Flywheel Question

[RottenBanana]

Hi Folks,

I have a (what I assume to be) stock '73 3spd manual transmission in my EB.

Is there an easy way to tell if it's an 11"?

Is a new flywheel needed? I would normally just have the stock flywheel machined, but noticed the following on Broncograveyard.com website: "You must have a flywheel that accepts a diaphragm style clutch."

Thanks for any help!

 

[DirtDonk]

Only if you're changing to a diaphragm style clutch. Is that what you're doing?
Only if someone changed it would you have anything different from an 11" setup. But that has happened before, so you just need to measure it.
You can count the number of teeth through the starter hole while turning the engine over by hand. Should be 164t on a Bronco.
Assuming it's a V8 engine? I'm not sure if the Inline-6 still had the 11" setup, or was smaller.

Stock original would have been a 3-finger style "Long" clutch plate. Most modern performance replacements are diaphragm style and the bolt patterns are slightly different.

Most replacement flywheels have dual bolt-patterns.
You'll need a 164t 28oz imbalance flywheel. If you ever replace your engine with an '81 or newer 302/5.0 you will need to swap it for the same size, but rated at 50oz imbalance.

Paul

 

[Broncobowsher]

The '66 Bronco was the only one with the little clutch. 11" clutch is the standard size for the V8. Here is a real easy check, is the bellhousing iron or aluminum? Iron is the 164 tooth truck bellhousing and 11" clutch. Aluminum is the 157 tooth car bellhousing and 10" clutch.

And the different pressure plate bolt pattern is what I remember as well.

 

[RottenBanana]

Thanks guys, I'll check the bell housing.

The plan is to change to a diaphragm style for sure. So it sounds like I'll need a flywheel, unless someone has changed this truck to a diaphragm style previously.

Thanks!

 

[Apogee]

I've machined an old 390 neutrally balanced flywheel for a 12" diaphragm style clutch on a 429 build I did for my '77 F150, wasn't too difficult. Otherwise a new flywheel would be in order if yours only has the Borg & Beck pattern.

 

[69_Sport]

I'm certainly not a flywheel expert, but a couple of comments made in this thread aren't necessarily true in my experience.

I replaced the clutch in my '69 with a Luk diaphragm style clutch, and I used the original flywheel. No replacement flywheel needed. The diaphragm style bolted right up with no modifications needed.

Also, Ford produced many, many Mustangs with 164-tooth flywheels and an aluminum bellhousing. I have both aluminum and iron 164-tooth bellhousings in my parts collection. I believe the iron versions were indeed used in trucks, and the aluminum versions in cars.

Not trying to start any arguments, but these observations are from my personal experience.

Doug

 

[RottenBanana]

Thanks guys,

I've decided to let a shop do the clutch replacement. They seemed well versed in the flywheel bolt patterns etc. So later this week it gets opened up

 

[DirtDonk]

Nothing is as consistent with our old vehicles, as their inconsistency after all these years.
I've used diaphragm style clutches on stock flywheels too, but I have also run into pattern mis-matches that required new flywheels be purchased.
No idea what the differences were, or why. But it worked out that way.

So the phrase of the day is: "Be Prepared" (which applies to any day with a Bronco!).

Paul

 

[RottenBanana]

Thanks for all your help Paul!

Once I'm done here, would you recommend a gear swap from the 3.50s to take some strain off the clutch? Currently running 33x12.50x15s. 95% paved roads with very very little light offraod.

 

[DirtDonk]

Yes, absolutely!
It's not a problem of ability, but of quality. You just don't have enough torque to make your engine feel strong with3.50 gears and 33's, and you never seem to have the right gear ratio in your 3-speed to make up for it.
Not that many members here haven't used that same combo for years, but I think you'd just be happier even on the street with something like a 4.11 instead. It's not a huge change, but it's notcieable on how much easier you can get rolling from a standstill, and you don't have as many options without an overdrive anyway.

But here's the kicker. So that you don't have to do it twice, what is your ultimate goal for the transmission? Are you planning an overdrive swap in the future? Or are you planning to keep it mostly stock-ish with the standard 3-speed?
And along those same lines, is 33 your ultimate tire size, or will you possibly be going larger still in the future?

If either larger tires or an overdrive are planned, then you'll likely want even lower gearing in the differentials.

Paul

 

[DirtDonk]

...95% paved roads with very very little light offraod.

I should have also asked, what speed are you running during that 95% road tripping? If you like high-speeds on the interstate, then maybe try to live with the 3.50's for now. But if you spend most of your time around town or on moderate speed back roads (like 45-60 or so) then the lower 4.11 is still going to be a big benefit for your clutch, for your fuel mileage even (maybe) and your engine's health.

It's all about the combination. But it doesn't hurt to leave it for now and see how you like it either. That's more direct than you can ever get from someone out here in internet-land.

Have fun!

Paul