Speedo Tab questions on Gen4

Before I just start playing with it to see what works I was curious what exactly these dropdowns do in the calibration tab under the speedo section. Of course when you hover over it gives me a description but doesn't exactly answer my question.

Under the Hardware section it has a drop down for Speed Output type with the options Wheelspd, VehSerial, and VehRepTOS. This is a swap so I do not have the wheel speed sensors hooked up at all for vehicle speed. I am assuming I would want to change this to VehRepTOS so it uses the output shaft speed for vehicle speed instead of the wheel speed sensors. Not able to find a definite answer.

Also under the Vehicle Speed Sensor section it has a drop down for Vehicle Speed Output which is disabled by default but also has a RepTOS in its drop down. I am assuming I would also need to set this to RepTOS.

and finally under the Wheel Speed Sensor section it has a drop down for Wheel Speed Output which is enabled by default. I'm guessing this also needs to be disabled.

If anyone knows what I need to set things at so the speedo will work without the wheel speed sensors that would be awesome

To many unanswered questions. Gen4 usually have a TCM that is going to get a speed from so you would only need to do a Tire Gear wizard but since you have neglected to post a tune file or give a better idea of your configuration it is difficult to give you an accurate answer.

Sorry I can post a tune file if need be. I didn't think it would be necessary for this question. I am running a 6L80 so it does have the TOS and I already did a Tire/Gear wizard to change the final drive and tire size. I am using pretty much everything out of a 11 Silverado minus the wheel speed sensors and no transfer case. I actually haven't tried it with just that yet since i'm not with the van today I was just messing with the file and noticed these things in the speedo tab and didn't know if I needed to change them before I flash it again tomorrow to make it use TOS since it appeared that it was using wheel speed sensors by default.

Here is my tune file if that helps. It does not have the Tire/Gear wizard done yet since I still have it open I haven't saved it again yet.

Attachment 141312

Only thing you would change, and that is if you changed gears and or tire diameter is the gear and tire wizard so you speedo and shift timing will return to a factory outcome

Well I gave the van its maiden voyage and I do not have any speedometer so something isn't right. BTW this is in a sprinter van so I effectively changed gears and tire size since I'm using the sprinter rear end and tires. The tire size is only about 1/4" larger than the Silverado tire diameter but the gear ratio on the Silverado was 3.46 and the Sprinter is 3.92 so I expected the speedometer to be inaccurate without running the tire/gear wizard but I do not have any speedometer function at all.

From what I gather looking at wiring diagrams the 4WD 6L80 has a VSS on the transfer case but the 2WD 6L80 does not have a separate VSS and uses the TOS for vehicle speed. However it also looks like it was using the wheel speed sensors for vehicle speed based on the settings in the speedo tab from my factory file and not sure what the gauges were using for its primary input for vehicle speed since that is Serial Bus data but its obviously not happy with something since its not working haha.

As a side note the van actually drove pretty nicely considering everything I have done. The only thing I noticed was some slight shifting flares, not sure if its because of the missing vehicle speed or the tune yet but they are pretty slight, maybe about a 300-400rpm flare past 2nd gear. I need to hook up the scanner and see if I can see vehicle speed in the ECM/TCM and if its just not displaying that data to the gauges.

I really appreciate any help or advice, i'm not afraid to say i'm a noob when it comes to tuning but I have been a tech for about 16 years and have a little bit of computer programming experience so I have a good understanding of how the PCM/TCM etc. function. Trying to determine if its a configuration issue or a physical wiring/sensor issue but also don't see much harm in playing with the speedo settings to see if they change anything.

https://ls1tech.com/forums/conversio...-question.html

I actually read that thread the other day when I started searching for info. I usually try to do as much forum searching as I can to find the answer before I post myself haha. Only thing with that thread was he is using a Dakota dash and I am using the OE cluster that came from the Silverado so wasn't sure if changing those settings would actually do anything in relation to the OE cluster since that is transmitted to the dash on a Serial data line. Most of the info I could find i'm not 100% sure would relate to me since almost everyone was trying to get an aftermarket speedo to work and wasn't sure if those settings are only intended for aftermarket speedo's or if they also effect the OE cluster.

In essence this would be like doing a 4WD to 2WD conversion with a 6L80 on a 2011 Silverado. I also searched for that conversion with no speedo afterwards and couldn't find much info which leads me to believe that I don't need to make any changes other than tire/gear wizard like you originally said. I guess I will just do a quick electrical diag for no speedo tomorrow just to make sure I don't have a popped fuse or wire removed or something stupid.

Appears as though you need to add the VSS out signal for an analog (non serial, Non CAN) speedo.

Quote:

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Originally Posted by Phestezio

Well I gave the van its maiden voyage and I do not have any speedometer so something isn't right. BTW this is in a sprinter van so I effectively changed gears and tire size since I'm using the sprinter rear end and tires. The tire size is only about 1/4" larger than the Silverado tire diameter but the gear ratio on the Silverado was 3.46 and the Sprinter is 3.92 so I expected the speedometer to be inaccurate without running the tire/gear wizard but I do not have any speedometer function at all.

From what I gather looking at wiring diagrams the 4WD 6L80 has a VSS on the transfer case but the 2WD 6L80 does not have a separate VSS and uses the TOS for vehicle speed. However it also looks like it was using the wheel speed sensors for vehicle speed based on the settings in the speedo tab from my factory file and not sure what the gauges were using for its primary input for vehicle speed since that is Serial Bus data but its obviously not happy with something since its not working haha.

As a side note the van actually drove pretty nicely considering everything I have done. The only thing I noticed was some slight shifting flares, not sure if its because of the missing vehicle speed or the tune yet but they are pretty slight, maybe about a 300-400rpm flare past 2nd gear. I need to hook up the scanner and see if I can see vehicle speed in the ECM/TCM and if its just not displaying that data to the gauges.

I really appreciate any help or advice, i'm not afraid to say i'm a noob when it comes to tuning but I have been a tech for about 16 years and have a little bit of computer programming experience so I have a good understanding of how the PCM/TCM etc. function. Trying to determine if its a configuration issue or a physical wiring/sensor issue but also don't see much harm in playing with the speedo settings to see if they change anything.

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The TEHCM in the transmission does not use the VSS, that's strictly for the engine and cluster on a 4wd, it does not affect the transmission function at all. On the 2WD I believe I am not sure if the ECM uses the OSS signal provided by the TEHCM to calculate road speed and send it to the cluster or it if uses the wheel speed sensors. I think if you play with the hardware choice selecting one after another and driving it you will eventually get a VSS reading again.

Just an update, I put about 20 miles on it today. I completely rebuilt the engine so trying to get some miles on it to get thru the break in period and tweak the tune before I take it on a road trip in 4-5 weeks.

I did run the tire/gear wizard to correct the final drive and tire size and scaled the trans parameters and the slight shift flares seem to have gone away so thats a plus. I did find 1 post of someone that has pretty much the same setup I have. 4WD to 2WD 6L80 with no wheel speed sensors and using the factory cluster. He changed the Speed output type and vehicle speed output both to serial and his started working. He also mentioned he had to change Output speed sensor to "fitted" under the trans tab. Mine is already set to fitted default.

So I tried setting both to serial this morning for the ride to work and still no speedo. I then left speed output type as serial and changed vehicle speed output to RepTOS for my ride home and still no speedo. I did however run the scanner to monitor the vehicle speed PID in the trans and I have pretty accurate vehicle speed based on the GPS, its within 1MPH @50MPH.

So i'm not missing vehicle speed data its just not getting transmitted to the cluster for some reason. I was pretty sure the speed data is sent to the cluster over the serial data line so changing both to serial made sense but that didn't work. I am thinking the same that I if I keep playing with different setting combinations I will eventually find the right configuration to get it to work. Based off of 4 settings I can see that could do with the speedo and the options each has there are 24 possible combinations, hopefully I don't go thru all of them before I get it working haha

Also a question if anyone has the answer, is the speedo tab data solely written to the PCM or the TCM or is it a combination of both? I have been doing write entire to both modules to make the speedo tab changes but not sure if I absolutely need to be writing to both modules to make those changes.