What Happened?

Joe Prochazka · #1 (**permalink**) 05-12-2004, 11:39 AM

I had this incident happen this past Sunday and I can't get it off of my mind and I thought that maybe you guys could help.
I have a toploader, new Hurst shirfter/linkage that I installed around 1 and 1/2 years ago and a McCleod Hydraulic TOB which I set up to release when my clutch pedal is about 1/2 way to the floor. I adjusted the shifter using the Hurst Plastic pin inserted through the shifter holes and it has worked flawlessly.

Sunday afternoon I took my boy with me for a ride..... rounded a corner that leads to a long strait with no incoming roads. I nailed it....shifted to second at 6500, held it to the floor and shifted to third at 6500. When I went fron second to third...my shifter locked up in neutral and my clutch WOULD NOT RELEASE. My engine was winding down from 6500 in second gear! MY foot had the clutch to the floor but the clutch was still engaged. WTF....I had my hands full for about 15 seconds trying to keep the car straight and jogging the shifter until it popped into third and the clutch released.

I pulled over and everything sort of went back to normal and made the drive home without incident. I have not even jacked the car up yet. I guess more travel in the clutch would be a good place to start.......and double checking the shifter linkage. Anybody ever heard of any thing like this ever happening? Ever?

decooney · #2 (**permalink**) 05-12-2004, 12:21 PM

...related or not, just wondering about a few things.

Do you by chance ever have a problem getting the trans into Reverse while at a dead stop? If so, Is there a difference between warm and cold usage?

Do you have a Lakewood bellhousing/scattershield and did you use the alignment procedure?

Are you losing any fluid at all for your Hyd TOB?

Joe Prochazka · #3 (**permalink**) 05-12-2004, 01:12 PM

Coonman..
shifter goes into reverse equally well whether cold or warm.

I do have a Lakewood and I did use a dial indicator to check alignment and it was almost dead nuts on. If I remember it was about .002 out in one quadrant.

just checked fluid level in TOB and it was a little low. No obvious leakage however I did reached inside the Lakewood and felt a light film of fluid at banjo fittings. They are probably starting to leak. I did bleed TOB and top off clutch master cylinder before I took the car out.

MidOHasp · #4 (**permalink**) 05-12-2004, 02:05 PM

Joe,

Why were you driving like that with your son in the car?

I know a woman in Children's Services.......

Just kidding

Joe Prochazka · #5 (**permalink**) 05-12-2004, 02:21 PM

JP

Don't think that it didn't shake both of us up a little....my kid has been around hot rods all of his life......... but this could have gone really wrong.

SCOBRAC · #6 (**permalink**) 05-12-2004, 02:50 PM

It's the pilot bearing binding under load. Go retighten the bell housing bolts to make sure you have limited the chance that caused it. Any change in the relationship between the bellhousing and the block can cause this to happen. In your case it was brough on by extreme rpm's. This is a common problem.

If you didn't use an actual bearing as opposed to a bushing you may have wanted to. Certainly you lubed the hole with a quality grease and packed a bit in behind the bushing you used. (it's ok most people don't either) It will either happen again or it won't. It may be having it happen will have loosened it up, or it may make it worse. The fix will be a new pilot bearing.

Good Luck,

Joe Prochazka · #7 (**permalink**) 05-12-2004, 03:02 PM

Thanks.....

I used a bushing...brass or bronze... and I did smear grease in the hole.

I will check all of the bolts in the bell housing...kinda scary to think that it could happen again.

Are you saying that the trans input shaft was binding in the pilot bearing?

Bruce Edwards · #8 (**permalink**) 05-12-2004, 05:03 PM

Joe,

What kind of pressure plate are you running? The diaphragm style will bend around the throw-out bearing and the clutch will not release at high RPM. For high RPM use you should use the old three finger style plate as it does not have this problem.

Joe Prochazka · #9 (**permalink**) 05-13-2004, 09:05 AM

Centerforce II pressure plate with weights removed.....diapham style.

Bruce Edwards · #10 (**permalink**) 05-13-2004, 10:04 AM

Joe,

Sounds to me like that may be your problem.

Joe Prochazka · #11 (**permalink**) 05-13-2004, 12:30 PM

Could be.....you know I have heard of guys over-extending these hyd TOB on installation and blowing out O rings, so I went real conservative on clutch travel when I set it up. I'm going to dial in more travel this weekend snd see how it feels.

I probably won't push the car so hard either. Not that the engine wouldn't take it. I threw a lot of dollars at the bottom end and valve train so I know it will hold up. They sure sound cool when they get above 6K.

Bruce Edwards · #12 (**permalink**) 05-13-2004, 04:13 PM

Joe,

Understand that at high rpm the fingers on the pressure plate are forced around the bearing. So instead of the bearing pushing on the fingers and the fingers pushing on the pivots to raise the plate from the disc the bearing moves forward and pushes on the fingers of the pressure plate how ever due to the high rpm and loads that go with it they bend and do not move the plate off the disc.
This is an inherent problem with this style plate. The same thing that gives you that nice soft pedal feel is the same thing that fails to work at high rpm.
The 3 finger type uses a solid bar and will not bend around the bearing. How ever because you are pushing in only three areas of the plate the pedal effort is higher to over come all of the force of the pressure plate.
Does any of that make sense to you?
I know what I want to say just not real sure I am getting it across the way I wish to.
The long and short of it is if you keep the rpm's down you should not have a problem with you curent set up. If you wish to really get on it and do high rpm shifts you will need to swap pressure plates to the 3 finger style.

Joe Prochazka · #13 (**permalink**) 05-13-2004, 05:07 PM

Bruce,
I understand that on a diaphram clutch, the fingers have a tendency to flex more (easier?) than the 3 finger type.
I did not know that at high RPM it would be prone to the type of problem that I had last weekend.
It's logical that the solid bar mechanism would give you a more positive action, thanks for going into detail. I'm just not ready to yank my clutch out just yet so I'll be keeping the R's down.

Bruce Edwards · #14 (**permalink**) 05-13-2004, 05:35 PM

Joe,

I had the same problem on a car we built for a customer. Everything was fine till you got it over 6,000 rpm and then the clutch would stop working till the rpm came down. Swaped it for the 3 finger and no more problem.
Just thought it would help if I went in to a bit of detail about what is going on. The larger the pressure plate the faster the problem comes up.
I had the same problem on my 63 Corvair convertilbe when I was a kid. If I wound it up to high the clutch would act up. Took a bit of time and playing with other cars till I figured out what was going on.
Trial and error can teach you a lot. That and my very good friend Uncle Murphy is never that far away and always showing me new ways of having things go wrong!