trans cross-member mod to run bigger exhaust?
 

so I currently have an MBRP "four inch" exhaust. well they claim it to be 4" but it is actually 3.5" and it is SUPER TIGHT to my t case and front driveshaft. enough so that when in 4wd and braking moderately, the front of the truck dives down enough to get the spinning driveshaft to touch the exhaust pipe, causing a hellacious noise.


so what I'm wondering: on the trans cross-member there is two removable "wings" that connect the cross-member to the top of the frame rail on both sides for extra support. are these super necessary? has anybody removed the one on the passenger side to allow room for exhaust clearance? like a 5" exhaust maybe?


-Sean

well I think the biggest question to ask here is why? a 4" straight pipe exhaust would more than support the mods you have in your signature line. anything bigger than that is extremely unnecessary, even with compounds and more fuel. my diamond eye kit is 4" OD and fits through that same space you're speaking of. took a lot of fitting and moving around and adding of extra hangers, but it doesn't rub.

I would work on the fitment before removing cross-member braces. just my .02

You will not flow more exhaust than your turbine outlet size. All going bigger does is change exhaust noise.

That said, I had a Diamond Eye 4" on my old W250. It fit with a bit of room. I have seen others claim it doesn't fit but when you look at the trans rubber mounts, theirs were near nonexistent. I had good rubber isolators. This helped get the transfer case away from the frame rail.

My theory on those wings. They help incorporate the whole frame rail height to help support the trans and transfer case. If you were to remove them, you'd only use that lower lip really to support all that weight. If you built another but used a plate that bolted outboard of the frame, the height of the frame with a tube to tie them together, you can eliminate them. This pic shows something for being inboard on the frame.

https://cimg6.ibsrv.net/gimg/www.die...4b3c41fb46.jpg

Hope this helps.

Click on the following link for a couple pics of modded crossmember to allow exhaust pipe route through... '85 W350 Cummins Crew 4xDually - Dodge Cummins Diesel Forum

I have that MBRP exhaust pipe as well on a 4x4.

Some creative tack welding & a slightly shaved clamp did the trick with zero rubbing.

I can't really prove it, but I think you are wrong here.

So, that picture of the crossmember, is that for a dodge and available for purchase??? It looks awesome... I could always make something too I guess...

This question is based on waning to twin turbo and wanting to go 5" when I do so

I just searched "aftermarket truck transmission crossmember" and it came up with that. I think it is for a Chevy but something that can also be easily made.

The most powerful guys in the sport go no bigger than 5 or 6" because that is what the turbine outlet size is. If there was an advantage, I'd bet they'd use it. The guys running triples I have seen have 2 4" exhausts dumping into the atmosphere OR collecting into a single 5". One of these trucks tows. If there was an advantage, I would think he'd use it.

It's not first gen dodge there isn't enough drop. looks like something for a street rod to get more ground clearance for a looooow truck.

Wait, are you talking about the outlet size of the turbine housing or the turbine itself?

The outlet of the housing.

In that case, I agree completely.

I`ve eliminated the two "wings" on a few (at least 20) Chevy and that many Dodge trucks over the years NO PROBLEMS. Chevy quit using them in the early / mid `70s. dodge a little later. the only thing I noticed was that Chevy used longer bolts (about 1&1/4") with thick walled spacer tubing to hold the cross member to the lower frame flange. they also did the same to the bolts that hold the steering box to the frame. the longer bolts can stretch easier than the real short ones that they used to use. and the longer bolts stay tight and the real short ones would always come loose.

good to know! I may go ahead and delete them when I decide to go 5" everything. if it doesn't seem to have the strength ill just build custom.


thanks