The transmission quote that almost bought me a new truck

The question

The transmission shop called on a Tuesday. My truck has 190,000 miles and a dent in the tailgate shaped exactly like the basketball hoop pole. It needs a rebuilt transmission, and the quote is $3,200.

So do you fix the old truck you own outright, or trade it in and sign up for a new truck payment?

Every number in this column is an example. Swap in your own quotes, your own loan offer and your own fuel log. Mine aren't prices. They're props.

The Dad Math

This was done standing in the driveway, phone calculator open, one hand resting on the hood like a doctor about to deliver news.

• Transmission repair: $3,200
• New truck payment (example): $767 a month
• $3,200 ÷ $767 = about four payments
• So fixing the old truck means paying four truck payments on a truck I already own. Outrageous.
• The new truck gets better mileage, so it basically pays for itself.
• The new truck has a warranty, so I'll never pay for a repair again. Possibly ever.
• Conclusion: every day I don't buy a new truck, I'm losing money.

I walked inside with this. My wife was making the kids' lunches. She listened to the entire presentation, nodded, and asked one question.

"What does the new truck cost besides the payment?"

I said, "Nothing." Then I said, "Well, gas." Then I went back outside for a while.

The real math

Two columns. Each one is the yearly cost of owning that truck, averaged over the next three years. Do it this way because a single bad repair month will lie to you every time.

Keeping the old truck (example numbers)

• Repairs. The $3,200 transmission now, plus about $1,500 a year in the usual stuff: brakes, a water pump, the sensor that's been lying to me since spring. Three years: $3,200 + $4,500 = $7,700. Per year: $2,567.
• Insurance. It's paid off, so no lender requires full coverage. Example: $900.
• Registration. Older truck, lower fee in a lot of states. Example: $100.
• Fuel. 12,000 miles a year at 15 mpg is 800 gallons. At an example $3.50 a gallon, that's $2,800.
• Downtime. Four shop visits a year, two hours each for drop-off, pickup and the waiting-room coffee. Eight hours at an example value of $30 an hour: $240.
• Depreciation. It's worth about $5,000 to a dealer today and maybe $3,000 in three years. $2,000 ÷ 3 = $667.

Old truck total: $2,567 + $900 + $100 + $2,800 + $240 + $667 = $7,274 a year, or about $606 a month.

The new truck (example numbers)

The deal: a $47,000 truck, minus $5,000 for the trade-in, plus $3,000 in sales tax and fees. That's $45,000 financed at 7% for 72 months, which works out to $767 a month.

The payment isn't the cost. That's the big thing driveway math forgets. Part of every payment is principal, which is just your money turning into truck. The real costs are the value the truck loses and the interest the bank collects.

• Depreciation. New vehicles lose value fastest in their first few years. Example: the $47,000 truck is worth $32,000 at three years old. $15,000 ÷ 3 = $5,000. Don't trust my number. Look up what three-year-old versions of the exact truck you're eyeing sell for, same trim, similar miles.
• Interest. After 36 payments of $767 you've paid about $27,600 and still owe about $24,850. So $20,150 went to principal and about $7,470 went to interest. Per year: $2,490.
• Sales tax and fees. That $3,000 is gone the minute you sign. Spread over three years: $1,000.
• Insurance. The lender will require full coverage, and a newer, pricier truck costs more to insure. Example: $1,800. Get a real quote before you shop, not after.
• Registration. Often higher on a newer vehicle. Example: $400.
• Fuel. Say 20 mpg. That's 600 gallons at $3.50: $2,100.
• Maintenance. The warranty covers defects, not oil changes or tires. Example: $500.

New truck total: $5,000 + $2,490 + $1,000 + $1,800 + $400 + $2,100 + $500 = $13,290 a year, or about $1,108 a month.

So the "four payments" I was so mad about? The new truck costs about $6,000 a year more to own. The better mileage I was bragging about saved $700 of it.

Now the part where the old truck has to answer for itself, because the math isn't the whole story.

If it's unsafe, the spreadsheet doesn't get a vote. Rusted-through frame, rotted brake lines, steering problems, a warning light on the airbag system. Get those inspected by a mechanic you trust, and if the answer is bad, replace the truck. No joke goes here.

If it's a work truck, count lost work. A breakdown that costs you a day's pay belongs in the downtime line at your real hourly rate, not my $30 example. For some people that line alone flips the answer.

If the repairs are stacking up, two major systems going in the same year, the old truck's column can climb fast. Keep receipts. A year of real numbers beats a feeling. And knowing the car servicing that can't wait, and the kind that can keeps that repair line honest.

The verdict

The rule: keep the old truck as long as its average yearly repairs stay below the new truck's yearly depreciation plus interest.

In this example, that's $5,000 + $2,490, which comes to about $7,500 a year. The transmission was $3,200. Even spread over a bad year with everything else that broke, it's not close. Old Blue would need to eat a transmission more than twice a year to lose this fight.

Two more checks before you decide:

• Average the repair bill over three years. One big repair feels like a sign. Divided by 36 months, it usually looks like a small payment on a truck you already own.
• Get a second written quote. Transmission prices vary a lot between shops, and "rebuild" and "replace" aren't the same job. Ask which one you're getting and what the shop's warranty on the work covers.

And the move that actually wins: drive the old truck and pay yourself the payment. The gap in this example is about $500 a month. Put that in a savings account you don't touch, and in three years you've got $18,000. That's a serious down payment, or a clean used truck bought with cash and no interest at all. If you want the old one to make it that long, read what it really takes to get a car past 250,000 miles.

One honest exception: if your family outgrew the truck, a second car seat that won't fit or a camper it can't safely tow, that's a different question. Capability isn't a cost-per-mile problem. Buy the least expensive truck that does the job and run these same two columns on it. To try it with your own numbers, use the BRO cost-per-use calculator.

Old Blue got its transmission. The basketball dent stayed. And my wife got to be right, which, if we're doing the math honestly, was the most predictable number in the whole driveway.