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Advanced Fabrication and Engineering For when your build is going off the charts. Wildly modified vehicles and straight up buggies welcome.

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  #1  
Old April 9th, 2018, 07:47
burntkat burntkat is offline
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Drop-out center transmission crossmember

Folks-

Quick question- I am building a tranny crossmember for my S10. It's 2X6X0.250 rectangular steel tubing, going to go right across the bottom of the frame rails (it just happens to work for my build- need to drop the tranny tailshaft about an inch). I want to be able to still get the transmission out, and I may well build off this for control arms front/rear if I go to links. So I will be gussetting the hell out of it, and plating/boxing the frame in the vicinity with 3/16.

As for the dropout- I figured I'd just borrow a page from a lot of the builds I have seen, and go with flat plate flanges to marry up the three sections (welded-on sections undr the frame, and the dropout). Would 1/4" be sufficient in that application? I will be using 4 1/2" bolts at each side.
__________________
-89 S-10: SAS, D44s front/rear. 5.7L V8. 700R4 with 4L60E upgrades. Built in my driveway.
-90 XJ 4.0, AW4, 231J: Clayton's longarms, RE 5.5" coils, hybrid 6" leaf pack, 33/12.50/15" MTs, Rancho 99012s and 99624s, Tera HD SYE, custom sliders, BW flares. Rehabbing with D44s, RE spring packs, RE 4.5" coils, and ACOS.
-94 ZJ: Budget boost, 31s. The wife's DD.
-97 XJ: Son's DD. 4" lift, ACOS, 4" spring pack, Upcountry coils, 31s
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  #2  
Old April 10th, 2018, 06:36
burntkat burntkat is offline
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Re: Drop-out center transmission crossmember

Kinda answered my own question-

Did some searching, found that while many shops use 3/8 plate, doubled up at the flange so you end up with 3/4" of thickness, 1/4" ought to be fine.

I'll probably up the hardware to 9/16", and Grade 8 goes without saying. Weld the nuts to the back side of the flange (yes I am aware this derates them from Gr8 due to the heat cycle, but still think I will be just fine) and, since it's a critical app, go ahead and safety-wire the heads.

Safety wire will likely be a waste of time- proper torque and threadlock should suffice. But I have the tools and wire laying around, and it's like 30 minutes of effort to drill the bolts and wire them up, compared to hardware dropping out and having a bad day. I had an issue with the transmission mount under my 700R4 shedding hardware twice in the past, so now I safety wire it. In truth I am not sure why it backed out, think it may have been from driveline vibration. I won't have to worry about it anymore, though!
__________________
-89 S-10: SAS, D44s front/rear. 5.7L V8. 700R4 with 4L60E upgrades. Built in my driveway.
-90 XJ 4.0, AW4, 231J: Clayton's longarms, RE 5.5" coils, hybrid 6" leaf pack, 33/12.50/15" MTs, Rancho 99012s and 99624s, Tera HD SYE, custom sliders, BW flares. Rehabbing with D44s, RE spring packs, RE 4.5" coils, and ACOS.
-94 ZJ: Budget boost, 31s. The wife's DD.
-97 XJ: Son's DD. 4" lift, ACOS, 4" spring pack, Upcountry coils, 31s
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  #3  
Old April 10th, 2018, 09:35
1990JEEPXJ's Avatar
1990JEEPXJ 1990JEEPXJ is online now
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Re: Drop-out center transmission crossmember

That’s how I built my crossmember. Welded the ends to the plated inner frame, welded a plate to the exposed ends, and the center is bolted up with (4) 1/2” bolts. My links are attached to the parts welded to the frame so I can remove my crossmember without removing the links


Last edited by 1990JEEPXJ; April 10th, 2018 at 09:40.
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  #4  
Old April 10th, 2018, 12:31
burntkat burntkat is offline
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Re: Drop-out center transmission crossmember

That's exactly how I'm looking to do this. I am seriously considering radius arms- front AND rear.

Yes, a *properly designed* 4-link is MUCH more flexible. No, it won't matter for my use.

Radius arms work, and can work well if attention to detail is paid. This is going on a SAS'd 89 S10 Blazer which presently has leafs front/rear. I am going to go to airbags, for adjustability.
__________________
-89 S-10: SAS, D44s front/rear. 5.7L V8. 700R4 with 4L60E upgrades. Built in my driveway.
-90 XJ 4.0, AW4, 231J: Clayton's longarms, RE 5.5" coils, hybrid 6" leaf pack, 33/12.50/15" MTs, Rancho 99012s and 99624s, Tera HD SYE, custom sliders, BW flares. Rehabbing with D44s, RE spring packs, RE 4.5" coils, and ACOS.
-94 ZJ: Budget boost, 31s. The wife's DD.
-97 XJ: Son's DD. 4" lift, ACOS, 4" spring pack, Upcountry coils, 31s
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  #5  
Old April 11th, 2018, 09:01
burntkat burntkat is offline
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Re: Drop-out center transmission crossmember

As it happened, I was near the steel yard while they were open for a change, so I dropped in and bought some 3/8X2 flat bar. Plan is to come out about 1.5" either side of the 2X6, pop two 9/16" holes centered up. Make 4 of those (2X9X3/8" flange plates), weld them onto the 2X6X1/4" tubing and proceed as above.

Yes, 1/4" would likely work just fine, even for something that the suspension links will attach to. But there's no kill like overkill. Especially when, you know, your arse is on the line.

I will gusset the welded-on portion to the bejesus belt, and the link arms will connect there.

TLDR: I am basically stealing design cues from Clayton offroad's XJ longarm kit (luckily I have one installed on my 90). This is going under an 89 S10 with springover SAS at present, which will eventually get radius arms front/rear, airbags, and an embedded system controller (Raspberry Pi).

Near term, and back on the XJ side of the house, I will build a crossmember more or less identical to the Clayton unit for my son's 97. No, I will not build one for you, nor am I going to be fabbing stuff for sale. This is a learning build for the kid- he's wanting to get into fabrication work as a career.
__________________
-89 S-10: SAS, D44s front/rear. 5.7L V8. 700R4 with 4L60E upgrades. Built in my driveway.
-90 XJ 4.0, AW4, 231J: Clayton's longarms, RE 5.5" coils, hybrid 6" leaf pack, 33/12.50/15" MTs, Rancho 99012s and 99624s, Tera HD SYE, custom sliders, BW flares. Rehabbing with D44s, RE spring packs, RE 4.5" coils, and ACOS.
-94 ZJ: Budget boost, 31s. The wife's DD.
-97 XJ: Son's DD. 4" lift, ACOS, 4" spring pack, Upcountry coils, 31s
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  #6  
Old April 11th, 2018, 09:02
burntkat burntkat is offline
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Re: Drop-out center transmission crossmember

Quote:
Originally Posted by 1990JEEPXJ View Post
That’s how I built my crossmember. Welded the ends to the plated inner frame, welded a plate to the exposed ends, and the center is bolted up with (4) 1/2” bolts. My links are attached to the parts welded to the frame so I can remove my crossmember without removing the links

If you had to change anything on your build, what would it be?

On my 90, when I installed the Clayton kit, I wish I'd installed a frame stiffener set first. I am still going to, but as I have the Clayton bit welded to the unibody, There's no sense in buying a commercially cut kit, I'd have to cut it up anyway.
__________________
-89 S-10: SAS, D44s front/rear. 5.7L V8. 700R4 with 4L60E upgrades. Built in my driveway.
-90 XJ 4.0, AW4, 231J: Clayton's longarms, RE 5.5" coils, hybrid 6" leaf pack, 33/12.50/15" MTs, Rancho 99012s and 99624s, Tera HD SYE, custom sliders, BW flares. Rehabbing with D44s, RE spring packs, RE 4.5" coils, and ACOS.
-94 ZJ: Budget boost, 31s. The wife's DD.
-97 XJ: Son's DD. 4" lift, ACOS, 4" spring pack, Upcountry coils, 31s
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  #7  
Old June 4th, 2018, 12:53
VAhasnoWAVES VAhasnoWAVES is offline
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Re: Drop-out center transmission crossmember

Quote:
Originally Posted by 1990JEEPXJ View Post
That’s how I built my crossmember. Welded the ends to the plated inner frame, welded a plate to the exposed ends, and the center is bolted up with (4) 1/2” bolts. My links are attached to the parts welded to the frame so I can remove my crossmember without removing the links

i built mine much the same.

frame stiffeners went on first. then the crossmember was located with the stock bolts. then the two ends with link mounts were burned on. center section dropped out when needed.

i sumped the trans mount into the crossember to get the crossmember higher. it worked well. if i were to do it again i would put a rather large draft on the pieces that bolt together. i put a couple degrees on the one i built, but after all the welding process it didnt go in/out as easy as i would have liked. add significant draft so the center section drops out easy.









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  #8  
Old June 4th, 2018, 18:42
burntkat burntkat is offline
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Re: Drop-out center transmission crossmember

Whats the hose clamp for?
__________________
-89 S-10: SAS, D44s front/rear. 5.7L V8. 700R4 with 4L60E upgrades. Built in my driveway.
-90 XJ 4.0, AW4, 231J: Clayton's longarms, RE 5.5" coils, hybrid 6" leaf pack, 33/12.50/15" MTs, Rancho 99012s and 99624s, Tera HD SYE, custom sliders, BW flares. Rehabbing with D44s, RE spring packs, RE 4.5" coils, and ACOS.
-94 ZJ: Budget boost, 31s. The wife's DD.
-97 XJ: Son's DD. 4" lift, ACOS, 4" spring pack, Upcountry coils, 31s
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  #9  
Old June 4th, 2018, 20:14
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Weasel Weasel is offline
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Re: Drop-out center transmission crossmember

Quote:
Originally Posted by burntkat View Post
Whats the hose clamp for?
to keep the hiems in the pvc control arms?
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Just add lightness
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  #10  
Old June 5th, 2018, 06:12
burntkat burntkat is offline
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Re: Drop-out center transmission crossmember

Ah, nice. It makes sense now, seeing it on a fullscale monitor. Damn, I'm getting old.

What is a "draft"?
__________________
-89 S-10: SAS, D44s front/rear. 5.7L V8. 700R4 with 4L60E upgrades. Built in my driveway.
-90 XJ 4.0, AW4, 231J: Clayton's longarms, RE 5.5" coils, hybrid 6" leaf pack, 33/12.50/15" MTs, Rancho 99012s and 99624s, Tera HD SYE, custom sliders, BW flares. Rehabbing with D44s, RE spring packs, RE 4.5" coils, and ACOS.
-94 ZJ: Budget boost, 31s. The wife's DD.
-97 XJ: Son's DD. 4" lift, ACOS, 4" spring pack, Upcountry coils, 31s
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  #11  
Old June 5th, 2018, 06:42
VAhasnoWAVES VAhasnoWAVES is offline
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Re: Drop-out center transmission crossmember

its a tool and die term...

instead if putting them vertical, angle the two flanges so it drops out super easy. draft them in the wrong direction and you will "lock" the center section in place.
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  #12  
Old June 5th, 2018, 12:30
burntkat burntkat is offline
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Re: Drop-out center transmission crossmember

Makes sense now, tapered.

I would think that the frenching of the mount like that would greatly derate the strength of the dropout- granted it's certainly still up to the job, though. Presume you used 1/4" box?
__________________
-89 S-10: SAS, D44s front/rear. 5.7L V8. 700R4 with 4L60E upgrades. Built in my driveway.
-90 XJ 4.0, AW4, 231J: Clayton's longarms, RE 5.5" coils, hybrid 6" leaf pack, 33/12.50/15" MTs, Rancho 99012s and 99624s, Tera HD SYE, custom sliders, BW flares. Rehabbing with D44s, RE spring packs, RE 4.5" coils, and ACOS.
-94 ZJ: Budget boost, 31s. The wife's DD.
-97 XJ: Son's DD. 4" lift, ACOS, 4" spring pack, Upcountry coils, 31s
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  #13  
Old June 6th, 2018, 06:32
VAhasnoWAVES VAhasnoWAVES is offline
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Re: Drop-out center transmission crossmember

yes, 1/4". the new mating surface to the trans mount didnt just bridge the crossmember and weld to the sides. it landed on the bottom of the crossmember and welded there too. then it was boxed in and closed out.

i bent 2"x.250" DOM links on that jeep. crossmember was fine when i pulled it off and to sell.
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