79rallypack

Has anyone got any information on can i replace a factory 85mph speedo on a 81 corvette auto, with a 140mph speedo from a 82 model corvette, and will it read correct, is there any modification required, also it has a broken needle can i just swap it with the 85 mph one? thanks

Big2Bird

Swap away.

spikebot 81

I sent my speedo to redline. They recalibrated and refaced to 140 mph . Still working fine after 8 years
https://www.redlineg.com/

mark79,80

Big2Bird

An adapter in the speedo cable would calibrate the odometer. The speedo calibration is in the head.

Fast81

BTW - 82 OEM speedo was 85 mph too. You'll have to use 78-79 if you want GM or use an aftermarket vendor to convert.............................

mark79,80

joewill

i believe the standard is speedo cable will spin at 1000 rpm at 60 mph. what your needle and odometer shows is based on that standard..
so yes, swap away..
but beware you are changing an odometer also and you might run into legal issues if the miles of the 2 devices are different.. at least disclose this at sale time.

naramlee

The Federal odometer law, 49 U.S.C. Chapter 327 (Public Law 103-272), prohibits the disconnection, resetting, or alteration of a motor vehicle's odometer with intent to change the number of miles indicated thereon. The law requires that a written disclosure of the mileage registered on an odometer be provided by the seller to the purchaser on the title to the vehicle when the ownership of a vehicle is transferred. If the odometer mileage is incorrect, the law requires a statement to that effect to be furnished on the title to the buyer. However, vehicles ten years old and older are exempt from the written disclosure requirements.



your also not trying to mislead or defraud, your after functionality, not trying to pass off a car as 5k miles

suprkoop

I sent mine to Roger Scott - Corvette Instrument Service, ( corvetteinstrumentservice@att.net ) in Florida. he changed mine to 140MPH and I kept the same mileage. The calibration for the speedometer is magnetic in the head itself, the plastic gear in the transmission matches the revolutions to the correct rate of speed. My trip odometer was not working properly but he was unable to repair that as the parts for the trip odo are NLA.

Street Rat

I have an '81 and tried this SWAP. No go without recalibration.

I sent my 85 mph speedo into Corvette Central. They have a speedo service.
They changed the face to a 140 mph speedometer and recalibrated it.

I would highly recommend having a speedometer service calibrate the combination.

The13Bats

I dont recall buying a car in 30 plus years except my wifes kia that the title didnt have mileage exempt,

79rallypack

The 140mph speedo that i purchased has a broken shaft that the needle is attached to (i think it is called the "speed cup shaft") does anyone know where /who i can get one of these from, i live in Australia or will i have to send it to the states to get repaired.

lowbuck72

No offense, but I used to have a Suzuki GS1100 E with an 85 mph speedo. At first I disliked it, but I grew to prefer it after a while. The amount of sweep in the normal driving range 55-80 mph was twice as much as on a 160 speedo, much more precise and easy to read. And if I did venture to stupidly exceed 85, using my tach, I could figure my speed. It's just an ego thing in my opinion.

jim-81

This is what I plan on doing.

Grumpy 427

I did the same thing with my 80 Vette i have a 150 mph speedo.

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bazza77

not sure if it's any good to you but I have a 1977 model Speedo sitting here no longer needed , it's complete so the shaft is there if it's practicle to transfer. You can have it for parts if you want.

79rallypack

That sounds great Thanks, do you have any idea if it has the same working bits. send me your number please or a PM. thanks.

79rallypack

Just confirming that your 80 Vette had a 85 mph speedo, and after you put it in the 150mph speedo you did not have to change the speedo drive in the gearbox. by the way i like your 240kph speedo

Grumpy 427

Yes i had the 85 mph one, redline calibrated it to work with the TH350 trans and 3.08 gears. Then i swapped out the 3.08 gears to 3.55 and had to change the small gear in the trans to the grey 21-22 tooth speedo gear to be correct. All good.