Shop Talk - Tear Down by JT

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dreaming. I made peace with leaving the car alone for all of another week or so. Knowing that I was pursuing more 1/8-mile no-prep situations than ¼-mile track races left me with an unsettling urge to maximize the potential of my car for little money. I have plenty of horsepower to get the results I need, but do not have the miles per hour I want. Let’s face it, weight reduction is at the top of my list but is insanely costly to do correctly.

What does that leave me with? Hmmm? There is always the dark secret, voodoo black magic called gearing. Yes, math will get me what I need, but I’m a creative person, an artist and a writer. The skillsets I possess use an entirely different part of the brain than math does.

ello fellow gearheads. I pray this finds you all enjoying wrenching, racing, and finding more ways to make money to wrench and race. I know I’m preaching to the choir, but I just hate that I can’t leave my car alone.

I mean, I get it performing perfectly and looking like a show queen but still find ways to completely stress out and rip her apart. When I parked it in the garage and put the cover on this past fall, she was in 100% perfect condition, but by the first snowfall I had a list of upgrades that my new Covid-induced budget could not afford. Believe it or not, that cold hard realization of having no money to make the upgrades actually made me stop

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Due to top secret classified information, I was forced to work by myself. That means finding ways to get creative in order to make my life easier. My homemade rear end support does a great job enabling me to drop, work, and install that heavy Dana 60 by myself with the help of my mid-rise lift. Torquing the ring bolts to 90 ft/lbs is a challenge by yourself, but this old wheel I got for free does a great job keeping my carrier solid while I pull on that wrench.

There she is all disassembled. I made sure the inside of that housing was hospital clean before putting any new parts in there. I had to purchase that little seat as it has the same name as our car.

I remembered a conversation I had with the great Dan Fletcher about RPMs, tire size and gear sets. He knew the math of that black magic instinctively. It was so impressive listening to him rattle off what difference a gear change will make in rpm and mph off the top of his head. I was probably too star-struck and knowledge-impressed to have fully paid attention during this priceless conversation and retained virtually nothing other than how to gain more mph using the set up I have. Thankfully there is such a thing called a gear set calculator out there in cyber world. You simply punch in your tire size, gear ratio, rpm and it will tell you the mph, (or solve for any one of those variables). Now, I apologize for being vague and secretive, but the kind of racing I do relies a lot on negotiating and having

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someone think my car is not what it really is. So forgive me for not giving exact specs on what my most recent changes were. Allow me to give you the two extremes of gear ratio changes and how they affect mile per hour.

A 3.73 gear with a 33” inch tall tire at 6200 RPMs will produce a mph of 163.25. Now simply jump to the other end of the spectrum and use a 5.13 gear and your mph is a meager 118.70. That is a 44.55 mph difference in the ¼-mile. My gearhead friends, who knew as a teenager that math was going to be an extremely important part of my racing addiction? I certainly didn’t! Football, wrestling, my car and girls were way more important at the time.

So much research, thought, and planning went into finding the perfect gear ratio, tire size and yes torque converter, to make Big Red do what I needed her to do. It’s no secret as I have written about it many times, but I absolutely love paying attention to the details. The things that some people overlook or find boring, I take to another level and find peace in it.

Setting a rear end up with a new gear set is one of those tasks that fully embraces who I am. The intense amount of detail that is required to do it properly excites me. This same amount of detail frightens other people or bores them to death, possibly because they can’t appreciate the beauty in it. I am talking about producing the perfect back lash and getting your shim count so perfect that your pinion depth has its own theme song. Don’t even get me started on torque specs. I use three different torque wrenches when setting up my Dana. I use one for ring bolt and main cap torque, one for pinion preload, and one giant hunk of metal 90

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With attention to detail and some much needed math, perfection was achieved. Every spec from head to toe was exactly where I needed it to be. At this point I just wanted it in the car.

I was able to set this in place completely by myself with the help of ingenuity and cool tools. By no means was it easy and at times things went wrong, but I was able to do it. The last time I rebuilt the rear my wife helped me get it in and out. The help of one more person goes a long way when working with a home shop.

It is hard to believe that this entire rear end was in a million pieces. I thoroughly cleaned, and/or painted, and waxed everything under the car once again.

To me, the attention to detail is not to impress anyone, it is to simply give me peace. It also helps me get some good grudge races from people who think she is just a show car/trailer queen.

Here is a staged mock-up of what my workbench looked like when I was setting up the pinion pre-load.

Like I wrote about, I am sorry I did not take the actual picture but things were way too intense at the time for me to think of anything else. Just imagine every shim and its size laid out in numerical order.

It took me forever to measure each one and do that. This is why this mock up picture only has a few.

But hopefully you get a better idea of what I meant.

that is capable of achieving the 250 ft/lbs I need to tighten my pinion nut.

I’m not the kind of person that is okay with “it feels right” or “this usually works.” No, I’m a detailed to the exact numbers kind of guy. It took me over 30 times of taking the pinion in and out just to achieve the preload number I was shooting for. When you work by yourself, that resulted in hours of what some would say “mindless and mind numbing” work.

Not for me, I call it peace. The math that was involved with those damn little shims and trying to achieve the perfect inch pounds was crazy, (yes, inch pounds). A word of advice, I highly recommend spending the money and buying a complete set of shims in all widths. If you are working with what you have laying around in your shop like me, trying to obtain a .043 inch shim stack is going to take some creative math solving. I am so mad that I didn’t take a picture for all of you to see how my brain functioned at that moment, but I was way too involved at the time to be thinking of future magazine pictures. But imagine a shop towel laid out on my workbench with all of my shims organized numerically on it. I had a calculator and a sharpie so I could take notes in case the current shim count did not work.

My new set up took me a little longer than I had wished for, but as they say,“the juice was worth the squeeze.”

After just a few test hits, I was able to not only see the data I had hoped for, but I actually felt it in the seat. The 1-2 shift is more violent than ever, and the new top end actually scared

Video of the first time those wheels turned after the rebuild. My daughter was sitting behind the wheel as I was outside listening to the freshly built rear and feeling things out. She had a blast piloting Big Red during this warm up / break in. www.rpmmag.com

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Here are some sample gear set changes that all affect MPH. I urge you to take a look at your current set up and see if you can make some tweaks. Be sure to know your transmission ratios, and where your torque converter flashes before entering the data. me. The change tamed my launch but increased the 60 foot time. I still need to experiment with air pressure for maximum traction.

The old pressure I used to use does not work at all on the big end as the tall tire is way too sketchy at a low pressure. I am confident

that with a little more testing and a lot more math, I will find the numbers and results I am looking for.

Dare I say I am finally done making changes? Ha! Who am I kidding?

Until next time – Keep Wrenching,

www.rpmmag.com

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