Truck no go!!!!!

[kn1ghtride]

Hello and HELP!!!!

I have a 1985 Nissan 720 4x4 that suddenly won't go.  I drove it a week ago in a snow storm in 4WD and had NO issues.  I parked it in the driveway getting it in just the right spot and went in for the night.  The next day I tried to visit my parents and when I let the clutch out- nothing.  I can put the truck in any gear with it running and no clutch- no grinding at all.  The clutch pedal feels a little stiff and sloppy at the same time.  I checked the resevoir and it has fluid in it.  Can anyone shed some light?  It just seems so weird it was fine one day and completely nothing the next day.  Slave cylinder?  Clutch?  Transmission?  If it was a slave cylinder, wouldn't it still go into gear and grind/stall?  If it was the clutch, wouldn't it slip first?  I am open to all ideas...

Joe

[datzenmike]

You've slipped the transfer case into neutral.

[DaveZilla]

Yup...

[Jim_Rockford]

transmission should still grind trying to shift it with no clutch..

[datzenmike]

Reverse for sure.  All other gears have synchromesh rings. They will act like a tiny clutchs. When you try to shift, the synchros will rub the other 'gear', and because it's disconnected in the trans case, will spin it and the primary driveshaft up to mating speed and engage. It's not perfect and if you shift fast/hard enough it may grind.

 

I'm thinking it's quiet because everything IS working.

 

This is an Occam's razor example. It could be a lot of different things, it could be aliens causing it but that would be vastly exotic. Instead, it would be simpler to have bumped it out of gear or if having used 4WD and parked it for the night, perhaps failed to shift it fully into 2WD. Easily done.

[Jim_Rockford]

syncos will not help shifting with out a clutch, even when new, they are only there to slow down the gearset when not being powered. under power they should grind like a bitch.

[datzenmike]

I've up and down shifted without a clutch and the synchros will make gear speed adjustments. The shifter may feel a bit stiff and you can sometimes hear the internal parts whine and speed up. Either way...

 

If the transmission was to grind... this one does not. Which strengthens the position that the clutch IS working and the transfer case is out of gear.

[xsdg]

syncos will not help shifting with out a clutch, even when new, they are only there to slow down the gearset when not being powered. under power they should grind like a bitch.

 

The grinding is just because the truck has enough inertia that the synchros can't pull up the transmission output shaft speed (and, because it's directly connected, the vehicle speed) in time, and so the dogs grind against each other.

 

If the transfer case is disconnected and is well-lubricated, then the output side of the tranny no longer has all of that inertia — it's no longer trying to turn the wheels — and so it makes plenty of sense for the synchros to be able to spin up the transfer case without causing the dogs to grind.

 

On my Cayman, I once accidentally tried to push the stick into first without clutching and I felt the vehicle trying to move forward before any grinding happened (at which point I went back to neutral, smacked myself, and snapped out of it).  Goes to show that whether grinding happens or not depends on the transmission design, the synchros, the amount of force on the shifter, and how much inertia there is in the system.  If you push the stick to the synchro engagement point, but never get to the dog engagement point, then it's impossible for any grinding to happen, because the dogs will never touch.