1981 280zx 5 speed

[Zed Head]

A good examination of just the 2nd and 3rd synchros might tell a lot.  Not sure which are easiest to remove.

If you know anyone or have a trustworthy shop nearby you might just take the whole gear assembly over as-is and let them take a look.  A guy who's seen many transmissions could probably tell you if a new oil gutter and reverse idler is going to produce a driveable unit.

The problem with banging the gears and working things hard is that it torques the shafts and bearings.  People often find pieces of the bearing retainers on their magnets.  The shift forks get worn and cracked, their retaining pins can break.  There are just many small things to check, especially on an unknown unit.  

On the other hand, I've installed transmissions then pulled them back out a couple of weeks later.  It comes down to what you're handy at.

[Dave WM]

ok checked the clearances, all looked good except for the OD gear which was more like .3mm vs the max of .17mm per the FSM.

I tried for better pics and better video, but could not get much better than what I shot. From the pic you sent Zed Head, I can't really tell if mine are any worse. they look better in person than the pic shows. (I think the oil and blurriness maybe making mine look worse in the pics).

I can't account for the larger clearance on the OD all the rest were well with in spec. The reverse idler had the tightest of all.

I was reading it like this, 1st gear was the largest starting from the adapter plate on the main shaft, then going forward 2nd and 3rd. The most forward gear was the gear on the main drive shaft, it had no given clearance.

The OD gear was on the other side of the adapter plate, last gear on the main shaft, clearance was checked between the gear and the washer before the nut.

This was the gear end play. I am not sure I can check the other items listed in the FSM without dissassy of the gear cluster.

Update, I found a different FSM for my trans and it said the OD gear end play should be .31-.35 so looks like I am ok on that!!

this second FSM seems like a better match they both have the same transmission number but on has ZX on the manual label is the one I was using and had the tighter clearance on the OD, BUT it does not show the anti baulking device. The other manual has the FS5W71b reference, no mention of ZX but does have the anit baulking device like mine and has the larger OD clearance that matches mine.

 

Edited April 13, 2016 by Dave WM

[Dave WM]

there is a couple shops nearby, that I will try to stop by maybe tomorrow. See if they will give me an opinion. My guess is it will be they cant tell anything with out tear down which is fair enough. I would like to put in the reverse idler just in case its fine, but sounds like that may be a waste of time unless I go with a complete tear down. Not sure my skills are up to that. So maybe the best idea is to bolt it up and just give it a try as is. At least I know the propeller shaft that goes into the rear bushing will be getting its supply of oil from the gutter. I don't plan to drive it hard, just was looking for a high speed gear so I can take it out on the turnpike and keep up without spinning 4k all day long.

[Mark Maras]

 IMO, Your skills have gotten you this far and if you have the bucks for parts, you can tear the main shaft down. Organization, simple tools with a clean workspace. Lay everything in order and the same direction as you disassemble it. Clean and inspect it one part at a time (It's a good idea NOT to have help in this step) and remember to set each part down in the same order, exactly the way it was. It's a good learning experience and an accomplishment you'll be proud of. You'll likely never have to deal with it again.

 

 

[Dave WM]

so maybe just start out with disassembling the main shaft on the front of the adapter plate. Looking over the FSM with the complete tear down looks daunting.

If I can get thru that with some lever of confidence maybe I can continue with the tear down. Will have to mull it over, thanks for the input guys! really appreciate it.

Re reading the FSM, looks like the main drive gear and 3rd gear are pretty easy, then gets a lot more complicated to get the 1st and 2nd. I think I have to read this a few more times.

 

Edited April 13, 2016 by Dave WM

[Mark Maras]

 The exploded view does make it look daunting but it's little more than sliding each pc. off the shaft, one at a time. The most important part of the process (the most difficult for me) is to maintain the orientation and order of the parts as you clean and inspect them. Keep it all straight and assembly is easy.

[EuroDat]

Third is easy to get to. You will have to pull the front counter shaft gear off to get the input shaft off. Pay attention to which direction it is mounted on the shaft. It fits on both ways, but one way it will be a little out of alignment and could cause whining noise later.

Looking at the reverse gear, looks like a PO has been driving it with a worn out clutch master cylinder or slave cylinder. Not enough clutch travel to fully disengage and he has been grinding it into gear.

The oversized tolerance on the baulk ring is a sign it could have aftermarket baulk rings. That means its been played with in the past.

Baulk rings can be touchy and cause problems even though they look good. Its not the outside teeth thats most important. The fine ribs on the inside make all the difference.

[Dave WM]

are the bearings a major pain to get off, I have a bearing puller but some of what they show looks pretty special?

I have a local junk yard that sells cores for 150$ but with out inspecting them I could be no better off. Just thinking ahead on that.

Edited April 13, 2016 by Dave WM

[Mark Maras]

  I was replacing the bearings, so I used a hammer, assorted punches and other useful implements of destruction to remove them. Crude but effective.

[Zed Head]

If I was in this situation I would work up a short list of "project stoppers".  Bail-out points, where I knew I wasn't going to get the results I wanted.  So far, it looks like the expectation is for something that shifts like the current 4 speed, but has an extra gear.  But if you've only experienced your good-shifting 4 speed, you might not really understand how a simple thing like a 2nd gear that grinds at 3000 RPM can destroy your fun.  Or a 5th gear that pops out while you're driving, or sloppy shifting from loose shift forks.  That's your dilemma, how to evaluate the quality of the parts, without having tried them.

Maybe we could come up with a list of specific things to check, like the detents on the shift rods, or the play and wear on the shifting forks.  Some of these things are easy to examine, like the shift rod detents.  If those are wasted from banging gears, the replacement cost might put you over the top.  Another thing that cna hide but look fine, is a broken synchro gear.  They can break in one spot but the break can stay closed.  That's why you need to get bright lights and a magnifying glass and pry around or tear things down.

That's how I look at these projects.  Avoid sinking too much in to it until you can lay out the path to success.

[Dave WM]

1 hour ago, EuroDat said:

Third is easy to get to. You will have to pull the front counter shaft gear off to get the input shaft off. Pay attention to which direction it is mounted on the shaft. It fits on both ways, but one way it will be a little out of alignment and could cause whining noise later.

Looking at the reverse gear, looks like a PO has been driving it with a worn out clutch master cylinder or slave cylinder. Not enough clutch travel to fully disengage and he has been grinding it into gear.

The oversized tolerance on the baulk ring is a sign it could have aftermarket baulk rings. That means its been played with in the past.

Baulk rings can be touchy and cause problems even though they look good. Its not the outside teeth thats most important. The fine ribs on the inside make all the difference.

EuroDat,  how are you able to tell the balk ring tolerance? Or is it that obvious in the photos I attached. I thought I had to pull the gears out to measure that?

My background has been in electronics, specifically vintage electronics, which my typical process would go like this:

Base line trial (with closely monitored checks of voltage, current, heat). The base line is used as a point of reference so I know if there are any fatal flaws that would make it not worth fixing (unattainable parts).

My initial thoughts were to correct the obvious (missing oil gutter, leaking seals, chipped teeth) install and make a base line run.

this keeps me low on the budget (but for the time to pull and reinstall which while difficult I think I can handle, I have good jack stands and I am reasonably strong so no $ outlay). Evaluate the base line (noises/shifting difficulty/overall performance). IF the above checks out then stop (do no harm). IF there are issues, then pull down get a rebuild kit (bearings/synchros) and rebuild. Time consuming but it is a hobby after all.

I hear you guys though on the why do the base line, just rebuild. Its just not the way I generally do things but then again I have no exp with cars so this is new territory for me.

I don't abuse things, so I hope the car will last a long time.

[Dave WM]

58 minutes ago, Zed Head said:

 

Maybe we could come up with a list of specific things to check, like the detents on the shift rods, or the play and wear on the shifting forks.  Some of these things are easy to examine, like the shift rod detents.

I did check the end gaps, they look ok, any pointers are welcome. the shift forks I don't recall a spec on the play but I can certainly get a reading and get back.

Edited April 13, 2016 by Dave WM