Clutch Replacement

[72O]

So my clutch went out the other day, how I know because of constant

grinding and clashing in my transmission later leading to smoke coming out.

 

I just ordered a new clutch set (LuK 06-006) today, and will be at my doorstep sometime this week.

 

My question is: What is the best way to replace the clutch?

 

I've researched online for "4x4 720 clutch replacement" and the guide says that it is easiest to pull the whole engine out.

 

This can't possibly be the best way? I feel that I could just remove the tranny instead but I have no idea, this is my first time replacing a clutch.

 

Any advice/guide/help is appreciated, thanks!  :thumbup:

[datzenmike]

The transmission is removable, but just barely. It does not 'drop out'.

 

Smoke from the transmission? Check th oil level right away.

 

Be sure the hydraulic clutch is working as this can simulate the clutch not disengaging.

[arizonajones]

http://www.amazon.com/Datsun-Nissan-Pick-Ups-1970-86-Canadian/dp/0801977495 - This Chilton manual is super-handy, if you don't have it. I like it a little better than the Haynes.

 

I have a 720 2WD KC that I did the clutch on. I bought the little transmission scissor jack @ Harbor Freight (I know, crappy tools... but...) I was able to sleeve the bell housing open and back enough to install the new clutch with the tranny resting on the jack - made it pretty simple. http://www.harborfreight.com/automotive-motorcycle/transmission-jacks/450-lb-capacity-transmission-jack-39178.html

 

Follow Mike's advice first though, check the hydraulic lines and cylinders before you mess with the transmission. 

[datzenmike]

The push rod between the slave and the clutch arm should move just over an inch. Less and it's not traveling far enough to work the clutch.

[72O]

Hydraulic clutch meaning the clutch master cylinder? What explains the grinding and raddling then?

[izzo]

It could be any number of things. Could be it ran out of oil, and gears are burned up inside the tranny.  Could be your clutch burned out and the clutch disc material is gone, and now its just the rivets on your flywheel. I would suggest you quit doing that unless you like putting more money into your rig.

 

Tranny comes out OK...  Jack the rig up, unbolt the starter, the slave, remove the driveline and shift lever.  Then pop the four bolts off the bell housing that hold it to the block.  Remove the cross member, remove the trans mount, slide the tranny back, roll it clockwise about half way and you can slide it out... then you can pull your clutch and inspect it.  If the clutch looks fine and so does the flywheel, i would inspect your trans.

 

You can spin the shaft in teh bell housing, possibly fast enough to hear it make noise if its in the transmission.

 

Check the clutch master fluid level, yes. But also check the gear oil in the trans. There is a square 17mm plug on the driver side. You can pop that out, stick your finger in there and see if you feel fluid....

[DaveZilla]

How loud is the rattling? and does it all the sudden get nice and quiet in 4th gear but rattling in 1,2,3, and 5th? This happened to my old 280zx and when I took it apart, a tooth broke off on the countershaft's gear, it was quiet in 4th only because 4th is direct drive 1:1 and doesn't use the countershaft. Time to replace the trans if that's the issue.

 

If it's noisy all the time, it could be a broken synchro ring, they're not expensive, but you do have to tear down the trans to replace, and that's also a good time to replace all the bearings. You'll usually find chunks of brass in your oil if you broke a synchro ring. I had to replace the bearings in one before and got the bearings from a bearing shop by matching the part numbers, a bad bearing can also make some noise, but it's not as loud as the first 2 problems I mentioned, more of a scratchy or grinding noise as you go thru the gears, you'll usually fins pieces of bearing cage, or a ball or 3 in your oil if you pull the drain plug and drain into a bucket or pan when a bearing goes bad.

 

As for availability of transmissions at the junkyards, many will work, but you may need to keep your front case and put it on the replacement trans if it came out of a different car. I replaced one of my 280zx trannies with one from a 200sx and the bell housing bolt pattern was different, but by sawpping the front cases out, it worked just fine. The speedometer was slightly off with this swap, but could have been corrected by swapping out the speedo gear inside the tail housing with the old 280zx gear, but I had to return the old trans as a core so it was too late for me to get the speedo gear out.

 

The smoke from a manual trans could be a blown rear main seal or the trans front seal, it wets the clutch causing it to slip, then the oil burns from the clutch friction, gear oil has a very distinct smell compared to motor oil so you can also tell which oil is burning that way, the gear oil has a much stronger smell even when it's not burning so it's easy to tell the difference.

[72O]

Yeah I only drove it for a mile to get home from work like this.

The clutch fluid was low, it's now at it's normal level but now my truck just runs and idles horribly.

I've been having engine related issues ever since I have had this truck and I am very tempted to do a complete rebuild/ check up on my engine and trans.

 

Do you think this is the way to go? Or just fix the clutch issue and move onto the next problem that comes along the way?

[72O]

So I just had a mechanic replace my clutch, flywheel, bearings, and slave cylinder.

Still continues to grind when I push down the clutch pedal. Is the slave not pushing to clutch fork far enough?

Replace master cylinder? Found a little fluid leaking out the sides, could this be the issue?

[DaveZilla]

the "grind" when you push down the clutch pedal sounds like a bad throwout bearing... Unless you're talking about a grind between the gears when shifting which would sound more like you need to bleed the clutch system. If there's air in the master cylinder, the clutch line, the damper, or the slave cylinder it won't let the push rod push out all the way against the pressure from the clutch fork. This would be noticable when idling in gear because the truck would want to creep instead of sit there as well as it being hard to shift along with a grind when shifting. In your post where you mentioned the clutch fluid level was low, it is very well possible it was low enough to suck some air into the system and it needs to be bled out again.

 

The fluid leaking out the sides of the master cylinder.. is it coming from the lines or right under the plastic reservoir? Best way to pinpoint a leak is to clean it up really good, then once it's clean and bone dry, look for wetness at the base, the line connections, and the bottom of the plastic reservoir (unless it's actually dripping, then just follow the drips). There is a possibility the master cylinder is shot but I'd try and bleed it out again to see if it improves before running out and getting a new one, but also a bad one can improve then need to be bled out again after driving it a few miles etc... then it definitely needs to be changed out. Any leaks at the base of the master cylinder where it bolts up to the booster or firewall is also a dead giveaway to a bad master cylinder. If it's leaking there or at the base of the plastic reservoir it's best to just change it out.

 

What I'll recommend without being able to see it first hand would be to clean everything up so you can pinpoint any leaks, replace if leaking at the base or at the bottom of the plastic reservoir. If not leaking, bleed out the whole system again, follow the clutch line to the other side of the firewall, you'll see a small square damper that's connected to the clutch line, there's a bleed valve on this part too, bleed it here first, then following the line down the system it runs from the damper to the slave cylinder, bleed it out from here too. i use some clear plastic aquarium tubing to put over the bleed valves which helps me see the air bubbles, and gives you a way to make the bleeding job a lot less messy. Once you're sure there's no more air bubbles coming out, close everything up and remove the clear plastic line if you're using one. drive the truck around and see how it feels and shifts, if it's better, leave it alone and you're done, but if it gets worse after driving it that's another sign of a bad master cylinder or slave cylinder.

 

hope this helps

[DaveZilla]

Just to think I'm just finishing up on a clutch replacement job on mine right now too... I'll put up a new post for my stuff tho...

[72O]

Thanks for all the info Dave, I appreciate it. This is a huge help for me.

My personal mechanic just replaced my clutch on Tuesday, the clutch kit and slave cylinder are new so I know they aren't the problem.

I just stopped by his house today for him to look at it and he bled out my clutch and found no bubbles in the lines. 

The master cylinder just had a small amount of clutch fluid at the base of the plastic reservoir thought but the clutch works perfectly fine.  

 

He told me that the grinding was from my transmission spindle (I think) due to my truck's high/rough idle problem.

But it grinds randomly at high or low idle, when I fully push in my clutch to shift, stop at a red, etc it grinds softly (sometimes)

 

He and I are going to tackle my vacuum hoses, compression, and carb this weekend. I will provide pictures and more info, solutions, or questions. 

[datzenmike]

If the plastic reservoir is leaking, remove but catch any fluid. (it will ruin paint) Clean the master and plastic mating surfaces. Warm the plastic reservoir in hot water, dry and install. The clamp will seal the plastic better if it is warm and soft.

 

Your fast idle should not cause the transmission to grind. The whole point of a clutch is it's supposed to disconnect the spinning motor from the transmission.

 

That said, try the following...

 

Engine running, clutch up or out and transmission in neutral. Depress clutch, count to three and slowly shift into reverse. Is there any grinding at all???? If there is, then the clutch is still not fully disengaged from the flywheel and pressure plate. If it shifts into reverse quietly, then the clutch seems in working order.

 

Grinding when up or down shifting while the vehicle is still in motion is worn synchro rings.