Help" Stripped Crossmember Chassis Rail Thread

[Petergee541]

Monkeys who (professionally) installed 2GR in my SW20 stripped the thread in the chassis nut on right rear bolt of cross member to chassis and delivered it to me without saying anything. Pretty sure the bolt is an M12 1.25. My idea was to use a halfinch UNF bolt and tap the nut with same thread in the chassis. Problem is that the half inch UNF bolt won't fit through the chassis to the nut and there appears to be a tube inside the chassis rail which I am initially reluctant to drill out. Surely someone has come across this problem before. Bolt is circled in the attached pic.

Would prefer not to have to cut, replace nut and plate chassis if possible.

2587

Any suggestions please?

[Paul Woods]

I've seen this, and i had to plasma cut the captive nut off from inside the boot, and reweld a new nut in place.

All depends if you can get the bolt out still or is it seized in place? If it comes out then just use a tap to rethread the nut, failing that it will need cutting out.

[cdwood2010]

Hi,

Apart from possibly helicoiling the thread (which might be tricky due to the fact that you can't see it and its upside down) then the accepted method of repair is to do as you described.

Don't think I've actually heard of anyone stripping one before.

Any comebacks on the guys who did it?

C.

[Paul Woods]

Don't think I've actually heard of anyone stripping one before.

You have! In the previous two posts above yours lol.

It's actually very common to find at least one of the four subframe bolts cross threaded, Toyotas fine pitch and peoples inability to enter a bolt straight.

[Petergee541]

I've seen this, and i had to plasma cut the captive nut off from inside the boot, and reweld a new nut in place.

All depends if you can get the bolt out still or is it seized in place? If it comes out then just use a tap to rethread the nut, failing that it will need cutting out.

I have the bolt out. It was less than finger tight and thread on the bolt is OK. What tap do you suggest to rethread the nut? Just retry with M12 1.25?

[Petergee541]

Hi,

Apart from possibly helicoiling the thread (which might be tricky due to the fact that you can't see it and its upside down) then the accepted method of repair is to do as you described.

Don't think I've actually heard of anyone stripping one before.

Any comebacks on the guys who did it?

C.

Response was "I didn't personally work on your car and the guy who did had left so I can't berate him"

Doesn't help also that the shop is over 600 miles from my place but with a few other issues that happened with the build, I doubt i would go back there if the shop was next door.

[Petergee541]

One of the MR2Australia Forum members kindly let me hack into a stripped out wrecked SW20 shell to see what I am up against Attached pics show from below and via a quick holesaw cut through the inner guard. Looks like this can be accessed this way or by cutting through the top of the chassis rail in the boot close to the boot wall. A single 50mm hole woulod appear to give sufficent access. Cut out above was exploratory.

Don't like cutting at all if I could get away with it. Inner guard hole would give reasonable access. (as would coming in via the boot).Any suggestions as to preference to do the least damage/weakening?

25882589

[cdwood2010]

In through the boot i think.

That way you can plate it up and youd never know anyone had been there.....

Personally i would whack a nut on top and once the bolt is in place, mig it to the old one to stop it moving if the subframe ever has to come off agian.

c.

[Petergee541]

So you suggest drilling out that nut so that a bolt would pass through. Then use a longer bolt and mig the new nut to the chassis on top of the current captive bolt?

[cdwood2010]

Yes. Trying to get that nut out doesn't gain you anything apart from more distress to that area.

A hole like the one you've drilled will be big enough to get in there with another M12 and a mig.

I don't think a hole that size will harm the strength of the chassis. BMW drill holes in everything.

C.

[Petergee541]

Thanks. I may even just drill a smaller hole in the chassis rail via the boot, just large enough for the new M12 nut and a socket spanner. Longer bolt and a spring washer and screw an "access" plate over the hole in the chassis in case the cross member needs to come out at some stage, which it will inevitably do at some stage as this is a track car.