Mirage775 Posted November 30, 2014 Share Posted November 30, 2014 Pulled my blown engine and swapped it with a rebuilt block last weekend. Every gear shifted fine, including reverse. Fired it up last week, went to 1st, and it grinded a little, checked the slave cylinder and it was dry? I just filled it up before the engine blew. Anyway, we got 1st through 5th to shift without grinding, but reverse grinds, just a little and won't go in, unless the car's not running, then, it'll go right in and work after starting up. Please tell me the synchronizer isn't shot and the slave might just need bleeding? Thanks Quote Link to comment Share on other sites More sharing options...
NewZed Posted November 30, 2014 Share Posted November 30, 2014 There is no reverse synchro unless you've swapped in a late model 71C transmission. You could have sucked in a little air when the slave rod extended, as it was removed from the transmission. Bleeding would be the thing to do. Quote Link to comment Share on other sites More sharing options...
EuroDat Posted November 30, 2014 Share Posted November 30, 2014 (edited) Just to add some other possibilities after bleeding the clutch. Are you using the same clutch/pressure plate or one that came with the new block? If its your original clutch, did you check the spigot bearing in the crankshaft. Things that can cause your problem are: -Air in you hydraulics reducing clutch travel. -Dry or binding spigot bearing in the crank causing drag and not disengaging input shaft. -Clutch disc sticking on input shaft splines and won't move away from flywheel not letting the clutch disengage. The clutch disc actually moves back and forth a small amount when disengaging and engaging. -For some reason its fitted with an adjustable slave cylinder push rod with incorrect adjustment. Shouldn't be in a 280ZX, but possible. Chas Edited November 30, 2014 by EuroDat Quote Link to comment Share on other sites More sharing options...
beermanpete Posted December 1, 2014 Share Posted December 1, 2014 Another item to check is the throwout bearing collar. The length of the of the collar must match the pressure plate height. If you changed the pressure plate it could be from a different year and needs longer collar. Quote Link to comment Share on other sites More sharing options...
Mirage775 Posted December 1, 2014 Author Share Posted December 1, 2014 There is no reverse synchro unless you've swapped in a late model 71C transmission. You could have sucked in a little air when the slave rod extended, as it was removed from the transmission. Bleeding would be the thing to do. OK, no synchro is good news, lol! It's the original trans. I'm hoping bleeding will fix it, but I won't get to try until next weekend or later... Just to add some other possibilities after bleeding the clutch. Are you using the same clutch/pressure plate or one that came with the new block? If its your original clutch, did you check the spigot bearing in the crankshaft. Things that can cause your problem are: -Air in you hydraulics reducing clutch travel. -Dry or binding spigot bearing in the crank causing drag and not disengaging input shaft. -Clutch disc sticking on input shaft splines and won't move away from flywheel not letting the clutch disengage. The clutch disc actually moves back and forth a small amount when disengaging and engaging. -For some reason its fitted with an adjustable slave cylinder push rod with incorrect adjustment. Shouldn't be in a 280ZX, but possible. Chas Same clutch and PP. Not sure what you mean by spigot bearing, but we used an alignment tool to get everything, aligned... The clutch has to be disengaging or it wouldn't go into the other gears, correct? Another item to check is the throwout bearing collar. The length of the of the collar must match the pressure plate height. If you changed the pressure plate it could be from a different year and needs longer collar. I'm hoping it's just got air in the lines, but I still don't understand why all the forward gears shift fine, but reverse doesn't....? Quote Link to comment Share on other sites More sharing options...
Leon Posted December 1, 2014 Share Posted December 1, 2014 I'm hoping it's just got air in the lines, but I still don't understand why all the forward gears shift fine, but reverse doesn't....? As mentioned, there is no reverse gear syncro. Quote Link to comment Share on other sites More sharing options...
duragg Posted December 1, 2014 Share Posted December 1, 2014 Mine stopped going into Reverse too, but I injured it accidentally by trying to shift into reverse multiple times during a bumpy race at 100 mph or so. Wasn't my best day... I took tranny apart this weekend and the reverse idler is all chewed up. Will replace with some spare gears. If you are holding the clutch in, select 2nd, then reverse and you still get a grind with car sitting still = your clutch is dragging and injuring your other syncros. Must bleed clutch after every time you remove the slave. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted December 1, 2014 Share Posted December 1, 2014 Grinding into reverse is usually the first sign of bad hydraulics. Dry slave cylinder indicates bad hydraulics as well. Pull the boot off of the master up by the pedal on the firewall, and the slave on the trans. If you see fluid, replace. I always replace both as a set. Quote Link to comment Share on other sites More sharing options...
EuroDat Posted December 1, 2014 Share Posted December 1, 2014 (edited) Same clutch and PP. Not sure what you mean by spigot bearing, but we used an alignment tool to get everything, aligned... The clutch has to be disengaging or it wouldn't go into the other gears, correct? I'm hoping it's just got air in the lines, but I still don't understand why all the forward gears shift fine, but reverse doesn't....? The spigot bearing is where the tip of the input shaft enters the rear of the crankshaft. There are two types available. A Bronze bush or a Ball bearing. If the bronze bush is dry it can cause drag which will make it difficult to get into reverse and require extra pressure on the stick to get it into the forward gears. The same goes for the ball bearing type. If the bearing is dry or seized it will also create drag with the same effect as the dry bronze bush. Your forward gears are still shifting fine because the synchros are doing their work and "synchronize" the two shafts. Its also a sign that they are still in good condition. Try this for a simple test while the car is standing still with engine running. Put it into fifth and then quickly shift to reverse. That way all the shafts will be stationary (while in fifth) and you should be able to get it into reverse before the input shaft speeds up too much. You should be able to get it into reverse with out too much grinding. The longer you wait after pulling it out of reverse the more it will grind. With a bit of luck it will just be air or worn out clutch MC or slave. Thats the most likly cause. Like Jon said, if you change them, change both. I would also get a new hydraulic hose as well. Old hoses can sometimes flex (expand under pressure) and reduce travel as well. I included a cross sectional drawing of the clutch. The spigot bearing is blue in colour. Chas Edit: Pilot bearings and Spigot bearings are the same thing. Edited December 1, 2014 by EuroDat Quote Link to comment Share on other sites More sharing options...
Mirage775 Posted December 1, 2014 Author Share Posted December 1, 2014 Thanks for all the help everyone! It'll be a couple weeks before I get back to the car. It only has 110k miles on it and like I said everything was working prior to pulling the old engine? I can't say anything about the spigot, Chas, as an old school mechanic friend of my dads helped me swap everything. He put my old flywheel, clutch and PP on one day when I wasn't there. I'll look into replacing both slave cylinders, if bleeding doesn't do the trick. I've never been good with transmissions... Quote Link to comment Share on other sites More sharing options...
EuroDat Posted December 1, 2014 Share Posted December 1, 2014 Hi Jason, I have some figures on push rod throw. Thats the amount it will travel when you depress the clutch pedal. Ill dig it up tomorrow and post it. It might be some help when you bleed the clutch and check how far it travels. Cheers Chas Quote Link to comment Share on other sites More sharing options...
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