Clutch or synchro issues?

[mechenginic0]

Hi all! This is my first post as a member of NICOclub, so TIA for your help, and I look forward to contributing whatever I can. Now on to the issue at hand...

I was driving along the other day about 55 mph and suddenly I could not get the truck ('86 D21, 2.4, rwd, 5-spd) into gear. I pulled over, waited a minute, was able to finally jam it into 1st, but nothing past that and ultimately had to stop and have it towed.

The clutch slave has failed on this truck once before causing similar symptoms, so I was hoping that was the case, but replacing the cylinder and bleeding the system took me back to square one. Of note, depressing the clutch pedal seems to fully extend the slave cylinder's piston, and this time the clutch pedal is HARDER to press in, vs. traveling easily to the floor when the slave last failed. The transmission will shift easily into gear when the truck is off, but it is like hitting a brick wall when the engine is running; no grinding gears, etc.

Some brief searches online suggested possibly bad pressure plate/springs, and the clutch has started slipping every now and then so I know it's on its way out. I was all set to order a clutch and flywheel set online but further digging around on this forum and other places seems to suggest that this may in fact be a synchro problem. I am at a loss as for how to diagnose it and was hoping someone here could shed some light before/while I drop the trans tomorrow. I have done plenty of my own work on other vehicles, but mostly in the realms of brakes, suspension, timing belts etc, so transmissions are still quite a mystery. Thanks again for any help you can offer as to what I should look for, what things SHOULD look like, what it might be, etc.

[Adverse Effects]

when i say hot or cold here i am talking about the transition and clutch the motor temp really dont play a part in it at the moment

so you can get it in gear when cold and engine not running

what about cold and engine running?

or hot and engine not running

it could be in the box its self and not the clutch (that is what it sounds like to me and heat will do strange things)

oww dose it have oil in the box have you checked the level?

[whomadewho]

A couple things you can try - Park the truck on a level surface, with the truck in neutral ( engine not running) try pushing the truck by hand. If the vehicle pushes very hard chances are the clutch is hanging up. You can also can have someone disengage the clutch start the engine and again try pushing the vehicle again, should push easy. The number one cause of transmission failure is low lube level and incorrect lube. Might try draining the fluid and look for brass or metal. If the pedal seems to push hard, could be a bad master clutch cylinder and even though you replaced the slave cylinder with all the parts coming from over the pond doesn't guarantee its good. If you replace the clutch find a quality new brand. I went with a Hayes high performance clutch. The biggest issue you're facing, is if you do R&R is the transmission any good ?? Also when you replace the clutch,if you have children send them to the movies and don't forget to go to church and seek forgiveness. Good luck.

[mechenginic0]

Thanks for your responses.

Adverse Effects: I was able to get it in gear when everything was hot and the motor was OFF, as well as the next morning with everything cold and the motor off. Started it back up and it would not go into gear cold, and obviously didn't go into gear hot the night before. So it seems it will not go into gear with the engine on, hot or cold, but it WILL with the engine off, hot or cold.

whomadewho: We had to push the truck around quite a bit to get it on the flatbed and into a spot back at my place, and it seemed to roll pretty normal (one guy could push it up a slight grade with me in it). I drained the fluid while I waited for the tow, in anticipation of dropping the trans. The oil was a little grayer than I think it should be, and the drain plug magnet was coated in metal shavings. Of note, this truck has 254k on the odometer, which doesn't work anymore. Likely somewhere around 275K on the engine and trans. I'm going to drop the trans this afternoon and take a look around, see if anything looks very off.

Thanks again for your help and advice, it's very much appreciated.

[Adverse Effects]

can you put it in gear and push the clutch in and then start the motor?

dose it want to drive off

[whomadewho]

275k - just getting broke in. If the transmission is bad you can go online - car-part.com used car parts Good site. Not uncommon to find a silver color when you drain the transmission, It's the metal & brass pieces that would concern me. You can have the flywheel resurfaced saves $$. Never worked on a 1987 but when you take it apart if POSSIBLE you might want to consider replacing the rear main oil seal.

[whomadewho]

Before you get started check the clearance of the fan blade making sure it doesn't make contact with the radiator or the fan shroud.