84' 4.9 i6 Fly wheel bolt pattern confusion.

[Jon M]

Hi folks, I'm stumped!

In my mission to replace all wearable, moving, or otherwise updatable part in Dolly, the 1984 F150 I have run into a road block. the fly wheel on the transmission is showing some wear and while it was shifting fine, I wanted to replace it (if for no other reason than the experience of learning).

Well I got a standard replacement kit and got to the business of bolting it up, but lo and behold the bolt pattern didn't match. it's the same 6 bolts and the sizes are the same but the holes are ever-so-slightly skewed... differently. I matched the new fly wheel up with the old one (face to face) and two opposing bold holes match perfectly but the other four are slightly off. I tried rotating it in a complete 360 circle, using every possible combination to make sure that there wasn't a very specific orientation but it still did not fit (or match the original). what am I doing wrong? this flywheel is from Rock Auto and from my model year and engine size, so I'm thoroughly stumped.

two other salient pieces of data:
1) I'm doing the M5OD-R2 swap
2) This is actually the second fly wheel I've bought. I picked up the clutch kit for a '92 F150 4.9 5-speed and when the fly wheel didn't match up, I assumed it was because of the generation. So I bought this one for but it is by-and-large an exact duplicate of the one from the '92 clutch kit - doesn't fit in the exact same way.

here are some photos. it was really hard to show how the holes didn't align but the last picture demonstrates with the two fly wheels face to face:







\

[Jon M]

One addendum. I say I put the fly wheels face-to-face but in reality in order to get the bold holes to touch the opposing wheels bolt holes, they are back-to-back. Sorry if any of this is confusing, I've burned a lot of brain cells thinking on this one...

[85lebaront2]

Look closely at the flywheels on the engine side for either a bunch of blind holes or a cast on weight, Windsor V8 flywheels and 240/300 six cylinder ones are the same size, but the V8 ones have an imbalance just like the balancer on the front does (it's 180° opposite on the flywheel).

[Rockhauler]

If I remember right the 300 6 cyl flywheel has the same bolt pattern as a SB 8 cyl. 5 holes are equally spaced and the sixth hole is spaced slightly different so the flywheel can only bolt on in one position. Hence putting them back to back you would never be able to line all 6 holes up.

Hope my memory is right.

Paul

[mat in tn]

it is very common for the bolt pattern to be irregular. this is how it gets bolted on in the only proper position. having the two back-to-back misaligns them. they must be stacked in the same order to be compared

[ArdWrknTrk]

∆∆∆. These guy's are absolutely correct.
You have to have them both face up (or down 🙃) to have the holes align.
.
If they use the bolt pattern common with Windsors (which are 28oz off) one bolt hole will misalign.

Clocking doesn't matter a bit with an inline-6, which has inherently perfect primary balance.
My brothers twin turbo BMW GT is glass smooth right up past 7,500 rpm (It's hard for me to judge shifts)

I'm surprised that more members that own a 300 truck don't make a bigger point of this.
They all talk about the low revving nature, but not how smooth it is.  
You should feel my 460 as it approaches 6k.  

[BigBrother-84]

Jon M wrote

[…] I wanted to replace it (if for no other reason than the experience of learning).

This is one of the major reasons I enjoy being here.
I learn so much things I don’t have to do myself, just for the fun of learning (secretly hoping I’ll never have to.  ).

Thanks Jon for this thread about a job you maybe didn’t have to do.

[Rockhauler]

Darn Jim us 300 owners are trying to keep how smooth they run a secret. A old 240 I once owned was so smooth at idle you had to look at the fan and belts to tell it was running.

Jon try that flywheel again just remember all the bolt holes will only line up in one position. Five of the holes are equally spaced at 60 degrees apart and the sixth hole is slightly different as its spaced at about 64 or 56 degrees from the adjacent holes. If you have a vernier caliper a quick measurement from hole to hole on both the flywheel and crank should locate the oddly spaced hole.

If your original flywheel isn't heat damage you could also consider getting the clutch side resurfaced.

Paul

[Jon M]

BigBrother-84 wrote

Jon M wrote

[…] I wanted to replace it (if for no other reason than the experience of learning).

This is one of the major reasons I enjoy being here.
I learn so much things I don’t have to do myself, just for the fun of learning (secretly hoping I’ll never have to.  ).

Jeff, you hit the nail on the head. I check this website at least once a week and just scroll just to read and learn. And This truck I'm working on is 100% to learn on (but also I need a truck, so I need to learn quickly).

Predictably, it turns out everyone was right! So I got the fly wheel on, and now I'm just waiting for the bolts I ordered to install the pad and plate. after that I can get this transmission on and maybe take the truck for a spin!

[Rockhauler]

Thanks for following up that you got the flywheel sorted out, don't feel bad that offset bolt hole has stumped lots of people over the years.

Best one I seen is a fellow who applied a couple dabs of silicone to hold the clutch disk centered while installing the trany. Put the truck up against a tree and had the tires pawing away but couldn't get the silicone to break free. Had to pull it apart and start the process all over.

Paul

[mat in tn]

what the??????