Auto Shop Tackles Model A Rear End Swap

Flathead High School’s 1928 Model A Tudor Project Car

By “Rotten” Rodney Bauman  –   Photography By the Author

If you as a youngster were fortunate enough to attend any type of high school industrial arts classes, you’ll more-than-likely acknowledge their value. I’ll tell you straight; back in the mid ’70s I gained from my own experience. Sadly, things are different today. High school vocational courses where heads and hands work together (apart from just keyboards and screens) have become fairly rare exceptions.

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02 Flathead High s 1928 Ford Tudor project in an old brick building
Having already spent 30-some years in this same ol’ building, here’s Flathead High’s 1928 Ford Tudor project, as it was when we first joined in.

A Glimpse into Montana’s Flathead High Auto Shop

When our rod-building buddy Greg Greene clued us into a long-ongoing 1928 Model A Tudor project in the Auto Shop of Montana’s Flathead High, Mrs. Rotten and I were intrigued. Upon our first visit, we knew we’d return. We couldn’t help but get involved—and we’ve continued going once or twice a week.

03 Problematic Ford Model A frame in the Metal Shop
Boxed next door in Metal Shop, the Ford Model A frame is solid. Here at this end, however, we see problems: upside-down coilovers and Panhard rod interference, just for starters.

Juggling Grades and Auto Classes Since 2001

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Before we go further, let’s talk about the teacher, Rob Hunter. He’s been right there at Flathead High since 2001. For Mr. Hunter, juggling all the high school grade levels, with Auto 2 and Auto 3 in the same building at the same time, adds up to a heaping-full plate.

04 Students wearing safety glasses and using a wire wheel for thread cleanup
Following instructions from Mr. Greene, a student dons safety glasses and spins a wire wheel for necessary thread cleanup. Next time these coilovers are installed and adjusted their threads will receive a bit of anti seize.

From an ’80s GM Chassis to a Boxed Model A Frame

Next, let’s talk about the hot rod project. It’s been there longer than the teacher—as far back as the ancient ’90s. We’re told it started out with a shortened ’80s GM intermediate chassis—yep, you’ve read that correctly.

05 Students examining the rear end of a 90s S10 Blazer
So, this was just brought in by students from an outdoor stash of parts. From a ’90s S10 Blazer here’s the upgraded rear end. First things first, students pull the inspection cover for a look around inside. Sure enough, it’s positraction. It’s also in need of attention.

Read More: How To Insulate Your Car The Right Way

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In its current stage of reconstruction, the 1928 Ford Tudor build is based on a properly boxed Model A frame. Between the ’rails resides a familiar Chevrolet 350/350 combination with a 10-bolt GM differential bringing up the rear.

06 Mr Greene demonstrating seal removal to Tharen and Zach
Axles and bearings will be replaced as necessary. Here Mr. Greene demonstrates seal-removal. Youngsters Tharen and Zach get it, so they’ll pull the opposite-side seal.

The Influence of Rocky Mountain Rod & Custom

The project’s finished bodywork is actually very good. Come to find out, it was our friend Scott Christensen of Rocky Mountain Rod & Custom who’d guided students through that phase years ago.

07 Empty housing of the rear end with OE spring saddles
With the upgraded rear end stripped to an empty housing, OE spring saddles still must go. Here for dueling grinders, welding helmets are double-effective eye protection.

A New Generation with a Passion for Cars

Now, let’s talk about The Class Of 2023. With eagerness to listen and learn, this group exudes natural, hands-on ability. They’re car-smart, too, but at one point it did become apparent that they hadn’t been raised by “traditional” hot rodders. When one suggested a high-tech crate engine, it seemed it was time for a talk. As I began, students gathered—and heads nodded as they were clearly paying attention.

08 New coilover and hairpin brackets from Speedway Motors
Just in from Speedway Motors, coilover and hairpin brackets are duplicates of what we’ve had. The new Panhard rod bracket will allow a bonus bit of adjustment.

Staying Timeless in Hot Rodding

“You guys are going to have some trouble building a hot rod here. You wouldn’t want it to go out of style right away, would you? For that, the best prevention is steering clear of current trends. On the other hand, if you study hot rod history, you’ll learn that past trends can make lasting comebacks. A well-executed ’50s- or ’60s-style build, for example, won’t go out of style a second time.

09 Mason taking measurements for side to side centering of the rear end
For initial tack welds the rear end must be properly located, first. Here young Mason (shop foreman) takes some measurements for side-to-side centering.

Read More: Coyote Swapped 1957 Ford Fairlane 500

“For style guidance, a stack of old magazines can be helpful. Just pick a year, or a span of two or three, and try to adhere loosely to a theme from a specific era. Here your A Tudor project is already a bit dated, but mostly in one minor respect. Before we go there, let’s discuss what’s already right.

10 Mr Greene and Mrs Rotten using a tram bar to square the rear end
Before we ever started, wheel alignment was good. Now that it’s centered side-to-side, Mr. Greene and Mrs. Rotten employ Auto Shop’s tram bar to square the fresh rearend.

The Right Components for the Hot Rod Build

“Having been available to hot rodders since the mid ’50s, a small block Chevy like the 350 engine you already have will continue to be an acceptable mill. Front and rear, your existing suspension is kit-form stuff from Speedway Motors. It’s designed for installation ease and strength, but style-wise it’s appropriate, too. As it all came from Speedway Motors, your 4-inch-drop I-beam and visible hairpins can be considered timeless, so you’re good there. For your build, perhaps apart from rolling stock, there’s not much backing up to do.”

11 Mason adjusting the hairpins Heim joint jam nuts
At this point with alignment A-OK, Mason snugs the hairpins’ Heim joint jam nuts. Next, let’s see if we can establish an acceptable pinion angle.

The Decision to Upgrade the Rear End

Once our little talk concluded, sparks took flight as the first order of business was to swap in a better rear end. Getting a clean restart wasn’t difficult. There was an appropriate-fit GM differential assembly sitting just outside the building so students brought it in for visual inspection of its internal workings. As it turns out, it’s positraction with a more-favorable 3.73:1 gear ratio, so following its rebuild something will indeed be gained.

12 Mason adjusting the hairpins Heim joint jam nuts
Here a small magnetic angle finder is handy. For an equal opposite of the transmission tailshaft angle, we’ll keep trying for 2 degrees up at the pinion.

Read More: Two Timeless Model A Hot Rods

Since the previous rear end’s weld-on brackets would be difficult to salvage for reuse, Mr. Hunter placed another order with Speedway Motors for exact duplicates—and a better-fitting Panhard rod bracket. Wouldn’t you know that the order arrived in time for our next visit.

13 Panhard rod bracket being fitted on the left side
We believe this Panhard rod bracket is intended to be on the left where the opposite-end bracket is already welded. With a notch ground in for clearance, this’ll still work.

Preparing for a Local Parade

In a nutshell, this year’s goal is to make the project driveable enough to safely run in an upcoming local parade—mainly so the group’s seniors get something for their efforts prior to graduation. Providing next year’s students show similar interest and aptitude, I’ll personally propose that we scatter the project for paint. First things first, there’s some fabrication work to do.

14 Derek widening the notch in the Panhard rod bracket
Our test-fit was tight, so for an ounce of prevention, Derek is grinding his notch a couple tads wider. This way, when it’s time for bounce-testing, we’ll know it’ll pass.

Introducing the Five Students Leading the Charge

Of a much larger class, we’ll be working with five main players: Brock, Derrick, Mason, Tharen, and Zach. For Mr. Greene and us Rottens, this’ll be a little different as we’re not used to working through the hands of others. We’re mainly here as consultants. This is all about the students honing their skills—in this instance with the proper installation of an upgraded rear end. MR

15 Mason and Mr Greene tack welding the Speedway Panhard bracket
At this stage the rear end is centered, wheel alignment is satisfactory, and so is our pinion angle. Speedway Motor brackets are fitting well, but we’re only tack welding for now Lastly, let’s locate and tack weld the new Speedway Panhard bracket to the right-side axle housing. Welding and holding are Mason and Mr. Greene.
16 Mrs Rotten and Tharen moving the rear end with tack welded brackets
Our Speedway hairpin, coilover, and Panhard rod brackets are now tack welded in place. Here Mrs. Rotten and Tharen roll the rear end back out for final welding. After Derek, Mason jumped in. To protect the new bearings, the ground clamp is kept close to each weld. Time to prepare this assembly for painting.
17 The completed rear end assembly ready for reinstallation
The finished rear end assembly is now ready to resume its position for keeps. Providing Heim ends and clevises have not been disturbed, alignment should be good. We’ll double-check all that, of course.
18 Brock Mr Greene and Derrick starting to install the replacement rear end
Brock, Mr. Greene, and Derrick are just beginning to install the replacement rear end. Inside the car, Tharen (just out of view) and Mrs. Rotten are allegedly working on wiring.
19 Derrick and Mr Greene attaching the right side hairpin
Here Derrick and Mr. Greene are wiggling fasteners in for the right-side hairpin. We’re not quite sure what Mrs. Rotten is doing, but we’ll continue to refer to it as “wiring.”
20 Brock and Mason reinstalling the coilovers in the correct orientation
Toward the end of this chapter, Brock and Mason reinstall the coilovers—in a proper up-side-up fashion this time around.
21 Brock installing the preadjusted Panhard rod
As this phase’s finishing touch, Brock handles the preadjusted Panhard rod installation. Sure, some double-check measurements were taken, and we’re good.

Speedway Motors
(800) 979-0122

Click on this issue’s cover to see the enhanced digital version of Auto Shop Tackles Model A Rear End Swap.

mr aug 2023

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