4wd DNE2 Project

[jaluhn83]

After some 5+ years of contemplating this project I've finally actually gotten somewhere.

The goal is to mount a US Gear/Doug Nash dual range box somehow behind the t-case so i can use a 2wd box instead of trying to find that 1 in a million 4wd unit. This also saves having to modify the t-case shifter & front driveline. Hardest thing to figure out was the shafting - I wanted to avoid trying to make a custom adapter shaft/coupler both for strength and cost concerns. The key as it turns out is that the slip yoke 1356 case uses an output shaft that is the same as the standard t-case input shaft.... this means that the DNE box will mate directly with this shaft and it's only necessary to make a mounting coupler to bolt the 2 together. Still got to add some bracing, drill holes and so finish work, but it's at least progress....

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[riotwarrior]

Hmm maybe u shoul search for fixed yoke brnco case...much shorter

 

[jaluhn83]

Length is a concern - I had wanted to use a 1345 for this reason, but the shaft design wouldn't mate - different splines and different spline design. I thought I could use a GM spec DNE since the spline count matched, but the spline shape was still an issue. Not sure what the fixed yoke case has for an output shaft.... might be an option, but it's also one more thing to try and find...

 

[LCAM-01XA]

The fixed-yoke shaft has the exact number of splines as the slip-yoke, and their shape appears to be very close as well. However, the fixed-yoke shaft has a slightly smaller OD than the slip-yoke one - our only fixed-yoke shaft is already in use and therefore cannot be measured, but if we go by yokes then the fixed yoke comes at 1.34" from tooth root to tooth root across its diameter, and the slip yoke measures at 1.37" or thereabouts. The slip yoke appears to have teeth that are deeper than needed to clear the shaft, whereas the fixed yoke is very tight on its shaft, so I wouldn't be surprised if the actual OD difference between the two shafts is less than the .03" the yokes would suggest. An attempt to slide the fixed yoke onto the slip shaft was almost successful, the yoke starts but then jams up - actually it's quite possible that some hammer time may persuade it to move further, obviously ain't trying that cause it would waste valuable spare parts, but the point is that turning the slip shaft down even .01" in radius may very well be enough to clear the fixed yoke properly. Which would suggest that the fixed-yoke shaft has only .02" smaller OD than the slip-yoke shaft - is that enough to not play nice with the DNE input would be for you to decide

If you were to go with that setup, the length you'd be saving is the lenght of the splined section of your slip-yoke shaft + another inch or so. Not sure if it's worth the trouble, especially if your truck is an extended cab and as such has plenty of length for the driveline without going into extremes of the "CJ with a doubler" variety.

 

[jaluhn83]

Interesting. I'd be curious if the yoke would fit on a standard trans output shaft - wouldn't be surprised if the difference is the yoke and the shafts are actually the same.

If I had a fixed yoke case that would certainly be a good way to go, but unfortunately I don't and I haven't seen one in the junkyard. The current adapter is ~6", so a fixed yoke case would gain 4-5" which is something, but likely not enough to matter too much.

The truck is a regular cab, so the rear driveshaft will be a bit shorter than I'd like but looks like it woln't be too bad. Haven't installed the setup yet in the truck to check out the driveline angle though. Can't be worse than the folks running around with a 18" lift though....

 

[LCAM-01XA]

Interesting. I'd be curious if the yoke would fit on a standard trans output shaft - wouldn't be surprised if the difference is the yoke and the shafts are actually the same.

Not sure I quite understand you there, you want which yoke tested on what shaft now? Speak up and I may be able to do something about it

Regarding the short shaft with the bolt-on yoke, every fullsize Bronco will have that. Older ones use a yoke just like the special one for the front shaft of a F350 (and those are a good source for it btw), but any OBS Bronco is most likely running a companion flange either way the shaft is short and the yoke/flange is bolt-on. Likely the same exact setup internally, just different yokes between the two.

 

[jaluhn83]

Well, very interesting.... I thought the fixed output 1356 was only on a very few 1 ton trucks, didn't realize the bronco used it. May have to make a trip down to the local junkyard and see if I can scavenge a bronco shaft to play with.

Naturally I figure this out after doing all the fab work on the current version of the adapter. Oh well, guess it keeps me busy...

 

[LCAM-01XA]

I have never ever seen a fixed output 1-ton case. A few things to consider regarding that:

1) with a slip yoke setup the piece with the smallest diameter is the t-case output shaft, which is generously splined (rolled), hardened, and really not all that very small. With a fixed yoke setup the the piece with the smallest diameter is the slip section of the driveshaft - this one only has 10 splines (machined), and IIRC it's diameter is smaller than that of the t-case output shaft.

2) the slip yokes in factory setup allow for more spline engagement length that the slip driveshaft. The slip yoke is also not only piloted on the t-case output shaft, but also supported externally via a bushing in the tail cone of the case. In comparison a slip shaft naturally has no external guides and supports, the two pieces just pilot within/onto one another.

So maybe the slip-yoke driveline setup is just somewhat stronger by design? Idk, I still like fixed-yoke cases, you can take each driveshaft off and still drive home just fine ysing the other one without the thing pumping itself dry thru an open hole. Also less likely to suffer case damage if the rear shaft decides to get a bit rowdy under there...

 

[riotwarrior]

Well, very interesting.... I thought the fixed output 1356 was only on a very few 1 ton trucks, didn't realize the bronco used it. May have to make a trip down to the local junkyard and see if I can scavenge a bronco shaft to play with.

Naturally I figure this out after doing all the fab work on the current version of the adapter. Oh well, guess it keeps me busy...

Pays to azk questions then build

I can get pic of Bronco fixed yoke if you like and as far as I can tell it could make for a nice eat compact setup compared to what you currently have....

Hence my suggestion to start with.

JM2CW

 

[FarmerFrank]

Hmmmm maybe you should have started this thread later on.... I contemplated doing the same but I figured I'd have to make it divorced with a small jack shaft between the TC and the od box.

 

[jaluhn83]

Pays to azk questions then build

I can get pic of Bronco fixed yoke if you like and as far as I can tell it could make for a nice eat compact setup compared to what you currently have....

Hence my suggestion to start with.

JM2CW

True.... but it's knowing the right questions to ask that's critical! Seem to recall i asked something about what cases would work and was pointed to the slip yoke 1356, but may have been on a different board.

Looked at picture online, looks like it may work, and seems to have the same bolt pattern so i could just shorten the existing adapter setup.

Have to find one though - local yard didn't have anything with one.

 

[riotwarrior]

Well now my interest is piqued....may want check mine out...naw..hope get 203 son for gear box and doubler...hmm 203/1356/DNE

 

[LCAM-01XA]

I figured I'd have to make it divorced with a small jack shaft between the TC and the od box.

That would certainly help the transmission tail housing adapter survive a bit longer. Unless you have a NP435, them got the cast iron adapter and pretty much don't give a #2 what hangs off their end

Looked at picture online, looks like it may work, and seems to have the same bolt pattern so i could just shorten the existing adapter setup.

If you're talking about the bolt pattern for the tail cone, yes, it's the same for all 1356s, regardless of slip of fixed yoke style. To make matters even more interesting you got 3 rear halves to chose from - the later ones are just ribbed but generally still pretty flat in the area on the back side of the front shaft output, while the earlier ones have 4 bosses there cast into the case for stuff to hang off, and said bosses may or may not be drilled and tapped already from the factory.

 

[jaluhn83]

That would certainly help the transmission tail housing adapter survive a bit longer.

I had thought about this - even with the DNE flush on the rear of the t-case it adds a fair bit of weight out there. I was planning on putting in some sort of support to take that load off the trans - probably some sort of spring suspension that will support the weight of the DNE but still allow frame flex. I am also not sure how well the rear of the t-case would handle the load since it's soft material and likely not design for too much load.

 

[jaluhn83]

Well now my interest is piqued....may want check mine out...naw..hope get 203 son for gear box and doubler...hmm 203/1356/DNE

No shortage of gears there... Not sure how hard the 203-1356 setup would be though. I had thought at one point about using the gear reduction out of a 1345/56 to make a doubler in front of a 1345/56 case. Actually seems like it wouldn't be too hard since we now know that the input/output of the 1356 matches, though you'd likely want to shorten the shaft some or else just have a long ugly case thing.

Big thing for me was avoiding any custom shafts or trying to fab/shorten a shaft since I was concerns about strength and/or cost to do so.