You are here: Ford F150 Home » How-To Technical Articles

F150 Y-Pipe & Cat-Back Exhaust Install

*1998 Ford F150 4x4 S/Cab with 4.6L V-8, 4R70W 4spd electronic automatic

Follow these instructions at your own risk.

Before I start I'd like to thank my friend Rene who did all of the TIG Welding. It wouldn't have been possible without his help and the use of his co-worker's workshop. THANK YOU! I owe you buddy.

Note: wear safety glasses while under the vehicle for eye protection as there's lots of dirt and grime under there just waiting to drop into your eyes.

Time For Job:

5-7 hours approximate if you have most of the right tools for the job.

Tools needed for the job:

safety glasses.
tig wire-type welder & welding helmet.
2 1/8 - 3 inch pipe expander tool**
pipe cut-off tool** (chain type with cutting wheels) or cut-off saw or hacksaw, cutting torch.
ratchet and socket for muffler clamps plus 10mm socket or wrench for skid plate bolts.
jack stands or lift.
extra jack stand for holding exhaust components up before welding or adjustable tie down straps.
flashlight or worklight if the area is dark.
long leather gloves (great for grinding with hot sparks).
hand held grinder with cut-off wheel.

**bought from www.jcwhitney.com.

Parts needed:

Flowmaster universal tailpipe kit (4 piece 3 inch) #15902
Flowmaster y-pipe #Y-250300A
one 3 inch exhaust pipe clamp (where rear pipe exits y-pipe for future changes if needed)
one 3-4 ft section of 3 inch diameter aluminized exhaust tubing (some shops will custom cut the length you need)
one 2.5 inch diameter mandrel bent 90 degree elbow
one 2.5 inch diameter mandrel bent 45 degree elbow
Dynomax Ultra-Flo #17220 Welded 3 inch in/out performance muffler (you can use the muffler of your choice as long as it's 3 inch in/out pipe fittings)
An exhaust hanger with strap for 3 inch pipe by the muffler
Vibrant Performance #1556 stainless steel exhaust tip. 3" inlet, 3.5" outlet, 20 inches long, slant-cut.

I bought everything from www.mopacauto.com (best prices in Canada) except for the two 2.5" mandrel bend pipes (www.JCWhitney.com) and the muffler which I bought slightly used.

Parts Cost:

Y-pipe $57.15
3" universal tailpipe kit $93.55
3" pipe clamp ~$4.00
3ft of 3" aluminized pipe $7/ft or $21.00
20" long 3.5" diameter stainless tip $54.00
Dynomax muffler, used $50.00 (new would be $100-150)
Exhaust hanger $5

Total System Cost: ~$282 + applicable taxes. Mig wire welder (TIG is best) rental 4 hrs $28, 24hrs $40.00CDN. You can rent a welder from Home Depot (if they rent tools) or www.unitedrentals.com or a TIG welder from Hamel Equipment Rental in Coquitlam, BC. TIG's are about $100 a day to rent with gas, if rented from Hamel on Friday it counts as weekend rental, same $100 rate. It seems very few places rent TIG welders on a daily basis, usually weekly so shop around.

All prices shown in Canadian dollars. For approximate US currency divide listed prices by 1.5 , ie. $57.15CDN y-pipe is about $39 US.

Procedure:

Wait until the vehicle has cooled off for at least 1/2hr if you've just driven it to avoid getting a burn on hot exhaust components.
Jack up the passenger side of the truck so you have more room to work underneath. Make sure to use jack stands for safety. Don't just rely on a hydraulic jack.
Disconnect the negative battery cable to prevent computer damage while welding.
On 4x4 models, remove the skid place under the crossover pipe. It's mounted with 4 x 10mm bolts on my 98. Remove the passenger side bolts and loosen the driver's side bolts and it slides off. You'll need to remove it so you can access cutting off the crossover pipe at the t-junction and for y-pipe fitment/welding.
Remove the muffler pipe clamp located after the T junction. If it's rusted on simply use a grinder with cutoff wheel or a hacksaw and cut through the u-bolt of the clamp on either side. Do not cut the exhaust piping itself.
Using the cutoff tool or hacksaw/sawsall, etc cut the exhaust pipe about 1 ft ahead of the muffler and roughly 2 ft behind the t-connection.
Using the grinder with cutoff wheel now cut the muffler support rods off the rear of the muffler and behind the rear wheel where the hanger is welded to the exhaust tailpipe. Cut as close to the pipe as you can as the hanger back there will be re-used. The old exhaust system should drop off as you cut the hangers.
It is possible to carefully remove the old exhaust system by pulling it forward over the rear axle. You may need to rotate it carefully to negotiate getting the tailpipe over the rear axle.
Physically remove the remaining 2 ft of pipe behind the t connection by twisting it around. Don't cut it off as you'll be using the remaining pipe to connect to the flowmaster y-pipe. It may help to use your cutoff wheel and cut some slits into the pipe to be removed otherwise the pipe may grab the front pipe simply from being distorted from the muffler clamp that you removed in step #5. It will come off eventually. Be patient and curse a bit. Mine was a b_tch to get off.
Take a tape measure and find the distance from the rear of the old muffler (where the muffler hangers are) to the remaining pipe after the t-connection. In our case it was approximately 57 inches.
Take the 59 inches, subtract the length of your muffler, in our case 19 inches, and also subtract the length of the short side of the y-pipe which is 15 inches. You're left with 25 inches. This is the approximate length of 3 inch pipe you need between the y-pipe and the muffler. You can cut a length of 3 inch aluminized pipe to that length with your cutoff tool or bandsaw or grinder with cutoff wheel. This measure is not critical, if you only bought 2 ft of 3 inch pipe for this that's ok. We'll adjust the length of the tailpipe pieces.
Layout the 3 pieces on your steel workbench. Make sure the muffler and y-pipe are horizontal on the same plane. In other words the y-pipe is wide in the same direction as the muffler is wide. Using the TIG welder or welder of your choice weld the muffler to the 3 inch pipe and to the y-pipe. In our case the lengths given above are an inch or so short for the 3 inch pipe because we butted each section to the next for welding (no slip joints) because the muffler was used with pipe welded into it already.
Position the 45 degree and 90 degree elbows in approximate positions and cut the driver's side pipe an inch or two long and cut it off at the t-junction a few inches from the joint. Then use a cut-off wheel on the grinder to get rid of the rest of the metal till the hole is flush with the passenger side pipe. Cut a piece of pipe off the old stuff large enough to patch the hole. Weld the patch on the hole.
Get some tie down wide straps or bungee cords and lift the finished assembly under the truck. Attach the straps to the fuel tank supports and the frame so the muffler section is being held up as shown in the pictures below.
Push the assembly forward so the short part of the y-pipe 2.5 inlet is slipping over the existing passenger side tailpipe. Be careful though, if you push it on too far the muffler/tailpipe will move toward the outside of the vehicle. This is due to the y-pipe being a V shape. Just slip it on enough so your muffler is still pointing straight back. At this point you can weld that connection making sure that your muffler is straight under the old support straps. Get creative with temporary straps to keep the muffler where it should be. Watch the vertical height too.
Now it's time for the driver's side of the y-pipe fitment. Slip the 45 elbow into the driver's side of the y-pipe. Trim it's length as needed positioning the 90 degree elbow so it lines up with the cut off driver's side crossover pipe. You'll need to trim the 90 elbow as well for length. Be careful. Cut too long, then fit the pipes again. It's better than too short. The 45 can fit into the slip joint of the y-pipe. The other connections can be butted end to end and welded in place. If the slip joints don't fit then welding will take care of it. Make sure all joints are fairly flush fitting, if not use a grinder to make adjustments. When everything fits, weld it up!
Now we have to fit the tailpipe section. They're all slip to fit pieces that need to be cut to the right length. The flowmaster kit is numbered. Start with the lowest number piece first as shown in the instructions that come with the kit. Have an assistant hold the first two pipes (slip jointed together) over the rear axle and mark the amount of pipe to cut off at the muffler.
Cut the first pipe to length, fit it in the muffler, attach the second pipe. Make sure the fitment is between the rear passenger side shock and the spare tire and not touching either one. Do the weld at the rear of the muffler to the first tailpipe piece now. Discard the 3rd piece in the tailpipe kit (#35) and use #36. We found this was the best fit.
Measure and mark the cut off on the 2nd piece going over the rear axle and cut that for length. If you're adding a tip, cut off enough so the tip brings comes back under the body. Fit it back in and slip on the #36 last piece bringing the pipe to behind the rear tire. Weld the joint just before the rear axle now and the last tailpipe section to the over axle pipe.
The rear hanger can be reused if you cut it off very close to the old pipe. What's left will be a straight rod hanging down that can be welded to your new pipe.
You may be able to reuse part of the old muffler hangers. I bought a new one that clamps to the pipe with a 3 inch muffler clamp, has a thick multi-layer rubber strap about 8 inches long with a big hole in the strap every inch or so. From that I used a big S hook to hook into the pipe running across from the old hanger to old hanger. Alternatively you could use a steel strap to fasten the rubber hanger or a threaded hook and a big washer and locknut to fasten it at the body.
Weld the tip to the tailpipe. Leave at least 1/2 inch clearance to the body panel for exhaust/engine movement.
On 4x4 models, replace the skid plate under the crossover pipe. We had to cut a 3/4 inch circle notch out of the skid plate for pipe clearance.
Check the fitment, if anything is touching try to adjust the hangers so it doesn't. The muffler hanger can pull either left or right.
Remove the temporary straps holding the exhaust after the hangers are all in place.
Spray some high temperature aluminum paint on the welds/joints to prevent corrosion. At high temperatures it may turn colour to a light brown but it still protects the metal.
Bring the vehicle off the jack stands, lower it onto the tires.
Reconnect your battery and fire it up. Enjoy!

Tips:

We used welding rod that was a combination of steel and stainless steel #309 I think which had the best results on the welds. Because of the stainless content the joints won't rust easily either. Some of the piping, especially the 3 inch straight bit I bought from Mopac had different metal composition making welding worse (you could tell) but it's still a solid weld. Perhaps there's some nickel or other alloy in the mix.
Be careful when cutting off the crossover pipe from the t-junction. Keep the cut off wheel away from the oxygen sensor and more importantly the torsion bar from the front suspension. It's a bit tight in there so keep some different sized cutoff wheels handy. We also used a small air powered cut off tool to get into the tight places.
Take your time. Measure twice, cut once! Think before you do. Reversing mistakes is a pain in the you know what.
We welded the entire system but you may want to make a slip joint where the pipe coming from the muffler joins the new y-pipe and seal it with a muffler clamp so that it's easy to remove if you need transmission work done. Otherwise I suppose you can cut the pipe after the y-pipe and weld it back on again later. I'm not planning to drop my tranny any time soon so we welded everything.
Watch the clearance to the transfer case/transmission when fitting the 45 and 90 elbows. It's a close fit with 1/2 inch clearance in one spot.
The OE 1998 exhaust tubing metal is funky stuff. If you can't cut through it entirely and have a little tang of metal holding two pieces together you can twist it for 15 minutes before it finally breaks. Amazingly frustrating stuff!
It looks easier than it is so if you don't have good help or the right equipment it's best to leave it to the pro's.

Pictures:

Here's the old junk

Driver's side cut off

Y-Pipe fitment before welding

New driver's side piping

Y-Pipe from muffler

Dynomax Ultra-flo Welded 3" SI/SO muffler

Patch from driver's side pipe

Temporary straps before welding

Shot from front

Another shot from the front

The Y-Pipe (aluminum paint is already discolored by heat)

Finished Y-Pipe

Over the axle

Shot from rear

Here's that big tip, note old hanger reused

Another "tip" shot

Sound Files (mpeg compression Wave file):

Click here to play an mpeg compressed Wave file of my OEM exhaust. Please right click on it and save-as to disk so you don't download it many times if you want to play it again. This sound clip was recorded with a cheapo computer microphone in my carport. There's a 1/4 inch hole in the muffler and it has the airbox mod with an open k&n filter so it may already sound different than your 4.6L F-150. Please note this file is 170kbytes in size and may take some time to download via dial-up modem.
Click here to play an mpeg compress Wave file of my finished exhaust system. Recorded again in the carport, same volume setting on the microphone but it appears too much when you stomp on it. Sounds sweet. You'll hear some squeaks from the springs, etc as I drive out of the carport up the driveway and roll back down into the carport and rev one last time. It's also 170kbytes in size.

Forum user "Hawkeye", from http://www.fordf150.net/forums/index.php forums, provided these sound clips of his 4.6L F150:

Click here to play his OEM exhaust sound. It's 93kbytes in size.
Click here to play his dynomax ultra-flo exhaust sound. It's 122kbytes.

Both sounds were recorded sitting in the cab of his truck.

I might post a video clip of driving off later on when I get around to it as the sound is different driving than sitting there and revving it. Even the OE exhaust sounds good when you rev it while not moving, which is deceiving.

This article has been generously donated by Peter Ferlow.