Sprinter 4WD Conversion Idea, GMT-800 IFS.


Engineer In Residence
Interesting Idea. I have a port in one of the yokes I could put some oil in. Not ideal, but may be worth a try. I can always drain if needed.

I checked the runout, and its under 5 thousands at the diff yoke, and about 10 thousands total on the shaft. I will check the slip yoke, but that's probably fine. I spun it up without tires/wheels, and its definitely the shaft, I marked and put a few hose clamps on it, and it seemed to help. Unfortunately the nearest place which will balance a shaft is several hours drive, so I will see if I can get it done next time I am in a bigger city.


Engineer In Residence
We have over 5,000 miles on the conversion now. Still rolling along fine.

Turns out the knocking on was the sway bar downlinks. I tightened them up (farther than the recommended spec). This has reduced the knocking significantly. It also reduce the free play in the sway control bar, and the van handles a lot flatter now. Its pretty good for such a tall vehicle really.

I took the driveshaft to a shop to get it rebalanced. They indicated it was way out at first run, and they stripped the weights off. I didn't realize they made weights this big, but they are 2x2" and almost 1/4" thick. The vibration is almost gone, but there is some over 65mph. I asked them to spin it up to 2500rpm (instead of 1900). They didn't of course. Since the vibration was much less, I was able to see the lower intensity components on my vibration analyzer app. There was one spike at 48hz (driveshaft speed), and another around 100hz. The 100hz is a second order vibration, and it likely UJ angle mismatch. It may be causing the 48hz vibration. My angles match, but vibes don't lie. So I am going to shim the pinion up another degree. Its not severe, but might as well get it taken care of.

I have some engine vibration under load around 1800-2500rpm. It wasn't present before the conversion. I probably have my trans mount too far forward and its pressing on the engine mounts. Some of the vibration is from the trans. Either my reman torque converter, or I screwed up the TCC damper valve. Its not hurting anything, but I don't enjoy extra vibration/noise. I have some new mounts on the way, and I will try to tweak everything for better alignment. I might end up filing the mount holes to shift the mounts forward 1/8". Access is a pain in there though...


Rendezvous Conspirator
@luthj I love your thread and your van. This part of your project is exactly why I always eventually quash any dreams I harbor about doing conversions/swaps/etc. - I just know that the necessary tweaking would last longer than my enthusiasm for managing it. :D


Engineer In Residence
Its a big project for sure. There are two other intrepid souls who wanted to do the same, and we are helping each other through the process. Of course this is on the high end of custom work (cause I am a bit crazy). I like to think those who followed are having an easier time...

Though the work/effort is kinda forgotten the first time you drop it into 4low, and drive out of a mud hole, or pull out of a ditch.


Engineer In Residence
Another 5k miles on the van, still working out a few bugs, mostly due to user error though.

Left upper control arm had one pivot slip in a bit. Messed up my alignment, did a quick reset in the bush, but need to redo the alignment when we do a maintenance stop. If I had to do it again, I may switch to the ford camber washers. Getting the forward bolt tight is a pain due to the brake line location.

The diff shifts a bit when I really load up the drivetrain, such as tight turns in 4PT. I need to reset the yoke angle, as its moved down several degrees. I probably didn't get the rear mount bolt tight enough. If I was doing the design again, I would probably add about 1/4" more lift at the front, for better diff clearance.

My new engine mounts are settling a bit, so I need to change the rear axle shims, this big poorly balanced driveshaft is limiting my top speed to about 65mph due to vibration. I am getting a bit fed up, if I can't get it right with shims, I will just order a new shaft $$$$$.

Speaking of shafts the front temporary shaft still works fine. However the slip has more friction than I would like, so when the shaft is really loaded, engine vibration gets transferred to the chassis. If I am moving its not noticeable, but at low speed its annoying. I may get a new shaft built at some point $$$.

I have been using the 4wd a fair bit, snowy roads, sandy tracks, etc. 4WD is no substitue for airing down, and I think my air compressor needs an upgrade after all the usage its been getting.

Here is the van getting buried in a sandy wash. Frozen crust on the top, and windblown sand below. you can see we were just drifting down the 20% slope Lockers and 4WD are a great way to dig yourself into a deep hole, experience has taught me that MOAR POWER usually doesn't help. 20Psi rear and 15psi front combined with lockers made for an easy drive out.


As far as the 4wd bits go, everything just worked when I needed it. On the fly shifting between 2HI, 4PT and 4FT is seamless, ESP and ABS work fine. Ride is quite good with correct air pressure. I still have a knock left side, which may be a loose bolt on the LCA. So after the alignment everything is getting retorqued.

I also need to do a third, and hopefully final, clearance at the front of the wheel wells. Still getting a bit of rubbing, so hopefully a sledgehammer can remedy that.


Engineer In Residence
Howdy folks, doing some winter maintenance during a layover for a bit. A few things needed adressed.

1: I slightly modified the GM parking brake lever arms to make them shorter, parking brake much improved.

2: Both my rear axle seals were leaking. Ended up having 0.01" vertical play (not lateral though). The bearings were worn. Shafts were fine, but there were seal grooves, so I opted for all-in-one repair bearings. The bearings probably got contaminated when the first pinion bearings got FUBARed by my screwup.

3: The front left stub axle shaft was leaking, and it also had some play. Not sure why though, the other side is fine. The shaft and bearing looked okay, but there was some corrosion pitting on the seal area, so I just bought a new stub shaft. I was able to pull the bearing without removing the diff.

4: I got a quote for new shafts ($1,050). So I will pick those up next week.

5: After fining some loose bolts, I probably need to switch to pinch nuts in a few places.

6: I made a few adjustments to reduce the UJ angles all around, so with the new shafts, hopefully I can have a vibration free cruise at 80mph.

7: I finally found the cause of the knocking. The shock towers move inwards slightly under the right conditions, and the upper plate contacts the remnants of the strut brace. I finally installed the bolts I had designed for, which secure the tower to the fender wall.

Tangentially conversion related, but my fuel tank is leaking around the sender. Not sure if its a crack or a hose issue. Not a pleasant repair though.





Engineer In Residence
Man I hate the new axles that don't have an inner race. Bean counters winning over engineers.
Yeah, thankfully the shaft bearing surface is actually okay, so If I need to go back to the original bearing I probably can. Just need to epoxy and smooth the seal surface in that case. I measured the shaft bearing surface and it was about 0.0004-0.0005 under spec, surprisingly. Most every vehicle with that design I have owned has needed bearings at 200k miles or so. Both GM and Ford.

A problem I have seen is that some replacement bearings are actually harder than the shaft, so the shaft wears first. OE bearings have rollers that are slightly softer than the hardened area on the shaft, so they wear first.

The original sprinter axle used a double row ball bearing which was retained with a big nut to the shaft (no C clip). Pretty rare failure point, I have seen a couple expediter vans with 500K+ miles and the original wheel bearings.


Engineer In Residence
Indeed, a friend hated his dodge with one. I have liked this 9.5" okay so far. Other than my own screwups, and the lack of a aftermarket pinion spacer kit. The shafts are pretty meaty, bearing size is okay, parking brake is reasonable to adjust. I wish it had a drain plug, meh. I had limited options for an axle with the right tone tooth count and inductive pickups. Though if I had to do it again I might go the ford route and custom tone wheels.


I think I finally found a rack boot which will fit over the GM tie rod and the spacer. I had one of the temporary boots I modified slip off the spacer, thankfully I caught it before any crap got into the rack.


Engineer In Residence
Another in the nearly finished saga. I had 2 new driveshafts made by a nearby-ish shop. Good quality shafts btw. Vibration is gone. Well I still have some TC clutch shudder, but that's a different thread.

Did a bit of front end maintenance. I bought some Meyle sprinter rack boots. They fit over the GM tie rods and the spacer, just barely though.

Last edited:

Forum statistics

Latest member