Sprinter 4WD Conversion Idea, GMT-800 IFS.

[luthj]

More minor refinements, trying to get bumpstop height more precise. This is a bit of a challenge with the compound curves of the lower A-arm



Roughed in a shock tower. I think I will provision for 2 through bolts to secure the tower, with backing plates in the engine compartment. The cycling loading on the tower is substantial.



I think I have settled on a engine mount design. I will probably leave the isolator mounting holes out, and drill them during final assembly. Just depends on how accurate of measurements I can get. There is a fair bit of room in the engine bay, but I am trying to avoid moving the engine/trans more than 1/4" from its current position. Though I can lower it about 1/2" at the front if needed to change driveline angles.

 

[luthj]

Laid under the sprinter with my square and ruler for a while (too long really, the neighbors were giving me the stink eye...). The sprinters lower A arm isn't quite symmetric, so I need to adjust the engine mount placement. I also got rough measurements for the 4 mounting bolts. Surprisingly they clear all my vertical structure. I did need to add one access hole for tightening the front one. You will also note the engine mount is narrower. I am not sure if I will recreate the sprinters subframe locating stud. I think I will stick with 1/4" long slots, that way I can adjust subframe positioning for optimal fender clearance and engine position. 32" tires just barely clear the rear of the wheel well.

The shock tower looks pretty good. I need final measurements for the GM shock length and bushing height, and to verify on the jig. I will postpone final adjustments (fillets, tab/slot etc) until I work out the Tbar carrier. So moving on to that and tone rings tomorrow maybe.

 

[luthj]

Reassembled the diff and checked the flange end play. Measured about 0.03" on both sides. My experience is that that is about the max the ESP/ABS module will tolerate. Looks promising though. The drivers side has about 2.9" of space for the sensor to mount, which should be enough. I figure a tone ring around 6.4" diameter on the drivers side, and maybe 4" diameter on the passenger side, both welded to the back of the output flange. I may need to use slightly shorter bolts on the flange. The PS I can just weld a bracket onto the axle tube, and use the MB spring collar to hold the sensor in a matching 5/8" diameter tube. On the drivers side I will need to bolt or bond to the case somehow.

Here's a first crack at a Tbar carrier bracket. With the fuel tank moved back 3 inches or so, I should have room to tie to the outside of the frame rail. Drilling the bolt hols will be fun though. The filler pipe is in this area, I think it can be moved enough to fit the bracket though. I am using the same 1.5" weld-in bushing as the diff mounts.


Given that the carrier will hang down 3" below the fuel tank, I will likely need to create a narrow skid plate that ties into the trans cross member. Otherwise it would be fairly easy to catch the carrier on uneven breakover, and mess it up.

 

[Paddy]

Just for info sake it should be known that the NP242 was the upgraded TC that they’d put in military HMMWV behind turbodiesels. So, even the non HD units are pretty good hardware, pushing 13k lbs of war zone equipment in harsh conditions. The HD is a stronger chain but same basic design. Also, this is a AWD system, although some units had a 2wd option, most are set up AWD/4wd only. They have 4 positions, AWD, locked 4wd, neutral, and locked 4wd lo. The 2hi position is added somehow on some units, and I’ve ridden read you can retrofit them to have Thisbe mode. I’ve only dealt with them in my hmmwv and I didn’t want anti 2hi in that rig.
The military units have a cooling loop installed in them also, if that’s any interest. They pump their own fluid up to the front to an air/oil cooler unit built into the trans cooler.

 

[luthj]

Just for info sake it should be known that the NP242 was the upgraded TC that they’d put in military HMMWV. So, even the non HD units are pretty good hardware, pushing 13k lbs of war zone equipment in harsh conditions.

I agree. From what I can tell, the only major changes to the military version were a wider 1.25" chain (rocker type), a 6 gear planetary set, and 32 spline input shaft. And a passive cooler as well. The 242HD uses a 32 spline output, but the typical 23spline input. Note that the 1.25" chain used on some dodge 242s is a different pitch, so its actually no stronger than the more common 1" wide chain. It is however much quieter than the 1".

The only significant failures of the 242 I have come across are usually people stretching the chain rock crawling in 4low with big tires and lockers.

 

[Paddy]

Ha,I didn’t see your reply here until now. Yes you’re right, although it’s easy to swap the input gears around to get different splines to work. For instance I swapped out the 32spline for a 23 spline so I can run my Hummer’s with a Cummins power unit.

 

[luthj]

I am considering just running the P242J in stock form, or maybe a 242HD from the 8 cylinder grand cherokee if I can source one. Mostly I am focused on getting the slip yoke I want. The earlier style with the seal on the shaft (not the yoke) has some appeal, as I can run without the rear shaft is necessary.

The 242J is cheap and plentiful, so I can have a spare on the shelf in/when I break or wear it out. I am not pushing mega torque anyways.

 

[Paddy]

I wouldn’t want AWD in a sprinter, if it were the same effort to use a 2wd/4wd box instead, unless the hubs are not freewheeling, in which case it wouldn’t matter.

 

[luthj]

I wouldn’t want AWD in a sprinter, if it were the same effort to use a 2wd/4wd box instead, unless the hubs are not freewheeling, in which case it wouldn’t matter.

Unlike your H1, the Jeep 242 has a 2WD mode, plus the 4WD , 4WD Full time, and 4Low. Hence why I zeroed in on the 242. Its a very versatile unit, with good strength.

Some useful info on NP input gears on this site.
http://www.novak-adapt.com/knowledge/np-nvg-input-gears

It looks like all the 24 and 23 series Tcases (not counting 241OR) use the same basic design input gear. All that needs matched is the gear cut style (bevel vs ?), Bearing shoulder, and shaft length.

 

[luthj]

Some more info on the chains used in 242 cases. The goal is a 1" or 1.25" wide 1/2" pitch rocker chain. 3/8" pitch chains are not nearly as strong.

https://www.naxja.org/forum/showthread.php?t=1122820

I think that roller rockers instead of roller pins make the chain stronger, based off of this page. The European 242(ECE) came with rockers, I think I will start pounding down that path.

Some math:
Roller Pin
____
Width | Ultimate Tensile LBS - 3/8" Pitch | 1/2" Pitch
1" | 3750 | 7500 < Current Standard Chain
1.25 | 4690 | 9300

Rocker Joint
____
Width | Ultimate Tensile LBS - 3/8" Pitch | 1/2" Pitch
1" | 7500 | 10,000 <- Euro Case
1.25" | 9375 <- 242HD/242D | 12,500

So basically the rocker jointed chain in 1" with 1/2" pitch out of a 242ECE will be stronger than the 242HD 1.25" x 3/8". (HV-061)

Here's the document I used to find info about the pitches/widths of chains.

http://www.novak-adapt.com/catalog/transfer-case-parts/np-242-parts

The H1 uses.5033 Pitch x 1-1/4 W x 72 links, rocker pivot. The euro 242 uses .5033\" pitch rocker joint x 1\" wide x 72 links.

It looks like the strongest chain that's easily found is the Jeep WJ. That 242 variant uses a 1.25" rocker chain with 3/8 pitch. Which puts its tensile strength at 9300lbs. Which is in the same ballpark as the H1 at 12,500lbs. I believe on V8 WJs had this 242 variant (242HD badged).

 

[Paddy]

Yeah I had to try like 4 input gears before I had the right one. There is the spline count, wide or narrow bearing, but there’s also like 4 different nose lengths and they are important in the sealing and mating of the tranny. It was a ********** but I finally got the right one out of a Jeep wj I believe.

 

[Len.Barron]

Pay close attention to that input gear bevel note; NP changed the pitch of those gears at some point (you'll need to research the year break if you need to swap input shafts). I found that out the hard way when I tried to swap a much later 27spline into an earlier 32spline case.

 

[wjeeper]

luthj some seriously good tech in here! I haven't had the time to sit down and read all of your posts, but I skimmed it and you have really done a thorough job.

I wrapped up building my AWD express suspension last year and came to a lot of the same conclusions suspension wise. I had a hard time getting the ackerman angle, and camber gain at ride height dialed in. (The joys of a SLA suspension) I got it "close enough" and it handles well and the tires haven't worn weird despite having a bad steering rack and not rotating them in 10,000+ miles. I was also able to safely net just shy of 10" of wheel travel from the suspension before i ran out of plunge in the CV's. However it required a totally different top ball joint arrangement than stock.

As you know from another thread I am working on getting a 242HD in my rig, its a great option to get a strong full-time transfer! I know there are a few naysayers that say its not worth the effort but having full time has enough benefits its totally worth any extra work in my eyes. I love it on days that it is snowy, but not quite snowy enough to run in part-time 4WD high. Also on uphill sections of washboards having engaged full-time eliminates almost all wheel-hop and allows the front end to help pull through the corners.


I have one a 242HD sitting somewhere but with my recent moves and building a house I am not so sure where it ended up.......may have to buy another.

My only regret with starting with the factory AWD Express is that with all the suspension tweaking I have done I just should have converted a 2WD model from the get go. I would have built it the way I wanted and had less compromises (mainly the weak front diff and higher initial buy in)

 

[luthj]

Pay close attention to that input gear bevel note; NP changed the pitch of those gears at some point (you'll need to research the year break if you need to swap input shafts). I found that out the hard way when I tried to swap a much later 27spline into an earlier 32spline case.

Yep, the change happened in 94, so anything made in 95 is late, and 93 is early. Anything in 94 is a crap shoot.

luthj some seriously good tech in here! I haven't had the time to sit down and read all of your posts, but I skimmed it and you have really done a thorough job.

I wrapped up building my AWD express suspension last year and came to a lot of the same conclusions suspension wise. I had a hard time getting the ackerman angle, and camber gain at ride height dialed in. (The joys of a SLA suspension) I got it "close enough" and it handles well and the tires haven't worn weird despite having a bad steering rack and not rotating them in 10,000+ miles. I was also able to safely net just shy of 10" of wheel travel from the suspension before i ran out of plunge in the CV's. However it required a totally different top ball joint arrangement than stock.

As you know from another thread I am working on getting a 242HD in my rig, its a great option to get a strong full-time transfer! I know there are a few naysayers that say its not worth the effort but having full time has enough benefits its totally worth any extra work in my eyes. I love it on days that it is snowy, but not quite snowy enough to run in part-time 4WD high. Also on uphill sections of washboards having engaged full-time eliminates almost all wheel-hop and allows the front end to help pull through the corners.


I have one a 242HD sitting somewhere but with my recent moves and building a house I am not so sure where it ended up.......may have to buy another.

My only regret with starting with the factory AWD Express is that with all the suspension tweaking I have done I just should have converted a 2WD model from the get go. I would have built it the way I wanted and had less compromises (mainly the weak front diff and higher initial buy in)

Thanks for the info. I am glad to know there are other folks who bucked the trend and skipped the SAS swap. I may be able to get more travel, but for now I am certain I can get 7", which was my design criteria. Surprisingly so many folks like to bash the 242 as not strong enough, which seems ridiculous given how much common it has with other well proven cases. I figure a 242HD (durango or WJ) with a 6 planet set is plenty strong for my application.


Some more info on the 242HD.

It appears that 98-00 (possibly 01-04 as well) Durangos used the NP242D, which is essentially the same as the jeep 242HD. Most likely easier to find as well. Input shaft may need swapped depending, as durangos used the short shaft.

It appears only 231c and possibly 241c have the 6 planet assembly. Should be easy enough to source whole or as parts.

Jeep was really bad about labeling the 242HD, sometimes its 242J, 242 WJ, or 242JHD. the only way to tell for sure is to count the output splines.

Swapping the wider chain and 6 planet set into a 231.
https://offroadpassport.com/forum/sh...+231#post34312

 

[luthj]

Updated my jig, and put it through the range of motion. 3.5" of droop and 5.25" of bump. That is just about the limit of the upper BJ mount. The axles have more articulation, so another inch might be possible with some clearancing of the upper arm, or a high angle BJ.

I am not sure if I can get all 5" of bump, as the fenders might interfere, I doubt it though, at least with 30-32" tires. I am considering increasing the ride height a bit, to get the travel more symmetric.


The guys over at Vancompass built a 4wd sprinter using the ML torsion front end. Some interesting photos of their approach. The GM torsion bars are a bit shorter, but I am considering bridging between the Tcarrier and trans crossmember.