Car: 1974 260z w/ 5spd transmission.

Problem: I cannot shift the transmission into any gear at a standstill when the engine is on. When the engine is off, I have no issues shifting.

Here are the following repairs/work I've done to try to solve this issue:

- New slave clutch cylinder, current master cylinder has no leaks or any issues, and bled the system of air in the lines.
- Clutch adjustment: pushrod on the slave cylinder extends quite a bit now so I'm sure there is enough pressure being made from the master cylinder
- Note: there are no visible leaks in the lines or the master/slave clutch cylinder, pushrod on the slave cylinder does not slowly retract when the clutch is depressed and held at bottom position.

Here are following repairs/work I haven't done yet:

- Flushed the transmission fluid and put new fluid (I don't know when it was last serviced either, I'm the car's 3rd owner)

Any ideas on what could be the source of my transmission issues? Will be greatly appreciated, thanks!

 

Welcome to ZDriver. Need a little more history here. Please tell us more about your car, how long you've had it, what the previous owner did to it and your own assessment of your mechanical skills.

Since 260Zs never came with a 5 speed, you've got a car with what I think is a nice modification (I want to eventually do this myself).

Has this car ever worked correctly for you? If so, were there any changes you made just before this started or did it "just happen"?

As far as I can tell, it sounds like your clutch isn't disengaging. Going through the cylinders, master and slave was likely a good thing to do.

I've noticed that new slave cylinders often don't have the correct length pushrod (usually too short). In my own case I reused my old pushrod when I replaced the slave cylinder.

I've read somewhere that when doing the four to five speed swap, there are some other parts that must be changed other than just the transmission. Not sure what they are but I think a search through this forum will help you out.

 

Thanks for responding beg3yrs,

More info about my car:
- RLS30 build date: 3/74
- owned it for 4 years now
- from what I can remember, the previous owner did not do a lot to the car other than maintain it (I wasn't able to get a list of repairs/work done). I do know that the transmission swap happened before the previous owner bought the car

My mechanical skills: amateur when it comes to car and pretty limited to the tools I have (I only have a basic spanner and wrench set). I got this car with the intention to learn and do most of the repairs myself with the help of a Haynes manual.

More on the 5 speed:
- when the car was bought: clutch was good and transmission shifted smoothly - Issues did not occur until 2 years ago when I started noticing that I was having trouble shifting into gear at low speeds or at a standstill. No problem shifting at speed. It wasn't bad then, but it progressively got worse to the point where it is now.

I didn't mention this in my initial post, but while the car is on and force is applied to the shifter when attempting to engage a gear, the car nudges forward a bit. Not sure what this means though.

I'll look at the lengths of the push rods and check if the new one is shorter than the old, thanks again.

 

That's a much better description, thanks.

Now that it is understood that it shifts well at speed, I'm leaning away from thinking the problem is in the clutch system and more toward the synchros getting worn inside the transmission. With everything spinning at speed the synchros may have an easier job of allowing gears to engage.

Probably time to take it to a transmission shop ...

Or, you could just give it to me and I'll get it fixed and installed in my 260Z ...

Kidding aside, as an FYI, there's a seller on eBay selling re-manufactured 5 speeds here: http://www.ebay.com/itm/Datsun-240Z-260Z-280ZX-rebuilt-5-speed-manual-transmission-OEM/401148269910?_trksid=p2047675.c100012.m1985&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D35389%26meid%3D752ed40e429b4952a4d883446c15e01c%26pid%3D100012%26rk%3D1%26rkt%3D10%26sd%3D401146595590
It will give you a price point for reference.

 

I missed the significance of the second paragraph in the quote. Seems it still might be your clutch system after all. This could be a symptom of the clutch not fully disengaging. Again, look at those push rods.

Second, good for you with the desire to learn and do repairs. Get yourself a copy of the Factory Service Manual (FSM). They're free online here: XenonZcar.com S30 Factory Service manuals

You'll find just about everything you need there. I find the Haynes manuals useful only if I just can't understand the FSM and need another way for something to be explained.

I started out several years ago with not much more experience and tools than you've got now. Check this out and you will see what perseverance can do: https://www.zdriver.com/forums/240z-...project-37922/

 

I hope its just the clutch system. Having work done on the transmission looks expensive and not too friendly for a college kid budget. I'll definitely look into those pushrods. Thanks again for the info and links.

 

A symptom of clutch wear is slipping clutch. At speed it works but the syncros are doing all the work by stopping the shafts. I think you simply have air in the clutch line. Air does not compress so it won't push the clutch rod. Verify this by having someone press down on the pedal and from under the car you check for movement of the push rod. It should move about 1/2 to 3/4 ". I doubt if yours is moving at all.
By the way, shitcan that Haynes (it has a lot of misinformation). Download the factory service manual and start buying more tools.The mechanics that know these cars are few and you can't afford $110 per hour for things you can learn to fix yourself.
Tom