housing bores and drilled passages inside the clutch shaft they ride on, and no the manual doesn't have detailed pictures of them. There are a couple tubes inside, but the fact that the low and high clutches work says oil is getting to the control valves. The fact that your pressure reading for reverse dropped way low and did not recover, indicates the problem is from the control unit to the reverse clutch. I have to believe you need to replace the seals related to the reverse clutch at a minimum. And it could be shaft sealing rings or seals and/or the clutch pack piston seals.

The only external thing I can think of causing it not to go into reverse would be if there was wear enough in the shift linkage that it was not moving the valve into the reverse position. However, if that was the case I would not expect it to come up to even 50 after it dropped for the shift.

Good luck.

[Anthony Rivieccio]

those are pretty Good answers Jim, Thank you !
I'll have another look at the manual to see if i think accessing the range change compartment might be worth lifting the top cover to have a look at the control unit to check for loose bolts and maybe a loose tube in case reverse is carried through a tube.

Beauty of All Creation to All !
may we begin the long awaited conversations necessary to bring us to a conscious evolution