My speedometers reading wrong

[suprahflyg]

:nono:

Hey could anyone tell me how to fix my speedometer? Its reading 6-10mph faster than what im actually going. i just put in a new clutch and tranny but i doubt it would be the tranny because my old one was reading wrong but not this bad.

 

[Dan_Gyoba]

6-10 mph at what speed? Does it get further out as you go faster? How about your odometer?

If you pull the instrument panel, you can adjust the zero for the needle. I need to do this a bit for my car again.

Once the speedometer is out, there's a lever which adjusts the spring tension, which will affect the rate at which the speedometer moves. Looser, and it will read higher. Tighter, and it will read lower.

 

[Backlash2032]

If you adjust the spring tension on the speedometer, will that adjust the odometer as well? Or does it only adjust the needle position?

 

[Dan_Gyoba]

Just the needle position.

If your odometer is wrong, due to changing the differential gearing, non-standard tire size, or wrong speedo gear, then you need to adapt it. If it's just the wrong gears (Pre-89 R154 with a post-89 differential for example) then you're best off just getting the correct speedo gear for the rear end you've got. These will come for the 4.10 (JZA-70), the 3.909 ('89-) and 3.727 ('90+) for the R154.

Some 4X4 shops can deal with speedo translation for nonstandard tire sizes.

 

[suprahflyg]

it usually depends on how i accelerate. like when i raced my friend itll be 1-3 mph off but reg driving itll be 6 or more.
and thanks for the tip ill see what i can do

 

[suprahflyg]

i also have a different tranny would that affect it or..?

 

[f00g00]

Depending on your setup, yes a different transmission can affect the speedo. They have a set of gears inside, a metal one built into the transmission that drives the plastic one attatched to the speedo cable. The one in the transmission is either 10 or 11,
I think the W58 is 11 and the R154 is 10, and the plastic drive gear varies and is usually in the 30's.
The two pics show the gear that the cable connects to, one in the housing the other is what you get from the company.
Both of these are 10 32 which means the gear inside is 10 teeth and the plastic one here is 32. They are designed depending on the transmission and differential. Tire size will also throw the speedo off but the gears are probably designed with only OEM tires in mind.

 

[suprahflyg]

alright. i got the speedo with the transmission. so i just tighten the needle thing in the speedometer? Also do i just take it apart or..?
Thanks for all the help too guys