4wd DNE2 Project

[junk]

I currently have my T-19, US gear, 205 supported on the US gear. But when I swap to the ZF-5, US gear, 1356 I plan to continue supporting under the US gear, but wonder about putting a U-mount up to catch the ZF also. So the ZF and US gear would be on a mount, but only tie to the frame at one spot. My hope was that would add rigidity to the ZF/ US gear connection without stressing things as the frame flexes.

Does your aux box have a mount on it? If so could you tie it into the ZF mount? This is looking great.

 

[LCAM-01XA]

I currently have my T-19, US gear, 205 supported on the US gear. But when I swap to the ZF-5, US gear, 1356 I plan to continue supporting under the US gear, but wonder about putting a U-mount up to catch the ZF also. So the ZF and US gear would be on a mount, but only tie to the frame at one spot. My hope was that would add rigidity to the ZF/ US gear connection without stressing things as the frame flexes.

Does your aux box have a mount on it? If so could you tie it into the ZF mount? This is looking great.

Actually with your setup I'd have already tried to bridge the T19 and the USG with a single mount near the USG, but I tend to be a bit on the overkill side. Regardless, I think you have a solid plan for after the ZF swap.

The problem in Jaluhn's case is that he has the 1356 before the DNE, and that thing hangs a bit low in the area between the ZF and the DNE. So it will be somewhat challenging to bridge the ZF and the DNE and add a single mount under them, all while clearing the 1356 somehow. That's why I suggested two separate mounts one behind the other on a modified single crossmember - this would IMHO make it easier to go around the t-case without ending up with a crossmember that hangs too low. So while the load from the drivetrain is spread on the crossmember in two locations, the crossmember itself is still attached to each frame tail in one spot, thus allowing for the same amount of frame flex as before and without transferring any of that load to the drivetrain mounts.

 

[jaluhn83]

Was going to rebuilt the 1356, but when I took it apart to change the shaft the internal bits looked in like new condition, so I'm thinking I may just use it as is. Still have to really clean and verify everything though to make that final decision.

I am for sure doing the oil pump mod. Got caught by that little bug once already with a 1345 case. Truck sort of went into permanent neutral going down the highway. Not fun. Very a good thing when the engine speeds up and truck slows down....

US Gear has no mount, could build one but I'd rather not mess with it. Not sure if I can get a cross memeber under it without hanging down too much.

Probably going to stick it in the truck and then see what looks like it will actually fit. Would not be hard to put a mount under the centerline of the USG/BW adapter and it would be roughly in line with the trans mount so that might work. The gist I get is that as long as the added mount is inline with the stock trans mount and not stiffer than the other mounts it should be okay. I guess it makes sense as the frame should twist roughly around a central axis, so it shouldn't see any additional stress. May do something like that and use bolts smaller than the holes and springs on the mount to adapter bolts so that it will support the weight but allow a decent amount of movement. Trial and error.

 

[LCAM-01XA]

I think the spring mount setup will not really be needed. All the ZF-style transmission mount does is support the weight of the transmission and t-case(s), it offers pretty much no resistance against drivetrain twist (that's what the engine mounts are for). Now if this were the older 4-speed style mount with like a foot-long steel C-channel bolted directly to the trans with a body-mount-like support on each end between the channel and the actual crossmember under it then yes, those would resist drivetrain twist (especially if poly is used) and thus put some decent torque on the transmission tail housing trying to rip it apart. But your single rubber block mount in the middle right under the trans centerline won't do that, so you can inline two of them and with healthy engine mounts I don't really see them causing any structural problems to the housings they're bolted to...

 

[jaluhn83]

I'm not worried about resistance to torque, I'm worried about frame flex not being exactly around the axis defined by the mounts. If any sort of twist/flex happens that is not exactly around this axis the mounts would move laterally relative to each other, hence why I want to ensure there's enough freedom of movement to allow this without loading the trans/t-case.

Probably worrying about it too much, but I'd rather be paranoid on this side then break something. Given the existing tendency for the ZF5 to crack and the fact that the back of the t-case is only designed to have a light tailhousing adapter on it I'm trying to avoid any additional load as much as possible.

 

[LCAM-01XA]

It is more or less the same thing tho - whether you're stopping the drivetrain from twisting under heavy load, or you're twisting the frame around the drivetrain via suspension forces, the end result is the same. That's why I'm saying do one crossmember with two mounts inline with the drivetrain, and do not make that crossmember tubular unless you have bushings on each end where it bolts to the frame rails. The mounts will only move laterally if each of them has their own crossmember. Think of this as a see-saw, except instead of kids at the end you have transmission mounts, and instead of center pivot you have a crossmember that is highly resistant to bending but quite tolerant to twist along its axis. The whole thing becomes like giant universal joint, the rubber mounts will take care of the driveline twist with respect to the frame rails, and the crossmember itself will twist as needed to accommodate frame flex. Hence my advice to not use tubing - tubing is very stiff torsionally, so something else has to give. Take a look at large trucks, their frames are designed to flex as their rear axle are essentially their own giant swaybars, and generally you won't find tubular crossmembers on these frames, just channels and I-beams - those will twist as the frame rails force them to, but their very center sections pretty much always remain flat and inline with the driveline.

 

[jaluhn83]

Trial fit in the truck today, looks like it will actually work decently. Had to clearance the cab floor a bit (1/2" or so) and had to pull the exhaust over a bit. Will have to put a mount on the exhaust there somehow to hold it over but that shouldn't be a major problem. No issue with the fuel tank thankfully.

Rear yoke on the USG is just about even with the rear of the cab, so the rear driveline should still be long enough to not have excessive joint angles. I have a mock up driveline to verify, but ran out of energy before putting it back in.

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[riotwarrior]

Sweet deal...very nice and cant wait here how it works for you.

 

[jaluhn83]

Progress report - had this thing in service since about may and it's been working well.

Used the mount setup above behind the 1356. Had to shorten the rear driveline and use a hybrid front u-joint. The USG/DNE uses a GM style 1350 yoke, so you need the GM straps and bolts and a 1350/1330 u-joint.

I was worried about vibration from the sharper u-joint angles with the shorter rear shaft but no noticeable issues.

One thing I was concerned about was supporting the weight of the USG box since it add quite a bit of weight with a pretty good lever arm on the t-case/trans. Problem is any solid mount would stress it when the frame twisted so what I wound up doing is fitting a pair of eye bolts on the rear of the USG and using springs and turnbuckles connected to a frame crossmember to provide some amount of support. Not sure if it actually really does anything but it seems like a wise idea at least.

I've done a fair bit of towing with the unit installed too with 2 loads grossing over 20k and all going up Tehacapi pass (6-7% grades) No issues with anything and the USG is very nice for towing like this.

Only thing I've found I'm not that happy about is the box gets hot, especially under load. Highest I saw was 270-300*, which is probably okay for modern gear lube but hotter than I'd like. I think the main issue is that there's very little air flow, so no way to reject heat. Having the exhaust 1/4" away doesn't help either. Long term I think I'm going to fit a cooler on it.

It's a very nice addition for driving, especially loaded. I'm running an underdrive (1.25:1) and 3.55 gears, so in low it gives me effectively a 4.43 gear ratio, and the spacing works out well for gear splitting as well. 5th under is pretty close to 4th dir (0.96) so it's not really good for splitting but that still gives a nice 9 speed setup. I don't think I've ever needed to split 1st, but everything about that is nice when heavy or on a steep hill. The USG shift is easy, in fact it's easier to shift that than shift the trans.

Even running empty I've found that starting in 2nd under works well and then going up through 5th before going to direct. Going back and forth from 5th under to 5th direct is also nice as it saves shifting and 5th under is essentially 4th and good down to about 35 mph with my setup. I try not to use 5th under for too long since it's adding a bunch of gear losses and wear that 4th direct doesn't have, but it's nice for when you have to slow down for traffic or whatever and then speed back up.

One thing that does take some getting used to is the shifting - the box uses a spring loaded shift setup, so it likes a very abrupt shift - keep the load on and then let off a touch and basically stomp the clutch then immediately let it off. If done right this is the best way to get a smooth shift. I'm always try to be very gentle and smooth on it, so this has taken quite a bit of adjustment. If you try to shift it gently though the box shifts as soon as it starts to unload and you get a very jerky shift since it snaps from one gear to the other while the clutch is still engaged or slipping. I've also had it shift as soon as I hit the button when not under much load. Once again takes getting used to.

My long range plan is to interlock the controls with the 4wd switch so it will alarm if the USG is in low and the t-case is in 4wd and power to the USG shift will be cut off when the t-case is in 4lo. With the USG aft of the t-case having it in low when in 4wd will bind up the drivetrain. So far I've only done this once and it didn't hurt anything though it did make the truck handle quite oddly. That was on a dirt/gravel road through - I think that there's a good chance of major damage if you tried it on pavement or worse yet shifted the USG while moving on pavement and in 4wd.

Overall though it's proven to be a good setup and I'm really happy to have finally gotten it installed.

 

[Black dawg]

Never checked temps on my usg unit, but it was noisy with 90w, so I used 140w non syn, and that made it much worse when hot, would actually smell gear lube like it was getting over heated. Ended up with 75w140 syn, and it is pretty quiet now, and no gear lube smells or extra noise when hot.

 

[jaluhn83]

I'm running synthetic 80w90 or 75w90. No noise issues. Noise probably means there's a problem and you're just masking it with thicker oil. I would guess the thrust bearing is going bad since that seems like the weak point. I personally would pull it apart and check all the bearings - easy to take them apart, and bearings are cheap and easy to fix.... running it with bad bearings could cause more serious damage though and the hard parts are basically impossible to come by.

 

[junk]

Did they base the US gear OD off of some standard commercial transmission parts? Or was it all custom stuff?

should add thats interesting on the gear oil. I've always used 90W but am planning to switch to synthetic to help it quiet down. Although I have an NP205 and T-19 right now so not the quietest drivetrain to begin with.

- Jeremy

 

[jaluhn83]

I suspect much of it is. The gears, shafts and case are obviously custom but most of the rest is almost certainly standard off the shelf parts. Think about, why would they custom make stuff when you could just get common ones?

Bearings are standard with the exception of the DNE2 countershaft thrust bearings - these are plain brass and may have been off the shelf but I've no idea off of what, probably easiest to just fab new ones if you needed them. The shift motor, switch and worm mechanism are standard 2 speed rear axle stuff. I'm betting the shift fork and collar are as well but haven't figured out from what yet.

Part numbers and info here:
http://www.oilburners.net/forums/showthread.php?65234-US-Gear-Dual-Range-Doug-Nash-Info/page4&highlight=

 

[jaluhn83]

Another update.... good and bad.

Good news is I've run 6 months and something like 15k miles on this setup including going across the country light and coming back pulling a gooseneck trailer and a parts truck at 23k gross. No issues and the dual range was a lifesaver with that much weight. I used 4th under quite a lot on all but the really steep grades.

That load was from CT to southern CA and then I turned around and took my other trailer and a different truck to norcal (~18k gross). The original plan was to also pull a car behind the flatbed on a dolly but that idea lasted about a quarter mile.... made it up to about 35 mph on a slight downhill and the trailer takes to whipping all over the road.... yep, that idea isn't going to work.

Round about 400 miles into that trip the entire transfer case & dual range assembly tries to fall off the truck.

Didn't have any real warning, just a sudden harsh vibration and loud thumping noise. In retrospect there was some vibration prior, but it was fairly minimal and easy to dismiss as road vibration. Couldn't figure out what was wrong at first till I crawled under and started playing with things - the rear output flange bolt on the dual range was loose and the rear of the dual range wiggled up and down a good 3/4" when pushed.

In total I found the following:
-The bolt and washer retaining the rear output yoke to the dual range shaft had come out completely.
-5 of the 6 transfer case to trans bolts were stripped. The one that was not stripped was one of the bottom 2. The other bottom bolt may have been previously stripped (IIRC one of the 6 was partially stripped, not sure though and can't recall for sure which)
-Both of the trans mount to trans bolts were missing. One or both of these may have been previously partially stripped.

Thankfully nothing serious was damaged, and between the one bolt and some creative ratchet strap use I got it secure enough to get to the gf's house in Alturas (destination for the truck on the trailer) and then was able to stick studs in the holes and get enough undamaged thread to get to the ultimate destination in WA. Long range fix is heli coil or replace the t case.

The big question that I'm still contemplating is what exactly the root cause was. The one undamaged bolt is at the bottom and both the middle as well as the one top bolt I took out had a solid 1/2" of thread pulled out of the case - ie the thread roots sheared and the thread was completely pulled out as a unit. This suggests to me that the case broke off downward - in other words it was not pushed up by the driveshaft bottoming out. I suspect the yoke bolt came loose first. However, even without the bolt it still wouldn't have been able to move that much. Any serious movement would also likely have caused more noticeable vibration.

I did initially have concerns about the extra weight added to the rear of the t-case and installed a spring/turnbuckle setup to try and add some support at the rear. These may have come loose over time.

I have found that shifting the dual range is hard to do smoothly, and it tends to cause some fairly severe torsional shock if you're not careful. I suspect these shocks are what caused the yoke bolt to loosen. I am also in retrospect unsure if I used loctite on the bolt.

I suspect the combination on the unsupported weight and vibration from the loose yoke is what caused it to fail. Interestingly I was on a fairly smooth flat section of road when it finally let go. The way the bolts stripped would require quite a lot of force, and I can't think of the way they would have progressively stripped. Maybe fatigue? It's odd to me that they all failed the same way.

It's nice that the bolt hole proved to be the weak link and not anything harder to fix. I would have expected the bolts where the dual range adapter meets the t-case to have been the weak spot since there's only 4 and they are only designed to support the stock extension housing.

The great unknown is of course if there's any other damage. There's nothing apparent yet, but it can't have been good for any of the trans/t-case parts.

 

[UMR_Engnr]

Bummer to read about the bad luck with your setup. The idea is intriguing and maybe with the extra crossmember all would be well.

When you remove the tailhousing on the tcase you lose the flange oil seal. Did you build a seal into your adapter? Did you seal the adapter to the cases?

Did the adapter to tcase hold up well with just the four tailhousing bolts?

Did you do anything to tie your existing speedo cable to the DNE?