Tranny cross member engineering (1 Viewer)

[Cammy]

Also posted in 40's tech with no real replies
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So I'm building a tranny cross member to take advantage of the AA tranny/t-case casting for a mount. I'm using 1x1.5x.125 rectangle tubing 31 inches long for the cross member. I want to plate the ends of the cross memeber to create a bolt on piece so what thickness would be best?
I have some .125 plate that I can use or should I consider using 0.375 thickness to counteract the lateral movement? I can gusset the .125 plate to add strength but don't want to do a lot of work only to have it fail.
Is .125 tubing strong enough to handle the load? My thoughts are that the motor mounts carry the engine weight and the rear crossmember shares a small portion of this weight plus the weight of the tranny and t-case. Any idea what the weight distribution is between the motor mounts and rear tranny mount?

 

[bustanutley]

I would suggest going to 1/4.

here is what mine looked like, also note that the square tube I used was 11GA (I think, may have been 16 GA) and it bent should have taken the time to get a bigger piece, oh well

 

[dustin]

mine is similar, but alot simpler. 1.5 x1.5x.25. I drilled holes on the outter mounts and welded nuts in the tube to make it easier to install. Similar rear t-case mount as the one above. No plasma though, so mine is more of an octagon.

-Dustin

 

[bustanutley]

no plasma for mine either

 

[Cammy]

Do either of you have concerns about cracking the t-case with that mount design? Something about hanging that much weight on aluminum worries me. Thats why I went for the under the tranny design.
My current design uses the Advanced Adapters mount in the adapter casting. The only concern I have is that the 1x1.5 tubing is below the frame rail (rock finder). I have considered modifying the stock skid plate with some type of slider to protect it but have not decided yet.

 

[bustanutley]

I'm not concerned with breaking the case from weight so much as rocks doing the deed AA has made there mount like this for years, however their design does not really allow proper pivoting of the engine assembly, this has caused the tranny and t-case interface to loosen up. I haven’t had any problems as of yet.

By all means if you have a means to mount under the tranny do it. This was not an option for my configuration.

 

[Toyland4x4]

I have the NV4500 and had the problem of them loosening up like you said when using the rear mount AA mount. So I had a 1/4" plate heavy duty skid plate bent up at the local metal place and used a GM auto tranny mount right on the skid plate ala j&#p style. It has not loosened up again and works really well. I counter sunk the mounting holes so the bottom of the skid plate is flat and smooth.

 

[Full_M3tal]

My T-case Crossmember Is 1 1/2" x 1" x 3/8, Motor Mounts Are Made Out Of 2" x 2" x 3/8, And Weld On Brackets I Made From 3 1/2" x 3 1/2" x 1/4" Sqaure tubing, There All Made Just Not Mounted... Need To Get My Engine Away From The Back Corner And Get It Mounted... Been Waiting To Do It Fo A Month Now.... If You Want I Can Post Some Pics Later On This Week...

 

[Full_M3tal]

Oh... I Aslo Plan On Useing A Bushing System For Easy Removal For T-Case Cross Member, It Will Look Similar To A Link Arm....

 

[Isotel]

This is my Xmember, i dont know if this helps.. Everything is 1/4" (Overkill is a good thing), The Bushings came from Mad 4wd, a Vendor on Pirate4x4.com.. I love how it came out, and so far i have removed it, and reinstalled 2 or 3 times during my build, and it Fits better than some factory x-members

 

[Cammy]

Very nice piece isotel. do you have a shot that shows the mounts in relation to the frame rail and also the t-case nose?

 

[VETTE60]

mine looks similar to isotel's and it is very easy to deal with because of the design of using tube with bushings on the outside. it was a bit difficult to get the angles exact but it worked out well.

 

[TLCObsession]

It depends on your drivetrain. I think the key element is that the mount should allow the same amount of movement as is present in the other drivetrain mounts. Too ridgid and something will crack.

 

[Cammy]

If you look at isotels pics you can see the mount pad on the AA casting just behind his crossmember. That is what I and mounting to on my rig. I wish I cound get as high as isotel on the frame but cannot at this time. I am 1 inch below the fram with my current setup and will let it fly for now. Looking hard at an isotel setup for the next iteration.

 

[BiffS]

mine is made from 3" X 1/4 wall hitch tube with the last 6" where the bolts go thru the frame having additional 1/4" plate welded inside for a 1/2" stress point. Factory tranny mount from V6 t case has been sunken into the center to keep a low profile. All work done with a drill and 4 1/2" grinder.

 

[orangefj45]

i like isotel's design as well. i'm more confident in a bottom mount than a rear mount setup. the rear mounts allow for more twist and oftentimes end up leaking. the bottom mounts support the weight much better and evenly, and bviously they have no chance of leakage or putting undue stress on the t-case itself.
we're doing a conversion on a 77 fj40 right now and should have the trans mount/skid plate done later this week. i'll post some pics when it's finished.

 

[Isotel]

Very nice piece isotel. do you have a shot that shows the mounts in relation to the frame rail and also the t-case nose?

the top photo on the above post is of the framerail mount,

T-case nose, well its a way different setup than a cruiser case, because i am running a Clocked Dana 300 behind a 700r4, you may need to get creative while dealing with a stock t-case.. mine was straight and simple..

 

[Cammy]

Isotel, after looking at your pics again I saw you t-case was something other than a stocker.

My 1"x1.5"x.125 piece turned out o.k. but shows some sag in the middle. I ordered some 1.5x1.5x.25 tubing that should be here by Friday. I hope Isotel doesn't mind being copied.

 

[Cammy]

I picked up the tubing to start my new cross member. Rather than 1/4 wall I ended up with 3/16 wall 1.5x1.5. I picked up a set of 4 polyurethene bushings from a local parts place for $10.00. Once I had the bushings in hand I went in search of tubing to put the bushings in. A couple of hours later I end up at a scrap dealer in town where after looking through dozens of scrap piles I scored some 1.5 inch schedule 80 pipe. Total investment for bushings, pipe and a 10"x14"x1/4" plate $19.00. Total materials so far, $37.00.

 

[Cammy]

New crossmember installed

Here's pics of the new cross member I built using Isotels idea and example. Turned out pretty good.