On the 8FGCU25 where we found the green crud, after cleaning it up everything began working normally again.
But further gossip filtering to us from dock personnel discloses that some operators had experienced loss of mast hydraulic functions as well as wheel drive on that truck. But they are saying that the problem would appear and then disappear if you cycled the key switch off and then restarted the engine. But the problems would recur pretty soon. It finally came to the shop and we started searching and that's when we discovered the battery acid issue.

daniel,
i've learned to never say never ;o)
but for just corroded connections i highly doubt it
clean em up and see if the problem goes away

Sorry, I have been out of town. Looks like the battery box is my problem, green crud on all the connections. I'll clean it up and let you know. Is it possible it fried the VCM?

The new part is NOT exactly the same (as I recall). Make sure everything is very clean and lubed when assemblying. I think the parts have to move pretty freely internal

Thanks! Pulled it out and the little spring inside was stuck inside sideways. Got one on order. I'll post back to let you know when it's back together to confirm this fixed it.

When the bottom spring of the valve is broken, the forks will lower very very slowly. The spring in question is not to be confused w/ the hand recoil spring.
Internal to the lower spool is a sliding valve (as I recall) that is spring activated. When that spring fails, the forks drop slow. Access to the spring is to get a pair of "opposite plyers" and pull out the section. Again be advised, once you remove the slide valve, it must be replaced, so be sure of your problem.
I isolated the problem before I condemed the control valve.

7777,
just to be sure, it it on the actual spool or on the one in front of it that is under the solenoid valve? The mechanical spool section feels like it has good spring tension in both directions.

Greg

The original post had a light on but the one I'm working on does not. I have the control valve out now. I will check the connections under the battery, but not having any faults showing, I am guessing it might be the spring. I tried to pull it out before I read that post, but since it was tight I didn't go any further on it for fear of breaking a good part. Great info guys, I have a good direction to go today.

Yes, after I posted I read, "lite on"

generally if the fork light on the dash display is "on" this indicates that the seat switch circuit is open.
This could range from a bad seat switch to an open in the circuit in the seat switch circuit somewhere. And i suppose in a worse case scenario the VCM. The usual symptoms were the dash light, no hydraulic or drive functions.

I think i'd concentrate on that and verify there is no problem there first before checking anything else.

Just my thoughts on this :o)

There is a bullitin on the series 8 toyotas'. In the lowering spool of the control valve there is a spring that is not capable to handle stress, and it breaks prematurely. Its much easier to remove the valve and take out the lower section of the spool. BE ADVISED, THAT AFTER YOU REMOVE THAT PARTICULAR SECTION (its in very tight), THAT IT GETS DAMAGED AND CANNOT/OR SHOULD NOT BE REINSTALLED.
P/N 67609-26601-71 about $132

gshort, recently we have found two 8FGCU25 models in our fleet where battery acid had leaked from the left front corner of the battery tray and puddled on the cover of the ECM/junction center mounted below the battery tray.
I don't know what material Toyota uses (plastic or resin?) to make the cover for this electrical center but I can tell you that battery acid will attack and damage it.
The first truck had a strange complaint about the transmission suddenly disengaging while traveling so we first began checking the OPSS (seat switch) circuits.
Not finding any fault in the seat circuits per se, we looked further.
The tech working that truck discovered holes in the ECM/junction center cover and removed the cover to look inside.
In the very bottom of the junction center are some cam lock harness connectors. He unlocked the connectors and you could see green corrosion traces had formed all across the bottom of the connector bodies.
We cleaned out the green stuff with electronics spray cleaner followed by blasting out with compressed air nozzle.
Then we sprayed electronics grade dielectric coating on both halves of all connectors.
We are currently beginning to work on a solution/remedy for this and so far we have decided do the following:
Clean the acid damaged area of the j-box cover and seal the holes in the cover with RTV.
Clean the battery tray and apply RTV to the left and right front corners of the OEM battery tray to form a "dam" against any further acid leaking off at those locations.
Drill a 5/16" dia hole in the floor of the OEM battery tray in the right rear corner of the tray.

Though our complaint was about travel malfunction, I would hazard a guess that mast functions could be affected too, since the cause seemed to arise in the OPSS circuits in the j-box.

Any update? I have an 8FGU25 with the same problem.

Probably will not travel either, Check seat switch wiring and switch for continuity and you will find source of trouble.

sounds dumb but check the seat switch and wiring for open circuit and frame contact, then check that the fuses are good and are all there. i have noticed an alarming trend of "stolen" fuses and it has given some tech's fits. they all check good but open holes are common so overlooked. the **** fuses fit cars and are very convenient. there are also some possible problems with the flow regulator valve in the contol valve but that's a pretty big job so kill the small s*&% first.