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txvepr

Could it be a slipping Clutch?

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So I just installed a 5 speed transmission in my 78 280Z. Used to have a 4 speed. Before installation, nothing was wrong with the clutch, and I did not think I needed to replace it at the time. It was strong and never slipped. I did not remove the clutch and it seemed to be in good condition as far as I could tell on the flywheel.

 

While test driving after the install, I notice that it seems like the clutch slips a bit at 3 & 4 gear shifts. The question would be is this a sure clutch going bad ? or could it be something along the lines of my clutch pedal/slave cylinder needs adjustment?

 

I find it odd that the clutch would go bad at this exact time, but I do not have experience in this area of installation.

 

Any ideas?

Thanks.

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I take it you are driving hard to get this problem.

From your description, it sounds like it is an adjustment problem. I don't think it would be the clutch peddle because it wasn't slipping before and changing the transmision doesn't effect the peddles.

Did you keep your throw out bearing and clutch fork or are they from the 5 speed?

The throw out bearing collars can be different and if it doesn't match the pressure plate (the Zeds have three different pressure plate heights) it can keep the pressure plate from releasing completely.

Are you using an original 280Z slave cylinder or an adjustable one? If it's adjustable, check the free play at the clutch fork.

If it's the non adjustable type, you should be able to push the clutch fork into the slave cylinder about 5 to 15mm depending on clutch wear and tolerances. Apply constant pressure and it will push in slowly. You are pushing brake fluid through a small hole in the master cylinder.

I have some data on clutch fork distance measured from the front of the belĺ housing. That would give you an idea if your pressure plate and bearing collar match.

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I take it you are driving hard to get this problem.

From your description, it sounds like it is an adjustment problem. I don't think it would be the clutch peddle because it wasn't slipping before and changing the transmision doesn't effect the peddles.

Did you keep your throw out bearing and clutch fork or are they from the 5 speed?

The throw out bearing collars can be different and if it doesn't match the pressure plate (the Zeds have three different pressure plate heights) it can keep the pressure plate from releasing completely.

Are you using an original 280Z slave cylinder or an adjustable one? If it's adjustable, check the free play at the clutch fork.

If it's the non adjustable type, you should be able to push the clutch fork into the slave cylinder about 5 to 15mm depending on clutch wear and tolerances. Apply constant pressure and it will push in slowly. You are pushing brake fluid through a small hole in the master cylinder.

I have some data on clutch fork distance measured from the front of the belĺ housing. That would give you an idea if your pressure plate and bearing collar match.

I apologize for hijacking your thread but Chas said something that rang my bell. 

 

I'm about to put the wide 5 speed into my 240.  I've got the taller collar but never put the clutch forks side by side.  I have one that's taller than the other, it has a large hole for the slave plunger and a smaller hole for a spring, I suppose.  The shorter one has no holes at all. 

 

Which one goes with the 5 speed?  My 280 doesn't have a spring so I'm guessing the shorter one, but I'd like to hear from the transmission guy, Chas.

 

Thanks!

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Like others stated, I think you might have a throwout bearing collar mismatch.  You likely left the throwout bearing in the "new" trans before installing it, but it might be taller than the collar in the 4 speed trans.  Get under the car and see if there is play between the slave cylinder rod and the clutch fork.  If there is no play and you don't have an adjustable slave from a 240Z, you will need to pull the trans and swap the collar back to the one from the 4 speed trans.  Don't drive it the way it is if the collar is wrong.  You will ruin the clutch and burn the flywheel.  

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The 5 speed stuff is on the left, 4 speed is the one on the right.  Notice the different height of the collar on the right side, 4 speed.  Hope this helps understand what Chas and Jeff are talking about.

 

It helped me, now I know which fork goes with the 5 speed.  :)

 

post-23570-0-71023000-1451312150_thumb.j

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This might be side tracking the thread a litle bit.

Site, your clutch fork with the hole is a pre July 1972 clutch fork. It goes with the adjustable slave cylinder push rod and return spring.

Back in the early days manufacturers didn't won't the clutch release bearing running all the time. It remains stationary until the clutch pedal is depressed. Maybe because of the high speeds involved and low temperature grease. I have heard people say low quality bearings, but I think that is a fable.

The low temperature grease getting overheated and not lubricating the bearing seems more feasable. Remember this bearing is running three times as fast as the wheel bearing.

A lot of people refer to the collar by the transmission, but that can be misleading. Its better to go by the year. Datsun changed the pressure plate the same time they changed the 71A to the 71B transmission. After that its all over the place. You can get a 71B 4 speed with thre different collars, just depends if its in a 240Z, 280Z or a 2+2.

The to drawing below show how you can get confused by using the transmission to determine collar height. The second drawing show the same, but per model Zed.

post-25317-0-95472800-1451317484_thumb.j

post-25317-0-32869900-1451317498_thumb.j

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Completely true Chas, but after 40 years, unless you are the original owner and know the history of the car, it's very possible that one or more of the components has been swapped.  I always check the collar height just to be sure and I've found them to be different than OE quite a few times.  

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Ack.  So many parts and so many possibilities.  Best to remember that the throwout bearing collar height is designed to match the height of the levers it sits on in the pressure plate.  Collar and pressure plate are a matched set.  92 mm (+/- an mm) from the surface of the flywheel to the surface that the fork tines ride on is the key dimension.  If you have that number you will most likely be okay.  I will never install a transmission again without confirming that measurement.

 

Attached a picture, not perfect but I think it illustrates.

 

 

Edit - almost had the perfect post but had times instead of tines.  Carp.

post-19298-0-09785200-1451322457_thumb.j

Edited by Zed Head
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I agree, not much original stuff out there anymore. The S30 series gives people the opportunity to swap around a lot.

The important thing to remember is the collar fits the pressure plate, not the transmission. You need to know which pressure plate your using and match the collar to it.

I'm wondering if the PO changed the collar and if so what combination he now has to induce this slipping problem. If the slave cylinder has no freeplay in the push rod. It's a good chance the problem is then in the collar.

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On 12/28/2015 at 11:10 AM, Zed Head said:

Ack.  So many parts and so many possibilities.  Best to remember that the throwout bearing collar height is designed to match the height of the levers it sits on in the pressure plate.  Collar and pressure plate are a matched set.  92 mm (+/- an mm) from the surface of the flywheel to the surface that the fork tines ride on is the key dimension.  If you have that number you will most likely be okay.  I will never install a transmission again without confirming that measurement.

 

Attached a picture, not perfect but I think it illustrates.

 

 

Edit - almost had the perfect post but had times instead of tines.  Carp.

post-19298-0-09785200-1451322457_thumb.j

Are you measuring off that ear on the collar?  Is that the tines the fork rest on you're talking about?  Thanks again for that helpful tip, I was going in blind. :rolleyes:

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Yes, from the contact surface on the ear.  Others have determined the same 92mm number, EuroDat among them I believe.  There's a thread out there somewhere.

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Wow. glad the sites back .

I am grateful for everyone's information. It turns out it was the Throwout Bearing , I had used the one that was on the 5 speed rather than the one I had on my 4 speed, which probably matches up to my current clutch.

We pulled it again and installed the different one. When I compared the two, it was very hard to tell the difference, measured with calipers and the big difference was the thickness of the bearing sides, and a very little on the throat. Not as apparent as those pics would suggest. Weird the part number was the same on the bearing part.  I saw those pics you posted. 

Once it was back on and buttoned up, the transmission pulls very well! and no slipping. Now to get used to shifting to 5th gear way out there.

I looked all over that 5 speed housing for any identifying numbers and could not find any to determine if mine is a early model or later, other than what the seller told me.

Is there a way to tell just from looking on the outside?

Anyway, I appreciate it, and now feel like I'm at least an expert on how to remove and replace a transmission!! wooot!

 

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31 minutes ago, txvepr said:

When I compared the two, it was very hard to tell the difference, measured with calipers and the big difference was the thickness of the bearing sides, and a very little on the throat. Not as apparent as those pics would suggest. Weird the part number was the same on the bearing part.  I saw those pics you posted. 

Is there a way to tell just from looking on the outside?

Anyway, I appreciate it, and now feel like I'm at least an expert on how to remove and replace a transmission!! wooot!

 

It's the distance to where the fork rests, from the bearing contact surface, that matters.  Marked up a picture to illustrate.

The bearing is only pressed on to the collar.  It's replaceable.  That's why the cluthc kits often come with only bearings, and people get screwed up.  The good kits have a collar that matches the pressure plate.

The best way to tell which five speed you have is to measure the 5th speed ratio by turning and counting.  The way to tell early from late is easiest by looking at the exhaust bracket hanger(s), at the very tail-end of the transmission.  Late has only one on the driver's side, early has two, one on each side.

TOCs.PNG

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Early trans w-ears on both sides, 5th gear ratio is .864/1. About 7/8ths of a turn.

The later close ratio, one eared trans, 5th gear ratio is .745/1. About 3/4ths of a turn.

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There are a couple of things that will help you identify which transmission it is.

 

Like Mark already said: Two "Ears" is the early model and one "Ear" is the late model.

The second is the bolt used to secure the speedo. If its above the speedo, its early. If it under the speedo, its the later.

 

The later is often referred to as a "Close Ratio" and there are two varieties. The early "Close Ratio" 1979-80 280ZX has the 0.772 fifth ratio and the 1981-83 280ZX has the 0.742 fifth gear ratio. They are hard to tell apart.

Edit: Trying to get this attaching files under control

Identification FS5W71B.pdf

FS5W71B ratios.jpg

 

Identification FS5W71B.pdf

Edited by EuroDat

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Wow, I never knew that there were two different close-ratio S130 boxes.  I always thought that the close-ratio box came in '81 with the F54 engine.

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On 12/29/2015 at 2:18 PM, Jeff G 78 said:

Wow, I never knew that there were two different close-ratio S130 boxes.  I always thought that the close-ratio box came in '81 with the F54 engine.

You'll get even more muddled-up when you realize that the casting change applies to ALL Nissan 5-speed boxes! A 5-speed with one ear and the speedo bolt at 6 o'clock may not even be a close-ratio gearbox at all.

http://www.gracieland.org/cars/techtalk/gearing2.html

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I'm pretty sure that, within the Z and ZX family, the exhaust hangers, one or two, will ID the ratio change.  I have a 78 Z 5 speed and an 83 ZX and the casting changes are there.  78 has two, 83 has one.  The speedo cog bolt orientations also.  If you get in to the odd truck or Maxima transmission, maybe not.  

Some of the later 5 speeds are actually shorter overall also though, so you're right - best take a bunch of measurements.  Pretty easy to mark front and back shafts and see what one turn in the front gives in the back.

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Leon, So true, it gets to be a big list when you include the roadsters, trucks, skylines, & 810 maxima. The FS5W71B close ratio only came in the S130.

One other thing to keep in mind: We are talking about the S130 coupe non turbo version. The 2+2 had the wide ratio box like the 280Z and the turbo had the borg warner T5.

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8 hours ago, Zed Head said:

I'm pretty sure that, within the Z and ZX family, the exhaust hangers, one or two, will ID the ratio change.  I have a 78 Z 5 speed and an 83 ZX and the casting changes are there.  78 has two, 83 has one.  The speedo cog bolt orientations also.  If you get in to the odd truck or Maxima transmission, maybe not.  

Some of the later 5 speeds are actually shorter overall also though, so you're right - best take a bunch of measurements.  Pretty easy to mark front and back shafts and see what one turn in the front gives in the back.

My point was that there is no way to know whether the transmission came from a Z/ZX just by looking at it. I've seen people get screwed over when they're sold a "close-ratio" gearbox judging by the casting only to find out that it's not actually a close ratio box.

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11 hours ago, LeonV said:

My point was that there is no way to know whether the transmission came from a Z/ZX just by looking at it. I've seen people get screwed over when they're sold a "close-ratio" gearbox judging by the casting only to find out that it's not actually a close ratio box.

I've not seen that.  Two hangers has always been a 3.321 first, one hanger is 3.062 first, with accompanying gear sets.  Maybe the 79-80 ZX 5 speed went to one hanger but kept the 3.321 first.  1979 has all kinds of weirdness.  It's the 260Z of 280ZX's.

I always check everything I look at as soon as possible.  I bought a diff from a guy who is a Z and ZX expert, building engines, drag-racing, works at an import shop,,, and even he got fooled on the ratio because of the car it came in.  He was sure it was 3.9 and it 3.54.  Still bought it.  $50, with CV's.

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The thread wss originally about a slipping clutch, so I think we have sucessfully hijacked the thread.

The biggest challenge identifying these transmissions is when you have a gearbox that has been removed from the vehicle. Or you don't know the history of the car it came from.

If we are talking about the ZX, it's like 30 years since the last one rolled off the assembly line. A lot can happen in that time.

The difference between the Z and ZX are the "ears" and the speedo adapter bolt position.

If you look at the truck boxes, the Z20, Z22 and Z24 all have the "tilted" transmission. The L20B will fit without any changes but the 1st gear is so low compared will any Zed you would have to notice the difference. The maxima was the same as the 280Z.

I don't know much about the Skylines, but I have heard they were fitted with the FS5C71A and the FS5C71B transmissions.

BTW the "C" means Competition synchros, commonly referred to as the Porsche type steel synchros. The W is for the Warner type bronze synchros.

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