Hey guys. Just after an explanation. The other weekend I swapped diffs over, from an open to LSD. Now my speedo is out by 13. What gearing would cause this. Example: My speedo said I was going 110, mates GPS on the phone said 97 on 2 different apps.
did you change the ratio? what was the previous accuracy of a gps reading related to speedo? are the tires and rims you're using close to factory? check with a different phone/gps (is this the smoothed out average speed of the gps reading or where it doesn't jump around?) what controls it reading is usually in the firmware of the phone & not the app, i know for nokia's you have 3 choices, speed (as in it checks and updates fast), speed & accuracy (middle), accuracy (it's a tad slower but it's more accurate), usually where the average user doesn't wander....
If you changed the whole axle over with an LSD carrier already fitted to it, it sounds like ~3.45 gears in there as well ((110 / 97) x 3.08)
Didnt check the ratio. Just threw the diff in. It was a whole assembly. It has 20s on it.. Before LSD it was pretty close to accurate. I used to sit on 110 and keep up. Now I have to sit on 120 to move along with the traffic. I changed the whole LSD unit. Its IRS..
well can you turn the tailshaft around and count the rotations it takes to make the wheel do 1 full spin? or whatever else along the same lines to get the ratio?
Is this the one I want? Speedo Corrector MkII Kit "Kit Back Catalogue"- Jaycar Electronics Phat_6ltr It was the 2 that you get off Android..
Nice not sure if it's noticable but any difference in speed? Should be revving up quicker. Also was the old diff stuffed? If not I may be keen
You've already worked it out, but I'll agree, going from 3.08 to 3.45 is the correct factor for what you have found. Not sure on the older cars, but I know on my LS1 to correct the speedo my tuner just updated it in the tune. If you want to play with ratios I have some info on my website, qldkev.net
When you get the speedo sorted, Can you let me know how hard it is to install the corrector box? I changed my diff gears about 3 years ago but I got too busy at the time to fix the speedo so now I just allow for it but I really should get it fixed up one of these days
The kit is easy to install. Should take you ~30 mins to put together. Another 20 to wire it in. All you need to do to wire it up to the car is this: VSS from ECU (Output) -> Jaycar Speedo Corrector (Input) Jaycar Speedo Corrector (Output) -> Speedo wire to dash Power & ground go to whatever points you want to use. Kit works great with my 3.73 gears. Also corrects the speed alert properlly too
