15A D8 Clutch locked out.

Hi,
welcome to the BB.
Boy, only ever did one of these up in about 1963/4.
If by frozen you mean the vertical linkage into the clutch housing is solidly locked, I can only think that the upper clutch throw out fork has worn right thru and is wedged against its trunion on the thrust bearing carrier thereby locking the mechanism.
If any of the over-centre locking dogs on the clutch engaging mechanism failed you should still have some rotational and for and aft movement in the vertical shaft.
Could water have gotten in and ice has frozen the linkages--just guessing you washed the unit before servicing it.

I also cannot see that changing fluids and filters could cause this unless there is an air lock in the hydraulic system of any sort of booster that may be on the clutch linkage but I do not recall these having a booster on the clutch.
Cheers,
Eddie B.

The top and bottom clutch release forks are tied together. Not likely one would move without the other unless something is broken. There is no booster involved. The clutch linkage is part of the transmission interlock mechanism. Could be something amiss there but I'm not sure what. I'd be looking to see if the interlock shaft that blocks the plungers is able to move and the spring loaded link operational.

Thanks Guys,
I've run this thing about 50 hours, ripping in water line , and now dozing dirt to level a field, it's quite the beast. Anyway we didn't wash it, but the plug in the bottom of the clutch is gone, looks like for a long time, but we haven't been any mud or water, with it.
To clarify on the clutch forks, the bottom one does not move but a hair, but the top one is solid.
I've got the service manual and parts book, so maybe me and my old cohort, can figure it out, just were'nt to egear to drop the clutch and converter. Our shops a dirt nob.
Thanks again

Plug is gone? Don't know much about 15a's but the 14a's had an oil clutch

15A's have a single plate dry clutch built much like the oil clutch.
Can you detect any movement of the sliding sleeve/collar? Maybe by prying.

Yea we tried to pry on the collar and also adjust the clutch both ways, could only move it one or two cogs ether way. it's pretty tight. Haven't got all the right tools (bigger hammer, different pry bars) but don't want to break anything. I heard from a guy in Australia that there might be a linkage between the trany and the clutch that keep it from popping out of gear, anybody know anything about that?

Yea we tried to pry on the collar and also adjust the clutch both ways, could only move it one or two cogs ether way. it's pretty tight. Haven't got all the right tools (bigger hammer, different pry bars) but don't want to break anything. I heard from a guy in Australia that there might be a linkage between the trany and the clutch that keep it from popping out of gear, anybody know anything about that?

Yes I saw that post on HEF. That is the interlock mechanism that I was referring to. Normally prevents any gear change without disengaging the clutch. I'm thinking that if one of the detent plungers was stuck it might interfere with clutch lever operation. I'd be looking for something minor before diving in.

Check section 110.1 in your service manual.

Thanks Old Magnet,
Looking at the manual, I think i see what your talking about, we're going to tie into it Monday, and see what damage can be done or hopefully undone. Jaluhn, I guess I don't need your PFD, but thanks anyway.