Sprinter 4WD Conversion Idea, GMT-800 IFS.


Engineer In Residence
I prefer the oil-based rust inhibitors, like Fluid Film, but they do require periodic re-application, usually annually.
I like them for hard to reach places, but I would like to recoat some areas of the wheel wells and subframe. The gravel chips are my main concern.

I got the gears out. Not terribly pretty, Not total carnage though.

here is the inner pinion race. and bearing.

The pinion bearing races have tiny craters, scattered about. I haven't removed the outer pinion bearing yet, that will be telling I suspect.


Well-known member
Fluid film is lanolin based, not petroleum.
True. I don't believe I said otherwise.

My point was that I prefer a corrosion inhibitor of that type (oil, ester, petroleum, etc.) to hard coatings that can crack and allow moisture to become trapped between the metal and the coating. The main drawback is that those inhibitors need to be reapplied to maintain protection, while a hard coating may last for some time before beginning to fail.


Engineer In Residence
Lanolin (from Latin lāna 'wool', and oleum 'oil'), also called wool yolk, wool wax, or wool grease, is a wax secreted by the sebaceous glands of wool-bearing animals.

It may not be petroleum based, but it is an oil film, which dries to a thin grease coating. I would also note that fluid films instructions also state that it can be thinned with vegetable oil if needed.

I am almost done with the new bearings. Just need to fill with lube and test everything. I dug around and found that I accidentally used the old crush sleeve. Not sure how I managed to do it, but I probably should have tossed it, instead it got cleaned with the loose parts. I figure re-using the spacer was likely the cause of the free play.

The good news is the bearings would have probably survived another 50-75k miles, they weren't atrocious, but better safe than sorry.
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Engineer In Residence
I put the rear end back together. After a test drive I rechecked the pinion drag, and it needed another 5-10 degrees on the nut to get it to 12 in-lbs. That took most of my weight on a 24" breaker bar, so the torque on the nut is at least 200 ft-lbs. That should be sufficient to keep everything tight. I put a paint mark on the nut and I will check it periodically.

Most of the vibration is gone, still have a bit at around 75-80mph. It feels like driveshaft, but that typically doesn't come on at a specific speed it builds through a range.
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Engineer In Residence
Feel free to have the last word on the matter. :)

The front driveshaft is a bit out of balance. I can't be bothered right now, as I can use the axle disconnect.

The one annoyance I have with the ARB locker, is that its diff gears are loud. With the front axle disconnected, they are quite audible driving around town. Its definitely gear noise, probably due to the tooth profile ARB uses. I will just put up with it for now. At some point I will evaluate the fuel economy penalty from having the front pinion spinning all the time.


Engineer In Residence
Been putting miles on the van full time now. A couple issues have come up.
  • Modest intermittent knock upper drivers side. Probably shock eyelet? Will investigate.
  • Steering has 20 degrees of play at center only. 90% sure it's the rack, which was new last year... I don't have the energy to rage currently...
  • With the van now fully loaded I am getting ESP activation on certain turn angles when on the throttle. I am pretty sure it's the different steering ratio of the GM knuckles. I have a software fix in the works. It's taking longer as the steering angle sensor CAN frames have a unusual crc checksum byte, which I need to recalculate when I adjust the steering angle and speed values.
  • Body roll at full load is more than I want. So an aftermarket front sway bar may be in our future.

Also, my 70 mph highway cruising economy is 17 mpg.


Engineer In Residence
Look like the knocking is the Reman CV axle. The shaft has about 25 thousands of axial play in the outer CV, so it knocks when the suspension travel speed is high. I have a rusty GM original (20 years old!) thats in good shape at home, so I will just swap it when we stop over for some remedial work.


Engineer In Residence
Been putting miles on the van. I have been trying to track down a driveshaft vibration at higher speeds. Its been getting worse, and now starts coming on strong at 65mph. Quite annoying, and its very strong at 70+. Looking at the slip yoke there is maybe 20 thousands of of play/runout at the UJ. This is without the support bushing or seal installed. So the play is just between the splines. I am not seeing obvious signs of contact between the bushing and the slip OD, and it doesn't look worn, so I assume the bushing is okay.

Both UJs are less than 3 degrees, and they are within 1 degree of each other. I found that raising the trans up a bit helped, which reduced the slip UJ angle by about 1 degree.

Any suggestions? My next steps are to check runout as best I can, and try to find someone to check the shaft for balancing.

Of note is that the vibration comes on as I approach 1/2 the shafts critical frequency. Its not present at speeds below 50mph, and only slightly up to 60mph or so. Consulting the online tables puts the critical rpm between 2500-3000 depending on wall thickness. Which corresponds to 58-70mph or so.

Another note is that it took a fair bit of weight to balance the shaft. 2x1" weights at one end, and 3x weights at the other. Tech thought the tube might have inconsistent wall thickness. I guess I could jack the wheels up and ******** around with some hose clamps to see if I can cancel it, probably not worth the effort.
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We had an old dumptruck on the farm that developed a bad vibration. I pressure washed the whole underside suspecting a build-up of mud in a wheel or yoke was to blame but it didn't go away. Next we swapped tires and wheels, no improvement. I suggested taking the driveshaft to be checked/balanced but was told that would cost too much. "Okay, so what are we gonna do?" was answered by drilling a small hole in the driveshaft and squirting in an ounce of 90wt followed by a test drive, adding another ounce, driving, and adding a final ounce. The effect was not noticeable after the first ounce, was considerable after the second, and was complete with the third. Dynamic balancing works.

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