Broken Transmission?, Grinding and then no go Options

[Charles Freeborn]

Well I had an unfortunate day at the track.

Basic specs - 2.0L puts out in the 160hp range. Sideshift 901 box with "S & X" gears. Open dif.
Hard braking into the chicane after front straight run - I hear a click, then grinding coming from the driveline. I try to limp it into the pits, but after another ¼ mile it's no - go with more and serious grinding noise. I'm trying to re-create from memory the particulars - going straight - left turns it will engage but when I made the final right to go down the back straight is was as if in neutral. I can't promise this is accurate as it all took me by surprise, and being a race car it's loud inside and hard to get accurate data with helmet on, etc. My first suspicion was that I blew the clutch (may still be that).
My only other suspicion that it's related to the dif, as after I got towed off the track and was pushing it back to my parking spot I had not taken it out of gear. While turning right to head to my space it rolled without resistance, but as I straightened the wheel to go straight there was grinding and it tried to engage w/engine. I put it in neutral and we finished pushing/parking. In hindsight I should have done more of this diagnosis (push while turning in gear right and left) to see what I could deduce, but it was a full paddock with a track day going on all around. I suspected the driver side cv / half shaft so pulled that one before flat towing home.

I've pulled the half shafts and there aren't any conspicuous failures in the CV's (haven't fully de-greased, but cages are intact and they still swivel - all the balls are where they belong). Turning by hand they seem to all be functional.

When I rotate the output flanges by hand they turn - seems to be appropriate lash. I tried all the gears with same result - no freewheeling where there shouldn't be any. I dropped the gear oil and found some usual fine shreds of metal on the drain plug, but no major chunks or debris. Oil (Swepco 210) was fresh.

Flanges @ the hubs seem to be intact - when I unbolted cv's I was able to hold the wheel as I backed off the CV bolts and there wasn't any freewheeling or grinding. I want to replace wheel bearings anyway, so that will be the next thing I tear down.

If it is the clutch, is there a way to do much of an inspection while still in the car. There are a couple of small holes @ top of bell housing that I can see the back of the flywheel through, and a minuscule portion of the t.o. bearing, but not much else. Next step there is to pull the starter?

Being a race car the rear pan area is cut out so I can see / access pretty much the entire trans while in the car.

So, I'm stumped. Any help appreciated.
Thanks in advance,
-C

[914 Ranch]

Any noise when pushing the car what about running with the tranny in neutral? And clutch cable tension?

[Charles Freeborn]

Any noise when pushing the car what about running with the tranny in neutral? And clutch cable tension?

Was pretty hectic, so not sure about those particulars - Will get it up on stands and run some more diagnostics.

Clutch pedal doesn't seem to have changed - still tension - but since there was no gear engagement I can't say if it's still operating. In my experience clutches go slowly, or catastrophically - neither present here. I think it's unlikely that the splines on the clutch disc all blew at once, but I guess it's possible....

I'll pull the rear hubs to see - bearings anyway - and if no obvious damage I'm resigned to pulling the whole mess out, look at the clutch and if no data there, crack open the trans..... Not what I had in mind for this week... less than 2 weeks until a race I was planning on entering...

[slivel]

Drain the oil and look for chunks. You will know very quickly. Been there and experienced what you have multiple times overs the years. Not fun!
My failures were ring and pinion twice and 2nd gear once and 3rd gear once. But I was putting about 300 hp through the box. I freshened the box every 3 or 4 seasons and that seemed to help avoid failures.

[Charles Freeborn]

We’ll I found my problem... sort of a good news, really bad news. Trans is fine - right as rain...
What happened is I sheared all 5 flywheel to crank bolts
The right turn/ left turn bit was coincidental. Was just the chunks of bolts wedging and failing. Flywheel and probably crank are toast. Not what I was hoping for.. not in the least ..

[Krieger]

(IMG:style_emoticons/default/huh.gif) That's a drag. Way more expensive than a trannny.

[Charles Freeborn]

(IMG:style_emoticons/default/huh.gif) That's a drag. Way more expensive than a trannny.

Yeah, not optimal... but in actuality my trans is a pretty pricy box - so I wouldn't want to have to dig too deep into that either. Flywheel and clutch are available enough, and Im' already scheming ideas for a flycutter that would reference in the pilot bushing and re-surface the end of the crank. 2 of the bolt remnants came out easily with no more than a magnetic pick up tool - the rest shouldn't be much worse. We'll see....

[GregAmy]

How in the hell did that happen...?

Since your flywheel and clutch were tossed around on the input shaft, I strongly recommend putting a dial indicator on it (at a minimum) to ensure it's not bent. Probably ok since it was centered in the crank, but check it anyway.

[slivel]

How in the hell did that happen...?

Since your flywheel and clutch were tossed around on the input shaft, I strongly recommend putting a dial indicator on it (at a minimum) to ensure it's not bent. Probably ok since it was centered in the crank, but check it anyway.

One or more of the bolts loosened. Then the load goes from clamping force to shear, and shear it did. Had this happen once when towing. Sheared all six bolts right at the brake drum and lost a trailer wheel. That was a PITA.

[Charles Freeborn]

How in the hell did that happen...?

Since your flywheel and clutch were tossed around on the input shaft, I strongly recommend putting a dial indicator on it (at a minimum) to ensure it's not bent. Probably ok since it was centered in the crank, but check it anyway.

One or more of the bolts loosened. Then the load goes from clamping force to shear, and shear it did. Had this happen once when towing. Sheared all six bolts right at the brake drum and lost a trailer wheel. That was a PITA.

That’s the best guess I’ve come up with too. Bolts loosened and then popped.

It’s a race car so loads are significantly higher.

[GregAmy]

I've been racing - and building - race cars for 35 years and I've never had a flywheel (or wheel) come loose.

Jus' sayin'.

(Now I gone and done it...)

Edit: I actually had a propellor almost come loose on a Grumman Tiger. The spinner has a backing plate that's sandwiched between teh hub and prop. Installed the prop, torqued it down, safety-wired everything. But it just didn't look right...so we pulled the prop and the backing plate was not perfectly seated on the bolt dowels and had "dimpled" between the hub and prop...had we flown it like that then it's likely the "dimple" would have worked its way loose, the prop would have loosened, and all the bolts would have sheared...that's exactly what happened to Sen. Inhofe in his Tiger in '99...he landed safely.

BTW, I always use red Loctite on flywheel bolts. I don't care what the book might say.

[Charles Freeborn]

The lesson learned here is that I didn't go through all the essentials before taking it on track. I've only owned the car for a few months and I knew that some of the PO's work was iffy... so it's on me.

Good news is that after conversations with highly experienced builders the consensus is that I can dress off the "weld transfer" material on the crank end (the crankshaft is made of harder steel than the flywheel), source all new clutch and flywheel parts, bolt it back up, and yes, Loctite on the bolts...

[wndsrfr]

We’ll I found my problem... sort of a good news, really bad news. Trans is fine - right as rain...
What happened is I sheared all 5 flywheel to crank bolts
The right turn/ left turn bit was coincidental. Was just the chunks of bolts wedging and failing. Flywheel and probably crank are toast. Not what I was hoping for.. not in the least ..

Those bolts were not loctited...
IMO you should not try to save the crank... or the flywheel.
I sourced mine from FAT performance... they put in five, yes FIVE dowel pins. If you're racing it you need something better than stock.

[Charles Freeborn]

Update:
The damage was not as bad as originally thought.
I made a Delrin thing on my lathe that references (very tightly) on the inside of the crank where the trans input shaft goes. Then cut PSA abrasive "donuts" and dressed the face of the crank. I also made a thin shield to keep debris from slinging around. It cleaned up pretty easily and only removed a few tho of material leaving just a couple of gouges. Well over 90% of the surface is fine.
Will put it all together, check for runout with a dial indicator, reset endplay and bolt it up.

[914 Ranch]

Run it, see if it makes noise.

[sixnotfour]

do you use the brakes or the engine to slow,,,I know a 914-6 racer that used the engine more than the brakes,,,,clutches and flywheels always failing...not to mention , engine rebuilds...

just from experience... hope yours is a fluke

[stownsen914]

You probably know this, but when you loctite, don't put it on the bolts - apply it to the female threads in the crank. If you put the loctite on the bolts, some of it can transfer as you insert the bolt. If loctite gets in between your flywheel and crank, you will think you're all torqued, but eventually the loctite in between the flywheel and crank will disintegrate, creating additional clearance and cause loss of clamping force. Basically the bolts will lose torque and come loose. Not saying this is what happened to you, but it's an easy precaution to take.

Scott

[davep]

I had a flywheel come loose on a client car back in 89. Cost me a bit since I was away at the Traverse City Parade that week and another shop had to fix it. One thing I learned about as a result was you had to use NEW bolts and Loctite every time. Naturally you also need new O-ring, bearing, felt seal, and lock plate, and I do the ball bushing in the T-O arm also. I would replace the crank seal also; just because.