1993 JCB 217S - Slow Reverse Engagement

[rpaoness]

Once run "hard" for a few hours, the JCB seems to have developed slow reverse engagement (2-5 seconds ish?). Initial thoughts on possible causes are:
- low fluid viscosity (unlikely "the" cause since forward and gear shifts seem fine and "crisp")
- sluggish or sticky valve or solenoid (weak solenoid? There was visual case-cracking and possible coil winding on these "old" solenoids)
- leaking reverse piston seal (contrary indication would be that once-engaged reverse seems fine, however the main pump might be "keeping up" with the leak, just slowing initial fill/engagement)

Service manual:
https://drive.google.com/file/d/1nE4QBg ... sp=sharing

[rpaoness]

Per the troubleshooting guide if the issue only appears when hot they recommend solenoid valve cleaning and checking. Sheet 63-1 of the manual. I was wrong on pull/mechanical return - they appear to be diametrically opposed solenoids that pull in either direction. Some debris in the the reverse direction could be the culprit, or a weak solenoid pulling. I still need to figure out which solenoid out of the 3 pairs is the reverse function.

[rpaoness]

Diassembly instructions on page 82-2 (sheet 622 of the pdf) shows the reverse/high clutch solenoid. Might be ok to just swap those two solenoids since I have to remove them for cleaning anyhow.

[kevm14]

Aren't they pairs? Or is it the pair that performs the switching function. So are you swapping the position of a single pair, hoping to get the opposite delay and maybe narrow down which solenoid is lazy?

[rpaoness]

Yes. Check out the pictures and you'll see.

[rpaoness]

I wonder if I should order this and plan on installing. Could be less risk than taking the machine completely out of commission if I can't get the old one back together due to corrosion.

https://www.ebay.com/itm/332545224557?_ ... S45A546TTB

[rpaoness]

No delay when cold. Seems 100% repeatable though - delay came back once warm. One other data point I thought about was experimenting with the bucket-lift neutral button on the loader control lever. Pushing it somewhat above idle while gently rolling disengages and then releasing reengages. Since rpm’s are up, if it was a failing piston seal it “should” engage faster with higher fluid flow. Seems to have the same delay, which I think points to restriction in oil supply, which would be a symptom of a lazy-when warm solenoid. I’ll try to get some pics of the solenoid and see if I can order an oem one from eBay.

[rpaoness]

New solenoid (and two outrigger cylinder seal kits, because $15 off three items and one of them drifts down overnight now) are supposed to be delivered today.

[rpaoness]

Attempted to swap the valve this weekend, but there are very deep counter bores in the valve body down to the 4mm allen key size probably M5 SHCSs that hold it onto the manifold. All bores were full of crap. used a pick and air blow gun to pick out and blow out the crap and got down to the fasteners. Sprayed some WD40 "specialist" penetrant onto them. I had just regular allen keys that went that deep and got one to break free, but no luck on the other three yet. Left them to soak in the penetrant oil - hopefully I can reattempt at some point soon. I am very worried about stripping the heads, which would require some pretty advanced retrieval methods, including potentially grinding off the entire valve body or removal of the whole manifold and then drilling/machining off the heads if I do.

See post in the yard equipment section on the "other" hydraulic problem that has now cropped up.

[rpaoness]

I replaced solenoid 5/6 believing that was the reverse solenoid from a different page in the manual, and no improvement to slow reverse engagement.

I now feel like quite an idiot, because not only is solenoid 4 visually cracked and probably electrically broken, it is also responsible for low reverse and there's supposed to be 4 reverse speeds. I thought 1st reverse and 2nd reverse were the "same". That was a dumb assumption. So I now need to swap the removed 5/6 solenoid for the 3/4 solenoid. I also feel dumb for whooping on the sluggish machine in reverse, not knowing I was starting in 2nd all of the time and felt like I had weak reverse. At least it isn't blown, and I know I can get low-reverse by swapping solenoids.

Hopefully the bolts come out of the 3/4 solenoid. I almost thought I wasn't going to get the 5/6 solenoid out because of one stuck allen screw. I was ecstatic when it finally came out.

5/6 is in the foreground in the picture, 3/4 in the middle, and 1/2 in the far-field.