DIY: Weld-in transmission cross-member and transfer case skid

[B00mb00m]

The main reason that I wanted a separate transmission support cross-member from my transfer case skid is so I can pull my driveshaft without supporting the drive train. While I was adding a cross-member I knew I had to strengthen the skid. I have been bending my current skid (3/16 steel) every time I wheel at my local ORV area. I did what everyone should do in this situation... I talked to the Wizard.

The reason why I wanted to DIY this instead of purchase the Savvy kit or Genright X-member+skid combo was three-fold.

1. First, given my experience with the UCF skid I was currently running, the holes on these frames are not accurate and require slots in the skids and I even had to open the slots an addition 1/2" with a dremel tool. I also wanted the new skid to for sure work with my UCF engine skid. The beauty of DIY is you can build it perfect, don't have to accomodate anyone's tolerances except that of yourself. Of course it also means you can f**k it up all on your own also.
2. Secondly, i had recently got some JL control arms for free and I wanted to try to hack one up and make a cross-member on the cheap. At some point, I think this happens to a lot of people, you start enjoying the process more than the result. I like building somewhat, i mean I'd like it more if I was better at the fabrication processes, but I really like designing.
3. Finally, I had yet to draw up any parst on my jeep in CAD. I use 3D modeling software at work most days of my life. I thought it was kind of odd I hadn't drawn up anything or really designed any parts besides like on-the-fly brackets and what not. This is the first of three things I wanted to design with bent up aluminum plate. So i used this opportunity to find a local fabricator I could work with to bend stuff for me.

Things you should probably do first:

1. SYE / Body Lift / Motor mount lift. This will give you the clearance to pick your drivetrain up so you can get the cross-member as high as possible.
2. With a body lift you can now move your fuel lines and rear brake line on top of the driver side frame rail. I think this is well-documented in Savvy Midarm installation, but if any one has questions I can show how I did it also. You must move your lines in some manner so you can weld the tabs to hold the cross-member on your driver side frame rail.
3. *Maybe the rubicrawler for those 42RLE folks. I do want to add the rubicrawer in future. That part does replace the part you currently mount to. I'm hoping it's the same, but it would be smart to do the rubicrawler before you build a mount for that bolt-pattern. ya'll know me, tho, I LOVE doing things 3 times.

Supplies you need:

1. qty 2 Bushings - these provide vibration isolation between your drivetrain and your frame.
   1. I did buy a set of 1.75" Bushing Assembly (BA175) from Autofab.
   2. I chose to use JL control arm bushings as they felt more compliant.
2. QTY 4 - Tabs - make your own or purchase. I bought low hanging tabs from Autofab.
   1. Bushing Tab - T106
3. Cross-member telescoping steel tube:
   1. ~14" of 1.5" OD x .120" wall DOM (no weld inside)
   2. ~3' of 1.0 X .120" HREW or DOM.
   3. Maybe 1.5" holesaw for mount.
   4. Pipemaster 1.25" od coping tool. I used this style tool on my coilover hoops and its awesome! It made the compound angle cope easy (though I still messed it up). I got mine from Summitracing PFR-P-T125
4. Some sort of skid.

Prep Work:
- Take measurements of your current setup. I recorded front drive shaft angle, transmission pan height, skid to floor height, and rear driveline angle. This will help you with a place to start or return to the old setup if you end up moving things around. Also reach on top of the transmission near the bell housing and find out where your closest point of contact is. This will be your limiting factor of how far up you can move the drivetrain (if you so desire).
- Support drivetrain. I used a floor jack and a piece of 2x6 under the transmission pan as close to the existing skid as possible. I also kept a back up jack stand under the end of transfer case when i was working under neath.
-Remove nuts attaching transmission mount to the transfer case skid.
- Drop skid.

Now you should have a view like this:

That giant can on the passenger side frame rail is going to be a problem. Temporarily remove it from this volume so you can mock up and install the cross-member.

Get a rough measurement here with how far up you can push the 1.5" tube and not contact transmission or transfer case.

Then get a measurement of how far out you will want to mount the tube center considering the item you need to avoid is the driveshaft at full droop. If you mount the tube center under the front UJ yoke, it's very unlikely you will have contact (if you leave the cross-member straight). Those of you with bent ends on the tubes (Genright esque) will have to position that respectively. Its in the 3.5-4 ballpark, and I chose 3.75" approximately.

Now that you have an idea of where things need to be it's time to start the creative process (the fun part).

 

[B00mb00m]

This post will describe mount and cross-member design and build considerations.

General process is this:

1. Mount tube under UJ as close to transmission / transfer case as possible.
2. Mount bushings and tabs flush with bottom of frame.
3. Mount tube to bottom of bushing.

This cross-member is similar to the TMR or Genright kit they all use a center tube with telescoping pieces out to the bushing mounts. First step is find out where you want to place the center tube. I chose a center tube of approximately 14" as it's what I had on-hand and it didn't interfere with anything. The fundamental part is you mount a larger tube in center slide in the wings in order to allow you to perfectly nail the span measurement frame to frame and mount to your bushings.

I used 1.50"x.120 wall DOM as my center tube. Now figure out how to mount it to the transmission. You can build your own plate mount and transfer the transmission bolt pattern over or you can attach your tube to the OEM mount. I chose to re-use the OEM mount. I cut off the bottom portion that mounts to the rubber isolator but you could probably keep this and cut the bolts off also. From previous step I knew I wanted to space the tube off 3.75" from the face of the OEM mount so that it was under the UJ yoke. I created two stand-offs by cutting the C's off a piece of square tubing.

I tacked the stand-offs in to see how it met my two goals. Is it as close as possible to the transfer case? Will it clear the UJ? I had to cut off and move slightly but after one "tack and cycle" it was dialed.

There are two methods you can follow for this next part. The frame rails are not parallel, so you can either mount the bushings to the end of the telescoping tube and adjust your frame tabs or you can mount the bushing square to the frame rail and notch your tube at an angle. Since I bought pre-fabbed tabs and i have the pipemaster i decided to mount the bushing square to the frame and angle cope the tube to match.

I'll give a brief example of how to harvest JK or JL bushings as these control arms are all over craigslist right now. It's as easy as cut the rectangular tube off the round bushing housing and grind the tube off, now you can use the housing for mockup. WHen you're ready for complete weld you can press the bushing out, weld and press the bushing back in.

With the mount fastened to the transmission I moved to placing the bushings on the frame. This is another bit of iteration. Ideally the bottom of the bushing is at the bottom of the frame rail. Remember the goal is to get the drivetrain as low as possible for tub clearance and UJ health and as high as possible for ground clearance. For ground clearance reasons I set flush with bottom of frame rail as the tab / bushing position. THen I adjusted the drivetrain height until i had ~ .25" clearance to the tub measured by trying to jam a finger between the bell housing and the tub. I erred on the side of caution here because i really did not want rattling and clanking between transmission and body. I had already clearanced in this area with the socket method at the time of my initial belly-up. It became apparent I couldn't get the tube flush with bottom of frame or risk making contact to the tub. So i went as high as I could then brought the bushing down so bottom of bushing was just higher than bottom of tube ~.125".

In pic below you can see how I use the pipemaster to set the cope to the tube. Once the cope was set, I pulled the mount notched the tube and repeated for the other side.

After the side is coped, I setup the bushing bolted to the tabs and tacked them in.

Note on coping with an angle grinder. Note how shitty this cope is dont do that. I did a lot better on the second one. This first cope I tried to cut on the scribed line with the cut-off wheel on my angle grinder. That sucked. On the second one I only roughed it in being sure to leave plenty of material next to line then used the grinder pad to approach the line and this worked a LOT better. So i had to fill in these gaps with weld.

When the fitment seemed good I pulled the center section for complete welding of the center only.

I complete welded tabs to the frame then reassembled on the jeep, bolted bushings down, bolted center section down put heavy tacks on the cope to the tube and between the sliding tubes. Pulled the assembly out, pressed the bushings out and complete welded.
I added a gusset on top of the tube to hold the bushing in place since i had to fill some gaps and i was pretty certain it pull out of place during welding.

I had to pry the bottoms of the tabs back out with a crescent wrench and hammer the assembly back in. I assembled both bolts in bushings then tightened up the transmission bolts.

For the exhaust, I picked up two straight sections from NAPA and cut and re-welded the exhaust hanger on the cross-member. Don't do what i did, i have to slide the whole back half of the exhaust off (two hangers) remove it from the hanger. I should've bolted the hanger onto the cross-member. When I do my rear midarm I will cut the tacks on the hanger and make it bolt-on.

You could really tune things in nicely if you had a tube bender or bought the tubes from Genright.

 

[B00mb00m]

This post will describe skid design and build considerations.

This method requies a fabricator for hire to bend the plate, as the size and strength is above that of normal hobby press brakes (3' of 6061-T651).

Material: 6061-T6.... In talking with the Wizard, this heat treat / alloy is critical for an aluminum skid. All three benders i talked to said, "nope can't bend 6061, it'll crack, use 5052." The problem is 5052 is good for bending... and hence it will tend to bend when you smack it with large pointy rocks on the bottom of your jeep. I literally showed them pictures of Blaine's plate with the heat treat markings visible. With the bender I ended up choosing, once i pushed back and said no i do need 6061 he changed his tune and said it shouldn't be a problem as the amount of bend here is very slight.

Thickness: Savvy skid plate is 1/4" 6061 and has substantial bracing from what I've seen. Genright sells 5/16 plate and I believe it's 5052 and they use their own bracing. My experience in the matter is only with 3/16 steel from UCF and it bends where it gets hit, so I definitely needed an increase in strength there against localized bending. Consultation with Blaine yielded a suggestion to use 3/8" as he does and to also include a rear brace. This was another reason to do a DIY skid, to upsize it over standard offerings. Genright sells the 5/16-5052 skid for $650 (!!) and I've copied their own stock image below, they appear to show a bend right in the middle of the skid under the body mount. See Genright copied photo below:

Dimensions:
Measure twice, maybe build a mockup because getting a single part bent up for $550 based on really not well validated dimensions can be a gamble. Confidence will be better if the skid is ordered after the xmember is built. Here are the critical dimensions, and make sure these dimension are taken with drivetrain at desired height (if you're measuring before building xmember). I took these measurements when my old UCF skid was installed:

1. Frame Rail to Trans Pan Depth, or measure only to the bottom of the T-Case or mount, whatever the low hanging part is. Note how the engine skid will mate to this skid. IF the new TC skid is above the bottom of the engine skid washers will be needed to space the engine skid down:
   
   
   
   
   
2. Trans Pan width or Engine skid width to determine width of flat section:
   
   
   
   
   
3. Frame rail width at front of skid, this determines where the start of the flat section must be:

If the jeep and laws of physics force the xmember to sit below the frame rail then a spacer will be needed to space the skid down from the frame rail. I did this with 0.5" thick x 2" wide 6061 flat bar. The amount of spacer should be considered when setting the dimensions of the trans pan. It can be subracted from Dimension 1.

FYI: If you err on the side of too little depth in the TC skid you can always space it down from the frame rail to get you there. If you err on the side of too much depth in the TC skid then you really have no option to change it.

The above dimensions can be used to create flat pattern dimensions, if you have CAD software, or send the final shape dimension so the bender and he calculate what is needed on the flat pattern. I adjusted the overall dimensions to get nice round numbers for the bend centerlines on the flat pattern. I provided ±.125" on the offset depth, which the bender had no problem with. So include whatever tolerance the bender needs in the minimum dimension considerations. I didn't put tolerances on any of the other numbers as I deferred to the process, and i didn't think they really mattered. This was NOT an engineering drawing it was basically a rough set of dimensions for the bender to try to hit as close as possible and i would make it work afterwards.

Bolt Pattern: Do not include bolt holes in your skid procurement and leave the outer edges untrimmed so you have as much flexibility in placement as possible. Probably the trickiest part of the whole skid build is getting the bolt drilled. Especially if you want to countersunk bolts, which I do because man bolt heads hanging down from this otherwise beautiful smooth skid setup is like a wart on the nose of a supermodel.

This would be slightly different process if you didn't have the spacer blocks. Get one side of the skid clamped into place on the frame. I started by clamping driver side in two places.

Then let the other side (passenger side) hang down slightly. Apply modeling clay (I raided my 5 year olds art supplies) size of quarter to the area where the bolt hole will be. Cut up a sandwich baggy and place it on top of the clay so it doesn't stick to the frame.

Clamp up this side tightly, and the clay will extrude through the bolt hole. Before removing the spacer, scribe the location exactly where it needs to be when the bolt holes are drilled.

Now as a bonus if using a little extra clay it will be almost like that three boobied alien in Total Recall. Center punch the center of the clay nipple. Remove the clay. Clamp the spacer onto the skid exactly where it was based on the scribe lines and drill 1/8" pilot hole. Now there are pilot holes in both parts. Separate and drill.

Repeat for other side.
OPTIONAL but extra credit is countersinking skid for flat head (allen) bolts. I hit the top of my bolts many time wheeling and TBH it scares me to put in allen heads here because of the stripping out risk but I'm doing it all for the smoothness (say that in your best Limp Bizkit voice). You know what to do with that cookie.

Here are the transfer case skid flathead bolts. These are on sale right now and very hard to find locally, 60mm plated M12-1.75 pitch. https://www.grainger.com/mobile/product/METRIC-BLUE-Flat-5YMV4?fc=MWP2IDP2PCP

Use a countersink with 90 deg tip for metric bolts. This is the CS I used. It it creates aluminum shavings instead of a spiral which makes a terrible mess. Maybe consider Less flutes.
https://www.grainger.com/mobile/product/3ZXD2
Skid Trimming:
With all the holes drilled fit the skid and spacers back onto frame. Scribe lines onto the skid along the outer frame rails. Remove the skid and cut the scribe lines with a circular saw using metal cutting blade. My Milwaukee 7.25" circ saw easily hogged through the 3/8" plate. Due to where I placed my skid in the fore-aft direction and due to my offset, I had to cut a little out of the front to clear the transmission pan.

Rear Skid Brace:
Finally, the skid brace. I believe the necessity of a brace with 3/8 is probably relative to how hard you plan on using it. I do plan on using it on the rocks. Blaine described his method to me and it's pretty dang slick way to fab a brace with minimal fitting work. The gussets are from 1"x3"x.120. Quantity is up to the user, 7 seemed about right, 3 in center, 1 on each slope, one on each top. I used a mitering metal chop saw to cut triangle U's with 1" base such that the tube yields 2 gussets per inch of length. Drill a bolt clearance hole in the center of the 1x1 face on the bottom. The vertical web will be handled by a profiled piece of 1/4 flat bar. Height is up to what you can fit. exhaust and UJ limited me to 3" total bar height. Place the flat bar along the end of the skid and trace the profile onto the flat bar. Cut along the line. Clamp the bar to skid, place the gussets at logical locations and tack them to the bar. Clamping the bar to a square tube will help keep it in line and square to the skid during tacking. Remove bar, complete weld then use the gussets as drill guides to transfer holes to the skid. A flange was added after the hole pattern was tacked to increase stiffness of the stiffener and keep it from twisting under load. This is another optional feature, but there is substantial increase in stiffness with the slight addition of weight of the 1.25x3/16 steel bar.

 

[B00mb00m]

Here's the final product. All smooth and ready to see some rocks! This was such a fun project. I'm pretty busy these days, as I'm sure you all are. What i loved about this project is I could break it into sections (xmember, skid and stiffener) and I could drive the jeep in between. Overall it was about 2 days work for the xmember, and 1 day each for skid and stiffener.

I had plans to be more organized in the write-up but it's a ton of information to get down. Lots of figuring on the job too, seeing what fits where. Hope this helps someone tackle this project. If anyone has questions or suggestions let me know. Id like to give a shout out to the Wizard of jeeps for his tutelage in this project. Thank you so much for the help.

 

[B00mb00m]

Also, I washed the jeep today. Do yourself a favor and clean the mud BEFORE you start working underneath. I can't count the amount of times I had dirt fall on my face. Here's a side profile showing how smooth that skid is.

 

[Bofa-Deez]

Bravo sir!

I build allot of my own stuff, and you are correct in saying that we enjoy the process more than the result. It's not really saving money, unless you overlook not being compensated for your time, but then again, I would just be wasting that time anyway. Besides, I often find myself with a whole lotta time, and little extra cash.

Your build was very well thought out and it shows in the resulting product.

 

[B00mb00m]

Bravo sir!

I build allot of my own stuff, and you are correct in saying that we enjoy the process more than the result. It's not really saving money, unless you overlook not being compensated for your time, but then again, I would just be wasting that time anyway. Besides, I often find myself with a whole lotta time, and little extra cash.

Your build was very well thought out and it shows in the resulting product.

I agree. I think what i like best about the DIY is you get to make it perfect for your setup. In these TJ/LJ situations where you have a 20 ish year old vehicle with a mismatch of wear and tear and aftermarket products it's about impossible for a manufacturer to make things perfect for bolting up and going. That's why i bought just midarm brackets and made my own links. Turns out i probably could've made the savvy arms work but getting everything setup then doing a CTL for control arms, lets me get it perfectly set.

 

[zebra12]

Really well done. Thanks for posting.

 

[Brianj5600]

Nice write up and results.

 

[B00mb00m]

Thanks for the kind words. As an update, the skid has worked really well for me, it gets worked and slides great, so much more functional than the old one.

One thing I had to change was notching the brace when I did the rear midarm exhaust. So keep that in mind if you're doing midarm in future.

 

[hosejockey61]

Very good write up!

How have the JK bushings held up so far? It's been on my list for a long while now and my plan also included using JK CA bushing mounts. I was going to just buy the TMR version but don't want poly bushings. How would you rate the NVH since installing the crossmember?

 

[B00mb00m]

NVH with the jk bushings has been no worries, not very noticeable. I do have a clunk upon acceleration right now that I haven't solved it might be then mount bumping into skid as I have like 1/16 clearance right now.

 

[B00mb00m]

Update: I remade the crossmember to clear the atlas. Couple things to keep in mind. The first time I built the crossmember I forget to include the sag due to weight on the bushings. So this time I went up an extra 1/4 to have plenty of clearance.

Second when I redid it I kept the bushings square to the tube and made uneven tabs to accomdate for the frame angle. I made the first "short" tab clamped it to the bushing and tacked the tab to the frame. Next made a 1/2" longer tab held it in place and ran 1/2" center punch through to mark the bolt location. Drilled then clamped up the other tab and welded it all complete on the outside edges only. This makes installation and removal much easier as tabs don't squeeze the bushing. This was a much better method than previous.

 

[Ephry73]

Also, I washed the jeep today. Do yourself a favor and clean the mud BEFORE you start working underneath. I can't count the amount of times I had dirt fall on my face. Here's a side profile showing how smooth that skid is.

View attachment 158829

Definitely enjoying the progression of this rig! Color is also one of my favorite ones on a jeep. The wheels are sweet as well. Thank you for sharing

 

[B00mb00m]

Definitely enjoying the progression of this rig! Color is also one of my favorite ones on a jeep. The wheels are sweet as well. Thank you for sharing

Thank you sir. Cross member is in the paint "booth" as we speak. This time I made the exhaust hanger removable and not welded in place like the dingus move I did last time.

 

[Ephry73]

Thank you sir. Cross member is in the paint "booth" as we speak. This time I made the exhaust hanger removable and not welded in place like the dingus move I did last time.

View attachment 222597

Dig it. Definitely digging those wheels

 

[sierradmax]

Very Nice. Always better the 2nd time around. I followed similar suit. I've contemplated installing a "slotted" plate to support the front output but not sure if there's enough hp or torque to warrant the need.

 

[B00mb00m]

Very Nice. Always better the 2nd time around. I followed similar suit. I've contemplated installing a "slotted" plate to support the front output but not sure if there's enough hp or torque to warrant the need.

View attachment 222795

I haven't heard of anyone needing to add a support, at least for 4.0 usage. What motor are you running? How deep did you go on atlas ratio?

Feel free to include any tips based on your build also. Maybe include some pics of your mounts. Do you have a bender or did you buy bent ends? What bushings did you use?

 

[sierradmax]

Stock 4.0, for now. I went 5:1 with the Atlas and am very pleased with a 109:1 ratio in 1st, and a 64:1 in 2nd. No bender. I cut a relief in the DOM, applied a bit of heat and bent by hand. Welded the relief back up to get the needed 1" offset. I chopped up my factory trans mount and exhaust hanger to re-use. For bushings, I took Blaine's advice a while back and bought four Autofab bushing tabs and two of their 1.75" bushing assemblies.

https://autofab.com/i-10268874-bushing-tab-t103.htmlhttps://autofab.com/i-9903086-1-75-bushing-assembly.html

 

[B00mb00m]

Stock 4.0, for now. I went 5:1 with the Atlas and am very pleased with a 109:1 ratio in 1st, and a 64:1 in 2nd. No bender. I cut a relief in the DOM, applied a bit of heat and bent by hand. Welded the relief back up to get the needed 1" offset. I chopped up my factory trans mount and exhaust hanger to re-use. For bushings, I took Blaine's advice a while back and bought four Autofab bushing tabs and two of their 1.75" bushing assemblies.

https://autofab.com/i-10268874-bushing-tab-t103.htmlhttps://autofab.com/i-9903086-1-75-bushing-assembly.html

Ah nice, so you cut a pie wedge out and bent and rewelded. I was thinking that if i couldn't get the straight one to work i would have to do that.