Transmission problem
1986 Nissan Truck 4 cyl Four Wheel Drive Manual 270000 miles
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I have a 1986 Nissan 720 pickup 4x4 MT with a z24 motor. lately my truck doesn't like to move, it will roll all day while its in neutral with no problems or binding of any kind. When I put it in gear (engine running or not) and have the clutch disengaged (pedal to the floor) it will only roll maby 2-3 in. then stop and it wont shift out of gear unless i power through it. I have checked the oil in the transmission and changed the transfer case thinking that was the problem. I know the syncros are going bad cause i have to clutch it just right and bring up the revs to down shift (up shifting is ok but sometimes have to do the same thing). My question is, is there something i can replace inside the transmission (if it is the culprit of the problem) or will i just have to bite the bullet and replace the whole thing?

A clutch engagement problem sounds like what you are experienceing.
Has the clutch master and slave been verified as functioning properly?
Check their operation. if this is good then another possibility is possible the pilot bearing binding on the input shaft so even though the clutch works the input shaft still turns making it very hard to shift .
And sounds like damage to syncros has occured.
Let me what you find

I believe they are both good. I troubleshot a little more earlier by putting the transfer case in neutral and shifted through all gears with engine running to see if I could find any binding in ant certain gear. When i depressed the clutch the main drive shaft stopped spinning and when i released it it spun with no binding in any gear. That leads me to believe that the clutch system is working properly.

With that info I would say internal problem for sure possible cause input shaft must be unable to free spin when clutch is engaged this will keep lay shaft turning. Making shifting hard also it would not roll because with clutch in the the input still turns the lay so with the driveshaft keeping the main shaft turning via rolling of the wheels it can't because the lay shaft is in a bind with the input keeping main from free wheeling.
Hope this makes sence
You will never know till you tear it down

Hi Nissan720,

With engine off, engage each gear including reverse and test if any gear it will free up with clutch pedal depressed.

KHLow2008,

With engine off (or on in this matter) as long as i haven't moved to that binding point I can shift freely into any gear, it is only after i have reached that binding point that i have problems shifting. Another tidbit of info is that when I do try to drive it (back into the parking spot only) the truck shakes while moving.

Hi Nissan720,

What I meant was engage 1first, roll till it binds.
Free it Engage 2nd gear, roll it till it binds. Repeat for all other gears and see if any gear will not bind.

Once the binding point is reached, does rolling the truck in reverse direction. free up the gears?

When the vehicle shakes when reversing, it could mean one of the forward gears is engaged and not freeing up.

You would have to strip the trans to find out the problem. Most probably excessive clearance due to a loose lock nut since you suspect some synchros are bad.