JD 955 NO PTO, NO FLUID pressure

beenthere · Jan 5, 2012

Look forward to what you find out. Hope it is all good and reasonable to find and fix.
Just passing these figs along for what they might be worth to you. First is cross section of tranny, showing the through shaft with charge pump on right and where hyd. pump attaches on left.
The second is removal note on charge pump housing, and precaution to not put it back on wrong.

Mechanos · Jan 5, 2012

I hope it is just a pin... but I don't see how shearing that pin would knock out the implement pump. I've attached a couple pages from the manual to help explain my thoughts.

View attachment hydro_trans.pdf View attachment transaxle.pdf

Look at the trans diagram. That shaft is a one piece shaft, splined on both ends. Now look at the transaxle diagram. The mainshaft through the transaxle has a splined coupler on each end. If you lost both trans and implement pump, you would have had to shear the gerotor pin in the trans charge pump AND wiped out the splines on one or the other of the shaft couplers. I think it would be more likely that a shaft broke than the splines stripping out of the couplers.

I'm just guessing, but a single shaft break in the cloud on the trans diagram would keep from transmitting power to the trans charge pump, the trans pump and implement pump.

I hope I'm wrong. Please post back and let us know what you find out.

beenthere · Jan 6, 2012

Mechanos
That sounds like good logic to me.

Mechanos · Jan 6, 2012

Hoopcoachd said:
No noise when PTO is engaged - nothing. Engine runs great but NO hydraulic pressure to transmission, front loader, or 3 Pt Hitch - nothing. No leaks, changed the filter and fluid; fluid was clear - amber, like new. My question is: Is there a shear pin or key b/w the drive input and the PTO shaft b/c the PTO shaft drives the hydro pump. I'm good with cars but this is my 1st tractor. '98 JD 955 diesel, less than 800 hours...

This statement is not correct. The mainshaft in the transaxle drives the implement pump. The mainshaft also drives the PTO shaft through a hydraulic clutch pack.

Hoopcoachd said:
How about a pin that connects the engine shaft to the hydraulic pump - it isn't splines, has sort of a u-joint held together by a pin. I will have time sunday to pull the floorboard and check - makes sense that when both PTO and hydraulics go at the same time it has to be a drive-link of somekind.

The driveshaft from the from the engine to the transmission IS a splined connection. The u-joint yoke is a split splined connection. Yoke slides over the splined shaft on the transmission and the two pinch bolts are tightened down to keep the yoke from moving.

Hoopcoachd · Jan 7, 2012

Finally had good weather and time this morning - went through the entire system again - finally thought to run the engine and actually look at the drive shaft instead of just pulling on it ...shaft snapped right up against the flange that attaches to the flywheel. Already ordered new shaft and u-joint BUT can't get a single cap bolt to budge. Stripped a 15mm gear wrench and totally bent my remaining 15 mm box - these aren't reverse threads are they? Other than having to get it out of the field and into a shop where I can use an impact wrench, what's the trick? This is just starting to get me PO'd a little - 6 15mm cap bolts and not one will budge!

Mechanos · Jan 7, 2012

Well that's good news. That shaft is 100 times easier to fix than the shaft I thought had broke. Then again, I was operating on the info you provided and that you'd verified that the driveshaft was spinning.

Anyway, you only need to remove 3 of those bolts. 3 bolts hold the rubber coupler to the flywheel and the other 3 hold the driveshaft to the coupler. They are tight. Maybe try a socket and a breaker bar. If that won't do it, put it in neutral and tow it into the shop.

Hoopcoachd · Jan 8, 2012

I agree - going to pick up a 1/2" 15mm socket - use with a 24" breaker bar - I was hoping 3 bolts would do it but the manual says all 6...have you ever used "cold spray" to free bolts? Thinking about try that as well. Got a few days to play, new shaft will take a week to get in stock. Honestly I was shocked about how small the drive shaft is. Does anyone make a HD shaft?

Mechanos · Jan 8, 2012

I've taken mine out with just the 3 bolts (and the two pinch bolts on the trans end u-joint). As far as "heavy duty"... it only has to transmit 33hp. Besides... if you make the driveshaft stronger... then it is no longer the weak link. The transmission or the transaxle is. Ask yourself this... would rather replace the driveshaft, or replace the transmission or transaxle shaft?

Mechanos · Jan 8, 2012

Forgot to ask... how did the old one fail? Did the weld break right at the flange? I would save the old pieces as you could probably take them to a driveline shop or a machine shop and have it repaired. Put that on the shelf and you will have a spare in case something like this happens again. I'd be willing to bet that you could have your existing shaft retubed at a driveline shop for a mear fraction of what JD is charging you for a new one.

beenthere · Jan 8, 2012

Hoopcoachd said:
Hit a small stump with bush hog just after engaging. Lost PTO output and all hydo..no trans, no pump. Does input shaft have a shear pin or key? What now?

Now that you have found the problem, I'd suggest making sure the slip clutch is in working order on the brush hog (or be sure the right shear bolt is installed) as they are your protection from damaging the tractor side.

If you were nearby, I'd loan you some of my Bluecreeper to loosen those three studs. It is a miracle (IMO) penetrant for stuck bolts and parts. Not well known, but sure does work.

http://www.bluecreeper.com/

Hope you get them loose.