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Hi guys , any help or insight on this repair would be appreciated...
The front driver side frame rail cracked and separated from the front crossmember . I'm not sure of the cause , but my 90 4runner is a big rock crawler , so I abuse it pretty good , but the fact that the frame itself fatigued and cracked was pretty surprising . My plan is to fab some custom L-brackets and hit all four sides of the frame to the crossmember , with additional gussets going diagonally to reinforce .
Anyway , this is a big project for me , and I'm considering just taking it to local 4x4 shop to have them do it ....
When the SAS was done it changed the way stress was loaded on the front end of the truck . I could go one with the formulas to compute the stress and no doubt put everyone to sleep.
Pretty much you just beat the snot out of it and it failed
If your planning to keep abusing this it is going to take lots of work to get it done so your not fixing it again in weeks or months.
I know how I would fix this . It comes down to just what you want and your budget will allow.
Thanks ya'll , I'm almost positive it's steering stress and torque related . I reinforced the steering box mount right near where it failed . I'll be camped out in the garage for the next few weekends
after looking at this, i went out and found some frame cracking on my '86 sas crawler... some of it looked like it might have been there before the p.o. did the sas, but then there was also cracking on one of his welds... the frame was cracked on the top, the sides, and worst on the bottom, where an inch-long half-oval area piece looked like the end was falling out.
so i welded in this 1/4" bar from the steering box reinforcement plate to the spring hanger, because it looks like there is a lot of leverage exerted by the spring in that area... i couldn't come up with a solid solution for the side-to-side play exerted by the steering, without having to pull the motor and the steering box, so i just welded up the inside corners as best i could, need to keep monitoring everything for cracks.
in a perfect world the cracks would get ground out into a groove, then welded up, but i couldn't get decent access to anything, even on the bottom of the frame.
i used a broco goweld mig welder, powered by a couple of glass mat batteries, it's rated at 200 amps/24v, so there was red-hot metal and plenty of penetration, using .035 wire... i drilled a couple of holes in the bar, using rosette welds to the steering box reinforcement plate, which was also 1/4" flat stock.
sloppy welds, messy flux core welding that took a lot of wire brush cleanup, we'll see if it holds up.
The repair is going well , just slow . I'm getting married in 8 days so not a lot of truck time available . But I got the frame rail and crossmember back together . I've also added lower gussets on both driver and passenger side , and I only need to add diagonal gussets between the rail and crossmember to combat steering box related torque and fatigue...
top plate
there's actually a gusset on the other side that isn't shown
passenger side
edit: and I hear you about access, there are some tough welding positions and angles in that area . Radiator , reservoir, steering box and lines are all removed at this point.
that looks real solid... you probably have hydro-assist? it really stresses things out.
the horizontal bar that you added to the stock cross-beam; i couldn't do that, because the radiator was apparently dropped to accommodate the body lift, it hangs beneath the stock beam... i'll probably have to put an L-bracket on the top of the cross-beam somehow.
the p.o. of this truck welded a bumper to the truck, it's a complete disaster, so i couldn't get a welder in there to do the L-bracket... have to cut the bumper off, later.
congrats on the upcoming wedding, hope that she likes to go wheelin'
that looks real solid... you probably have hydro-assist? it really stresses things out.
the horizontal bar that you added to the stock cross-beam; i couldn't do that, because the radiator was apparently dropped to accommodate the body lift, it hangs beneath the stock beam... i'll probably have to put an L-bracket on the top of the cross-beam somehow.
the p.o. of this truck welded a bumper to the truck, it's a complete disaster, so i couldn't get a welder in there to do the L-bracket... have to cut the bumper off, later.
congrats on the upcoming wedding, hope that she likes to go wheelin'
hydro-assist would actually reduce stress on the frame and the steering box due to the ram being mounted to the front axle. This keeps all the a lot of the steering stress on the axle. Only additional part seeing extra stress is the power steering pump.
good point... i think that the box sees a higher psi because of the more powerful hydro-assist pump? but as you mentioned it's more the axle and steering components that concerns me, because among other things i'm using the steering stops on the axle, per the original factory design.
the correct way to do hydro-assist is to limit the cylinder travel, not use the steering stops, they should only be there to prevent external forces from turning the tire too far.
05-28-2015, 09:01 AM
Only going by the pictures .
It comes down to just what you want and your budget will allow.
