MG Sports Cars

engine swaps and other performance upgrades, plus "factory" and Costello V8s

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limey222
Michael Cubbon
Portland, OR
(129 posts)

Registered:
08/01/2015 12:55PM

Main British Car:
1969 MGB GM 3.4L V6

Clutch not disengaging on my new GM 3.4 conversion, let me have your opinions
Posted by: limey222
Date: August 28, 2015 03:29PM

Hi Everyone,

This is a last call for everyone to give their opinions before I have to pull the engine and transmission out.

Here's the scenario, low mileage 94 camaro engine, low mileage camaro T-5 which has reconditioned, New complete clutch assembly and HTOB from BMCAuto, new Lockheed clutch master cylinder etc. The system has been bled many times, an endoscope shows normal operation of the HTOB which displays the correct amount of travel. In captured video you can see the HTOB pushing and moving the pressure plate fingers. The clutch pedal is moving the clutch master cylinder through its entire stroke.

If I put the car in first gear or any gear, press the clutch pedal to the floor and try to start the engine, the car tries to move forward as the starter motor turns, which to me indicates either that the clutch is not disengaging or some other serious condition exists. The clearance was set at .100" using the supplied spacers as recommended. Pedal pressure feels like a heavy spring being compressed.

Due to other commitments I won't be able to pull the engine until sometime in October but I'm trying to determine what the problem might be prior to that


ex-tyke
Graham Creswick
Chatham, Ontario, Canada
(1095 posts)

Registered:
10/25/2007 11:17AM

Main British Car:
1976 MGB Ford 302

authors avatar
Re: Clutch not disengaging on my new GM 3.4 conversion, let me have your opinions
Posted by: ex-tyke
Date: August 28, 2015 05:01PM

Quote:
...which to me indicates either that the clutch is not disengaging

So, if that's the fundamental problem in a nutshell....so what gives?
If it's getting enough stroke for disengagement and not doing so, then I'd suspect a problem with the clutch installation itself. ie is the driven member stuck to the clutch facing or maybe the driven member is installed backwards.


Jim Stabe
Jim Stabe
San Diego, Ca
(747 posts)

Registered:
02/28/2009 10:01AM

Main British Car:
1966 MGB Roadster 350 LT1 Chevy

authors avatar
Re: Clutch not disengaging on my new GM 3.4 conversion, let me have your opinions
Posted by: Jim Stabe
Date: August 28, 2015 05:12PM

I tend to agree with Graham, clutches are pretty simple devices if installed correctly. One other thing I have seen happen is someone lets the transmission hang on the splines of the driven disc when installing. This can bend the driven plate and cause it to wobble and not disengage properly. Are you positive that the fingers are traveling far enough to release the clutch?


limey222
Michael Cubbon
Portland, OR
(129 posts)

Registered:
08/01/2015 12:55PM

Main British Car:
1969 MGB GM 3.4L V6

Re: Clutch not disengaging on my new GM 3.4 conversion, let me have your opinions
Posted by: limey222
Date: August 28, 2015 05:39PM

So, if that's the fundamental problem in a nutshell....so what gives?
If it's getting enough stroke for disengagement and not doing so, then I'd suspect a problem with the clutch installation itself. ie is the driven member stuck to the clutch facing or maybe the driven member is installed backwards.

JIm, that's the part that bothers me, i raised the suggestion that it might of been put in backwards with the guy that assembled the clutch for me. Brian at BMC had also mentioned this as a possibility. Naturally the guy who did the work says no way, he has 30years working as an auto mechanic.

The video I took shows the HTOB stroking about 1/2" and the fingers moving that amount.



Edited 1 time(s). Last edit at 08/28/2015 05:51PM by limey222.


ex-tyke
Graham Creswick
Chatham, Ontario, Canada
(1095 posts)

Registered:
10/25/2007 11:17AM

Main British Car:
1976 MGB Ford 302

authors avatar
Re: Clutch not disengaging on my new GM 3.4 conversion, let me have your opinions
Posted by: ex-tyke
Date: August 28, 2015 06:24PM

Quote:
The video I took shows the HTOB stroking about 1/2" and the fingers moving that amount.
That should be enough for disengagement


Sidecardoug
Doug Rowe

(50 posts)

Registered:
07/04/2012 05:09PM

Main British Car:


Re: Clutch not disengaging on my new GM 3.4 conversion, let me have your opinions
Posted by: Sidecardoug
Date: August 28, 2015 07:24PM

One thing you might try before pulling it all out - I'm assuming this is a hydraulic throwout bearing ;

Look and see if you can adjust the pushrod between the clutch pedal and the master cylinder - if so, try to lengthen it a couple of turns and see what happens. I have a 95 Camaro, 3.4 donor car, and when I purchased it, it would not want to go into reverse,either hot or cold, but if I shut the engine off, put it in reverse, and then let the clutch out it worked OK. I could also shift into the forward gears OK with the engine running.

I really wasn't concerned,as the car is to be a donor, and I won't be driving it. After replacing the master cylinder on my Subaru, I started having a similar problem with it, and no other adjustments had been made.-
also, the clutch started to engage after just an inch or so of travel from the floor. I was able to adjust the pushrod length and the problem disappeared. I haven't inspected the Camaro to see if the pushrod is threaded or not.

Hope this helps!

Doug


DiDueColpi
Fred Key
West coast - Canada
(1259 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
What if the Hokey Pokey really is what it's all about?

authors avatar
Re: Clutch not disengaging on my new GM 3.4 conversion, let me have your opinions
Posted by: DiDueColpi
Date: August 28, 2015 07:38PM

I've seen the video and the HTOB definitely moves far enough.
So that leaves something in the clutch assembly.
There is a possibility that the disc is stuck to the flywheel or pressure plate as Graham suggested.
Particularly if it has gotten damp at some point.
If you have the nerve Michael, jack the rear wheels off the ground and start the engine up in 4th or 5th gear. Push the clutch pedal fully in and the jab the brakes on. That should shock the clutch enough to break it free without causing any damage. If it doesn't work you're no worse off.
Like the others though, I suspect that the disc is in backwards. I'm basing this on the video. You can see more of the shaft splines through the clutch fingers than I think you should.
I wasn't thinking about it earlier but you could shine the scope through the clutch fingers to get a look at the disc orientation.
If your "guy" put it in backwards then he's been doing it wrong for 30 years.
Another possibility is that the input shaft is too long and is fouling on the pilot bearing. The only way to tell is to take it apart and measure.
Lastly as Jim said, the disc could be bent from letting the trans hang during assembly. Generally it's minor and results in a clutch that shudders or won't release until the pedal is on the floor. (Most guys blame a juddering clutch on inferior parts when it's really an inferior installation).
The disc has to be bent pretty severely to lock the clutch up completely but I've seen it done.
Even watched a "good" technician bend the input shaft nose by pulling the trans on with the bolts.
So if you can't slide the trans completely home" by hand " then something is wrong. And needs to be corrected.
Anyway, the sad reality is that the trans has to come out to find the problem.
Could be worse. Nothing's broken and no one got hurt! ;-)


Live like you mean it.
Fred



Edited 1 time(s). Last edit at 08/28/2015 07:40PM by DiDueColpi.



limey222
Michael Cubbon
Portland, OR
(129 posts)

Registered:
08/01/2015 12:55PM

Main British Car:
1969 MGB GM 3.4L V6

Re: Clutch not disengaging on my new GM 3.4 conversion, let me have your opinions
Posted by: limey222
Date: August 28, 2015 09:48PM

Thanks for all of your suggestions so far.
I don't think it could have got damp, it has been inside the whole time. I personally cleaned all of the protective oil off the flywheel with brake cleaner and then dried it with a lint-free cloth. There were three guys holding up the transmission as they attempted to slide it in place, They had some difficulties I remember and they reluctantly used the bolts to draw it up the last inch or so (which would have been the entry into the pilot bushing I guess).
I had never done this work myself so I didn't know what bad practices to look out for at the time. I don't remember them letting it hang where it might bend something . The tried the pilot bushing on the shaft before installing it and it was nice fit.
I'm not getting good feeling about any of this. The guy that oversaw the clutch install and transmission mounting is coming over tomorrow morning to take a look.


Jim Stabe
Jim Stabe
San Diego, Ca
(747 posts)

Registered:
02/28/2009 10:01AM

Main British Car:
1966 MGB Roadster 350 LT1 Chevy

authors avatar
Re: Clutch not disengaging on my new GM 3.4 conversion, let me have your opinions
Posted by: Jim Stabe
Date: August 29, 2015 02:21AM

The transmission should slide into the splines and pilot bushing without having to pull it in with the mounting bolts. Did you use an old input shaft or installation tool to center the disc before installing the pressure plate?


limey222
Michael Cubbon
Portland, OR
(129 posts)

Registered:
08/01/2015 12:55PM

Main British Car:
1969 MGB GM 3.4L V6

Re: Clutch not disengaging on my new GM 3.4 conversion, let me have your opinions
Posted by: limey222
Date: August 29, 2015 02:47AM

We used the installation tool that came with the clutch assembly from BMC


limey222
Michael Cubbon
Portland, OR
(129 posts)

Registered:
08/01/2015 12:55PM

Main British Car:
1969 MGB GM 3.4L V6

Re: Clutch not disengaging on my new GM 3.4 conversion, let me have your opinions
Posted by: limey222
Date: August 29, 2015 02:47PM

OK, the guy who oversaw the original install checked thing out and just reconfirmed what we already knew. He looked at the endoscope videos and commented that the clutch fingers didn't seem to be moving far enough. He said they should be approaching a straight configuration at the end of the master cylinder and HTOB stroke (people please confirm that he is right on this as to my mind that would require more travel than the HTOB has).

Following Fred's suggestion I placed the rear of the car on axle stands just high enough for the tires to be off the floor, also left the trolley jack in place and chocked the front wheels. Then I started the car in 5th with the clutch pedal down to the floor (the wheels were spinning at a high rate even on idle). I then stabbed the brakes numerous time to no avail so I don't believe anything is stuck.

Hence the decision was made that I have to pull the engine and transmission out after I get back from my vacation so it ill b late Sept - early Oct.
The guy told me that the clutch disk is marked on one side so you get it right on installation. He also said that it has a very shallow boss on one side and deeper one on the opposite side so he strongly feels that it was installed correctly.

He is questioning whether some of the clutch components supplied by Brian (BMC) were incorrectly manufactured as he has seen variation in flywheel thickness etc over the years. His main concern is what i would do upon removal if everything looked correct, how would I (he) know if something was incorrectly manufactured. I am assuming that Brian knows what he is doing at this stage.

Here are some points to consider, the engine originally had an automatic transmission attached (which was never supplied) it came out of a 1994 model. I sourced a manual 1994 V6 Camaro bell housing and removed the original lever set-up and made the necessary internal minor mods inside the housing that Brian instructed me to do.
I bought the entire clutch kit from Brian, I just visited his site and noticed that he now lists two clutch kits for the 3.4 V6, one for up to and including 1993 and the other for 1993 and later. Since my setup is a 94 I wonder if he supplied the right one or if there any differences between the two kits that could cause these problems. His invoice doesn't specify which one he shipped...just a thought. I will contact him and ask.

Other thoughts, the pedal goes all the way to the floor and is quite heavy, and the entire stoke of the master cylinder is being used.

Please feel free to continue your suggestions and comments.



Edited 1 time(s). Last edit at 08/29/2015 02:59PM by limey222.


limey222
Michael Cubbon
Portland, OR
(129 posts)

Registered:
08/01/2015 12:55PM

Main British Car:
1969 MGB GM 3.4L V6

Re: Clutch not disengaging on my new GM 3.4 conversion, let me have your opinions
Posted by: limey222
Date: September 01, 2015 07:32PM

OK, I have now read several posts about my problem on two different sites. The leading contenders for what is causing my clutch problem are either the clutch disk is installed backwards or that the pilot bushing is to blame so I want to make sure that I understand the theory behind this latter opinion,

As I understand it, it is a case of the pilot bushing basically becoming a press, interference fit on the shaft thereby locking up the crankshaft and input shaft as one so that no matter how well the clutch is operating everything remains locked together? For such small diameter bushing you would think that it would eventually break loose and allow independent rotation..... probably would overheat though if left as-is. Am I right in my assumptions?
Adding credibility to the pilot bushing theory is the fact that whenI was watching the shop mechanics mate up the engine and transmission, for the last 1-1/2" or so of travel they had to rely on the bolts to cinch up the two mating surfaces. An incorrect fit on the pilot bushing would surely cause that.



Edited 4 time(s). Last edit at 09/01/2015 07:41PM by limey222.


Preform Resources
Dave Craddock
Redford,Michigan
(359 posts)

Registered:
12/20/2008 05:46PM

Main British Car:
72 MGB V6 3.4

Re: Clutch not disengaging on my new GM 3.4 conversion, let me have your opinions
Posted by: Preform Resources
Date: September 02, 2015 09:01AM

Having to force the assembly together would have made me suspicious of something amiss right then.
Dave


ex-tyke
Graham Creswick
Chatham, Ontario, Canada
(1095 posts)

Registered:
10/25/2007 11:17AM

Main British Car:
1976 MGB Ford 302

authors avatar
Re: Clutch not disengaging on my new GM 3.4 conversion, let me have your opinions
Posted by: ex-tyke
Date: September 02, 2015 09:18AM

Quote:
This is a last call for everyone to give their opinions before I have to pull the engine and transmission out
While comments are pointing towards an engine/xsmn removal, it is possible to remove just the transmission without removing the engine - would save a bit of headache for you.


limey222
Michael Cubbon
Portland, OR
(129 posts)

Registered:
08/01/2015 12:55PM

Main British Car:
1969 MGB GM 3.4L V6

Re: Clutch not disengaging on my new GM 3.4 conversion, let me have your opinions
Posted by: limey222
Date: September 02, 2015 09:58AM

Not an option on my car at least, impossible to access the top bell housing bolts for a start.



limey222
Michael Cubbon
Portland, OR
(129 posts)

Registered:
08/01/2015 12:55PM

Main British Car:
1969 MGB GM 3.4L V6

Re: Clutch not disengaging on my new GM 3.4 conversion, let me have your opinions
Posted by: limey222
Date: September 02, 2015 10:02AM

OK, some new developments, and I'm holding my breath on this one. Thanks to something Ray posted I tried something last night. I have the rear wheels just off the floor with axle stands and I chocked the front wheels. Then I put the car in 2nd gear, applied the parking brake and started the engine. The rear wheels never turned. Then after putting the clutch all the way to the floor I released the parking brake. Before the wheels would turn, this time they didn't so I slowing and progressively let the clutch out. At about mid travel the wheels began to turn and continued when I let the clutch fully out. Obviously something that was previously hung up has finally released.
I couldn't take the car out on the road because the brakes badly need bleeding after some work. At lunch time someone is coming over to help me bleed them so I can begin to road test the car and make sure that the T5 gears are selecting OK (another concern of mine right now) and the clutch is really working OK.


DiDueColpi
Fred Key
West coast - Canada
(1259 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
What if the Hokey Pokey really is what it's all about?

authors avatar
Re: Clutch not disengaging on my new GM 3.4 conversion, let me have your opinions
Posted by: DiDueColpi
Date: September 02, 2015 03:26PM

You need to go buy a lottery ticket right now!
That's the best possible outcome that you could hope for.
Way to go Michael.

Cheers
Fred


Sidecardoug
Doug Rowe

(50 posts)

Registered:
07/04/2012 05:09PM

Main British Car:


Re: Clutch not disengaging on my new GM 3.4 conversion, let me have your opinions
Posted by: Sidecardoug
Date: September 07, 2015 03:41PM

Definitely sounds like an issue with the pilot bushing/bearing Does your engine use a bushing or a bearing?

I would have someone listen for any untoward noises while you drive it slowly. If it is a ball bearing, it could be that the install pushed the inner race out of line with the outer race, thus causing a bind, and possibly harming the balls or race. If you hear a growling noise, I would advise disassembly right away - it can be a real bear if a pilot bearing seizes - once had to use wood splitting wedges and a sledge hammer to separate a trans from the engine on a Volvo- AFTER having to remove them as a unit...When they separated, the trans shot about 15 feet across the floor. The inner race had welded itself to the input shaft, and the force of the wedges pulled the inner race out of the bearing, balls all over the floor. Not fun !

If you cannot remove the engine/trans as a unit, this could be a major problem for you, so close inspection
& perhaps using a stethoscope might be a good precaution to take.

Doug


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