Sprinter 4WD Conversion Idea, GMT-800 IFS.

[shade]

I wouldn't do it on anything other than a long, straight section of road, but when driving in a straight line with all tires of the same circumference, engaging 4PT shouldn't hurt anything. I do it regularly as part of the recommended monthly cycling of my truck's transfer case. Engagement & disengagement is always smooth, with no indication of a rotational imbalance in the drivetrain.

I'm sure you still want to know PT from FT without having to wait for it bind up in a turn, though. That little panel you had made will look sharp.

 

[luthj]

With the lever down low and my lack of experience with this setup, I was avoiding reaching down in traffic (which is unavoidable during the day). I will take a drive once the evening rush dies down.

I think the pinion needs to come up a bit. I was hoping to avoid that. I could also lower the tcase a bit as well. I need to do the math to see which one would result in more clearance at the bell housing.

 

[b dkw1]

Final runout is about 10 thousands, which is reasonable I think.

Tubing has that much runout.

 

[luthj]

Tubing has that much runout.

Makes sense. I am going to adjust the pinion (its a pain to do). If that doesn't do it, I will remove the balance weights, I suspect they are making it worse.

I was looking at final driveshaft options once I get some miles on the current setup. Looks like 90s ram pickups used a CV front shaft. A quick search shows 1330 and 1350 options depending on year. I need a matching companion flange, and I confirmed that Np208s had the same 32 spline front output, though I will need a slightly smaller ID seal.

Did a short drive in 4wd etc. Shifts fine between 2PT and 2FT. Both when stopped and moving. I missed and got into 4PT when backing out of my driveway. Couldn't even make the turn. Its definitely louder with torque going through the front end. Some gear noise, but a bit of engine vibration getting transferred. Its very noticeable idling in drive, shift in/out of 4WD and the engine vibration goes away. Not sure if there is anything to be done about it though.

The front pinion bearing area was fairly warm after a short drive. I would say 145F, the Tcase was in the 120F range. Of course it has a lube pump. I will keep an eye on it.

Steering was pretty much normal. A little bit of torque steer and front lift on heavy acceleration (though maybe it was lack of squat?). Other than the extra noise it was a seamless transition. There is a bit of driveline play with the Tcase diff, so there is a modest clunk going on/off throttle at low speeds.

 

[luthj]

Making progress on the arduino and status panel. Should be able to run wire tomorrow.

 

[Herbie]

Making progress on the arduino and status panel. Should be able to run wire tomorrow.

I don't know what those TO-220 components are, or what you're driving with them, but they look awfully close together. Without a heat sink, those often need a little room to breathe, if you're using them anywhere in their nominal range.

 

[luthj]

I don't know what those TO-220 components are, or what you're driving with them, but they look awfully close together. Without a heat sink, those often need a little room to breathe, if you're using them anywhere in their nominal range.

Those are just some logic level FETs (so cheap they don't even have a part number on them). I am using them to drive some 20mA LEDs, so thermal issues won't be present. Being so cheap I doubt they would handle more than a couple amps without a heatsink.

Having them lined up like that made my soldering easier, cause I could bend the legs over to bridge the common terminals without jumpers.

 

[luthj]

Got it wired up enough to test. Indicator lights work fine. I need to determine if a dimmer tied to the headlights is needed. If so I will need to make a quick switching circuit, probably just FET switching a parallel resistor. For some reason the Due didn't invert the input pin logic with input_pullup mode. Took me a while to figure it out. Easy enough to fix by inverting the variables.








I ended up using some RJ22 termination blocks and CAT5 Ethernet cable for the LEDs.



I need to run the wiring for the front axle actuator, and cut out part of the console for the new panel. I have some fitting on order so I can plumb the front locker, but that may wait a few weeks.

 

[shade]

Looks sharp. If the photo is realistic, I think you'll want the dimming option.

 

[luthj]

I was hoping I could find a happy medium that would work day/night. I don't think that is possible though. Too bad my van doesn't have canbus headlight info, would have made implementation a bit easier.

 

[luthj]

A friend put me on a canbus decode for a W203 sedan. While not exactly the same as the sprinter, its very close.

I was digging through the data, and it looks like the ESP module has the ability to command the min/max gear in the 0X208 frame.

https://github.com/rnd-ash/W203-canbus/blob/master/DAT_TRANSLATOR/DECODED/w203_w209%20CAN%20C%20ENGLISH.txt

ECU NAME: BS_208h, ID: 0x0208. MSG COUNT: 16
MSG NAME: AKT_R_ESP - ESP / ART-wish: "Active downshift", OFFSET 0, LENGTH 1
MSG NAME: MINMAX_ART - Should speed requirement of ART, OFFSET 1, LENGTH 1
MSG NAME: GMAX_ESP - Target gear, upper limit, OFFSET 2, LENGTH 3
MSG NAME: GMIN_ESP - Target gear, lower limit, OFFSET 5, LENGTH 3

Being 3 bits long, I am guessing its simply the binary representation of 1 through 5. I will have to give this a try to see if I can lock out 1st gear in low range.

I also tried sending the shifter status bits for winter mode and "FPT" mode (whatever those are). With no results from the TCM. I will test them while driving at some point just to make sure.

 

[shade]

From a post on the W205, it looks like Winter mode could do several things, if active.

W & S Mode - MBWorld.org Forums

E-Class (W210) - W & S Mode - What does the switch with the W & S on the transmission console do . I have an E430 Thanks

mbworld.org

I haven't seen FPT mode mentioned.

 

[luthj]

Yeah, its all translated from German, and uses MB internal acronyms.

I wrote a quick snipet of code to flip the bits for 2nd gear lower limit. Low and behold, 2nd gear is selected. Of note is that it also showed R2 (which is the higher reverse gear). I am not sure if that fluid circuit is part of the sprinter valve body, so I need to do some testing. I can't drive the van right now, as the drivers seat is out.



This opens up a number of interesting options. The first is that I can lock the van into any gear I want. A rotary knob on the dash for example. A better option would be to have the arduino check the max gear selected with the +/- function on the shifter. Then set the min gear to that value.

I am also thinking of adding a dash switch, which allows me to select R and 1-5, or R2 and 2-5 operation. Choices choices...

 

[shade]

Manually selectable AT operation may be an interesting benefit, but if you dive too deeply into manual settings, will that impact the stability control system? I know ABS isn't necessarily tied to AT operation, but stability systems can be tetchy.

 

[luthj]

Manually selectable AT operation may be an interesting benefit, but if you dive too deeply into manual settings, will that impact the stability control system? I know ABS isn't necessarily tied to AT operation, but stability systems can be tetchy.

That is the ABS/stability frame I am tweaking, so MB thinks that function is necessary. You make a good point. I should have the program check those values before changing them. If they are non-zero, then they will be left alone. I am not sure what they would be used for, but no reason to override the stability system.