What did you do to your NNBS GMT900 Tahoe/Yukon Today?

[iamdub]

I know where it crosses over, I was stating that the engine is closer to the ground, that’s why they needed a shallow oil pan. The frame is only 4” tall, 1/4” wall tubing so the body can be dropped on the frame without cutting the floor up, and then the frame and the rockers lay on the ground aired out. There’s not much room for exhaust. I’m pretty sure the engine is lowered, the mounts are mounted lower on the frame too ( I think the pan almost hits the ground) so when the body was dropped it doesn’t hit the hood since the frame up there is stock to the back of the engine mounts. It takes a lot of work for a stock floor body drop and it’s tight underneath.

I'm familiar with SFBD, did a couple Toyotas years ago. I was about to ask if they kept the stock frame from the firewall forward since that's what's usually done (no sense in reinventing the wheel).

Your PM about having to have cats makes more sense as to why the difficulties in routing. If you just had a lift so you could get under it and take pics of the underside to post up, that'd make things easier to explain.

 

[Fless]

View attachment 250000 View attachment 250001 View attachment 250002 View attachment 250003

Waterproof?

 

[Rocket Man]

I'm familiar with SFBD, did a couple Toyotas years ago. I was about to ask if they kept the stock frame from the firewall forward since that's what's usually done (no sense in reinventing the wheel).

Your PM about having to have cats makes more sense as to why the difficulties in routing. If you just had a lift so you could get under it and take pics of the underside to post up, that'd make things easier to explain.

I’ll just install the headers, and if I need to modify the y I can do that, then I’m taking it to a muffler shop to do the rest.

 

[iamdub]

Yesterday:

Had a tune scheduled for 1630. Tuner lives an hour away so I had to get that exhaust finished up cuz I'd have a headache driving it that far with the racket it makes.


Doug Thorley Y-pipe has the ball-and-socket connection, my Tahoe has the flared flange:




Used a grease pencil to mark the collector where I wanted to cut it, before the tapered-down part:




Cut off the ball-and-socket from the collector and the flange from the factory Y-pipe and beveled the edges of each since it was a butt weld:




Finished. Cleaned the welds and sprayed with high-temp primer and paint. I also sectioned out a couple inches between the flange and flex joint:




It's still much too loud for my liking, but at least it's now coming out the tailpipe instead of under the floorboard. I have an electric cutout on the way so I'll be chopping up the exhaust again. I may install a second flow-through muffler in series with the current one to quiet it down or maybe reinstall a factory muffler. With no cats, I'm sure a stock muffler would still have a meatier sound to it.

 

[iamdub]

Took it on it's first actual drive an hour away to the tuner. Temp stayed at 210 and oil pressure did as expected. Even sat in traffic due to a disabled semi on the incline of the Mississippi River Bridge. I filled up with a fresh tank of Chevron 93 about 15 miles away from the tuner and checked the surge tank to see if it was still bubbling (still purging air, not leaking head gasket!).

On the long stretch of flat, straight highway near my house, I set the cruise at 70 and recorded my gauge readings, including the MPG:




Tuner doin his thang:




On the way home, on that same stretch of highway at same cruising speed:




...And at 80:





It's not the fresher fuel since it's always gotten around 18 on that stretch (that's always been my test circuit for this). I shot a text to the tuner to ask if there's anything he did that would explain this (something intentional like lean cruise?) or if there's just that much more power/efficiency at that RPM with the mods. It's his day off so I don't expect to hear back for a while. Either way, good numbers

 

[Rocket Man]

Yesterday:

Had a tune scheduled for 1630. Tuner lives an hour away so I had to get that exhaust finished up cuz I'd have a headache driving it that far with the racket it makes.


Doug Thorley Y-pipe has the ball-and-socket connection, my Tahoe has the flared flange:

View attachment 250008


Used a grease pencil to mark the collector where I wanted to cut it, before the tapered-down part:

View attachment 250009


Cut off the ball-and-socket from the collector and the flange from the factory Y-pipe and beveled the edges of each since it was a butt weld:

View attachment 250010


Finished. Cleaned the welds and sprayed with high-temp primer and paint:

View attachment 250011


It's still much too loud for my liking, but at least it's now coming out the tailpipe instead of under the floorboard. I have an electric cutout on the way so I'll be chopping up the exhaust again. I may install a second flow-through muffler in series with the current one to quiet it down or maybe reinstall a factory muffler. With no cats, I'm sure a stock muffler would still have a meatier sound to it.

Pretty good weld. Mine will need the same thing since my Kooks have the ball and socket but I’ll leave that up to the muffler shop since it needs a whole new system from the headers back. I’ll have to drive it with open headers to the shop.

 

[Tonyrodz]

Pretty good weld. Mine will need the same thing since my Kooks have the ball and socket but I’ll leave that up to the muffler shop since it needs a whole new system from the headers back. I’ll have to drive it with open headers to the shop.

That'll be fun.

 

[iamdub]

Pretty good weld. Mine will need the same thing since my Kooks have the ball and socket but I’ll leave that up to the muffler shop since it needs a whole new system from the headers back. I’ll have to drive it with open headers to the shop.

Thank ya. They could be better, though! I half-assed it since I was in a rush and it'll be sliced apart again for the electric cut-out.


We need before and after vids of yours!

 

[GreyStone]

@iamdub ~ are you still running 3.73's out back?

 

[gooffeyguy]

Yesterday:

Had a tune scheduled for 1630. Tuner lives an hour away so I had to get that exhaust finished up cuz I'd have a headache driving it that far with the racket it makes.


Doug Thorley Y-pipe has the ball-and-socket connection, my Tahoe has the flared flange:

View attachment 250008


Used a grease pencil to mark the collector where I wanted to cut it, before the tapered-down part:

View attachment 250009


Cut off the ball-and-socket from the collector and the flange from the factory Y-pipe and beveled the edges of each since it was a butt weld:

View attachment 250010


Finished. Cleaned the welds and sprayed with high-temp primer and paint. I also sectioned out a couple inches between the flange and flex joint:

View attachment 250011


It's still much too loud for my liking, but at least it's now coming out the tailpipe instead of under the floorboard. I have an electric cutout on the way so I'll be chopping up the exhaust again. I may install a second flow-through muffler in series with the current one to quiet it down or maybe reinstall a factory muffler. With no cats, I'm sure a stock muffler would still have a meatier sound to it.

You need to update your sig and remove the dechromed, lol