Help needed please? New clutch? If so what else to replace? I need your help! Thanks
 

I have a 96 GMC K3500 Sierra LWB crew cab with a Knapheide utility bed on the rear. It is a dually. Traded for it about a year ago. Has the 6.5 & 5 speed with about 199K miles - I have put about 2-3K miles on it since I got it.. It is not my daily driver, however, I need it to be if it is needed if you know what I mean.

So down to business. About a few months ago I noticed when I would get home and try to shift into reverse it would not “drop” into reverse. I would have to let the clutch out and then re-clutch and try again and usually after one or two tries it would drop into reverse and back up just fine. Well that “behavior” started happening in the forward gears as well. When we had a cold snap (around 20 degrees for about 5 days) I was driving it and I noticed when trying to shift into 1st or 2nd it is like the gear shifter just hits a brick wall. Nothing. Does not drop into gear it just pushes back into your hand as you try to push it into gear. I would usually have 4th or 5th OK. So I discovered ( needed to get home) that if I let the clutch out at a standing stop in 4th gear and let it out enough where it just started to move the truck I could then put the clutch back in and it would shift into 1st. Off I went. I made it home with a few times of having to get creative in what gear I would launch in etc… Now with the warmer weather it behaves the same way so I do not think the cold had anything to do with it. The clutch lets off near the top of the pedal stroke if that means anything. I still shift with it on the floor – but I feel it engage as I get nearer the top of the pedal stroke.

I am not an expert in clutches. I am used to automatics – tearing then down and rebuilding or taking them in for a core swap etc… I did check the fluid and , while it is dirty, it is full. Also no leaks that I can see.

So I am thinking based on what I have read here that it needs a new clutch. I did not ask when I traded it how many miles were on the clutch. It did shift fine until these last few months. If the truck is off you can shift just fine into any gear you want. But when running not the case.

So I have a friend who knows about clutches and he is willing to help me with the project next week.

I have two questions please:

1. Does it sound like the clutch needs replacing?

2. When you replace the clutch what else should you replace to do the job right? ( such as slave cylinder, throw out bearing etc…)

I appreciate any help and please let me know what you think. I want to get it fixed right the first time.

~GOD BLESS~

john

If you decide to replace clutch go to a single mass fly wheel

Is that a part that would be seperate from a "kit"
 

Going to a single mass flywheel - would that involve buying the clutch kit and also the new flywheel? If so about how much extra are we talking? Does that also mean that you have to install a different clutch to accomidate the new flywheel?

Thank you!

~GOD BLESS~

john

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I was also thinking about the question I have as to what else should one replace when you are going into put in a new clutch. I appreciate any information anyone can provide.

Thank you!

~GOD BLESS~

john

I used a single mass flywheel from a 6.2 school bus $20 is what I give for it Maybe you can find one cheap enough might what to change the rear main seal while the trans is out regardless of condition and maybe new gear oil in the trans i would not bother replaceing the slave cylinder unless you are having issues this does not require removal of the trans.

On a 96 the slave cylinder is part of the release bearing retention/activation system and does require the trans be removed to replace it.
On rock aito there is a master,line and slave kit for $101.00 - AMS AUTOMOTIVE Part # PM0434
EG:
http://www.ebay.com/itm/6-5-GM-CHEVROLET-DIESEL-SINGLE-MASS-NEW-FLYWHEEL-/271436613401?pt=Motors_Car_Truck_Parts_Accessories&hash=item3f32e20719&vxp=mtrhttp://www.ebay.com/itm/1996-2002-Chevrolet-GMC-1500-2500-3500-6-5-V8-Diesel-New-Clutch-Kit-/390567499321?pt=Motors_Car_Truck_Parts_Accessories&hash=item5aefa31639&vxp=mtr[color=grey][size=-2]

OK so I need to think this through a bit more..
 

It sounds like you DO NEED the tranny out to replace the slave cylinder as it is part of the release bearing rentention/activation system... So I should look at replacing that as we'll have the tranny out.

What is the downside of staying with a dual mass flywheel?

I am asking because it may come down to how much money we have to use for the repairs and I would rather like to get a good clutch and replace the slave cylinder if I can afford it instead of going to the single mass flywheel.

I just do not understand what the advantage of the single mass flywheel is please.

Thank you all

~GOD BLESS~

john

No you don't have to remove the trans to do the slave cylinder look under the truck right in the starter area And the advantage to a single mass flywheel is there are no springs to explode or fly apart busting the bell housing and or the engine block So no advantage other than with a single mass flywheel when shutting the engine off it is recommended that you depress the clutch.

On a 96 like mine the slave is integral to the release bearing and you do have to remove the trans to change it-Mayhem it's not like previous years.
Look up part ACDELCO Part # 386433 on rock auto for a picture-might be worth while to buy a master cylinder,line and slave as a pre bled kit and install it all together-it's real tough to separate the line from the old slave.
The dual mass flywheel is a bonded a multipiece that fails-the advantage of the single mass is it' won't come apart.

Thanks for clearing the slave cylinder issue for me racer I did not realize they changed the design

Whether you change the flywheel or keep the original, my recommendation is, if it's in the bell housing replace it or resurface (original flywheel) it. It sux to get the clutch replaced and find out you have to pull the trans because the next weakest link failed (and it will fail). Murphy's 3rd law of transmissions.

Excellent info... AND and additional question please...
 

I have a single mass flywheel on the way - should be here today. Hope to get in some hours tonight and tomorrow to get it all buttoned up by tomorrow evening.

Might have to keep the orginal master cylinder due to budget - I noticed that it has a metal line running from the master cylinder then it turns into a rubber line after about a foot - when looking at it from under the hood.

I had a friend who had a car that had a rubber line coming from the master cylinder and it had gotten old with age and would not let him shift into gear when the car was warmed up as the hose actually was colapsing on itself (keeping him from being abel to shift into gear untill it colled down and then he could shift).

So my question is should I replace the line to the master cylinder with an all metal one? Can the rubber fatigue and cause problems such as not being able to shift into gear?

Thank you for any information.

~GOD BLESS~

john

It has to have some flexibility in the line just to prevent being stressed and crack from the engine/trans torquing up with every shift-I would buy th prebled master/line/slave combo.

Changing out the line is a not a fun process-I have done it before and it sucks.

OK - that makes sense and I looked at it again... But what causes? Help needed please
 

That makes sense that it needs to be flexible to handle the torque etc... I looked at it again and it is a type of braided line - not the rubber hose I said it was earilier. Guess I'll look into the master cylinder replacement with the new line.

But , in your opinion, would cause a sympton where you depress the clutch and when you try to shift into 1st gear it does not allow you to shift (like hitting something - just pushes back on you pushing) so you let out the clutch and then depress the clutch again and it will let you shift into 3rd. So I let out the clutch in 3rd gear just enough to let the truck start to move forward, then I immediatley depress the clutch and it will then allow it to shift into 1st??? I can not figure this part out...

Thank you!

~GOD BLESS~

john

Sounds like air is getting into the system from a bad master or slave,when you push the clutch the second time the air is compressed and more fluid flows in and gives a longer clutch stroke letting you change gears-like pumping the peddle with spongy brakes.

I would say you are on the right track and need to go with the prebled kit for ease of installation.

Since that is the only part that is not in the "replacement plan" then it makes sense
 

OK - I understand your explination. Since the Master Cylinder is the only part we are not replacing and it behaves that way now then perhaps it makes sense to replace it with new line so the job is complete from top to bottom if you will. Especially since we are making the switch to a single mass flywheel also... might as well do it right huh?

Thank you!

~GOD BLESS~

john

In the long run it's the easiest and cheapest solution.

Klien on thing you will want to have on hand when you put the trans back in is 2 bolts the same size and pitch but 6 to 8 inches longer than the bell housing bolts,These make great guide pins so you don't struggle as much.

Not a lot of room up there for long guide pins.

It's not that tough to put the bell housing up by itself and then you only have the trans to deal with but you need to be sure to guide the slave/release bearing over the input shaft as you go.

Help needed - after the repair it is acting up when shifting - any thoughts?
 

Thank you for all the info. So we pulled a long night last night and now the truck is back on its wheels and has about 100+ miles on the newely rebuilt clutch.

We replaced:
- New single mass flywheel
- clutch & bellhousing
- throughout bearing
- Master cylinder
- Slave Cylinder
- I am sure I am missing something (sleep deprivation)
- If it is part of the clutch system we replaced it.

My buddy, Perry, has a nice shop and a lift that can hold the 3500 so with his help we pulled it off. We also found a few universal joints that had some play so we replaced them as well. Oh and a new rear main seal also.

Problem: So when we got ready to drive the truck it started out just fine. Shifted great and no issues. We hit the interstate and put about 30 miles on it and when we got off at an exit and came to a red light it down shifted from 5th to 4th to 3rd just fine. I came to a complete stop and then when it went to a green light I could not shift into first. It was like the shifter would just not go into gear. Same thing with second & 3rd??? So I pumped the clutch several times and still could not get into first. I discovered that if I put it in 4th gear and then just start to let the clutch out until you feel it engage and try to move the truck you can then depress the clutch again and it will shift into 3rd and then repeated that (let clutch off in 3rd gear and depressed the clutch again) it now shifted into 2nd. That got us moving. Perry said we must have air in the line so we went back to the shop and decided to rebleed the system - several times.

It came off the lift and back onto the street and again from the start it seemed fine. Shifted into all gears OK. Some times when shifting into third I feel in the shifter knob a little bit of feedback when pushing into gear. No grinding just a little firmer push "past" something to get into 3rd. That is sometimes not all the time. So after the bleeding I got on the interstate to drive it home (about 60 miles) and it did great getting me through the side streets onto the interstate. But when I got off at the off ramp the same thing happened again. Unable to shift into 1st, 2nd or 3rd - unless you let the clutch off a little in a higher gear and then try again one of the lower gears. I was able to get into 2nd and started home from the interstate. I got onto my gravel road so I could test the 4WD. It shifted into 4HI fine and the clutch seemed to behave letting me shift into 1st, 2nd with no problems etc... Went into 4WD LOW and some thing shifted fine. So I went back to 2WD HI and it seemed to shift better but wouldn't you know - just before my house I stopped at a stop sign and from a complete stop no 1st or 2nd ( that is unable to shift into 1st or 2nd) So I got rolling in 3rd and that got me home. In the driveway for reverse at first it would not drop into reverse. So I depressed the clutch and the tried again and it dropped into reverse.

When it is shifting fine it runs great - no funny noaise or grinding etc.. Then you get this syndrom of being unable to shift into the bottom gears (1st, 2nd, 3rd) unless you play with the clutch and let it out in a higher gear in odrer to try to get into a lower gear.

So now we are thinking that perhaps we have a bad part in the mix somewhere? The classic "new part" that has failed problem. We have replaced everything.

I am asking for your thoughts, suggestions, ideas etc... I really need your help.

Decided not to drive it today, however, will get it out again tomorrow for a 4 hour road trip (round trip) to see how it does. Fluid level is fine. No leaks....

Any ideas?

Thank you!

~GOD BLESS~

john

Could be that the new clutch disc is hanging up on the input shaft splines some and keeping contact with the flywheel or pressure plate?
With a bit more driving it will probably wear in.

Thank you for a theory as to what is going on...
 

I drove the truck all day yesterday and again at times it shifts just fine and then you come to a stop and depress the clutch for 1st gear and - no luck. I put about another 100 miles on it since the last post. I thank you for the theory about the clutch disc hanging' onto the input shaft splines some and keeping contact with the flywheel or pressure plate. I had hoped that the long road trip yesterday would have been enough to break it in if you will. Spent a good bit of the miles on Hwy 31 which runs North/South through Birmingham. Plently of traffic ights to stop at along the way.

If you think of anything else please let me know. I am thinking of going over to my friend Perry's place tomorrow to look it over again.

Thank you.

~GOD BLESS~

john

Is there any difference when you pump the clutch peddle when trying to get in low gear from a stop?

Wondering if there is any air in the system?

Good question!
 

The answer is ... I think it makes no difference. For instance when I came to a stop just a mile from my house this morning, after driving for about 40 minutes, I came to a complete stop. Went to netural. Let out the clutch. Sat for a few seconds. Then depressed the clutch and could not shift into 1st, 2nd or 3rd. I pumped the pedal about 10-12 times still no first. I ended up shifting into 4th and just let the clutch out enough for it to bite and start to move the truck. Then I depress the clutch and I could shift into third - again let off enough to just start to move the truck and then depress the clutch and I could shift into 2nd. That was good enough to get moving and of course no problem upshifting into 3rd or 4th. Also down shifted fine at the house from 4th to 3rd to 2nd. Went into neutral then reverse just fine.

One an occasion pumping the clutch will allow me to get into 2nd then I can get the truck moving and then shift up from there, but I would say just pumping the pedal has never fixed the "can not shift into 1st" from a dead stop.

And keep in mind that for about 1/2 or even 2/3rds of the drive it will shift into 1st, 2nd etc. just fine (may require a bit of a push) - so it seems to be happening when the truck is warmed up and off and on with the problem. Just makes me scratch my head... What did we do wrong or what new part might be a bad part out of the box??? Oh and I have also had it happen when the truck was cold. Argh...

Thanks for your help!

~GOD BLESS~

john

Sounds like the input shaft is still turning when the clutch is depressed-since there is no synchro in first you can't even try to force first-the other gears have synchro's so they help the shafts match speed enough to shift properly.

You are certain the disc is not in backwards-they are usually marked flywheel side when new,if the cone of the spline is facing the flywheel it can create constant friction that will do what you describe.

The flat face of the disc faces the flywheel and the cone side of the splined area faces the transmission.

Great - something to look for tomorrow... And a Question please
 

I like that what you are describing because it sounds like it explains what I have been experiencing. It is for certain something we can look at tomorrow.
I am 90% certain it went in correctly - however, I may be wrong so we will check it out.

Question - if it is in backwards would I still be able to drive it like I have been doing? Would it still shift OK some times etc?

(Please realize that I am a newbie when it comes to clutches, however, I do have 28 yrs of working on cars - just always been automatics! So feel free to get elementary on me when explaining things)


Thank you!

~GOD BLESS~

john

I have never put 1 in backwards but have heard of it being done,but I think it would react as described and shows itself right from the start.

Once you are in motion shifting could be reasonably normal because of the synchro's.

I am guessing the trans shift good with the engine not running?

Yes...
 

When the engine is not running the transmission shifts just fine - some times for reverse you have to let clutch out, depress clutch and then (when not running) it will drop into reverse. So I would say it does shift OK when not running....

I am second guessing myself thinking that maybe once or twice when not running it would not shift OK - but I know the majority of the time when engine is off it shifts OK.

~GOD BLESS~

john

That tells me that the trans input shaft is still turning when the clutch is depressed.

that can only mean taht the disc is hung on the input shaft making contact with either the flywheel pr pressure plate,or the disc is in backwards and hitting the flywheel or the release bearing is not moving the pressure plate far enough.

The only other problem I have encountered that causes a similar issue is when a torsion spring falls out of the disc and gets caught between the pressure plate and the disc-that usually makes for a very firm peddle though.

OK what about the "noise" I sometime hear???
 

It sounds like you are describing what is most likely the culprit.

There are times when I am sitting , engine running, in neutral and I can hear a slight metalic like grinding sound. Never heard that before. It sounds like it is coming from the clutch bellhousing. If I put it in gear and release the clutch then go back to neutral it will some times stop the noise. It is not very loud, however, loud enough to hear over the engine running. Sorry I did not mention the noiose before - so could that support the theory that something is hung up and making contact with the flywheel?

The clutch pedal feels fine during its entire stroke. So based on what you posted that should mean the torsion spring is in the right place.

My wife is not feeling well so I drove her into work today and let the truck sit. I called my buddy Perry and told him what you suggested and he said he would be happy to take a look at it whenever I can bring the truck to him.

I am wanting it fixed! So I can shift and down shift and use 1st gear when needed etc... I know we will get there and I greatly apppreciate all of your help.

Thank you again.

~GOD BLESS~

john