BACKYARD MECHANIC: Speedometer error an easy, inexpensive fix

Advertisement

Advertise with us

QUESTION: I recently switched a 263 six-cylinder engine with a power glide cast iron transmission to a 1978 305 V8 with a 350 tranny. The only problem now is my 1960 Pontiac speedometer does not match with the 350 transmission. When I am travelling 60 m.p.h., the gauge is showing 83 m.p.h. An auto electric company will make a compatible set of gears for a huge amount of money. Is there an easier way to solve this problem? Right now I am using a GPS. Eckler has gears that go in the transmission end of the cable. Is this a solution or is there another cure without spending a fortune?

Read this article for free:

or

Already have an account? Log in here »

To continue reading, please subscribe:

Subscribe and receive a limited-edition Free Press branded hat or tote.

Digital Subscription

One year of digital access for only $205*

  • Enjoy unlimited reading on winnipegfreepress.com
  • Read the E-Edition, our digital replica newspaper
  • Access News Break, our award-winning app
  • Play interactive puzzles

*First annual payment billed as $205.00 + GST for one year. This annual subscription will automatically renew at $233.00 + GST every 52 weeks (10% off the regular annual price of $259.35). Offer available to new and qualified returning subscribers only. Cancel any time.

To continue reading, please subscribe:

Add Free Press access to your Brandon Sun subscription for only an additional

$1 for the first 4 weeks*

  • Enjoy unlimited reading on winnipegfreepress.com
  • Read the E-Edition, our digital replica newspaper
  • Access News Break, our award-winning app
  • Play interactive puzzles
Start now

*Your next Brandon Sun subscription payment will increase by $1.00 and you will be charged $17.95 plus GST for four weeks. After four weeks, your payment will increase to $24.95 plus GST every four weeks.

Hey there, time traveller!
This article was published 22/11/2013 (4620 days ago), so information in it may no longer be current.

QUESTION: I recently switched a 263 six-cylinder engine with a power glide cast iron transmission to a 1978 305 V8 with a 350 tranny. The only problem now is my 1960 Pontiac speedometer does not match with the 350 transmission. When I am travelling 60 m.p.h., the gauge is showing 83 m.p.h. An auto electric company will make a compatible set of gears for a huge amount of money. Is there an easier way to solve this problem? Right now I am using a GPS. Eckler has gears that go in the transmission end of the cable. Is this a solution or is there another cure without spending a fortune?

ANSWER: This is old-school mechanics and there is a relatively cheap way of correcting the speedometer error you have in your classic Pontiac. You need to change the speedometer gear or gears at the transmission. Right now the speedometer is reading about 38 per cent too fast. You need to install gears that will slow the speedometer cable by the same 38 per cent.

At the transmission, disconnect the speedometer cable and then remove the bolt and clip that hold the speedometer-driven gear support into the transmission extension housing. With the clip removed, the driven gear support can be pulled out (there is an o-ring seal on the outside edge, so it may seem snug). The speedometer-driven gear can then be removed and you should count the teeth on this plastic gear. You need a larger gear with 38 per cent more teeth.

GM makes many different driven gears. I am familiar with about 17 different gears starting with 18 teeth and ranging up to 45 teeth. Each gear is also identified by colour for quick identification at the factory. It has been some time since GM used mechanical speedometer drives but many of these parts are still available. They are also available from the aftermarket or through transmission shops.

If you already have a gear that is 32 teeth or larger, you will also need to change the drive gear. Again, this is relatively easy. Remove the driveshaft and the four bolts holding the transmission extension housing onto the transmission. The driven gear is a plastic gear held in place by a clip on the transmission output shaft and it can simply be unclipped and slid off. There are eight different drive gears available ranging from seven teeth to 20 teeth. A little math and you should have a speedometer that is close to reading correctly. If you feel a little unsure about doing this, a transmission shop can change the gear for you in a few minutes.

QUESTION: I have a 1997 Chrysler Intrepid with a 3.5 engine. The motor surges at slow speeds and at high speeds after it warms up. It appears to be better for a few minutes while it’s cold. This has been happening for the last four months, or 4,000 km. Things that I have done to correct this problem are: replaced the exhaust gasket, the “check engine” light was on so replaced that module; however, no other codes show up, replaced the fuel filter and replaced the accelerator sensor on top of the engine.

None of these made a difference. The car does not stall but is a constant aggravation to drive. The transmission shifts perfectly. It has lots of power, but this surging is always there. It has only 144,000 km on it and is extremely well-maintained. All codes are updated on this car. When it is put on the computer analyzer it does not show a problem but the problem is evident to all Chrysler mechanics that looked at it. Would you possibly have any suggestions?

ANSWER: The most common cause of a surging condition like this is an intake vacuum leak. Check all hoses and connections carefully but you may want to also check for a leak at the intake manifold gaskets, as they have been known to leak where the upper manifold bolts onto the lower manifold.

If you can’t find a vacuum leak, suspect the EGR valve. The valve may be physically staying open slightly and this would create a surge without necessarily setting any trouble codes. When you remove the valve, you may be able to see if the valve is mechanically sticking or blocked open with carbon. Replace the valve if these problems are present.

Jim Kerr is a mechanic, instructor of automotive technology, freelance journalist and member of the Automobile Journalists’ Association of Canada.

kerr.jim@sasktel.net

Report Error Submit a Tip

More Stories

Home residents turn to agency after operator lays off 70 staff who unionized

Nicole Buffie 4 minute read Preview

Home residents turn to agency after operator lays off 70 staff who unionized

Nicole Buffie 4 minute read Wednesday, Jul. 15, 2026

Residents of a Winnipeg retirement home have taken matters into their own hands after the majority of the facility’s home-care aides were laid off following their unionization.

A committee of residents have banded together to work with a private agency to staff Shaftesbury Park Retirement Residence after many of its existing aides complete their final shift on Monday.

“It is heartbreaking because there are a lot of vulnerable people here who are not capable of advocating for themselves,” said Joelle Robinson, who has lived at the home since 2023 after she suffered a brain aneurysm. “We’re trying very hard to make it so that our residents aren’t completely up the creek.”

Robinson, a retired lawyer, joined Terry Hopkinson and several other residents of the South Tuxedo home to create a committee and send out a request for proposal to eight companies that specialized in seniors care.

Read
Wednesday, Jul. 15, 2026

Dauphin hospital could be closed 9-12 months

Tessa Adamski 6 minute read Preview

Dauphin hospital could be closed 9-12 months

Tessa Adamski 6 minute read 2:01 AM CDT

BRANDON — A 78-year-old woman who has stage 4 lung cancer says she’s “frustrated and scared” knowing the hospital in Dauphin may not reopen for up to a year and that would require her to travel for treatment.

“I know it’s affected a lot of people, probably worse than me, but in my personal case, it couldn’t happen at a worse time,” said Janice Nybo, who lives on a farm a few kilometres south of Dauphin.

“I’ve been using that hospital quite a bit in the last three months.”

Severe flooding in the basement of the Dauphin Regional Health Centre, owing to a massive amount of rainfall in late June, caused a power outage and damage to its HVAC system. The building was evacuated on Canada Day. Fifty-four patients were sent to nearby health centres, including 24 patients who were transferred to the Brandon hospital.

Read
2:01 AM CDT

Bee2gether Bikes out of The Forks after lease confusion

Gabrielle Piché 5 minute read Preview

Bee2gether Bikes out of The Forks after lease confusion

Gabrielle Piché 5 minute read Wednesday, Jul. 15, 2026

Tandem bike rentals aren’t on offer at The Forks this summer — and the longtime company behind them is claiming financial loss, calling the change unexpected.

Read
Wednesday, Jul. 15, 2026

Manitoba Miracle forward signs five-year contract with club

Ken Wiebe 7 minute read Preview

Manitoba Miracle forward signs five-year contract with club

Ken Wiebe 7 minute read Wednesday, Jul. 15, 2026

Cole Perfetti is betting on himself. And the Winnipeg Jets are counting on him to take the next step in his development.

In what has been an interesting off-season to date, general manager Kevin Cheveldayoff knocked another important item off his to-do list as the Jets agreed to terms with Perfetti on a five-year contract that carries an average annual value of US$6 million.

Perhaps the most important part of this transaction was that it allowed the two sides to avoid going to arbitration next Monday, which would have been bad for business for both parties.

Although it’s easy to say that it’s just business, a one-year term in arbitration, no matter the amount, would have left neither side satisfied and it would have meant Perfetti was just one year away from the opportunity to explore unrestricted free agency.

Read
Wednesday, Jul. 15, 2026

Order of Manitoba awarded to 12 high-achievers

Morgan Modjeski 4 minute read Preview

Order of Manitoba awarded to 12 high-achievers

Morgan Modjeski 4 minute read Yesterday at 9:03 PM CDT

It was a full circle moment for a CFL superstar whose game included giving back.

Former Winnipeg Blue Bombers running back Andrew Harris was one of 12 Order of Manitoba recipients honoured at the Manitoba legislature on Thursday.

“It’s an indescribable feeling,” Harris said after the ceremony while holding one of his sons in his arms.

Harris joined Juno award-winning artist Chantal Kreviazuk, Canada’s chief public health officer Dr. Joss Reimer, former premier Brian Pallister and others who have enriched the province, said Lt.-Gov. Anita Neville as she honoured the recipients.

Read
Yesterday at 9:03 PM CDT

Climate change consequences keep piling up

Editorial 4 minute read Preview

Climate change consequences keep piling up

Editorial 4 minute read 2:00 AM CDT

Has Mother Nature slapped you around enough yet, or are you finally starting to see the big picture?

Manitoba has seen floods and large, damaging hail already this summer, as has Alberta. Roads are still closed in the Parkland area of Manitoba because of flood damage. The insurance industry is talking about record-breaking claims — and that’s just among those who actually had insurance. Many didn’t have coverage for things such as overland flooding. Residents of affected areas are slowly finding out that, while governments talk a good game about helping people recover from disasters, the help is limited and rarely covers the full extent of damages.

Forest fires in Ontario have sent smoke plumes deep into the United States, and have caused a series of evacuations and air quality warnings in that province. Social media abounds with eerie photos of orange, smoke-filled skies in Thunder Bay, Toronto and places in between.

As recently as July 9, the federal government was reasonably optimistic about the number and extent of forest fires in the country, saying that fires had burned 1.4 million hectares — considerably less than last year. But in just one week — between July 9 and 16 — an additional one million hectares of forest burned, with 859 active forest fires now burning across Canada. This brings the amount of forest burned this year to the third-highest level trailing only 2023 and 2025.

Read
2:00 AM CDT