I have researched, called z places and asked questions on forums but there is still some fog with my 77 coupe 4 speed to 81 zx 5 speed conversion. My clutch isnt engaging all the way so my trans is slipping. This should be straight forward since I have a 77 280z coupe and got the trans from a 81zx coupe-non turbo. According to every one my flywheel should be the same for 77 and 81 280s (225mm). According to everyone my clutch should be the same for 77 and 81 280z. (that includes clutch disk, pressure plate and bearings).

If all these parts are interchangeable between 280z and 280zx then why is the collar for a type b 4speed larger.(I assume type B is the 4speed that came on my 77) See comparison here;

http://www.zparts.com/zptech/articles/trans_swap%20parts/4tobear_specs1.html

That means the pressure plate for the 4 speed is different than the 5 speed but everyone lists only one clutch. If it isnt fully engaging would the taller original 77z collar make it engage better or disengage even more. The collar that is in it is the 81zx collar that everyone says to use.

FYI: I have adjusted my pedal shorter, longer and to spec. The new clutch cost around $200+ so I dont think its a cheapo. (someone said he thinks its a crappy clutch and thats is my problem)

1977 280z * ZX distributor mod * 4x4 front calipers

Hi louisf:

You have several things out of wack in your thinking ... which may be leading to your confusion.

1. Eric, on the site you reference - states that the data isn't 100% reliable... that is true. So there is no reason to believe that the 4 speed and 5 speed use different throw-out bearing collar lengths.

The truth is - all the transmissions that I have measured - Type A, Type B, Four Speed or Five Speed have the same transmission input shaft length. So you have a fixed amount of space for any combination of Clutch Disc, Pressure Plate, Throw-out Bearing, Throw-out Bearing Collar - to fit onto.

2. The 280Z Clutch Assemblies as well as the later 280ZX Clutch Assemblies are NOT the "same". Just because you can use a newer design part (Clutch Assembly) to replace an older and no longer available part - it doesn't follow that they are the "same". It only means that the newer part can preform the same function, fit in the same manor and have somewhat the same form. So don't think of them as being "the same" - think of one as being a "replacement" for the other.

3. The height {distance measured from the flywheel to the top of the Pressure Plate Fingers} or call it the thickness of the various Pressure Plates used - determines the length of the Throw-out Bearing Collar that has to be used.

The thickness or height of the Pressure Plate depends on when it was originally produced, who produced it and to which specification (240Z, 260Z, 280Z or 280ZX) it was produced. Because the 280ZX Clutch Assembly will fit, preform the same function and attaches in the same manor as the original 240. 260 or 280Z units, the 280ZX Assembly is considered "a replacement" for all of them.

If you order three Pressure Plates, from three different sources - but all for a 280Z - you have a good chance of winding up with two or all three being different thicknesses. - you have about the same chance of them all being the same, yet different than your OEM Pressure Plate.

For a time - some manufacturers offered two different "thicknesses" of Pressure Plates... and it was up to you as to which one you wanted to order; but for the most part that is a thing of the past now.

In effect - the original 240-Z Pressure Plates were the thickest... and require the shortest Throw-out Bearing Collar, they also had the lowest clamping force. The newest 280ZX Pressure Plates were the thinnest and require the longest Throw-out Bearing Collars.

Over the years, all the manufacturers consolidated the various Pressure Plates into one spec.. to be used as a "replacement part" for all the others. The real kick in the butt is the fact that different manufactures used different spec.'s... some used the 280ZX spec. and some seem to have stuck with the 280Z spec. The two are very close, but not identical.

4. If the throw-out bearing collar is slightly too long - it will retain light pressure on the Pressure Plate Fingers (via the throw-out bearing) .. and wear the clutch out pre-maturely. If the throw-out bearing collar is longer still - it will not allow the clutch to fully engage.

On the other hand - if the throw-out bearing collar is too short - the clutch will not disengage completely and you can't shift gears with the engine running.

Looking at your description - my guess would be that you need to next shorter Throw-Out Bearing Collar. Which is more than likely the 280ZX Throw-out Bearing Collar.

Unless you are the original owner of the car - and you have done all the clutch replacements in the past you really have no idea of which clutch assembly was in the car, nor which Throw-out Bearing Collar was used...

When swapping only the transmissions - a good rule of thumb is to use the Throw-out Bearing Collar that was used with the CLUTCH in the car (not the one that came with the new transmission). If you change both the transmissions and the Clutch Assemblies at the same time - - - you have to pay very close attention to the height of the old clutch vs. the height of the new replacement. Then you have to use a Throw-Out Bearing Collar that matches the needs of the new Clutch Assembly.

Hope I phrased all that correctly.....

FWIW,

Carl B.

thanks Carl your explanation helped alot. I assumed the zx junkyard 5 speed trans had the zx collar but who knows. Instead of dropping the trans again(need mechanic) I may just shorten the slave rod.

Hi Louisf:

You can try that if you have an old/extra slave rod... but it may not work. You can only pull the clutch fork back so far... and if the Throw-out Bearing Collar in there is too long - the throw-out bearing still won't completely release from the pressure plate fingers...

good luck,

Carl B.

Carl is correct. Changing the rod will likely have no effect on the problem at hand. When the clutch is engaged there should be very little BUT perceivable play in the clutch fork. This ensures that the throwout bearing is not keeping the pressure plate lightly disengaged or allowing the TO bearing to be turning even when not in use (declutching). I replied to your post over at Zcar with more detail if you want to look there.

If my PP isnt to the right spec is there a formula that I need to follow to get the correct engagement. PP height + collar = correct height. Or do I just get a smaller collar and hope it works.

Think you are missing the point here, there are 2 different throwout bearings a short and long, sounds like you have the long one and need the short one!

ok. just wanted to make sure I got it right before we drop the trans again. Didnt want to do it a third time. thanks everyone

If my PP isnt to the right spec is there a formula that I need to follow to get the correct engagement. PP height + collar = correct height. Or do I just get a smaller collar and hope it works.

Hi louisf:

Yes, it is more than likely that there is a formula to follow - I don't know what it is. So the process is always a trail and error procedure, unless you are installing all new OEM Parts (like a 280ZX Clutch Assembly, Throw-out Bearing Collar and Throw-out Bearing).

There are actually three or four different lengths of the Throw-out Bearing Collars, so if you are using used parts... mixed/matched of unknown origin.. you are back to trail and error...

Just to add a bit of trivia:

Nissan mechanics actually had a special tool - a base plate to which the Clutch Assembly was bolted, then it was possible to get an accurate measurement of the installed Pressure Plate height... and from that one could derive the correct Throw-out Bearing Collar length. As I recall one could also measure the pressure it took to compress the clutch fingers, to see if the Pressure Plate was within spec.'s

If you are going to pull the tranny again - be sure to check the clutch assembly itself. We are all guessing it's the Throw-out Bearing Collar length, based on your initial description of the process, the parts involved and the symptoms..... but it is still possible your clutch just went out - or you have a rear main seal leaking oil on the clutch disc etc...

good luck,

Carl B.

I had one more thought to add:

If you haven't already, open the bleed on the slave cylinder to confirm that the problem isn't elsewhere.

I did a clutch swap on a 240z and found I couldn't engage the clutch when I was done.

To make a long story short, cracking the bleeder open solved the problem. In hindsight, I think that should have told me the release port in the MC wasn't opening back up.

Al