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ZF + TRex = Drive Line problems

stevenson44

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May 17, 2010
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I am seeking guidance from those who may have been in a situation like this. Lots to unpack here:

77 Bronco on a 74 Frame
302 + ZF + Dana 20
AA adaptor and BC Broncos Plate-style Cross Member
JB Fab twin sticks
Duff's TRex arms + 7degree C bushings

Front driveshaft hits the cross member on mockup. BC Tech says that the double cardan adds almost 4”which should clear the cross member by .25”.

Looks like the 7degree C bushings in concert with the built in caster from the TRex arms have given me a ton of caster. I do not yet have the custom front driveshaft, but I'm pretty certain that it will not clear.

Any thoughts or recommendations?
29253d5c13f71db613392db46b824568.jpg

85dbacd0ec57f18fb683f9cf52a91165.jpg

41125a7754d3673a2685315be192866a.jpg



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Timmy390

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I THINK I've read about "clocking" the D20 up one set of holes to get more clearance with the BC cross member. But that was with the old style CM.

Can you grind on it and it clear or is it a HARD it on the CM?

That plate style looks very nice.

Tim
 
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stevenson44

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Thanks Timmy,

Agreed, the plate looks great. I need more clearance than grinding on it.

I may be able to clock the TC up one set of holes, not sure what that does to the Twin Sticks.


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Timmy390

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Thanks Timmy,

Agreed, the plate looks great. I need more clearance than grinding on it.

I may be able to clock the TC up one set of holes, not sure what that does to the Twin Sticks.


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I think the bracket on the twins needs to be modified when clocking the D20 up one set of holes. I know that JB Fab now has a specific set of twins listed for the ZF/M5ODR2 install.

I assumed it was due to the D20 needing to be clocked up

Someone posted the needed modification on the twins. I can't remember whom......

Tim
 

Slednut10

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Even with the tube style crossmember, I had to clock my j-shift d20 up one set of holes. I also had to modify the twin stick bracket by welding a nut on top of the bracket right above the original tapped hole to compensate for the height change of the transfer case.
 

Timmy390

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I don't see that plate cross member for the ZF listed on BC.

Is that the one for the 6 speed?

Tim
 

TN1776

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I went through something similar recently with my ZF swap. In my case the problem is more pronounced as I also installed an Atlas transfer case which hangs a little lower than the D20. BC's suggestion was that I clock the Atlas up higher, but I cannot do that since I have the old school "CAGE" radius arms (most similar to the Duff extended arms). So I had to cut and modify that beautiful crossmember, by cutting a section of 5" iron pipe in half, welding it to the bottom of the crossmember, then cutting a section out of the crossmember above the newly welded in pipe section. Not the worst process to go through, but I accepted it as a product of my specific combination of goods, and I don't blame BC for the fit problems in the slightest.
You can easily do something similar (and much less pronounced) to clear your driveshaft on that crossmember, if it comes to that. you need a lot less clearance than what I did.
 
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stevenson44

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Even with the tube style crossmember, I had to clock my j-shift d20 up one set of holes. I also had to modify the twin stick bracket by welding a nut on top of the bracket right above the original tapped hole to compensate for the height change of the transfer case.


Understood, thank you slednut


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stevenson44

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I don't see that plate cross member for the ZF listed on BC.

Is that the one for the 6 speed?

Tim


Timmy,

I believe this plate cross member is the newest version for the zf5.
I'm going to follow up


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stevenson44

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I went through something similar recently with my ZF swap. In my case the problem is more pronounced as I also installed an Atlas transfer case which hangs a little lower than the D20. BC's suggestion was that I clock the Atlas up higher, but I cannot do that since I have the old school "CAGE" radius arms (most similar to the Duff extended arms). So I had to cut and modify that beautiful crossmember, by cutting a section of 5" iron pipe in half, welding it to the bottom of the crossmember, then cutting a section out of the crossmember above the newly welded in pipe section. Not the worst process to go through, but I accepted it as a product of my specific combination of goods, and I don't blame BC for the fit problems in the slightest.
You can easily do something similar (and much less pronounced) to clear your driveshaft on that crossmember, if it comes to that. you need a lot less clearance than what I did.


Thank you TN. Did you consider moving the cross member toward the rear of the vehicle a few inches? I was thinking about using the 2 rear existing cross member holes in the frame and drilling/tapping 2 more (per side)


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DirtDonk

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Hard to see all the details from my phone, but would it help if you were able to turn the crossmember around literally flip it 180 so that the plate part is much closer to the transfer case and CV section? And maybe even move it further back with some new holes in the frame.

In factory form the crossmember is literally right up against the transfer case. this new set up with the longer transmission obviously puts things back farther away from the original holes in the frame, but couldn't you just make new holes for the crossmember to move closer? It looks like the crossmember itself is made to work in potentially multiple locations and positions.
I think I see some stuff you've plumbed in there up on the frame, but it might have to be moved to give you the best chances of success.
 

DirtDonk

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Ahh, brilliant minds, as they say…
I missed your comment before I hit send.
 

Madgyver

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I'd cut and reweld the crossmember. maybe flip the drivers side. lots of room to work with. and make room for exhaust route. That's just me.
Curious to see your resolve.
 
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stevenson44

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Ahh, brilliant minds, as they sayÂ…
I missed your comment before I hit send.


DirtDonk, you are the man sir.

How do you feel about tapping new holes in the frame vs putting a sleeve in there?


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jmhend

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Dec 25, 2007
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I am seeking guidance from those who may have been in a situation like this. Lots to unpack here:

77 Bronco on a 74 Frame
302 + ZF + Dana 20
AA adaptor and BC Broncos Plate-style Cross Member
JB Fab twin sticks
Duff's TRex arms + 7degree C bushings

Front driveshaft hits the cross member on mockup. BC Tech says that the double cardan adds almost 4”which should clear the cross member by .25”.

Looks like the 7degree C bushings in concert with the built in caster from the TRex arms have given me a ton of caster. I do not yet have the custom front driveshaft, but I'm pretty certain that it will not clear.

Any thoughts or recommendations?
29253d5c13f71db613392db46b824568.jpg

85dbacd0ec57f18fb683f9cf52a91165.jpg

41125a7754d3673a2685315be192866a.jpg



Sent from my iPad using Tapatalk


Silly question.... it appears that you could move the transmission crossmember back about 2" (I see you have already drilled the frame) can you disconnect it from the frame and adjust the crossmember to the other holes then test your clearance? It may not be 100% but I would suspect it gets you closer.

Just a thought.
 

rguest3

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I agree with the last comment.

I have not done the ZF transmission conversion, but the Crossmember looks to be really far forward to me. Is this correct for this transmission? It looks like you have plenty of room to move the Crossmember back and use the forward holes to mount transmission.

Just about any other conversion (4R70W, 6R80, AX-15) I have done the Dana 20 is much closer if not almost touching the Crossmember.
 

bigmuddy

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Dec 28, 2004
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6,447
Maybe I am missing something but it looks like there is a lip turned down on the engine side? although I guess it adds rigidity, IMO it seems like a bad design as that lip would catch on rocks, sticks whatever.
 
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stevenson44

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All of your comments regarding the crossmember are spot on.
The website (and this forum) shows a few variations throughout the years. I was surprised and excited when this plate version showed up, it is beefy and good looking. I do wonder tho, if it is the correct application.

BC indicated that the lip does in fact face the front of the truck. I think that moving it back 4” combined with the double cardan drive shaft will give me enough clearance.

Advice on tapping the frame vs bolt through?

Thank you.


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Apogee

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...Advice on tapping the frame vs bolt through?

I would weld a tapped sleeve into the frame, that way I could plug weld the outside and leave it flush on the outside with no apparent "extra" holes. Functionally it doesn't really matter though if you run a smooth sleeve and run a bolt and nut instead.

The wall thickness of the frame itself isn't thick enough to sustain enough threads to handle any significant levels of torque without pulling out, so unless you're using #10 or 1/4" fasteners, I wouldn't go there.

Tobin
 

DirtDonk

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Agree. I've drilled and tapped the frame for other things, even to including the factory style transfer case skid plate. But I would not do it for the trans crossmember.
I've even landed hard on the skid plate with no apparent weakening of the bolt/frame interface. But with continued torque loads over time, and a constant heavy weight on them at the same time, as said it's just not enough thread engagement for my liking.

Are there any access holes nearby? Something you could use to put a "handle-nut" in there? That's a nut with a long rod or handle welded to it that allows you to feed it inside the frame.
But I prefer a "nut plate" instead. Or rather that sleeve just mentioned.

Can you give more details about the installation of said sleeve Apogee? You're talking about drilling larger holes (to allow the thick-walled sleeve to be inserted into the frame?) and then welding the inserted sleeve in place?

I know we've talked about it in the past, but what did Ford use at that point? I just had mine off a few months ago and did not look.

Paul
 
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