speedometer too slow

[mickeypowa]

Thanks everybody for your answers !
Ok, I will try tomorrow to spin directly the driveshaft to see if both wheels spin, and try to have the good rear ratio.

For the calculator you put in the link, it will give me the number of teeth I must have on my speedo driven gear. but I need to know the number of teeth of the speedo drive gear, so how do I know it ? I suppose I have to withdraw the speedo cable from de transmission and then ?

 

[Kwik_Cutty88]

Thanks everybody for your answers !
Ok, I will try tomorrow to spin directly the driveshaft to see if both wheels spin, and try to have the good rear ratio.

For the calculator you put in the link, it will give me the number of teeth I must have on my speedo driven gear. but I need to know the number of teeth of the speedo drive gear, so how do I know it ? I suppose I have to withdraw the speedo cable from de transmission and then ?

You'll have to pull the speedometer cable housing out and have a look inside. Here's a chart that shows how many teeth each gear has by color.

 

[UNGN]

When you pull out the old gear, you can count the teeth on it and calculate the new gear required.

You have actual speed and indicated speed and the number of teeth on the old speedo gear. you should be able to calculate the number of new teeth required on the speedo gear... but you need to know what you currently have.

Because the difference is over 1.6:1 swapping only the driven gear probably will not get you close and the drive dear will need to be changed. An external adapter to speed up the signal to the speedo by 1.6 is your best bet.

Because 1.6:1 is the difference between Miles and Km, you could make a sticker to go over the KPH on the speedo to say "MPH" and have a 200 mph speedo 😎

 

[MrSony]

All Cutlasses were left hand drive?

Also OP, consider using this calculator. You'll need to know your speedometer gear drive size, tire diameter and rear end ratio. This will tell you what driven speedometer gear size you'll need.

http://www.tciauto.com/tc/speedometer-gear-calculator/

Whoops, meant right hand drive.

 

[UNGN]

Whoops, meant right hand drive.

Some cell phone cameras reverse the image. I thought French overseas territories drove on the right. I know Guadeloupe does. French are sticklers for "not being English".

Unless the car is from Australia or New Zealand.

 

[UNGN]

Whoops, meant right hand drive.

I thought French overseas territories drove on the right. I know Guadeloupe does. French are sticklers for "not being English".

Unless the car is from Australia or New Zealand.

 

[MrSony]

Left hand drive Cutlass, cool man. Speedometer cable gear inside the transmission is probably broken, it's plastic so it breaks over time. What size tires and what rear end ratio do you have? That will determine what gear you need.

I thought French overseas territories drove on the right. I know Guadeloupe does. French are sticklers for "not being English".

Unless the car is from Australia or New Zealand.

It's right hand drive. IF you look at the cluster in the video it's on the right side and the numbers and such are not reversed like they would be in a flipped image.

 

[mickeypowa]

Ahaha ! No, my cutlass is a left hand drive actually. Here in tahiti we drive on the right and we have the steering wheel on the left. It was imported in 1980 on the island, I think there was an oldsmobile seller here at this time...
Maybe it's the gopro used for filming which modify the shape of the screen and make you believe it's a right hand drive ! 😉

I wasn't able to lift my car properly today to check the speedo driven gear, I have to buy new jack stands, so tomorrow I hope !

 

[mickeypowa]

Hello guys !!

1) Ok so I have made the drill test on the speedo cable, and the needle doesn't move up and down when I put 650 RPM (I have only one speed on my drill). So maybe it's the square section of the plastic speedo driven gear which is used and need to be changed. ?

2) So for the drive and driven gear colors, I checked for some info on youtube :
I found this video :

the guy drops all the rear part cover of the transmission, so I guess I should do that but he doesn't explain how to withdraw the cover he directly shows it nude : how can I withdraw it, I have to remove all the driveshaft ?!

Or can I just do like this guy, and "pop off" the driven gear housing, to look for the color of the driven gear and maybe I could see the drive gear across ?

Sorry for these questions but I'm quite a beginner..


For the tape test : I have retried it but I turned the driveshaft, so both rear wheels spin, both wheel make 1 complete revolution when the driveshaft make 2 and a quarter revolution, so I guess I have a 2.29:1 rear end ratio !!

 

[UNGN]

To take off the tailshaft, you need to remove the driveshaft. Wrap tape around the loose U-joint on the driveshaft to keep the heads from falling off the two unclamped U-joints and and spreading needle bearings every where.

The speedo gears currently in your trans appear to be for approximately a 3.73:1 Rear axle. You probably have a 10 tooth Green drive gear and 30 tooth Blue driven gear : .3333 Ratio.

For 2.29:1 gears you need a .543 Drive/driven ratio.
1) a 19 yellow Drive by 35 Orange/pink gives .543 - perfect
2) a 19 Yellow Drive gear and a 34 light green driven gear give .559. (will be about 1KMH off at 60KMH)
Or 3) the cheapest option - if you have/keep your 30 tooth Blue driven gear and go into the tailshaft and just swap in a 17 Tooth drive gear (red) -$15 on Ebay for .567 (will be about 2 KMH off at 60KMH).
A 16 tooth drive gear would be perfect, but I don't know if they make these.