high impact

iTrader: (5)

I swapped a manual valve body 4L80 trans into my T56 2000 firebird. I plugged the stock T56 vss harness into the rear vss sensor. The speedometer is working but reads 90 mph when I am going 30 mph. I figured it was just speed sensor settings in HP Tuners that I could change but it didn't work when we adjusted them. What do I need to do to get my speedometer work from the vss? Thanks!!!

mrvedit

Is HP Tuners reading the correct or wrong speed?
By changing the HP Tuners settings for Tire height and rear end ratio, you should be able to get the speed correct.

Jake's Performance

iTrader: (2)

The T56 uses 17 tooth reluctor. The 4L80E (and 4L60E) use a 40 tooth.

Change the settings for a 40 tooth reluctor.

high impact

iTrader: (5)

Will try that ^^^^^^^^ Thank YOU JAKES!!!!!!!

mrvedit

Now I'm curious where that would be changed in HP Tuners.
Did you have the PCM's OS (segment) changed from Manual trans to Automatic?

high impact

iTrader: (5)

No, I am still on M6. Will I have to have hp tuners do that? We already tried adjusting tire and gear sizes. The reluctor makes sense so hopefully it's not difficult to find and adjust

mrvedit

Sorry, I don't know the details of how to change the PCM from M6 to A4.
But I'm sure a bunch of people here do know the details. Hopefully they will share.

Jake's Performance

iTrader: (2)

The area in red needs to be changed from 17 to 40.

mrvedit

Since you are running a manual valve body you may not need to reprogram your PCM from M6 to A4. However, if you ever change to an automatic valve body you will have to get the A4 OS/Segment which includes the shift tables, TCC tables, etc.

high impact

iTrader: (5)

Changed to 40 and speedo still reads extremely fast. Do I need to figure out how to plug in the front sensor as well?

got-a-ls1

iTrader: (12)

just changing the number wont do anything. there is additional math you need to do but here is the easy way for you... enter in the following in the general table for 26" tall tires

mile - 127,224
rev trans- 40.0000

ratio 4.10
trans revolutions/mile - 3,180.6444

this will set you up with the proper values for pulses per mile. go back to the gear/tire calc click commit (just leave the tire and gear empty for now) and you should then be able to change the tire size to dial your speedo in perfectly. make sure your "calculated tire" and the tire size under the current tab match.