Vehicle speed reading wrong on scan master

[2BAR86]

I noticed after I put my 86 T back together from sitting for 10 years [emoji30] my lock up wasn’t working. My speed is reading 45mph on the scan master when I’m running 75mph. The cluster speed is close when I run my gps. I have since put a different torque converter in that is a known lock up. I have replaced the vss with a used one, and still have the same issue. Any input would be great!

-Matt


Sent from my iPhone using Tapatalk

 

[pacecarta]

are you running a postons 145speedo with a reduction adapter on transmission

 

[2BAR86]

are you running a postons 145speedo with a reduction adapter on transmission

I am running the 145 speedo. So I’m guessing I don’t have the adapter and need one.


Sent from my iPhone using Tapatalk

 

[2BAR86]

I did some research, people are staying to take it to a speedometer shop and have it re calibrated.


Sent from my iPhone using Tapatalk

 

[TurboBob]

thats one way.

you can have your chip set to lockup at a lower MPH, then the only thing off will be the scanmaster reading.

B

 

[2BAR86]

thats one way.

you can have your chip set to lockup at a lower MPH, then the only thing off will be the scanmaster reading.

B

Okay! That might be my only option, the only speedometer guy in town retired and recommend a place in California. Thank you!


Sent from my iPhone using Tapatalk

 

[dank GN]

have you triple checked your voltage at the ecm to make sure the voltage going to all your sensors is 5.00 volts ? There is a offset that u can put in to match your cars exact voltage like mine is 4.97. Just search on here for scanmaster voltage offset I’m sure something will come up and explain it to u

 

[No disintegrations]

I am running the 145 speedo. So I’m guessing I don’t have the adapter and need one.


Sent from my iPhone using Tapatalk

I am running the 145 speedo. So I’m guessing I don’t have the adapter and need one.


Sent from my iPhone using Tapatalk

It seems that pacecarta and Bob are both right. If your cluster is right the adapter would seem to be installed. Bob is saying only the scan master is wrong which requires a different lockup mph for the chip to work due to it being fooled. Lastly the scan master will remain incorrect due to it being separate from the cluster.

 

[2BAR86]

I believe my dad just changed the speedo gear to match mph on the cluster. I will look into the scan master voltages and see what I can find.


Sent from my iPhone using Tapatalk

 

[pacecarta]

the chip could be recalibrated for the adapter so scanmaster and lockup are working correctly but it wont fix the issue the adapter creates for cruise if you have that
just get rid of the adapter at trans and remove the 145 overlay (the original 85mph will be under it) , kirban does recalibrated 145 speedos that dont need an adapter if thats what you want .

on the voltage ..the signal is digital generated trough an optic sensor on back of speedo ..voltage doesnt affect rate

 

[pacecarta]

for future readers ...unless you are on classic fast/dfi which doesnt use vss and dont have cruise control ..ditch the adapter

besides screwing scanmaster and lockup it also screws with cruise control .
on tt alky chips he reduces timing up to 35mph so with the adapter full timing wont come in until around 60mph
he also uses mph to provide a knock ignore during launch ..again this will remain longer than it should
he also uses mph to split the 1-2 3-4 timing and the adapter delays the point where timing should be lowered
thats why theres a question on the chip order form if your speedometer is accurate (if sm is wrong the ecu wont function as designed
it also screws up the odometer so lets say your vehicle shows 60K ..if its been running an adapter driven 145speedo overlay its actually 100k

 

[2BAR86]

the chip could be recalibrated for the adapter so scanmaster and lockup are working correctly but it wont fix the issue the adapter creates for cruise if you have that
just get rid of the adapter at trans and remove the 145 overlay (the original 85mph will be under it) , kirban does recalibrated 145 speedos that dont need an adapter if thats what you want .

on the voltage ..the signal is digital generated trough an optic sensor on back of speedo ..voltage doesnt affect rate

Great info! Thank you for your input. I will go that route so everything is operating as designed.


Sent from my iPhone using Tapatalk