flywheel Options

[ldredman5]

Hi all,

I took my car to a local mechanic because after restoring my 914 that my grandpa bought in 77, it didn't have 5th gear. They tore the tranny out along with the cluch and flywheel. They then told me it would cost $8000 to fix it. I told them to...well you can use what ever phrase you want. I have sence bought a tranny for $150 on craigs list that works great. My problem is that the flywheel keeps coming loose. After pulling and putting in the tranny 3 times im getting tired (and fast) of doing this much work to drive it 50 miles. This last time i pulled it i washed out the bolt holes and bolts and put red loctite on them and it still came loose. The only thing i havent dont is replace the flywheel, bolts, and the flywheel washer plate (the one that goes between the bolts and the flywheel). If I replaced the bolts and the washer plate would that help? Someone told me not to use red loctite and use this bolt goo stuff that works like loctite. Should I do that instead? Any help would be nice.

Thanks

[ThePaintedMan]

That sounds like another issue like balance, and you're lucky/skilled to be able to catch it each time before it comes completely off! But, just so you know the flywheel bolts are "stretch" bolts that are supposed to be replaced each time the flywheel comes off. Fairly cheap place to start in my opinion. Next would be a replacement flywheel if this one isn't balanced right. Guys?

[ldredman5]

I am having the flywheel turned. I didnt know the bolts where "stretch" bolts. Could I replace them with non stretch bolts or get original parts from somewhere like pelican?

[ThePaintedMan]

I am having the flywheel turned. I didnt know the bolts where "stretch" bolts. Could I replace them with non stretch bolts or get original parts from somewhere like pelican?

The bolts from Pelican are stretch bolts too, sorry I forget the correct term. But that is the correct bolt to use. They stretch under load, providing spring pressure which helps to hold the bolts in. Once torqued, they loose some of this ability and that could be part of your issue. Again, its the cheapest thing that I would try first, if it were mine. Used flywheels are expensive. Try turning it, assuming its still balanced and with new bolts. After that, I wouldn't be the one to talk to.

[914werke]

Not so sure about that stretch bolt theory but the thin metal lock plate must be replaced each time. If you look at the underside of the 5 shoulder bolt heads there are serrations that bite into that plate & lock it in place.
Use once, then toss.
You may also have an issue with balance as mentioned so Id have it spun with the friction disc & PP by whomever is cutting it.

[Dr Evil]

$8000?! Yikes.

Ya, bolts are one time and plate is two time use. Plate has two sides (IMG:style_emoticons/default/wink.gif) Bolts have serrations under the heads that cut into the plate and keep them from backing out.

[bigkensteele]

Wow - $8000! Did you go in there wearing a dress and gucci purse with a small dog sticking out of it? You can buy my car right now for that money and it has a newly rebuilt tranny, overseen by the Doctor.

I would agree with the balance comments above, and I would also stress that you don't drive it anymore. If it is a balance issue, then you are also damaging your crank and main bearings. I would pull the motor and start digging. It will get expensive much more quickly than it will get cheaper.

[ThePaintedMan]

Sorry Rich, I only knew that they were at least a 1 or 2 time use thing. I know on Fords the flywheel bolts, head bolts and other heavily loaded hardware are all considered "stretch" bolt because they expand some (albeit very little) when torqued. Same concept, but different ways of achieving the result I guess. I of course found out the hard way when I rebuilt my T-Bird in high school and used Home Depot fasteners. About 3,000 miles after I got it running the bolts started backing out and the center of the flywheel sheared away from the outer. (IMG:style_emoticons/default/headbang.gif) Needless to say, don't reuse hardware that sees heavy duty and certainly do not if you are already experiencing problems. Cheap insurance. The balance stuff is purty important too.

[rnellums]

Sorry Rich, I only knew that they were at least a 1 or 2 time use thing. I know on Fords the flywheel bolts, head bolts and other heavily loaded hardware are all considered "stretch" bolt because they expand some (albeit very little) when torqued. Same concept, but different ways of achieving the result I guess. I of course found out the hard way when I rebuilt my T-Bird in high school and used Home Depot fasteners. About 3,000 miles after I got it running the bolts started backing out and the center of the flywheel sheared away from the outer. (IMG:style_emoticons/default/headbang.gif) Needless to say, don't reuse hardware that sees heavy duty and certainly do not if you are already experiencing problems. Cheap insurance. The balance stuff is purty important too.

(IMG:style_emoticons/default/agree.gif) I re-used flywheel bolts the first time I rebuilt and had the flywheel shear them off as they backed out. Had to split the case again and have the crank and flywheel machined. Not fun.

[Dave_Darling]

That brings to mind the question:

How is the flywheel? What about the end of the crank? Those can get pretty beat up if the flywheel comes loose.

--DD

[ldredman5]

The back of the flywheel and the mate side of the crank are a little worn. I don't think it's all that bad. Haven't heard back from the machine shop yet. Should hear from them this evening. New bolts and washer have been ordered. Thanks for all the help. When putting the bolts back in should I use loctite?

@Bigkensteele. Hahaha. No. But I think they wanted me to bend over and take one for the team.

[Harpo]

Head bolt, rod bolts and main bolts have a torque to yield strategy meaning the bolt is taken past the point of its elastic strength. This can only be done once. Most other bolts are not torqued this high and can be reused more than once safely.

Hope this helps. I'm a fastener engineer at Chrysler

David

[craig downs]

Yeah I know all about reusing the flywheel bolts. This is what happened when I reused them. I was about 5 miles coming home and heard a odd noise. When I separated the transmission from the engine and removed the clutch this is what I found. 3 bolts were loose 1 was sheared and 1 was still tight. I looked at some other used flywheel bolts I had and the threads were really stretched and I threw those away. My advice never reuse them.

[ldredman5]

Thanks for the pictures. That is what my flywheel looked like. We're you still able to use it?

[Dave_Darling]

I'm not actually an expert (even though I play one on here!) but there's no way I would try to use that flywheel or crank without significant re-machining.

And maybe not even then.

--DD

[Bleyseng]

I would question the end play as the crank might be slamming back and forth do to too much end play which will loosen the bolts too.

[craig downs]

The bolts were torqued with a new aluminum disc and the end play was set at .003. I disassembled the engine and had the crankshaft and flywheel machined at DPR and had it drilled for 5 dowels. Here is how it looks after machining. The crank still looks a little rough but the idea was to face it off just enough to create a flat surface again. After 2 years I haven't had any problems.

[ldredman5]

Thanks for all the info.

[Cap'n Krusty]

NONE of the fasteners in a 914 are "torque to yield". NONE. The flywheel bolts are reusable, as are all the other fasteners in the engine. Many techs use new connecting rod nuts each time, but that may be being somewhat overcautious. I do that. Torque to yield technology wasn't applied to any production Porsche until many years after the 914 was built. If your flywheel comes loose, it's likely to be because of damage to the end of the crank or the mating surface of the flywheel, or to bolts that have been seriously overtorqued at some time. There is NO "aluminum shim" anywhere near the F/W. There IS a steel lock plate for the bolts, and it's a single use item. I doubt too much end play would loosen the bolts, either. BTW, 911 F/W bolts have been one use hardware since about the time the 2.2 engine came into use, and are VERY sensitive to the effects of too much torque.

The Cap'n

[ldredman5]

Ok. Thanks cap'n. Other steel lock plate is on its way.