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Attach truss to diff or not?

Pyleit

Pyleit

Well-known member
Joined
May 21, 2020
Member Number
825
Messages
423
When adding a rear axle truss, what is the concensus on welding it to the pumpkin? Required? Optional? Don't bother? Higher risk of spinning a tube if its not welded? This is the truss in question, currently not attached at pumpkin. I know preheat, nickel rod, peen, and slow cool when doing it, but is it needed? Not rock bouncing, just JV and sand hollow crawler
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I hate not having support in the center of a truss ,all the force the top links are putting on the diff. housing out at those welds is better than a foot away from centerline is asking for cracks. A double shear mount welded to the truss and small spine welded to the cover is more than enough support for that truss. That cover‘s made of 1/4” plate and held on with 14 3/8 bolts ..I’m betting you could hang the whole rig from it !
 
I built a rear 14 bolt for a customer once and didn't tie it into the pumpkin, just the tubes. He sent me a picture a couple years later of the truss twisted to shit. Basically the tires were bound up and the pinion tried to climb the ring gear and when it did the upper links held the center of the truss in position while the axle spun upwards. Made quite a mess of the truss!

Weld it to the pumpkin or buy a pinion guard/support kit for it.
 
SLOWPOKE693 said:
I built a rear 14 bolt for a customer once and didn't tie it into the pumpkin, just the tubes. He sent me a picture a couple years later of the truss twisted to shit. Basically the tires were bound up and the pinion tried to climb the ring gear and when it did the upper links held the center of the truss in position while the axle spun upwards. Made quite a mess of the truss!

Weld it to the pumpkin or buy a pinion guard/support kit for it.
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A unsupported truss just looks like it’s inevitably gonna fail ..I‘ve never seen truss tear off but from what you said it’s sure possible!
 
I run a pinion support, and didn't bother welding to diff. My world has not yet ended.
 
This is a 4 seat buggy with 450ish HP on 43" sx stickies that I will be wheeling like its a rental. If it is going break ill find it. Ill weld it to the pumpkin and if it cracks off ill get a pinion bridge
 
Pyleit said:
This is a 4 seat buggy with 450ish HP on 43" sx stickies that I will be wheeling like its a rental. If it is going break ill find it. Ill weld it to the pumpkin and if it cracks off ill get a pinion bridge
Click to expand...
Do both now and save yourself the headache later. My customer twisted his with a stock Jeep 4.0L/auto using a Rubicrawler box into the stock Rubicon 4-1 T-case with 42" Red Label BFG's. You probably have double the HP and that sandpaper you wheel on isn't exactly easy on parts.
 
My friend pointed a 14b pinion skyward on his ZJ on 37s with a 5.2 at Moab the first trip out doing something easy, weld that to the pumpkin!
 
You don't have to use nickel rod. 35 thou S-6 MIG wire works just fine just make sure you preheat/post heat peen and wrap in a welding blanket or too over night. Will work just fine.
 
I had the old school thick bent upper link mount on my last rig. Welded to the tubes and the center cast above the diff cover with a pinion support. When we removed it the center weld was cracking and both tubes seeped gear oil. The pinion support was the only thing keeping it from failing and was under tension removing it. I also spun the long side tube in my front 60 on that rig.

My new rear axle has the tubes welded and a full length truss with a pinion support. My new front has the tubes welded in and a full length truss.
 
I would also recommend Rockmound Brutus AAA rod, it welds leaps and bounds better than Ni55 or Ni99 rod, also has much less shrinkage compared to Ni rod. Not to mention the 127k psi tensile strength is fantastic. Lil pricey but worth every penny. I always use it on diff housings and cast to dissimilar metal repair
 
i thought mine was good to go because i have truss welded to tube, truss tied into rear diff with a shit ton of bolts, but these top three bolts all loosen up, they were 3/8 grade 8 with steel lock nut, since then i have drilled out the out side two to 7/16 and its doing much better.

i think this winter i will have to weld the tubes and add more welds to the pumpkin.

this is behind a 22r toyota , not even a worn out v-8 so they move its crazy

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