Crossmember critique needed

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Eskimo

Eskimo

SILVER Star
Joined
Sep 6, 2002
Threads
62
Messages
1,358
Location
Danville, PA
Website
www.rnrfab.com
In trying to get a flat, flush skidplate on the FJ, and because of where the tranny and t-case supports are, we're running into an issue with the front output/driveshaft. The crossmember will be approx 4" in FRONT of the output, so clearance needs to be made for the driveshaft. (D/S will be a 2-piece unit, so it will exit straight out the front, angled to the right a little bit)

This picture is a view looking from front to rear..

Black is the frame rails.
RED is 2x4x.120 box tubing (configured as 2" deep, 4" high) used for the crossmember.
BLUE is a flange so the crossmember can be removed.
GREEN on the bottom represents 3/8" x 2" plate that will be welded inside the 2x4, and on the top represents 2 pieces of 1x1x.120 box (one right next to the other, basically making is 1x2x.120)that will be bent to form an arch over the top of the output.

Think this will work? This piece will be the only member supporting the tranny/t-case, and their associated loads. The t-case and tranny are mounted on rubber mounts, but the x-member will be attached solidly to the frame.

My thoughts are that the 3/8" should damn near be enough to support it anyway... but the hoop over the top will add rigidity. The actual unsupported length of 3/8" should be 4-5" long. Since the 3/8" plate will be slid inside the box tubing, we *could* add another 1/8" strip to the bottom of the 3/8" without losing any clearance..

I want something functional, that we can build (i.e. no 4340 or Titanium), that's pleasing to look at at the same time.
crossmember-maybe.webp
 
looks beefy....REALLY beefy.....even overkill....

IMO, sleeve thru the frame for side plate mounting....easier access to the bolts in the future. Scab-plate on the inside frame if you have strength concerns.
 
way over kill especaily the 3/8s you could do that with 1/4in or less maybe. Here is what i did...

www.yankeetoys.org/stewarts/FJ40SOA/soa3.jpg

www.yankeetoys.org/stewarts/FJ40SOA/soa4.jpg

1x1x.125 wall square, 1/4in plate in the middle to support the toybox mount(mini truck)

used 3x3x1/4in angle welded to the inside of frame to moun the crossmember to.

i jacked the rear engine mounts up 1in. The bottom will be almost flat..maybe 1in sticking down to clearence around the drum brake.

Stew
soa3.webp
soa4.webp
 
wngrog said:
I went down 1" off my frame so I could have good access to the backing nuts and so I could go straight across.
Click to expand...

Not sure I follow you on that... could you explain please? I *am* copying your skidplate a little, going to try and have the edges bent up past the frame rails at about 30*, and just make simple "L" brackets outside of the frame to bolt the skid up to. the frame rails and the crossmembers will support the skid during use... the bolts just hold it in place.

I like the Wok Taxi's simple frame mount for the crossmember... I'm overthinking my flange idea... and we have loads of poly YJ spring bushings laying around.

As much as I'm trying for a totally flat belly, the high rear output of the t-case might make me drop the driveline about 1" in the rear to help the angle (Running a Toy CV on the rear output, as Jesse didn't recommend hanging a 42* CV from a Toy case).. as well as lowering the suspension an inch or so... as it sits now, I'm at 29-30* at ride height.. (I could get that down to ~26-27* if I lower the suspension a little, and dropping the t-case 1" would get me under or at 25*).. She's sitting 23" to the frame rail at 20psi. Hopefully the smooth skid will let me drag over things at a lower height... I'd have 3-4" of uptravel at the front.
 
Depending on how long your wheelbase is, 23" to the frame may be higher than optimal. Unless you are over 110" long, I would say drop it another inch for a little help on the driveline angles.

I've pretty much settled on my wheelbase at 116" and belly clearance of 22".

Ed
 
Rock Taxi said:
Depending on how long your wheelbase is, 23" to the frame may be higher than optimal. Unless you are over 110" long, I would say drop it another inch for a little help on the driveline angles.

I've pretty much settled on my wheelbase at 116" and belly clearance of 22".

Ed
Click to expand...
Ed, with Leaves and a standard springover it is hard to be under 23" on a full bodied 40..
 
Mace said:
Ed, with Leaves and a standard springover it is hard to be under 23" on a full bodied 40..
Click to expand...

Heck, I'm WAY under 23" to the frame right now... Rollin on 26's :D

Actually, at trail pressure with my SX's , I'm surely down from 23... and I plan on lowering the suspension a little bit, moving the rear spring hangar up a little, and pull a leaf if need be. Uptravel is over-rated, right? :P (Currently have about 4" uptravel at the front springs, ~5 at the shock)

'course, the "full body" is about to go bye bye.

(And no, those aren't my shocks... they are loaners so they body doesn't flop around on the trailer)
twentysixes.webp
 
mine is 23.5" at the bottom of the frame rail.....just measured tonite....course, there is no rear axle, no tranny or t-case weight, and the back of the rig is hanging by the engine hoist, so it may not be totally accurate.... ;)
 
Pics of the project please Woody! I can only imagine what it looks like!

Goebs
 
Goebeler said:
Pics of the project please Woody! I can only imagine what it looks like!

Goebs
Click to expand...

pics this weekend....

tires are all off it now too....started the upper axle housing work for the upper link tabs last night, nother hour-two with the welder and that'll be done, and the housing under the rig...then I can use the engine hoist for the engine (imagine that) and with luck, my tranny will be done tomorrow, in time for weekend mockup for mounts.
 
Got a great simple design that works..........1 year in place and no problems with a 248-1 crawl ratio..465/ToyBox/4 speed T-case behind a 350 ci.

but can't post the pix..keep getting this message.....

POST requests from foreign hosts are not allowed.
any volunteers to post pix?
 
Eskimo, what frame height did you end up with?
 
Right now, with the tub off, and no weight over the back, it's hard to say.

Without getting into too much work and re-making the spring hangars and such, I think 22-23" will be attainable.

My skid is going to be flush to the frame at the bellhousing area, but will slope down to 1.5" below the frame at the rear t-case output... I got to 26* static angle on the driveline before I pulled the body by dropping the rear of the driveline down some..

It's really hard to measure my junk now, because it's sitting on 225/60-16 tires, as well as being naked. (the cruiser that is)
 
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