bad day testing

This is what happens when you launch a little 488 at 4000 rpm off a frank merkl transbrake. You spit the driveshaft to the ground, snap both radius arms and loose all control:



https://www.facebook.com/video/embed?video_id=10151770430749669





Hope this works. Now back to the drawing board on making another set of extended radius arms  

Damn you Frank!    And damn the guy that planted that tree!  

Looks like the front diff was bouncing a lot would suggest looking into stiffer shock settings and possible a stiffer spring, also saw very little if any weight transfer to the back but that could be caused by being on sod with mud tires boggers don't hook worth a crap on grass.

lghting94 wrote: Boggers don't hook worth a crap on grass.

Or pavement/bricks. Found that out when I took my truck to the local car show and drove it down the street sideways.  

Karl, that looks just like what my truck was doing at the two races that I went to this year. Bad things happen when the front end is hopping like that.

At least it's not squaring the rear like I thought. Found part of my issue in a stupid me way. I used 2"x.120 wall tube thinking I would be good. I needed 2"x.375 wall tube. I still need to pull the front axle to see what broke inside causing it to lock up then shear the arms. That's why the front end started hopping. Pinion yoke only goes less than 1/4 turn in either direction with hubs unlocked on an open front. In other words "rut rogh raggy"

Dang That was cool and sucked at the same time!!! could of been a lot worse if you had hit the tree in the center ! glad you didn't get hurt and hope you get your truck up and going without incident the next time!

From watching the video front end was bouncing from the start which probably shucked a set of spider gear teeth and maybe a crosspin binding up the front gear at which point front driveshaft had no choice but to exit by snapping yokes/joints. I see no reason other than hitting the tree the front radius arms bent unless they didn't have a good enough pivot point in the rear. I would suggest watching the video on a large screen tv as slow as possible(one frame at a time) and see what is really happening. It is amazing how much more you see happening at super slow speed. I've been there and broke those same parts(except radius arms).

The arms were broken right after launch and the drive shaft spit out. I never actually hit the tree, just rolled under the branches. Steering was useless and front brake line was severed when the axle did a complete flip so the pinion was facing forward. Luckily, the wheels turned slightly to the right to allow it to miss everything.

I saw the front was bouncing. With the addition of the new FOX 2.0 air shocks, I needed to see where I was for the correct spring weight on them. My coils are really there for looks and are not under load like a normal suspension. They instead act more like bump stops. The shocks now control everything. I went this way vs going full on coilovers to keep me in class rules. They were set at 200lb to give an initial setting to start with, after they get rebuilt, I'm going to make adjustments to them in the valving as well as oil level and nitrogen pressures to fine tune the way everything acts. It's a work in progress.  

Pulled the front axle out and apart. It's about as bad as I expected. If something is worth doing, it's worth doing right, and I did it right! I managed to bend or break every single piece of the front suspension except the coil springs! Arms were broken, brake lines trashed, new hydraulic steering lines were kinked, new 1 1/4" chromoly track bar bent into an "S", bent both of the 3/4" chromoly rod ends, bent both of the 3/4" grade 8 bolts holding the track bar, even bent the upper bracket, both U-joint loops are egg shaped, broke the driveshaft. Not only that, but the brand new Fox 2.0 air shocks have dents in the main body, so they are trash.

I'm going back to the drawing board on this one! With the really bad wheel hop, I see I needed more spring pressure (coils were unloaded, and the air shocks did all the work, they were set at 200 lb/in). The 2'x.120 wall DOM tube obviously didn't hold up, so I'm wondering if I really need extended arms at all. Since the orginal rear brackets double as a mounting point for the trans crossmember, I'm thinking now to make new rear brakets and just go with a set of stock arms, back to the stock rate springs, and back to a conventional style shock. I would then trim up the original rear brackets and be done. I would love to go coilovers, but some tracks require I keep a "stock style" suspension to be able to run, so I need to keep seperate coil an shock. Any of you fast mud guys have any thoughts??

Damn,that sucked.i thought i only had that kinda luck.  

I kinda wonder if having air shocks supporting vehicle weight (instead of springs) is creating a problem. I would think it could possibly mess with a shock's valving/dampening, making it harder to find a usable valving setting that was stiff enough.

I'm thinking part of the problem was the surface you where on, may want to save the testing and tuning for the mud?

Just giving everyone an update. I fixed the front end issues by sending the broken arms up to Scott at Racing in the Dirt and he rebuilt them similaro to what I had but used a 2"x.250 wall main tube and then gave them a lower brace (similar to a ladder bar look) using 1.25"x.095 wall tube. Bolted everything in and took it out to test at a race on Saturday. Good news is front end stayed together, bad news is I broke the rear output of my np205 transfer case out at the launch. Ended up pulling the 200' hole in front wheel drive (Honda Civic style!) where the chevy before me got stuck with his 4wd  Going to replace the broken t-case and have at it again in a couple of weeks. Need to get this broken monkey off my back!  

You'll get it Karl, them cheby guys can feel it coming.

I know. I'm wondering if I acutally hurt the t-case when I did the front end damage. The splined section connecting the rear output to the input gear is stipped. Or I could have done it myself when putting the front driveshaft in. I typically pop just the front into neutral (205 has the 2 links) when putting in the front driveshaft so I can gain access to the yoke. After popping the front back in low, I never checked to see if the rear was fully engaged. It's never been a problem before, but this could have been the final straw. Oh well, too late to cry about it now....