Alfa Romeo Forums banner

1 - 10 of 10 Posts

·
Registered
Joined
·
5,492 Posts
Discussion Starter #1
Normally I post on the tech forums but this has me stumped. Car is 74 GTV. I rebuilt the trans 4 years ago and have put maybe 7000 miles on it, trans was awesome! Butter smooth up and down shifts, no noise, it was fantastic -- car had the original (heavy oil burning) motor during the time. Decided to pull and rebuild that motor, and install another hot street motor, Ive posted about that. I pulled the old motor, installed the new motor, with a good used clutch and pressure plate. Everything was great for a few months, no problems -- probably 1000 miles or so. Then here is what happened in chrono order
a. All of a sudden, the trans would not shift into first at idle. What I mean to say is that it would 'hard stop' and not get into gear-- no grinding, just a hard stop. Then if I dropped into 3rd and engaged a little bit, it would get into first. This went on for about a month (couple hundred miles)
b. Next phase, grinding when going into first at idle. Followed quickly by grinding when going into second or reverse at idle. Severe grinding
So I checked clutch arm movement and get nearly .5 inch movement. Thinking maybe its weird hydraulic stuff, I bleed, bleed, etc -- no change. Then I change the master and the clutch hose -- still gettting plenty of throw at the arm. No change. Now, I'm thinking maybe the pressure plate has broken spring / clutch plate delaminated/oil on surfaces making it stick. So I pull the motor, replace the pressure plate/clutch/throwout with new Sachs kit. Check the spigot bush as well, its within spec and a spare input shaft rotates nicely with no binding. Pull the clutch arm out and check for cracks -- none. check the splines for burrs/etc -- disk can move easily fore and aft on the splined shaft. Flywheel surface looks fine, no oil, no sticky stuff, etc. PUt all back together. No change after the first, initial engagement to first gear -- the first one worked easily, After that, it just ground and ground. Same with reverse.

Remember, clutch arm throw has always been about 1/2 inch. It still is. Although I havent taken out the pedal box to put eyes on, the pivot cant be broken, the clutch pedal is same height as brake, I have 1/2 inch throw where it counts, ie everything downstream to release bearing is working as expected. This is many hundreds of clutch engagements/disengagements trying to diagnose this issue -- So to me, the pivot thing seems unrealistic at this point.

Now I pull the trans out and crack it open. I can;t see anything wrong here with the trans. Synchros are engaged to the crown teeth, no excessive wear seen, nothing broken, no metal bits in the pan, etc. Forks are where I set them to with no apparent wear. Sliders centered on tripods with no apparent wear. Input shaft needle bearing (4/3 needle) seems a bit sloppy but not outlandish. Remember, this entire trans was essentially blueprinted 4 years and ran absolutely beautifully until I swapped the motor over -- and ran beautifully for a few months after that as well. I guess I will disassembly the mainshaft and check everything but as assembled, all gears turn easily, nothing binding, etc.
Im trying to imagine how exactly the grinding is happening. I still don't get it. Even if the input shaft is continually turning -- I dont get it!

Any ideas? Sorry for the long post, trying to be complete in the description/work so far. I try to be pretty meticulous and think things through, I;ve gotta say I am stumped on this --


Happy Easter/Passover Everyone. Thanks, bob
 

·
Premium Member
Joined
·
2,540 Posts
Pilot bushing keeps tranny input spinning when foot on the clutch? Is 1/2'' enough? Too much run out on disc, plate, flywheel? Input shaft should stop when you put a foot on clutch at idle with wheels stopped. Jack up back end, get wheels off the ground and check if wheels are forced to rotate in N or gear with foot on the clutch.
 

·
Registered
Joined
·
144 Posts
I had the same issue with clutch in the car would pull slightly (like an auto box) and would crunch gears and would not go into 1st without going into 2nd first
It eventually broke the weld on the clutch pivot arm before the master cylinder, I'm only guessing but I think the weld was letting go a little, I did check the movement of the slave cylinder before it broke and I was getting the correct amount so assumed like you it was not clutch related
I replaced the arm for an updated one and the problem went away
 

·
Super Moderator
Joined
·
10,628 Posts
Pilot bushing keeps tranny input spinning when foot on the clutch?
The problem could be many things - I sure can't tell which one. But Brad's idea (listed above) has some merit: the pilot bushing came with the new engine; everything else worked great before that went in. I know you measured the pilot id and checked the fit with a loose input shaft. But what if the input shaft can't go into the bushing deeply enough? What if the face of the input shaft is pressed against the base of the flywheel? Admittedly I'm grasping at straws here.
 

·
Registered
Joined
·
5,492 Posts
Discussion Starter #6
Good thoughts, keep em coming. Remember, everything worked great for a couple months with the new motor in, then the issue developed (I think the hard stop on getting into gear and the current grinding are related, but i can't say for sure) . I can for sure measure the diameter of the input shaft and the pilot bush, (I think I did that already) ; I had thought about the possible 'bottoming out' of the input shaft face into the flywheel, but I dont see how that is possible to happen gradually. I;ll try to measure some more.
 

·
Premium Member
Joined
·
844 Posts
The flywheel on the NEW motor. Where did it come from ? Was it originally attached to the OLD motor and then moved to the NEW motor? or was it always attached to the NEW motor?

Regardless I'd take the flywheel down to the machine shop and have the "step" checked. The "step" being what Alfa calls the the height of the "wall" around the flywheel.

Hope this helps
 

·
Super Moderator
Joined
·
10,628 Posts
Remember, everything worked great for a couple months with the new motor in, then the issue developed .... I had thought about the possible 'bottoming out' of the input shaft face into the flywheel, but I dont see how that is possible to happen gradually.
Yes, I agree. Somehow, I was thinking the symptoms started immediately after the engine swap. OK, cross off the "pilot bushing hole too shallow" theory.

I suppose it could be a lack of sufficient movement in the throw-out mechanism. Either due to a broken shaft/pivot in the pedal box, bent/broken throw/out fork (though you've inspected that), some hydraulic issue or ???
 

·
Richard Jemison
Joined
·
7,394 Posts
Similar to issues on my Coupe" and described in a post on my "Spider Improvement Thread" below.
But the issue is basically a design flaw in the slave cylinder as the bleed hole is located (when vertical) about an 1/8 inch below the top of the cylinder. The fix is in that post. But it is compounded by the short length of the rod to the release lever which allows a larger air pocket and less movement with the petal stroke.
I decided to sleeve the factory slave reducing it to a 7/8" bore. On removing the factory slave for modification I noticed a design/build problem with the bleeder opening into the bore of the slaves. I looked at both the factory aluminum and steel ones, both had the opening to the bleeder about 3/32" below the top of the cylinder`s bore. Since the slaves are mounted horizontally this would allow a small amount of air to be trapped after bleeding. Drilling with a 1/4" drill created a taper to allow air to be bleed out and that area filled with fluid.

As well the rod length was short allowing a larger air pocket length behind the piston. To check push the release lever forward to collapse the piston into the cylinders forward wall. If it`s more than an 1/8" movement the the rod needs to be lengthened to eliminate the slop.

Also the clutch MC should be adjusted so that it`s piston can return right up to the "bleed back hole to the reservoir and not positioned well behind it. If you lengthen the push rod a couple of turns at a time testing its position by again pushing the release leaver forward, once you have gone too far the leaver will be maintaining pressure on the slave with the petal "up".

You are surely aware that bleeding the clutch (and brakes) requires bleeding the outlet tubes at the master cylinders as well as below at the slave or brakes, as a final action.
 

·
But Mad North-Northwest
Joined
·
10,534 Posts
If it was working fine for 1000 miles the problem isn't likely bleeding unless one of the cylinders went bad. I'd be looking real hard at that cutch pivot shaft.

You are surely aware that bleeding the clutch (and brakes) requires bleeding the outlet tubes at the master cylinders as well as below at the slave or brakes, as a final action.
The clutch MC outlet is at the bottom, so bleeding there doesn't actually help much. The problem is that the MC (at least on my GTV) can slope slightly upwards towards the front of the car, so you can sometimes get some bubbles trapped at the front top of the cylinder. What I do is bleed at the slave with the front of the car jacked up high to get all the air out the line and the slave. Then lower the car, jack up the rear high, and jiggle the clutch pedal for a while: this moves any air remaining in the MC to the reservoir opening where it can escape. You'll see some small bubbles come out, then you're done.

On the brake master the outlets for the LF and rear are at the top of the cylinder so they self bleed. Just fill the reservoir and leave those fittings loose until fluid starts coming out, that'll bleed the MC on the car from dry no problem. Then bleed the calipers and you're done.
 
1 - 10 of 10 Posts
Top