Speedo on OD

[foxfire42]

How is the Speedometer connected to the Laycock Type J OD?

[Brian T]

There is no provision for a gear driven speedo on the later J overdrives as electric speedos became the norm, the signal is taken from the ABS ( antilock brake system )

[foxfire42]

Oh rats and Mice!!!!! In this day of electronic advancements I thought for sure this would have been easily resolved. Assuming it will be accurate when not in OD city driving will be fine and highway just stay slower than the traffic. That should be easy since the I-10 here in AZ is 65 and 75.

Seems I saw where some kind of magnets (?) that were attached to the drive line and housing reading the revolutions. Can't those signals be converted into a mechanical system to run the Model A Speedo?

Any inventors out there?

[Dick M]

The Laycock OD speedometer gear drive is located on the output drive shaft going from the OD unit to the ring & pinion. The speed of this shaft is what drives your speedometer. Thus, it does not matter weather you are in direct drive or overdrive modes. I have 378 gears in the rear. My speedometer reads spot on without an adapter. The best way to check to see if your speedometer is accurate is to use a GPS to determine your actual speed. If your speedometer is not reading accurately, you can give the speedometer reading and the GPS speed reading to a speedometer shop. They can make an adapter gear that goes inline on the speedometer cable which will result in your speedometer reading accurately. You can call Chuck at Commercial Speedometer in West Sacramento, CA (916-371-8107) if you can not find a shop in your area. He is very knowledgeable and can get your speedometer to read accurately.

[Tom Wesenberg]

But Foxfire has no mechanical opening for a speedometer drive gear.

Back in the 70's and 80's I installed a couple cruise control units for customers, and they had magnets fastened to the driveshaft. I don't know of any speedometer units like this though. Corvair ran the speedometer cable from the front wheel bearing dust cap. Too bad more cars didn't do this.

[Dick M]

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I did not read in Firefox's post that he does not have a speedometer cable output. However, I have the J type and mine does have the speedometer cable output. I was just recalling my experience.

[Tom Wesenberg]

Originally Posted by Dick M

I did not read in Firefox's post that he does not have a speedometer cable output. However, I have the J type and mine does have the speedometer cable output. I was just recalling my experience.

You're right. I was going by what Brian said in #2, and assumed this applied it Foxfire, as no opening was found.

[Brian T]

The Laycock O-Drive for the model A uses parts of the stock shaft and torque tube, so you will still have the original stock speedo drive parts, pictured below.

As I have repaired many of these O-Drives in the past I feel your pain, your description tells me it is stuck engaged,----these units are generally reliable, however someone at Laycock decided to make changes that cost them dearly.

Pressure valves seized allowing the oil pressure to become way over the normal 350 to 400 PSI causing parts to bend and jam, not unlike a boiler ready to explode, however they can still be repaired but parts are very expensive, that would go a long way to buying a Mitchell.