Engineers? - Passenger side tcase brace function

[BadDog]

@K85 Octane
Yeah, mine is single too, just 3" diameter. And even with the dropped "mock up" position, the CV has only about 1/16 clearance with the front axle in straight drop (hanging), much less articulation. It's going to still need some mild clearancing on the tabs. If it stays (roughly) and works where it is, it will have a set of one piece full width spacers before real trials begin. And thanks for the update on your brace. But I wonder how you have clearance. If my case were clocked up, that would be going through the floorboard by my reckoning, or do you have it clocked down (for the same reason as my drop)?

@Tnsejed
Thanks for the reference running without for years. I've seen that before too, but always wondered if that was a "it's ok, until it's not" scenario. With many miles of unimproved roads awaiting in my imagination, there's going to be a lot of rough use even without rock crawling. And I like to imagine I'll be more proactive than to let the slip become a problem. It also has an accordion cover on it (desert use, not mud, at least very often). But I haven't heard of breaking the bolts at the bell housing. Mine has a G8 bolt there, but that just means it would likely break out of the block first.

 

[rampage]

@Capt Ron There's a great thread on here from a long time ago about this. I do think a broken case was involved but I think it was not enough plunge that it ended up being. This must have been a decade ago or more. If I remember the discussion correctly.

There are trucks with it and without it. Definitely a driveshaft plunge type of brace but I always wondered about the reasoning why some have it and some don't. All Transfer case mounting rules apply, You want to keep the bushings relatively inline with the center shaft, and let the motor mounts do the torque resistance. Or you put to much force on the case and transmission trying to resist the forces. This thing doesn't apply here. I ran my truck without it for years.

I always wondered to if it was some sort of accident protection deal as well. Or abuse prevention method to keep the case intact.

For whats it worth though the bolts break off at the bellhousing. Like what @obijuank5 said, the shafts that don't get greased get bound up pretty good.

And there you go, to prevent breakage from the shaft bottoming out under extreme spring compression.

If you’re going to go through all the work of modifying it you MAW just make a custom one that suits your needs.

 

[BadDog]

Yep. A "custom" one based on the original.

 

[imiceman44]

I have a question for the engineering types. Not looking for "GM engineered it, leave it alone", I can figure that out on my own, and that's basically where I am pending review. I'm hoping for real answers to what and why.

First off, exactly what forces is it meant to handle. By it's design, it would seem well suited only to be managing only linear tensile loads along its length. Like suspension compression shortening the drive shaft. To a lesser extent, compression loads like lengthening the drive shaft. And almost nothing in any other direction.

The reason for asking is that it's proving very tight in there to get my exhaust routed between the shackle hanger and that bar. Life would get a WHOLE lot easier if I modify that bar so that for most it's length it runs more parallel to the transmission center line with a kick out to connect to the case. Even with gusseting that's obviously going to hurt it's ability to manage the linear loads since it will introduce a substantially larger force vector trying to bend the rod where the gusset ends. But is it likely to matter?

So here's an engineering point of view.
That bar in tension does more than brace front to back, being a straight shot ant twist will tend to stretch it longer so it also helps with torsional resistance.
As long as you keep it attached to the engine/ transmission combo you are still in good shape, just don't attach it to the frame or body.
As for needed or not, I have run a few without, but not the aluminum cases.
I know it's a pain but you are building for reliability, put something in

 

[BadDog]

Great, thanks. Yeah, no way I would attach it anywhere but the general area where it was originally attached. And I definitely plan to put something there, the only real question is "how much freedom do I have to deviate from straight bar brace".

 

[K85 Octane]

I am clocked up, flat, with 1” body lift, and a small hole in the floor that may not have been necessary.
My exhaust all runs down the driver side. Couldn’t fit a 1” exhaust down the passenger side.

 

[imiceman44]

Great, thanks. Yeah, no way I would attach it anywhere but the general area where it was originally attached. And I definitely plan to put something there, the only real question is "how much freedom do I have to deviate from straight bar brace".

It still needs to be straight, where it connects to can deviate on both ends.

 

[BadDog]

It still needs to be straight, where it connects to can deviate on both ends.

See, that's the problem. I need to dog leg it to clear the exhaust. If I keep it straight, then there is no point to any of it. Moving it up on the bellhousing just moves the interference point back a few inches, and loses another 1/8" of clearance, and puts it right against the floor pan. Even without the floor pan, moving it up at the rear also doesn't help since again, it just removes 1/8" of clearance, and it's not practical (without surgery or convoluted mount) due to the case tab sticking out above the bar mount surface. Basically, no amount of moving the ends in any reasonable fashion is going to help at all because the ways it needs to move it can't.

Again, the only goal here is to determine if it is practical to make a non-straight version of that brace, and if so, what would that need to look like. If it's almost entirely to absorb front shaft slip forces, then it seems quite practical to create a gusseted offset (offset about 1-1.5" in and up right in front of the case), and make sure the shaft slip is maintained to prevent excessive loads that might expose the weakened brace design.

Is that workable? It seemed the answer was trending strongly to "yes", but then your final post seems to indicate it's a non-starter. Does that correctly state your position?

 

[rampage]

See, that's the problem. I need to dog leg it to clear the exhaust. If I keep it straight, then there is no point to any of it. Moving it up on the bellhousing just moves the interference point back a few inches, and loses another 1/8" of clearance, and puts it right against the floor pan. Even without the floor pan, moving it up at the rear also doesn't help since again, it just removes 1/8" of clearance, and it's not practical (without surgery or convoluted mount) due to the case tab sticking out above the bar mount surface. Basically, no amount of moving the ends in any reasonable fashion is going to help at all because the ways it needs to move it can't.

Again, the only goal here is to determine if it is practical to make a non-straight version of that brace, and if so, what would that need to look like. If it's almost entirely to absorb front shaft slip forces, then it seems quite practical to create a gusseted offset (offset about 1-1.5" in and up right in front of the case), and make sure the shaft slip is maintained to prevent excessive loads that might expose the weakened brace design.

Is that workable? It seemed the answer was trending strongly to "yes", but then your final post seems to indicate it's a non-starter. Does that correctly state your position?

Re-read the last part of his statement:
“where it connects to can deviate on both ends.”

That says the answer yes.
I think he’s just saying to make the middle part straight.

 

[imiceman44]

See, that's the problem. I need to dog leg it to clear the exhaust. If I keep it straight, then there is no point to any of it. Moving it up on the bellhousing just moves the interference point back a few inches, and loses another 1/8" of clearance, and puts it right against the floor pan. Even without the floor pan, moving it up at the rear also doesn't help since again, it just removes 1/8" of clearance, and it's not practical (without surgery or convoluted mount) due to the case tab sticking out above the bar mount surface. Basically, no amount of moving the ends in any reasonable fashion is going to help at all because the ways it needs to move it can't.

Again, the only goal here is to determine if it is practical to make a non-straight version of that brace, and if so, what would that need to look like. If it's almost entirely to absorb front shaft slip forces, then it seems quite practical to create a gusseted offset (offset about 1-1.5" in and up right in front of the case), and make sure the shaft slip is maintained to prevent excessive loads that might expose the weakened brace design.

Is that workable? It seemed the answer was trending strongly to "yes", but then your final post seems to indicate it's a non-starter. Does that correctly state your position?

Gusseted works. It just can't be a bend that would straighten out when under tension

 

[beags86]

So your worried about exhaust clearance? Does the exhaust hit it now? Honestly if that bar and the exhaust rubs a bit, who cares?
The bar Isn't going to take out that bar and vice vs. or if you still worried what about dimpling the exhaust some.
Idk. Seems like you spliting hairs on something that doesn't matter to much.

 

[K85 Octane]

Agree, keep it as straight as possible for as long as possible. Any offset needed sounds good if you do it at either end.
Or you could dent the exhaust a little. It wont hurt anything.

 

[BadDog]

Thank you for all comments.

Yes, denting the pipe has always been on the table, but only if necessary. So has adding a few bend pieces to create a sort of helix to get off the shackle hanger at the front and shift to be off the rod further down, and then back to the tailpipe beside the tcase. All such are on the table, but my first best option is to keep it simple by just making room by moving that bar to the center.

As for rubbing, I'm more worried about buzzes rattles and thunks. And if it's very close, when the motor torques and/or frame twists, it's going to hit. Over time as the (now new) motor mounts give way, it's going to get worse. And so on. I prefer to have more clearance.

Also, even 1/2 degree of clocking error up top will eliminate more than the gap currently present. I had it "finished" some time back with the lower horizontal positioned as shown above. But due to the problems mentioned here (no space to move lower), and a tiny error in clocking a weld up top, I had only about 1/2" clearance under the AC box, which I judged not enough.

So I cut it on the top horizontal so I could rotate the turbo side down to reclock with the drop down section (lower part of that shown in pics above). In doing so, the lower section dropped with it making the part that dips over the frame rail closer than I would like to the frame rail. Maybe 3/8" of clearance, and again, the motor goes that way when it torques, factor in motor mounts, etc. So, I will need to reclock the lower bend as well. If I could clock the lower counter clockwise (from front) and move a bit to center, that would give plenty of clearance on the frame rail, but put the the topic bar inside the pipe. Of course that could be addressed by making a few more cuts and tweaks to get all the competing pieces shifted as needed, and hope they all wind up where I want them because the margin of error along the whole thing is about 1/8" either way to avoid aforementioned rattles and thunks.

OR I can move that bar toward the transmission, move the lower section over 1/2" or so, and suddenly there is comfortable clearance everywhere (and frankly wouldn't have had to reclock the top either, but that ship has sailed - already cut) with room for break-in and hard use shifting of things.

There are a lot of things that could be done to address, or live with rattles/thunks, but I would rather have the room IF the desired simple modification of the bar is acceptable. Which it seems like the general consensus is that a gusseted offset as described will be just fine. And that makes all this SO much simpler...

 

[K85 Octane]

Can never live with rattles of thunks, nope

 

[dyeager535]

Whats the reason for not dimpling the pipe?

Optically not the nicest, but any testing I've ever seen, even crushing the pipes up near the exhaust ports does nothing to affect power.

 

[1-ton]

So here's an engineering point of view.
That bar in tension does more than brace front to back, being a straight shot ant twist will tend to stretch it longer so it also helps with torsional resistance.
As long as you keep it attached to the engine/ transmission combo you are still in good shape, just don't attach it to the frame or body.
As for needed or not, I have run a few without, but not the aluminum cases.
I know it's a pain but you are building for reliability, put something in

I agree with your assessment. You should know because you sold me one of those t-case brace brackets that I run on my crew cab. If you do not have one of those t-case brace brackets on an automatic (i.e. T400 /4L80E ) trans then the rear of the transmission case will break. If you do not have that t-case brace bracket on a SM465 then the t-case adapter will break. If all your driving is in 2-Hi then you do not need the t-case brace bracket at all. I have all my brace brackets on my crew cab...the ones that go from the motor mounts to the bell housing inspection cover, and the one that goes from the t-case to the bell housing.

 

[imiceman44]

I agree with your assessment. You should know because you sold me one of those t-case brace brackets that I run on my crew cab. If you do not have one of those t-case brace brackets on an automatic (i.e. T400 /4L80E ) trans then the rear of the transmission case will break. If you do not have that t-case brace bracket on a SM465 then the t-case adapter will break. If all your driving is in 2-Hi then you do not need the t-case brace bracket at all. I have all my brace brackets on my crew cab...the ones that go from the motor mounts to the bell housing inspection cover, and the one that goes from the t-case to the bell housing.

I have different plans for my cases.

 

[kennyw]

My thought would be to modify the engine mount side to change the overall angle slightly after bending the t case mounting point slightly. Bending the rod in the middle will not allow the piece to work under load as it will just bend back under tension. Even with gusseting it will bend at the end if the gusset.

 

[yblow]

Why not just make something like this ebay item#181313570548 tube bushings with a bracket from were your bar mounts on TC to the frame. You might have to move you exhaust a little, either way your modifying your exhaust. If your real hell bent you can install some mad dawg fender well headers and have all that space wide open on the frame.

 

[sweetk30]

like said before going from t-case to frame tends to break the adapter or trains tail area with drive line and frame flex combined . @yblow thats why gm went away from the frame bracket and to the bar setup .