Tuning for Dakota Digital 8K Pulse VSS

[Time2Kill]

I've got a customer that I'm helping on a 6.0L LQ9/4L80E swap in a 1982 Chevy K10 truck. We're running the 6.0L LQ9, 4WD 4L80E (2007), and NP208 transfer case that was in the truck when he picked it up. Since the truck uses a speedo cable and we're keeping stock gauges, we bought a Dakota Digital 8K VSS pulse generator (http://www.dakotadigital.com/index.c...109/prd109.htm). Does anyone have any idea how to tune for this? I had HPTuners do a segment swap for the 4L80E if that makes any difference.


I found this thread: http://www.hptuners.com/forum/showth...ital-pulse-gen and followed the instructions from mecanicman. Basically, changed General VSS pulses per Rev trans value from 40 to 8 and used 20% of the value that was in General VSS pulses per mile and Final Drive Gear Ratio Trans Revolutions per Mile.

Doing that, the PCM seems to read the VSS, although its about 30% too low (expected as the tune I'm using has 3.73 gears and 30" tire whereas the truck with the swap has 4.88 gears and 33" tires). I haven't gone thru and corrected for that error yet because I tried to use Blue Cats spreadsheets and program that he just released, but the results from that program are VASTLY different on the General VSS pulses per mile and Final Drive Gear Ratio Trans Revolutions per Mile. The VSS doesn't even read if I use the values from his program/spreadsheets. Does anyone know the actual way to tune for this? Should I continue with using the 20% of the stock values and correct from there or is there some other way to tune for this VSS.

We did correct the drive and driven gears (15T and 45T if I remember right) on the speedo cable so that the speedometer is reading correctly in the truck. We are reading 55MPH with an actual speed of about 52~53MPH.

[mecanicman]

why not finish following instructions? Use hpt with your new gear and tire size or apply you 30% error to to both General VSS pulses per mile and Final Drive Gear Ratio Trans Revolutions per Mile. Recheck, possibly make one more smaller adjustment and your done.

[Time2Kill]

why not finish following instructions? Use hpt with your new gear and tire size or apply you 30% error to to both General VSS pulses per mile and Final Drive Gear Ratio Trans Revolutions per Mile. Recheck, possibly make one more smaller adjustment and your done.

I'm still trying to get this to run. The transmission REFUSES to shift with anything I do. The transmission shifts in 3rd gear and will not shift out if I use the settings from BlueCats program, or if I use the settings from the other forum, the transmission shifts to 4th gear by time I hit 5mph and will not shift out of 4th no matter what unless I command it with HPtuners.

I've corrected for Speedo error as well and HPTuners reads correct to my GPS now, but I can't get the transmission to shift.

[mecanicman]

post your original untouched file as well as what you have now.

[Time2Kill]

post your original untouched file as well as what you have now.

I appreciate the help although I think the original instructions I found went about programming the Dakota Digital VSS the wrong way.

I've attached three files, the untouched tune which has all the stock 4L80E settings, the tune that was adjusted by 20% of the values as described and then GPS Corrected, and a third file with proposed changes that I believe will make it work.

*EDIT*

I had more info here, but I realized it was wrong. I've got it figured out now, going to test tonight and will report back my results. Pretty sure I've got the Dakota Digital sensor figured out with the help of Brendan over at LT1swaps

I'll post all the info here once I can verify.

[Time2Kill]

Finally got the Dakota Digital VSS 8K Generator Sensor figured out. It is extremely easy to do with Bluecat's Transmission Table software found here: http://www.hptuners.com/forum/showth...Table-Software

Basically, all you need to do is calculate your VSS pulses and the software will do the rest. To calculate the VSS, you take 8 (since the Dakota Digital is 8,000 Pulse Generator) and divide it by your speedo gear ratio which is your driven speedo gear divided by the speedo drive gear. So in my case, my speedo ratio is 3 (45T/15T). I then get a VSS pulse of 2.66666 by taking 8/3.

Now go to Bluecats software, select your transmission, and then change the VSS from 40 (or whatever the default is for your trans) and change it to the VSS you just calculated. Once you have that in, change the tire diameter and gear ratio and Bluecats software will give you the rest of the numbers you need. I just used his software and the results were great!!!

[tirediron]

Time2Kill,
I tried this on a LQ4/4L60e swap in a 77 Vette. It did generally function properly but would hunt between gears at times. The 8K pulse generator doesn't have enough pulses to truly function great. This will be evident on the HPtuners digital dashboard with the speedometer constantly jumping around in a range of 10-15 mph above/below your true speed. If you are using a manual trans everything should be fine.

[longboxdime]

Just used time2kill method with bluecat trans tool on a 1987 gmc 1/2 ton 4x4 with a 5.3 and a 4l60e it worked awesome with a dakota digital 8k pulse generator. I would like to say thanks to both!!!

[cobra30689]

Time2Kill,
The 8K pulse generator doesn't have enough pulses to truly function great. This will be evident on the HPtuners digital dashboard with the speedometer constantly jumping around in a range of 10-15 mph above/below your true speed. If you are using a manual trans everything should be fine.

Hate to dig up a 9 year old thread but this describes my issue to a T. I thought I was chasing an RFI problem.....wrapped the twisted pair in RFI shielding tape, and clipped a couple of ferrite cores around the VSS wiring on both sides of the connector into the engine harness, to no avail. I have a manual trans, and while I have a working cable driven speedo in the dash....I am getting weird idle issues when the vehicle is stopped, as speed read by the PCM can jump from zero to 5-8mph occasionally.

[TheMechanic]

If it happens enough that it will consistently occur try disconnecting your alternator and see if it corrects it.