Ford flywheel and clutch

[Antony]

I've got a small problem that I'd like some advice on regarding my GTD 40.

I've had the car for 10 years now, and for a considerable time it has suffered from a slipping clutch. I didn't build the car, so unfortunately don't know all the details of what went into it. Only to say it had a Renault transaxle and Ford 302 (from GTD, so possibly a marine spec unit?).

Last year, I managed to destroy 5th. Completely. Oops

Oh well, I got in touch with Chris Cole (nice guy), and now have one of his lovely Renault 21 Turbo boxes now ready to go back into the car.

But... I decided to take the clutch off to get a new one to fix the clutch slip, and now the the problems start. Chris suggested I have the flywheel skimmed to remove the glaze. But the surface not only is discoloured from the heat, but also covered in small cracks.

I thought I would be able to easily buy a replacement, to be on the safe side, But....

I guess it's not a standard Ford unit for a 302. It only has 121 teeth, and I have heard mention it is for a Ford 3.0 V6. It has some big old balancing holes drilled in it, and I've also heard a flywheel needs to be balanced to the crank, as they are matched. On the rear face of the flywheel there are some numbers stamped into it and there is a big counterweight.

Can anyone give me any advice on:

Can a standard flywheel be skimmed? How much can I take off without weakening it to machine off the cracks. Is this a good idea, considering it isn't a race engine.

If I buy a new flywheel, what do I need and from where?
And finally, will I need to take the crank out to balance it all? That's a big job I'd rather not have to do.

Thanks

Antony

 

[Howard Jones]

This is what a new one looks like. Have a honest flywheel ballance guy look at you flywheel and see if it does indeed need to be replaced. If it does you will need to reballance the motor. No way around it. Centerforce makes a better clutch for then Deloreans. Same thing.

 

[Randy V]

Antony - I think you could probably remove as much as 1mm from that surface if you needed to and maybe more. I would take it to a good automotive machine shop that has a Blanchard grinder for flywheels. They'll know what to do..
I've had a lot of flywheels that were worse than yours resurrected...

 

[Mike Pass]

If your flywheel can't be resurrected then talk to a good engine builder. They can take a new flywheel with the balance you have and then match balance it to exactly the same balance as your original thus saving you a lot of hassle. You can get new steel flywheels for your setup in a range of balances from Mick Sollis at Southern GT. You can also get AP clutches which should solve your slip issues.
Cheers
Mike

 

[Antony]

Thanks guys, that's good news. I really didn't fancy dropping the crank out. I'll have to look up an engine build shop in North London/South Herts. I know of a place that I've used to have a head skimmeded in the past, they might be able to do it or at least say who could. I like the idea that they can copy the balance of my old one. I would stick it on the lathe at home or work, but I've been told the heat will have hardened parts of the surface, and make it not possible to cut, it needs grinding.

Can anyone confirm what the flywheel is, and where I can get one from?

FYI, here is a pic of the remains of 5th! Managed to limp home after that, I really thought I'd blown the clutch but found 1st to 4th still worked.... just.

 

[Jason Lycett]

Maybe if you get you existing flywheel balanced, and then got it remachined and balanced back the same as it was before, in theory it should still be in balance with the engine, and therefore not need to rebalanced with the crank?, anybody got any thought' s on this?

 

[Eric A.]

Maybe if you get you existing flywheel balanced, and then got it remachined and balanced back the same as it was before, in theory it should still be in balance with the engine, and therefore not need to rebalanced with the crank?, anybody got any thought' s on this?

I wouldn't think that taking a small amount off of the clutch surface would change the balance of the flywheel. If you need to replace the flywheel, a good balance shop should be able to match the old one. If they cannot match balance to the old flywheel you would need to have the crank out and also have the weight of the pistons and connecting rods. All of the moving parts need to be balanced together for a perfect match.

 

[Randy V]

When the flywheel is ground, it takes an even amount off the face of the entire flywheel - thereby leaving the flywheel in the same state of balance that it was in to begin with.

 

[Paul Thompson 'Hooligan']

When the flywheel is ground, it takes an even amount off the face of the entire flywheel - thereby leaving the flywheel in the same state of balance that it was in to begin with.

Generally true, but if you look at the GTD flywheel, it has a bucketload of balance holes cut in one area. A skim over the whole area will remove additional weight from the side with no holes. Not much, but a few grams for sure. (and right on the outside edge where it would have most effect)

The flywheel is off an 3.0L Essex Ford V6, eg early Capri/some transits? or an Australian Capri. Cast and not available new from Ford any more but you should be able to pick one up from somewhere. Looking at your existing one I'd get it skimmed and possibly rebalanced if deemed necessary.

A previous discussion on GTD Flywheel balance issues: http://www.gt40s.com/forum/gt40-tec...t/19312-std-gtd-flywheel-posn.html#post170807

 

[BruceA]

Antony. Interesting to see your 5th in such a state. Can you tell us what you were doing when it decided to expire? From what Ive found, its usually the heat issue that buggers them up as they are furtherest from any decent oil supply.
What Ive done with one of mine is to make the 5th gear wider, and hopefully stronger as well by making up a new set. They are only 18mm wide and there is scope to go to 22mm.

 

[Howard Jones]

Has the existing engine rotating assembly and the flywheel been balanced as a unit before now? Was it balanced with the clutch you have in it now? How old is the current engine and how hard has it been run? Could it use a re freshen? If the engine is in good shape and has been previously balanced I guess you could have a second replacement flywheel "mirror balanced" to your current flywheel. Do it before you have it resurfaced. If you are going to change the clutch then you will be effecting the balance further so I would "mirror" the new clutch pressure plate and flywheel as a unit against the old one.

On the other hand if it hasn't all been balanced together then nows the time. The V6 that these flywheels come from have a completely different balance profile than a 50 ounce externally balanced 302 as well as the earlier 34 ounce 289's. If you try and run a new V6 wheel with a V8 the imbalance will destroy the engine in short order.

If it was mine I would rebalance the whole thing unless the guy who looks at your flywheel just needs to take a couple of thou off to clean it up.

Talk to the GTD guys over there. They have a lot of experience with this.

If it comes to it, I think I can find a new flywheel here in California. You would be much better off finding one over there. $$$$$$$$$$$$ shipping.

 

[Jac Mac]

'''28 oz early 289/302 along with 351c/w/m'''--- Not 34 oz. Mirror Balancing is for gamblers & quick fix Charlies--do you fit that category?

Also, your slipping clutch, I hope your doing an upgrade in that dept, if not your asking for the same problem all over again.

 

[Andy Green]

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I’ve seen this type of failure before on Lotus Esprit Transmissions, which use basically the same Renault UN1 transmission. These have been on high mileage cars and we believe the failure is caused by a combination of insufficient gear width and fatigue loading, specifically from torque reversals (i.e. on engine over-run)<o></o>
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Bruce’s comment about producing a wider gear would help and so would having the gears shot-peened, which would improve there fatigue resistance.<o></o>
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[Howard Jones]

Jac's right again. 28 it is. That's the problem with working from memory. Oh and that's nearly the same answer Jac gave me when I asked this same question because I didn't want to take my nice new FMS crate motor apart. I didn't heed Jacs warning so I "mirror" balanced, my V6 GTD flywheel using the brand new never used FMS flywheel that came with the engine.

3000 miles later..... Spun the rear main bearing and a couple of rod bearings. I'll never know what really caused it but the people I showed the crank to all said it wasn't lack of oil. After putting in a new crank and balancing the whole thing right the SECOND TIME INSTEAD OF THE FIRST TIME the engine runs like a top. I run this car up to 6K revs all the time without any problems.

Moral of the story..... Listen to JAC!!!!!

 

[Antony]

Thanks a lot for all the advice guys, I'm pleased I posted something before doing anything. It's so helpful to be able to find all this info out from everyone around the world. Sorry it's taken so long to get back to this thread, but I've been a bit busy with work and stuff, so hopefully I'll get chance to get the car back on the road soon, before I miss the summer.

In answer to some of the questions:

I'm not sure why 5th gave up, I know these boxes can shear the shaft where 5th overhangs the rear bearing. There was plenty of oil in there, and it had chance to warm up. The car has only done 12,000 miles, but who knows about the geartrain. I was going "quite" fast. I think I'd just come off full throttle and there was a bang, which I thought was the clutch going, so I coasted to a halt and pulled off the road. That seems to match perfectly with the load-reversal fatigue mentioned. I'm interested in the wider gears, but considering the mileage I do, I'd be unlikely to get round to it.

Yes, I will be replacing the clutch with something a bit stronger (doh!)

Paul Thompson - the name rings a bell, did you have a GTD in Harpenden?

I had planned on getting a new (302) flywheel from the 'States until I found out all this info. Good job I didn't get one! I've just cleaned the flywheel up, and will take it to an automotive machine shop, or engine builders.

Once that's done, next thing is the clutch!

Thanks again.

 

[BruceA]

Antony. Thanks for your replys. As a picture is worth a thousand words, I studied the photo you have of your failed 5th gear. If I am correct, the alignment of the gears is out. Its not common, but I have heard of it happening, the big nut that secures the gears onto the secondary shaft may have come loose, the rear thrust bearing separates, and the shaft drops down slightly, the gears then partially separated, were running on thinner metal and when you took your foot off, its quite a loading on the gears .. and poof --- instant teeth removal. If you've still got the box, Id have a look at the rear secondary shaft nut and see if it is loose - just for the theory anyway.

 

[Antony]

Bruce - very interesting, It's always nice to know what happen when there is a failure. Unfortunately I haven't got the box any more, so I can't tell you if the nut was loose. I do have some full-res pictures if you want to look at those! The explanation sounds very plausible, and does not involve fatigue, just a build problem. I have a nice new box now, so I'm hoping for no more problems.

Antony

 

[Paul Thompson 'Hooligan']

Paul Thompson - the name rings a bell, did you have a GTD in Harpenden?

I wish!!:laugh:

No - I've never owned a 40, but have been blessed to have worked on many and competed in a few too.

After driving Martin Weigold'd '6GTD' in the Isle of Man, I'm returning to my usual drive of Roy Smart's 'A11GTD'....Both excellent machines - thanks chaps!