Printable View
i am working on a customers 79 chevy 4x4 truck and i cant get the speed signal to line out at all. most ive got it to read was 8 mph. it has 38" tall tires and a 4l60e with the dakota digital pulse generator. i think it is 8 pulses per mile instead of 40. but i tried changing that without a noticable change. can someone point me in the right direction?
sorry it has 8000 pulses per mile.
this also has the 6.0 out of a 2001 chev pickup.
Which Vss part number do you have?
You need to know the pulses per revolution. Pulses per mile are calculated using tire diameter and gear ratio.
Why don't you make your life easier and use a 4L60E stock Vss?
It's sen 01 4160
The vss is in the tail shaft. A 4x4 doesn't have a tail shaft and in using the factory 79 transfer case
Using an in-line VSS pulse generator is a great way to get a VSS signal to the PCM.
The accuracy of a cable driven speedometer is a function of the ratio of the drive gear (on the transmission output shaft, or transfer case) and the driven gear (typically the sleeve that is inserted into the transmission or transfer case).
As long as the cable driven speedometer has been accurately calibrated for tire diameter and differential gear ratio, via the drive and driven speedometer gears, then the pulse generator should output 8K pulses per mile.
The speedometer segment of the calibration is then adjusted such that the PCM interprets 8K pulses as equivalent to traveling one mile.
The only issue you may have is that HPT does not have tables for all of the speedometer parameters you require to configure the pulse generator.
Go to the speedometer section under general, put all the info back into these boxes that was present from the stock tune.
Change General VSS pulses per Rev trans value from 40 to 8
Take a calculator and take the value from General VSS pulses per mile and multiply by 0.2, put that value into General VSS pulses per mile(0.2 or 20% derived from 8/40, differance in signal generator)
Take the value from Final Drive Gear Ratio Trans Revolutions per Mile and multiply by 0.2, put that value back into Final Drive Gear Ratio Trans Revolutions per Mile.
If you choose choice one below, change Final drive gear ratio if different from what is in truck.
Save.
You now have two options. I recommend number 1 as it is how I do it.
1. Flash the truck with the above mentioned changes. Go for a drive with a GPS or some method of accurately measuring your speed. Do a specific speed by the speedo and see what your gps shows. (I typicall do 60 mph by speedo, but you will have to decide what is safe and reasonable based on how much it is out when you start driving). You make a correction ratio based off your actual gps speed and your speedo.(by speedo I mean reading from hpt, not actual speedo). Speedo indicated speed/actual gps speed. If your speedo is showing higher then actual speed the pulses per mile are to low and your correction factor will be 1.xx. If your speedo is showing lower then actual speed the pulses per mile are to high and your correction factor will be 0.xx
This correction factor must be applied to general vss pulses per mile, final drive ratio Trans Revolutions per Mile, and all tables in the transmission tab that are speed based.
2. Use the Gear/Tire Calc under speedometer tab to correct for gear and tire size. This will apply all the corections as required but has limits as to how big a tire it allows and there for causes problems
It is critical that the pulses per mile and trans revolutions/mile are changed by the same ratio every time. Not doing so can burn up the trans and or lead to problems with you trying achieve specific shift points.
Mecanicman ... that is quite the write up - nicely done. But what a PITA.
Kalebm22 ... post up your tire manufacturer, tire model, and size (i.e. 285/70-16) as well as the differential gear ratio in the truck.
I will try and come up with some numbers to input for a quick and dirty test of your VSS pulse generator.
I wanted to point out that this is the WRONG way to go about programming for the Dakota Digital sensor. I especially want to update this thread since its the number one search result when searching for the sensor.Quote:
Originally Posted by mecanicman
This is the wrong approach because the LSx PCM is expecting to receive the signal from output shaft of the transmission so it knows how fast the output shaft/driveshaft is spinning. The Dakota adapter is NOT giving the pulses directly from the output shaft, it is being changed by a ratio because it is actually giving you how fast the Speedo cable is spinning. Therefore you cannot just put in 8 for the General VSS Pulses per Rev Transmission because it isn't reading how fast the transmission output shaft is spinning. To get the correct number, you need to divide 8 by your speedo cable ratio which is the driven gear divided by the drive gear. In my specific vehicle, that would 45 tooth/15 tooth for a ratio of 3. So my General VSS Pulses per Rev Transmission would be 2.666666 (Dakota Digital Signal of 8 divided by Speedo Ratio of 3). This will tell the PCM how fast the transmission output shaft/drive shaft is spinning.
Now you can hand calculate the other two numbers or use Bluecats Transmission Table software from here: http://www.hptuners.com/forum/showth...Table-Software
To use his software, just select your transmission type and then change the VSS from 40 (or whatever your default trans VSS is) to the number calculated above, which in my case was 2.66666. Now enter in your tire diameter and gear ratio and Bluecats software will calculate your trans tables and your Speedo table.
If you want to calculate it by hand, you need to figure out how many times your driveshaft spins in a mile. That number goes Final Drive Ratio: Trans Revolutions Per Mile.
Once you have that number calculated, take it and multiply it by your VSS signal and it will give you General VSS Pulses Per Mile which should be extremely close to 8,000 if you did everything right. 8,000 is the number you want to shoot for because the Dakota Digital is giving 8,000 pulses per mile. In my specific case, it came out to about 7950, but it will never be exact because of rounding, and specific ratios etc.
I highly recommend using Bluecats software. I hand calculated all my values and then verified with Bluecat and was within 99.98% of the same values, difference I'm sure is in rounding. I used Bluecats software to enter in my final numbers into HPTuners and my swap in a 1984 K10 Silverado with a LQ9, 4L80E, and NP205 works great now. Following the other directions posted above resulted in my truck being STUCK in 4th gear because the truck thought it was doing 100s of MPH even though the speedo was reading correctly.
My instructions work fine, you just didnt follow them all. I can see your point about including the speedo gear ratio. But your transmission was not shifting most likely because you didnt edit the trans revolutions per mile. I do this all the time using the method I pointed out above, never had an issue and use the same dakota digital sensor.
I followed your instructions exactly. I corrected with GPS after I made my other post in the trans tuning forum on this subject, still didnt work. I explained above how the sensor works and I don't see how else you could program for it and call it 'right'.Quote:
Originally Posted by mecanicman
I did change the trans revolutions per mile and I'm pretty sure that's why the truck wouldn't shift. The truck thinks its going way faster than it really is since your cutting that value lower than it should be.
Old thread I know but I wanted to say I used the method TIme2Kill explained and my speedo is within 2 mph. My pulses were around 10,000 though and not the 8000 mentioned. This is on a 2000 fbody 6 speed car with a th400. I wired right to factory 6 speed vss harness which was,Red pcm 20 (green/black) and 21 (purple/white). It doesn't matter which wire connects to which wire as these are high and low signals with no polarity.
Ok so I have a 87k10 and I did a 5.3 4l60e w/np208 tc swap from a 06 Tahoe I have tried getting it tunned with hptuners and have failed it's cost me a transmission already lol so if u could help I would greatly appreciate it. I installed a sen-01-1 Dakota digital 8k on the tc told the tunner that the vss signal need to be changed to 8k and he says he did but some where down the line some thing went wrong and my transmission won't shift. I have 4:11 gears and 35' tires I don't know how to figure out the correct formula needed for hptuners so I could just give the tunner this info and he can input it In the computer and get me on the road with out it costing me ANOTHER transmission 😠😪. Oh and the tunner is now asking for a shirt-5e he say that that's the only way the sen-01-1 will work?Quote:
Originally Posted by Time2Kill
My question is, is with the Dakota digital pulse generator, besides wiring in place of the factory vss wiring pins 20 and 21, what else needs to be done on a stand alone harness? Is there a reference signal required? I'm still fighting this issue, as the scanner reads zero mph while moving. It will shift 1-2-3-4 but not until you let off the throttle, and will not rev over 4500. And it will start in gear. Any help? The details are 2000 5.3/4l60e/doubler and 205. I've tried messing with the speedo pulse settings but no luck.
edit: finally got a good answer.. if you are attempting to electronically shift a 4l60/4l80e, there needs to be more like 80000-120000 pulse signal, this is per lt1swap Brendan.... just an FYI and the sensor needs to be in between the trans and tcase, novak adapters sells one
When you say go to Bluecats and generate the other 2 numbers can u specify which of the 2 go to which place?Quote:
Originally Posted by Time2Kill