[grivera]

I’m starting this thread on Joe’s behalf (Va68Goat). He is currently in a friend’s shop finalizing a 4L80e install, among other work. Previously, the car had a TH400 with an H-pipe. After installing the 4L80e, the factory x-member was altered and positioned garter toward rear of car. In this configuration, the H-pipe as previously constructed doesn’t fit without sitting too low. The same is the case with an x-pipe.

I’m sure others on here have been through this before- any issues setting up the exhaust with an x-pipe and still tucked up high? Here are some pics .

BTW - started thread and added pics from phone, not sure why pics are sideways.

[Sirrotica]

In some of the cars I've done in the past, I've had to put a cross pipe in with a bend (dogleg, roughly 30 degrees, from memory) under the drive shaft to get drive shaft clearance. The car had 2 1/4 pipes, the crossover was either 2 inch, or 1 7/8 pipe. (tough to remember exact details after almost 45 years, 1977, has passed) That wasn't a 4L80E conversion, but an H pipe on a dual system, with headers, on a 77 T/A with a 4 speed. The weird crossmember designed for a front mounted catalyst was what limited space under the car.

Adding the crossover H pipe was done after the car was driven with the new dual system, and adding headers. The car had no mufflers on it, just 2 cats installed under the rear seat, and tailpipes. The dual cats were to keep the car legal as per PA state inspection statutes. The car sounded like it had cherry bomb glass packs on it though, not my favorite sound.

Adding the H quieted the car, and got rid of the crackly exhaust sound, as a bonus it picked up some low end, and mid range power too. The owner, and I were both happy with the addition of the H pipe.

That was my solution to the problem back then, maybe it can be used on Joe's car too.

One other thing from the pics, you may need to take 2-3 inches out of the intermediate pipes and add a like amount ahead of the bends to move the bends further back for crossmember clearance. It looks like the bend is going to rattle on the crossmember humps, just my observation from the pics.

[ID67goat]

I personally like a true dual system with no crossover, but if you want to keep the crossover you probably need to do this to make it work with your existing system:

Originally Posted by Sirrotica

In some of the cars I've done in the past, I've had to put a cross pipe in with a bend (dogleg, roughly 30 degrees, from memory) under the drive shaft to get drive shaft clearance.

[JSchmitz]

Originally Posted by Sirrotica

The car sounded like it had cherry bomb glass packs on it though, not my favorite sound.

Adding the H quieted the car, and got rid of the crackly exhaust sound, as a bonus it picked up some low end, and mid range power too. The owner, and I were both happy with the addition of the H pipe.

I had a SBC Chevelle with Flowmaster mufflers once. It sounded terrible. Like glass-packs (Which I always hated). Clattering sound like the rods are gonna fly out of it. Added a crossover and it sounded great. Strange how much it affected the sound.

[Formulajones]

That is generally what an H or X will do as it equalizes the pressure/pulses, quiets things down a bit.

Never really liked exhaust systems without a cross over, depending on the mufflers used they either sound like tractors or they cackle and carry on. Of course they are worth a bit of power too that I'm not willing to give up either for such a simple mod.

[HWYSTR455]

Just to point out, this is a RARE manifold car, and, I suspect that with new head pipes, the issue with lining up with the crossmember humps would go away.

If you buy the head pipes from pypes, the X pipe would work.

Aftermarket crossmembers sweep back, kind of like a 'W' with the ends pointing out to the sides. Not only would it allow use of the original mounting position holes, they also offer the ability to space the tail of trans up/down.

3 angles are needed to calculate pinion angle, tailshaft to horizontal, driveshaft to horizontal, and pinion yoke to horizontal. Working angles of the U-joints are critical.

If the rear is not square in the car, to OE specs, then you really should also calculate the offset. If the car wasn't born with the rear in it, and you end up with a vibration, it will need to be corrected. 60mph is not a good speed to determine vibrations these days, with 70-75mph interstate speed limits.

Using an X or H pipe allows both engine banks to use both exits, and it in essence, make the engine 'think' the exhaust is 'bigger'. The opposing bank exhaust pulses can also help evac gases. They are worth the effort, especially on larger engines, and manifold cars.

.

[NeighborsComplaint]

Originally Posted by JSchmitz

I had a SBC Chevelle with Flowmaster mufflers once. It sounded terrible. Like glass-packs (Which I always hated). Clattering sound like the rods are gonna fly out of it. Added a crossover and it sounded great. Strange how much it affected the sound.

No H pipe + 2 chamber Thrush Welded is my new nirvana. Car sounds just like it did before I loused it up with the H. I don't hear any "rods ready to fly out" sound either. Shop that installed says he takes out more H and X pipes than he installes on classic muscle. They're fine with a quiet exhaust if like your car to sound like a Mustang.

https://youtu.be/jy2-6x7sJR8

[ponjohn]

I plan to use one of these for my 73 Ventura.
Not sure if they make one for the A-Body.

This may provide the space you need.

[Formulajones]

I run a 4L80E in my A-body with a 3" Dr Gas X and have no issues with tucking it up under the car.

The X (or H) just simply needs to be under the driveshaft at the yoke, behind the cross member. Plenty of room there. No different than having the 400 in the car. In fact I didn't have to touch my exhaust system for the swap. The 4L80E trans mount is only moved back 1 1/2 inches. It's not a huge change.

Sounds as if his H pipe must have been configured right up against the cross member with the 400 turbo with no wiggle room at all.

[Va68goat]

grivera,
Yeah, thats correct. When I bought the car, it had headers...I bought the downpipes when I bought the RA manifolds.

[HWYSTR455]

I was meaning correct downpipe = pypes if you choose to use the pypes x kit.

.

[JSchmitz]

Might want to check the driveshaft angles if it hasn't been done. The trans mount might need spaced up?

[Half-Inch Stud]

Ahem, Hope the install is going well.

However, no X/H-pipe here, and i can pull away in thrid with Stock 4L80 converter and 9.0:1 compression. Low-end seems fine with 4:1 dual exhaust.

[Va68goat]

Here are a few more pictures. As you can see, when we moved the crossmember back, we came across a ridge on the frame rail. My buddy made a spacer that eliminated the ridge so the crossmember wouldn't wobble. This worked out pretty good because it raised the crossmember up a little so we were able to tuck the exhaust even more but now the H pipe and can't clear the driveshaft.

Would I lose that much power by keeping the straight dual exhaust compared to having an X pipe of H-pipe?

We checked the pinion angle and it's right in the middle of spec. When I purchased the car it had a 700R4. I got rid of that and had a TH400 built. Now that I have a 4L80E, is there that much a difference in these transmissions to indicate that the exhaust was installed for a 700R4 and would that require me to change the entire exhaust to accommodate the 4L80E? I'm also curious to hear the difference in sound now that the H pipe is gone. I really liked the way my car sounded before. We're still in the middle of working on the exhaust and we're going to try and make the H or X but I'm not too sure if it's possible where the H is located.

-Joe

[JSchmitz]

Originally Posted by Va68goat

We checked the pinion angle and it's right in the middle of spec.

It's more than just pinion angle. It's pinion angle vs. driveshaft and trans yoke vs. driveshaft. I'm dealing with this now on my LS conversion. I'm having to space the transmission up as high as I can (Without cutting floor). Also have to get some adjustable upper control arms for the rear end in order to get it right. That's why I asked. Looks like the crossmember is already spaced up high though. so maybe you're good there.

X2 on the E-brake cable. Something strange there.

[grivera]

Originally Posted by JSchmitz

It's more than just pinion angle. It's pinion angle vs. driveshaft and trans yoke vs. driveshaft. I'm dealing with this now on my LS conversion. I'm having to space the transmission up as high as I can (Without cutting floor). Also have to get some adjustable upper control arms for the rear end in order to get it right. That's why I asked. Looks like the crossmember is already spaced up high though. so maybe you're good there.

X2 on the E-brake cable. Something strange there.

Joe has adjustable upper control arms as well.

[Va68goat]

We eliminated the H-pipe and went with the straights duals. I may consider doing an X pipe later on but for now I'm going to run straight duals. We took the car for a test drive and all went well. Beside the trans swap we did a lot of upgrades. Working on getting the transmission computer programmed now. Here is what we did-

- TH400 to 4L80E with a US-Shift Quick 4 Gen 2 (TCI Throttle position sensor)
- Rear/upper adjustable control arms (replaced all bushings)
- Rebuilt the rear end with Strange 3.55 gears
- Moser axels and bearings
- New driveshaft
- Dakota Digital Gauges
- Jeep steering gear box
- Floor and trunk pans
- Exhaust tips
- New carpet
- Converted all exterior and interior lights to LED's

We're going to work on programming the trans. It came with a stock program but the converter is locking up too early (3rd gear). I've done some reading and asking around and it the consensus is to have the converter lock up around 48 mph. The US-Shift allows me to set 4 programs. I'm thinking I may keep the preprogrammed setting but change when the converter locks up. Anyone here have any experience programming the US-Shift Quick 4 Gen 2 trans computer?I'd like to get some thoughts on programming the computer for a little more aggressive shifting and maybe another program for a road trip (long distance). I can provide a copy of the engine dyno sheet if that is needed.

- Joe

[Formulajones]

Do you have a laptop?

It's best to use a laptop for the tuning where you can go in and get very detailed with transmission parameters.

With a laptop you'll see where you can play with the converter, have it lock in just 3rd, just 4th, or both, or not at all. It has ability to lock and unlock at any rpm and mph you choose. The Quick 4 is a nice piece.

[Va68goat]

Formulajones,
I do have a laptop. I have a MacBook and since US-Shift doesn't have the software for a Mac, I was able to convince my wife that she needed a new laptop.

I hooked up the new laptop to the trans controller but I think programming and making changes to the current program is a little over my head so I just looked around and didn't change anything. I spent a little time today reading about it and watching some videos. Just not that confident in making any changes. I was going to talk to tech support at US-Shift and get some help but I'd like to get to a point where I'm comfortable making some changes.

[darbikrash]

I can't really tell from the photos, but is the rear end supported at ride height? If it's drooping, then the driveshaft angle is not correct. Maybe put the car on the ground to establish ride height for the rear diff and see where you are.