Welders, fabricators, suspension guru's...

Todd Simpson · 05-22-2006, 05:46 PM

I've got some play in my trailing arm and thought it was the monoball.

Finally got everything apart and found the tub mounting holes elongated. See the nearest hole around 5 o'clock. It's enough that the bolt can move.

How would you fix?

nabilious · 05-22-2006, 07:02 PM

Tough one. The right way would be to get everything flamable outta the way, weld it up, then clean it up with a tap. sounds like it would wreck an afternoon, but then your stylin' again.
Good Luck.
Nabil

afterburn 549 · 05-22-2006, 08:04 PM

Hmm..there are all sorts of ways to do stuff, from cutting off and weld on new, too cut a pc to fit the whole and weld it in and re drill.......I would go for the latter as you can index it ezr with the other side

DarrylD · 08:16 PM

I'd clean-up the metal around the bolt hole so a weld will penetrate it, clamp a piece of copper plate to the back side of the hole and lay a MIG weld bead in that worn area, then use a carbide tip Dremmel tool bit to remove the excess bead and make the hole round again.

lateapex911 · 05-22-2006, 10:40 PM

The first method will have you needing to grind the backside flat for proper monoball fitment, than having to get a drill bit in there exactly concentric with the hole on the opposite side. And sill as it sounds, drilling an exactly circular hole, to the exact size, will be difficult in that position.

The second method requires similar back grinding, but much less, possibly some front grinding as well for a goor washer fitment, but has you freehanding an exact circle and size. That sounds difficult given the position as well.

I would measure the monoball bolt, then drill the exact hole you want in a plate the same thickness or greater than the bracket thickness. Grind teh face of the bracket to bare metal, spray on some weltd thru primer, then cut the plate to fit on the face of the bracket, and position the monoball in it's final position with the bolt through the holes. Tack weld in two spots, then remove the monoball and bolt, and final weld the plate to the bracket. Observe normal welding precautions.

This will allow you to have the exact sized hole in the exact space, and will keep the fussy work done under the car to a minimum. (I assume the bolt has 1/8" extra length.)

911pcars · 05-23-2006, 12:17 AM

Yep, I agree with Jake.

What Jake describes is "sistering" a predrilled plate onto each side of the mount, then weld in place. The result is a reinforced control arm mounting bracket containing new bolt support holes.

Sherwood

rnln · 05-23-2006, 12:50 AM

Can someone point out what wrong? I can't even imagine the area.

lateapex911 · 05-23-2006, 11:28 AM

I couldn't tell from the pic either, but the poster desribed the hole as being oversized , esp in the 5 O'clock area. I took his word for it!

DarrylD · 05-23-2006, 12:57 PM

Does this help explain the problem? The solid circle approximates where the original hole was and the dotted line shows where it's (to quote Larry the Cable Guy) "wallered" itself out to an oval shape.

rusnak · 05-23-2006, 01:42 PM

Sounds like a good excuse to buy the adjustable camber boxes from Smart Racing, shorter Turbo trailing arms, and Turbo brakes.

At least that's what I'd want to do.

Dan in Pasadena · Dan in Pasadena's Garage

"Cut to Fit, Bend to Suit, Paint to Match"

Been using this credo since I was a draftsman (remember those? Sorta like a blacksmith!) waay back in the Dark Ages.

rusnak · 05-23-2006, 01:55 PM

I was wondering, why would the hole get wallered down, and on the inside? If the bolt likes the lower position, then is there a related alignment issue that is forcing the bolt down in the first place? Maybe the answer is to repostion the entire hole where the bolt is now?

Just useless ramblings......

Todd Simpson · 05-23-2006, 02:07 PM

Darryl nailed it with this picture.

It's just out enough to create a small amount of play at the end of the trailing arm. I had noticed some weird high speed handling that felt like the rear was toeing out. I've even got it on video, steering left to go straight under the bridge at Summit Point.

I like Jake's idea a lot, and if I were using stock bolts that's what I'd do. The thing is, with a '71 tub, the engine and trans need to come out if you ever want to remove a trailing arm. (I think the factory fixed this around '73, clearancing the torsion tube so you can pull the bolts out the other side.)

For that reason, I'm using Smart EZ pins, and those require a nice round hole at the stock location to work. They cannot extend in length at all.

I have a welder coming here Friday and I'll get his thoughts on the best option.

Oh, and to the upgrade point, yes, I'm using this opportunity to put 30mm torsions in the rear AND buy the equipment necessary to do my own alignments and corner balance. One less thing to go to the shop for.

Chuck Moreland · 05-23-2006, 03:07 PM

The bolt is never a precision fit in that hole, it relies on the pinching by the bolt to prevent motion. The bolt was under-torqued.