1350/1354 D&D Doubler Issue.

[Kage]

1994 Ranger (ish) 4.0, 5 gear, 1350/1354 doubler, 60/14 Bolt on 37’s.

About every 3,000-4,000 miles, the ¼-20 socket head cap screws that hold the two adapter plates together like to loosen up and allow all the fluid in the crawl box to dump out. The first time this happened, a 600 mile u-haul ride home was required to rescue the truck. The second time (this past weekend) I was able to limp the truck home, though it still caused damage to the crawl box.

I am uncertain if I used lock-tite the first time that I put the thing together (too many beers I guess), so that would explain the first failure. The second failure, the thing defiantly had lock-tite put on it. Both times I used the Ultra Grey RTV with no noticeable leaks until the cases worked themselves loose.

There is no noticeable damage to either the cap screws or the aluminum plate that they bolt too. Also, I am not using any extra mounts to hold up the doubler (factory type transmission mount, and stock motor mounts) that could cause some weird stress to the cases.

I’m not sure where to go from here to keep this from happening again, but I do know that I'm getting tired of fighting this problem. I am not finding many other posts about this type of issue (the closest one being what 4x4junkie mentioned).


Any ideas would be appreciated.

 

[alwaysFlOoReD]

Perhaps it's time to use mechanical type of lock system. I've never done any of the following so due diligence on your part is required.
1] Safety wire uses bolts with the heads drilled with a hole so that safety wire can be wrapped thru all bolts.
2] studs and nylocks
3] flat and lock washers
In all cases I'd be inclined to use Heli-coil or equivalent.
Good luck,

Richard

 

[sbsrlewis]

I placed a 2nd stock skid plate behind the 1st one and then put a block of rubber between the t/c and plate. I have had any issues with anything coming loose.


Steve

 

[wizkid00104]

I have encountered issues where loctite does not work of there is oil or grease residue. If that gear lube got into the threads where the bolt came out of, loctite wouldn't have helped.

Maybe consider using a lock washer with the screw.

Or go to a larger bolt size by drilling and tapping, and then use a UNF threaded bolt instead of UNC.

 

[wahlstrom1]

Build a mount off the back of the second case and like mentioned, clean all threads of oil and grease before applying liberal amounts of loctite. The issue your having is being caused by the lack of support allowing the cases to vibrate under load and cause undue stress which is causing the leakage.

 

[Kage]

Thanks for the quick replies guys!

For the fasteners:

At this point I think I am going to go with Vibration Resistant Flange Fasteners (the ones that have the serrated attached ‘washer’). The hope being that the thing will bite into the aluminum enough to keep from backing out. Safety wire will be the next step if these fail (not that I’m looking forward to doing that as it would be a royal pain to get in there and wire them up).

Due to the way this thing is drilled, I cannot go up in screw size as there isn’t that much meat there. If need be, I can do a heli-coil, but I don’t think that is necessary at this time.

Locktite:

I cleaned out the threads real good before putting the locktite on this last round (Carb cleaner, and air dry). I am planning on using Red Loctite this time to see if it helps out at all. I don’t know if the ATF/Blue locktite had a reaction that made it break down this time, or it was just plain bad luck.


Extra mount:

You folks have convinced me to go ahead and add an extra mount (somehow). I am still uncertain if it is better to try to capture the rear care (limit its ability to rotate) or jus use something that has a ‘bump stop’ type of a thing to just support the weight.

My fear with capturing the rear case is that it might bind up some stuff causing one of the many aluminum things under the truck to die.

 

[wahlstrom1]

Make sure you build the rear mount with the same material as the other two mounts, and don't preload the mount, it's simply there to keep it from moving from where it's already at.

 

[4x4junkie]

That is weird... those are about the only bolts that have NOT come loose on my doubler, and I didn't loctite them either.

I agree the weight of the case hanging unsupported probably isn't helping, however I also have to wonder if you simply might not be getting them tight enough (hex-head bolts do suck a big dick ).
What I did was stick a long enough allen wrench in there so it would stick out the end of the case a bit, then I put a piece of small steel tubing about 10-12" long over the end and twisted that MF'er until it felt like the wrench was about to snap in two. If you have good-quality tools (Snap-On, even Craftsman) it should (hopefully lol) spring back OK (a socket-bit set might work even better still).
I also used nothing but RTV sealant between the two plates (no paper gasket or anything).

Be sure any new fasteners you get are the same grade D.D. machine provided (I can't recall if they're metric or SAE, seems like the kit had a little of both... It'd be Class 12.9 if metric).

Good luck with it.

 

[Kage]

Make sure you build the rear mount with the same material as the other two mounts, and don't preload the mount, it's simply there to keep it from moving from where it's already at.

I've got the Ruff Stuff Poly Motor mounts and another 'raw' poly mount I was planning on using for a trans mount. The plan right now is to try to make a bridge of sorts to create a support/tie-in for the rear case that is attached to the trans mount. That way everything should move in the same orientation and not create any weird binding issues.

Now how I have it worked out in my head, and how it actually works out will probably be grossly different from eachother

That is weird... those are about the only bolts that have NOT come loose on my doubler, and I didn't loctite them either.

I agree the weight of the case hanging unsupported probably isn't helping, however I also have to wonder if you simply might not be getting them tight enough (hex-head bolts do suck a big dick ).
What I did was stick a long enough allen wrench in there so it would stick out the end of the case a bit, then I put a piece of small steel tubing about 10-12" long over the end and twisted that MF'er until it felt like the wrench was about to snap in two. If you have good-quality tools (Snap-On, even Craftsman) it should (hopefully lol) spring back OK (a socket-bit set might work even better still).
I also used nothing but RTV sealant between the two plates (no paper gasket or anything).

Be sure any new fasteners you get are the same grade D.D. machine provided (I can't recall if they're metric or SAE, seems like the kit had a little of both... It'd be Class 12.9 if metric).

Good luck with it.

For what its worth, the screws in my kit were 1/4-20 Grade 5 socket head cap screws. So I ordered some grade 5 vibe resistant screws hoping that it'll help out.

I've got a good set of allen wrenches and I torqued the bolts pretty dang good both times (keep in mind, a 1/4-20 bolt into alu. should only be torqued to around 3-4 ftlbs). I am certain that I grossly exceeded that number

I'm half tempted to say fawk it and tig the two plates together.

 

[4x4junkie]

I'm guessing I put around 15-20 ft-lbs on mine. I don't think they were grade 5 bolts though... They seemed much, MUCH harder (that amount of torque I put on them would've ripped right open the socket head of a grade 5 bolt, if not twisted the whole head off). I wonder if maybe that's your issue.

Welding the plates together is not a bad idea either, especially if it's in the position you want and don't think you'll ever be re-clocking it again.

 

[Kage]

Well it turns out I can't see the forest full of tree's. I had a chance to play with it tonight and I gave everything a closer look. It turns out that the damn SHCS are bottoming out so that depending on the screw, they are 'just' touching the plate, or they're about 0.005" away from touching.

I'm thinking this just might be my problem

I'd never tried to put this thing together without sealant, so I suppose that's why I never noticed the issue before. I am confident enought that this is what has been causing my problems, and it should be resolved now.

If the bastards back off again, I'm going to weld it up as I don't see a need to clock this setup again anytime soon.

Thanks for the help folks!

 

[4x4junkie]

No prob... Good luck on it.