Sprinter 4WD Conversion Idea, GMT-800 IFS.

[luthj]

Did some quick reworking on the Canbus program with improved debug output. Found a couple errors. A user contacted me with a currently unusable T1N 4x4 conversion with ford parts and Chrysler NAG1/Tcase. So I am doing a bit of a hail mary with my Canbus bridge module.

Here is the sample output (this is adjusted to compensate for the Ford axle swapped van). I am using the typical serial console output for debug purposes. I misspelled a variable name, that had me chasing my tail for a few hours. Hexadecimal outputs can look suspiciously like decimal!

wSpeedXr is the raw integer value. wSpeedL/R is the corrected value. cData is the output bytes, and bData is the input bytes. I jacked the front right wheel, and spun it manually.

lMsgID=0X200


wSpeedRr=0
wSpeedLr=221

wspeedR=0
wSpeedL=89

wspeedAr=0
wspeedA=0

cData [4]..[7]
0-59-0-0-

bData [0]..[3]
0-DD-0-0-

I should be getting my wrangler trans mount tomorrow. If it fits, I am nearly ready to pull the sprinters trans, and reassemble with the Tcase/housing.

 

[Len.Barron]

Pulled a Tcase mounting stud. They are a bit unusual. The Tcase size is about 5/8-3/4" long b y 3/8-16 thread. The trans side is 1" long 3/8x24 thread.

I think the best option is to go with 1350s all-around if I can find all the necessary yokes. Thats a common size for trucks in the 8-10klb range, and will reduce my spares count.

I'm surprised the tcase studs weren't metric...??
Watch for clearance of the 1350cv joint at the tcase, some models have just enough and some don't. I've never messed with a 242 so I'm not sure if will allow the extra diameter in that area.

 

[luthj]

I'm surprised the tcase studs weren't metric...??
Watch for clearance of the 1350cv joint at the tcase, some models have just enough and some don't. I've never messed with a 242 so I'm not sure if will allow the extra diameter in that area.

Thanks for the warning. I will do a couple measurements.

I was somewhat surprised myself on the imperial fasteners. The rest of the case has metric fasteners... The 6 bolt flange design predates the Automakers going to metric, so maybe they left it unchanged for reverse compatibility? I could have measured and googled wrong. I'll know when I get the studs!

 

[shade]

I was somewhat surprised myself on the imperial fasteners. The rest of the case has metric fasteners... The 6 bolt flange design predates the Automakers going to metric, so maybe they left it unchanged for reverse compatibility?

I wish Pokémon Go was actually a stealth metric system trainer.

 

[mountainhick]

Thanks for the warning. I will do a couple measurements.

I was somewhat surprised myself on the imperial fasteners. The rest of the case has metric fasteners... The 6 bolt flange design predates the Automakers going to metric, so maybe they left it unchanged for reverse compatibility? I could have measured and googled wrong. I'll know when I get the studs!

I pulled the studs on my 242D TC yesterday. They are imperial 3/8" 16- 3/8" 24

 

[luthj]

Got some parts today, exciting progress, even if there was little labor involved.

First up is the wrangler trans mount.









Next is the dorman studs. Looks like 675-080 Is a bit too long. I will just use a thick washer, though for 15$, it may be easier just to order shorter ones.

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I also got a 10 degree taper reamer for the Upper BJ hole. Its a good match for the ford BJ.

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Starting to look like something useful now.
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[luthj]

Put the Tcase back together. Easy job, just need to keep the sealing surfaces clean. I replaced all the seals, and a couple bearings. Most were in great shape, but easy enough to do the high load bearings on the bench. I needed to bendthe lock ring on the rear output shaft bearing, as it wasn't tight enough. All bearings got greased as well. Don't forget the O-ring on the oil pump pickup tube.

PS: I know it looks pretty nasty on the outside. I cleaned one case, but decided to use the other. The baked on (from the oven) dirt was not coming off. Don't worry, I cleaned the inside.

 

[Len.Barron]

Looks like you'll have plenty of clearance for the 1350 flange/yoke. Shift lever might be the only issue.

 

[luthj]

I have been struggling with random speed sensor plausibility errors, and EM interference errors/codes. The FWB has been installed on my Right front sensor for several weeks now. I changed the output stage to use a RC differentiator circuit. This creates a positive/negative square wave (roughly emulates a true AC signal form the sensors).

I was doing some bench testing on the FWB. I think I have found the cause of the interference codes and plausibility codes.


I hooked up my fluke 115, and set it to Hz. I have 2 PWM signals available on the board, ~490 and ~980hz. I fed both of these as inputs, and monitored the output.

The good news is the RC output seems fine at both frequencies. But when I put my meter on the output I noticed the frequency was jumping around, almost plus/minus 10%! It would be stable for 500ms second, then jump. Maybe its the meter? Nope, the pwm output is rock steady.

So change resolution on my el-crapo scope. Low and behold, once every so many cycles, the output goes low for 10 microseconds. It does this seemingly randomly. Which explains why the ESP module doesn't always freak out. Its averaging logic/circuit must smooth out most of these errors.

I caught a failure in a photo.







The output is symmetric voltage wise, with no DC component. The frequency doesn't change with response to duty cycle, (from 20-80%), which is also good.

So, now I need to figure out why the uno randomly writes low... It seems to happen regardless of the input frequency. So I suspect either a bug, or some badly written code.

This also means that the ESP module is probably okay with a 2.5V square wave signal.

 

[luthj]

I made a few changes to the program. I swapped the high/low states so the output pins default to high instead of low. I also moved the sanity check to a different If statement, and changed the zero-input force stop value to 3x the current cycle time. It seems to be working now. I have 1.5% frequency variation, but that matches the PWM pins. I also checked with both interrupt/input pins being triggered, and the software keeps up just fine, even at 90mph (about 950hz). I will rig it up and road test it tomorrow. Fingers crossed.

 

[shade]

I made a few changes to the program. I swapped the high/low states so the output pins default to high instead of low. I also moved the sanity check to a different If statement, and changed the zero-input force stop value to 3x the current cycle time. It seems to be working now. I have 1.5% frequency variation, but that matches the PWM pins. I also checked with both interrupt/input pins being triggered, and the software keeps up just fine, even at 90mph (about 950hz). I will rig it up and road test it tomorrow. Fingers crossed.

You mentioned using the right/front sensor. Does the program care which sensor is used? I was thinking it'd be nice if it's agnostic so if that sensor fails, you could switch over to the left/front.

 

[luthj]

The program takes two inputs, and makes two outputs. It doesn't care where they come from. The ESP module will still let you drive with one sensor/input funky/broken, but you get the dash christmas tree, no/weird ABS, etc. I could connect both inputs to the same sensor, and thus generate two outputs.

Currently I have one front sensor wired through the box (only one circuit active) the other (left front) is still connected directly to the ESP module. No reason to make this more complicated!

 

[shade]

No reason to make this more complicated!

You could remove an adapter and fill the space with a electric motor-generator. You know you want a diesel hybrid 4WD Sprinter, and you already have the battery bank to make use of it.

 

[luthj]

After some more trouble shooting, I have found what I hope is the final issue with the FWB. The input has a low-pass 2nd order filter, it was designed to block all noise above 1khz. For some reason its blocking above 600hz. So at around 60mph the speed signal drops out. I am guessing I just need to compensate for the impedance of the WSS, as that is combining with the first stage. Should be easy enough to fix once I get the motivating to pull the PCB and solder a new set of resistors. Other than that issue, the program changes resolved the frequency drift, and it looks great on the scope.


I took a break from electronics to switch gears (pun intended). I started pulling the front diff apart for refurb. There are no good universal kits for the diff. Even the "master kits" are lacking bits. So its just easier to assess all the wear parts and order what I need.

Everything looks good thus far. Well, except the obvious bad carrier bearing on the drivers side. I need a two jaw puller to get that outer race out. The other side just dropped out surprisingly. The pinion bearings are still nice and tight, so I figure the backlash was from the worn bearing. I won't be replacing those. I am not going to touch the adjusters until I put it back together. That will probably save me hours of fiddling.

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[luthj]

Sometimes cheaper is better. Wal-mart sells a caustic degreasing product called Purple Power (similar to simple green, but half the price). I just dilute it about 4:1, and toss all my steel parts in to soak. No gear oil smell now!

IMG_20190811_141701342

Also works well on aluminum. It can discolor it, so care needs to be taken.

On an related note. I now know what I want for a parts washer. I am going to take a cheap dishwasher, and put it in the garage. Put some quality detergent in, use the heated cycle, and leave it running for 4-5 hours. Cheap to buy, easy to use, easy to repair.


On the web, many folks like to bash the front axle disconnect, saying the synchro collar is made of "pot metal" or "powdered metal". Mine is definitely made from solid steel not sintered. Despite this the misinformation is rampant. IFS MUST be weak! Or something bro-tastic and expo-sexual in nature.