I recently replaced the 4.30:1 rearend in my NA Supra with one out of a turbo, I think it's 3.89:1, mainly for better fuel mileage. Well, my speedometer read about ten mile per hour too slow at highway speed, which is a real good way to get a ticket if you forget to make the mental adjustment to the reading.
Lucky for me I work at North Hollywood Speedometer, a shop that restores and custom builds guages; mainly VDO german stuff and classic american cars. We also custom make speedometer cables and ratio-adapter gear boxes for them.
Since Toyota trannies don't have replaceable driven gears for the cable like American stuff then the ratio box is the only option. There's like a hundred or more different ratios that can be made with the gears available, so even with way different gears and tires the speedo can be made accurate. There wasn't clearance with the crossmember to mount the box directly to the transmission, so I made two new cables to locate it in the engine compartment. I'm not sure about R154 or automatics. It's best to have it as close to trans as possible to avoid the speedo pointer bouncing at low speeds. Which brings to the next point: bouncing speedo pointer.
If it is bouncing around at low speeds and then smoothes out around 50 or 60 or so then it is a worn out cable. It might help to pull it out and lube it, but most likely it's just worn out. They may look fine, but they get to where they have too much twist. One end turns part way, winds up the slack and then unwinds as the speedo end spins, and that's why the pointer bounces. But if it bounces at high speeds only, then it's a problem within the speedo itself, usually dried up old grease. We're talking about 20 year old cars hear, so very possible. My shop doesn't really have parts for these, but I pulled mine apart, washed pieces in parts washer and reassembled with fresh grease and works smooth as butter.
So if you are experiencing any of these issues, I may be able to help. I'd love to say I could give a cheaper hook-up kind of price, but not too likely. Cables are $45 and the ratio box is $75. If you have to set it up like I did it will require two cables and the ratio box.
If you need a cable, I'll just need to know the length. (should've recorded mine at least, oh well)
If your speed's innaccurate I will need a measurement known as a cable count: pull the cluster out so you can see the end of the cable. Use a piece of tape or small wire so you can easily see how much it turns. Roll the car over exactly 52 feet 9.5 inches (1/100th of a mile) and count the turns. An accurate Toyota should make 10.8 turns, just for reference. Do it a couple times, the more accurate you get this the more accurate your speedo.
Shameless plug for my workplace? Somewhat. But I remember seeing a few threads in the past related to this so maybe there aren't too many solutions out there. Here's mine.
Here's the pic of my ratio box zip-tied to the charcoal canister.
Lucky for me I work at North Hollywood Speedometer, a shop that restores and custom builds guages; mainly VDO german stuff and classic american cars. We also custom make speedometer cables and ratio-adapter gear boxes for them.
Since Toyota trannies don't have replaceable driven gears for the cable like American stuff then the ratio box is the only option. There's like a hundred or more different ratios that can be made with the gears available, so even with way different gears and tires the speedo can be made accurate. There wasn't clearance with the crossmember to mount the box directly to the transmission, so I made two new cables to locate it in the engine compartment. I'm not sure about R154 or automatics. It's best to have it as close to trans as possible to avoid the speedo pointer bouncing at low speeds. Which brings to the next point: bouncing speedo pointer.
If it is bouncing around at low speeds and then smoothes out around 50 or 60 or so then it is a worn out cable. It might help to pull it out and lube it, but most likely it's just worn out. They may look fine, but they get to where they have too much twist. One end turns part way, winds up the slack and then unwinds as the speedo end spins, and that's why the pointer bounces. But if it bounces at high speeds only, then it's a problem within the speedo itself, usually dried up old grease. We're talking about 20 year old cars hear, so very possible. My shop doesn't really have parts for these, but I pulled mine apart, washed pieces in parts washer and reassembled with fresh grease and works smooth as butter.
So if you are experiencing any of these issues, I may be able to help. I'd love to say I could give a cheaper hook-up kind of price, but not too likely. Cables are $45 and the ratio box is $75. If you have to set it up like I did it will require two cables and the ratio box.
If you need a cable, I'll just need to know the length. (should've recorded mine at least, oh well)
If your speed's innaccurate I will need a measurement known as a cable count: pull the cluster out so you can see the end of the cable. Use a piece of tape or small wire so you can easily see how much it turns. Roll the car over exactly 52 feet 9.5 inches (1/100th of a mile) and count the turns. An accurate Toyota should make 10.8 turns, just for reference. Do it a couple times, the more accurate you get this the more accurate your speedo.
Shameless plug for my workplace? Somewhat. But I remember seeing a few threads in the past related to this so maybe there aren't too many solutions out there. Here's mine.
Here's the pic of my ratio box zip-tied to the charcoal canister.
