Hole saw through trailing arm crossmember, safe?

[Reyals Bemus]

I'm converting to an automatic transmission and would like to run a new exhaust system between the frame rails out to the back of the truck. The front crossmember is no longer a problem since it has been removed altogether.

Do you guys think its okay to punch two 3" holes through the trailing arm crossmember? It wouldn't weaken the crossmember enough to be unsafe would it? If anyone has done this before, pictures would be nice!

[travz500]

Originally Posted by Reyals Bemus

I'm converting to an automatic transmission and would like to run a new exhaust system between the frame rails out to the back of the truck. The front crossmember is no longer a problem since it has been removed altogether.

Do you guys think its okay to punch two 3" holes through the trailing arm crossmember? It wouldn't weaken the crossmember enough to be unsafe would it? If anyone has done this before, pictures would be nice!

personally I would route around it even if running 3" exhaust must be a big motor better than possibly weakening 50 year old parts

[theastronaut]

There are already two wide slots stamped into the crossmember that leave that area open so I doubt that cutting it would make it much weaker. I'm going to cut 4" holes, box the open side of the crossmember, and weld 4" pipe through the opening to strengthen the cut.

[TBONE1964]

The only way I would do it that way is to use a piece of 3 in i.d pipe with 1/8 inch wall thickness about 2 inches wide and weld that in the hole. That would add extra strengh to the crossmember. You will have to punch a 3 1/4 hole in the crossmember. I would use a hole saw for this, so it is nice and clean.

[wayno]

I am also curious on this subject as I am going to lower my truck - do you have to then contend with the trailing arms right after you cross through the member?

[Reyals Bemus]

Oh just to clarify, I am NOT running 3" pipes. More like 2" or 2 1/4." My engine doesn't make near enough power for a dual 3" system!

I just thought 3" holes would provide adequate clearance for a 2" pipe and allow it to move some with contacting the crossmember.

Thanks for the info and pics so far! I like the idea of restrengthening the hole by welding a short length of pipe into it!

[lil_sahara450r]

Hopefully some more people will chime in on this with opinions and pics because I'm thinking about cutting a hole and welding in a peice of pipe in rather to buying one of these http://www.performanceonline.com/196...pension-19834/

[pdxhall]

It's not going to be any weaker than that aftermarket one and there are many that have done it.

[argonaut]

On a street driven truck with stock type powertrain, you'll probably never know the difference.

[Bishops Trucks]

There is no problem doing that as long as you weld in a piece of pipe as stated above.

[SierraMtns]

Any updates on guys punching out the holes with a hole saw? Would 3.5" hole be to big? I am planing on running 3" pipes.

[The Rocknrod]

I did the hole cutting thing first. Then mocked up my truck at the position I wanted it, chassis height and all including the drive shaft engine and transmission. Which convinced me to purchase the POL cross member. Buy the way, that thing is "heavy wall" steel, more so than the stock cross member.

[vince1]

Do they make large hole saws for cutting through steel like that? I would think that the cutting edge would need to be sprayed with that carbide looking stuff that you see on sawzall blades.

[Brandons63]

You would need a torqie drill that's for sure! And some Popeye forearms! I have some 3 - 4 inch wood/metal blades and a magnetic drill press that might work but would rather use a plasma and something Round as a guide

[The Rocknrod]

Take a piece of sheet metal use C-Clamps to clamp it to the back side. This will be used for keeping the hole saw center drill bit in place. Now drill your hole with the hole saw. I did it, worked great.

[siggyfreud]

I did it on mine. Then I took 4" steel pipe and welded it in place to add some rigidity back to it.

[BR3W CITY]

One of the beauties of owning heavy, old trucks; you can drill a hole in almost anything and it'll be fine. My trucks gone through 3 engine combos, 3 trans types, and a few suspensions...so almost everything's had a few speed holes in it.

Like the other guys have said, a little reinforcing won't hurt (especially if your near an edge or wanting to "notch" the thing instead of go straight through).

That being said, tubular crossmembers are veeery nice.

[_Ogre]

you can drill a hole in almost anything and it'll be fine

watch for wires