Vibrations-Exhaust System

i looked under my truck tonight to examine the exhaust system and how it is supported. Looks like the exhaust manifold is integral with the block. There is a flange bolted to the integral manifold that feeds a single pipe on each side of block. The 2 pipes (1 each side) have a rigid support attached to the firewall. All other supports except one, have rubber attachments to the frame to absorb vibrations and allow for expansion. On the driver's side, just downstream of the catalytic converter, there is a curved solid Rod support attached to the frame with no rubber dampener. However, the rod is curved around the pipe and appears flexible enough to not be a problem. If the exhaust system is the source of the vibrations people feel it has to be coming into the cabin through the rigid supports bolted to the firewall. Seems strange to me to have a rigid support that close to engine. There is a large temperature increase from ambient to operating temp. I am guessing the exhaust pipe gets over 300-400 deg F. The rigid support may cause the pipes to be highly stressed in that the bolted attachment to manifold and bolted rigid support can't be more than 24" apart? I know Toyota has smart people designing these trucks. I just can't imagine that rigid support is needed. It is located on the curved pipe as it drops thru the cavity between the engine and firewall so there should be some flexibility to allow exhaust pipe to expand and thermally grow away from manifold as it heats up. I wonder IF you unbolted the firewall bolt IF the vibration would go away? The manifold connection and downstream rubber mounted supports look adequate to support the exhaust system. Has anyone ever seen a rigid support so close to an exhaust manifold?

 

Which support are you talking about that is a rigid support from the exhaust to the frame? I haven't seen one, do you have a picture? I may just be overlooking it.

There is another rod that goes over the exhaust on the 4x4's driver side but it is referred to as an exhaust blocker bracket or something. Probably to keep the exhaust from travelling up and hitting the front driveshaft but I'm unsure. It is not bolted to the exhaust though.

Vibration can very well travel through rubber too. The hangers only "reduce" vibrations felt but if it is much larger to start, well, it doesn't do much good.

 

Yeah, I don't get it. How exhaust could be rigidly to the chassis, let alone the firewall?

 

If you are lying under truck forward of transmission, each pipe curves vertically upward and ends up bolting to the exhaust manifold. About halfway up the rise there is a black bar that is bolted to the firewall (single silver/gray bolt) and the other end is bolted to the exhaust pipe. You need a flashlight to see it. From memory the bar was about 6" long and vertically oriented hanging down, about 1/2" wide. The first thoight I had is " engine vibrations will travel to firewall". I remember seeing 2 catalytic converters in series on each pipe. I didn't realize there are 2 per side? The support is between the manifold and the first converter, heading away from manifold. There is also an in-line bolted joint so pipes can be removed w/o flange at manifold.

 

Maybe these are "shipping bolts" dealer forgot to remove?

j/k

Sorry, not trying to make fun of you, I just have hard time visualizing it. Please take and post a picture if you can.

 

Yea OK, maybe tonight.I will get under truck tonight and take pic

 

Do you have this vibration syndrome?

Are you going to pull the bolt and drive it a bit?

 

I am almost certain those bolt either to the transmission (may be engine, can't remember which right now), but if you can get pics of something bolting to the firewall, that would be an interesting area to look at.

I also suspect those provide a separate load path to reduce stress on the manifold and/or minimize deflection.

 

Chuck: I have a slight vibration between 2000-2300 but if no one on here had mentioned it I would not even have noticed it. I know that with an engine and all the connection points, a resonance is likely to occur at some rpm range just hopefully not to the level of being annoying. The people saying it is like a belt sander and causing numbness makes me think a bolt is loose?

I suspect the rigid supports are to protect the unusual manifold design but that hard connection looks perfect to impart vibration into the body, floor, steering wheel. If I had vibration that made hands numb I would be putting a torque wrench on these rigid support bolts. I might loosen both up and drive it to see if whatever slight vibration I have goes away but if it is needed to protect manifold I am hesitant to do it.

 

It would make sense if they bolt to the transmission near bell housing or somewhere.

 

I've looked quite a few times under the engine, etc. I can't believe I would've missed a solid connection between the exhaust and frame. I'm taking a look this evening.

I've been noticing that there is some unfiltered exhaust rasp that feels like it's coming through near the brake pedal. Like there's one of those "sound induction tubes" or some intentional vibration/sound path. You know, to be more "trucky".

 

Guys, I may be wrong but I will take pic tonight. I thought the bolt was to the firewall. In any event, I am almost positive there is a rigid (no rubber) support on the exhaust pipe on each side.

 

Ok , I was wrong. The rigid supports are attached to transmission housing which is good as the engine moves as a unit. I attached 2 pics of that. I also attached 2 pics of the curved Rod that I thought was a support that has no rubber. It is NOT an exhaust support. I don't know what it does? It is located on drivers side at cross member where pipe turns 90 deg to go over and join passenger side pipe. I have 1 pic of exterior frame attachment and 1 of interior frame attachment.

 

It is an exhaust pipe stopper bracket only on 4WD versions

 

What does it do? Why doesn't 2WD have it? Pipe routed differently because no transfer case?

 

I would have to take a closer look but typically stopper brackets prevent a clash with other components under extreme circumstances. Either "normal" operation or some failure mode. I have a hard time believing the exhaust can flex that much to hit that bracket during normal day to day driving, but I plan to get a camera under there this weekend to check a couple suspect areas.

 

I agree. Just can't see it moving that much. I did notice that the exhaust pipe on 4WD is not a round cross section as it traverses across to the passenger side. It looks kinda flattened out. I thought mine had hit something but I looked at 2 others at dealer and all are formed same way. Probably to maintain another inch of ground clearance

 

Totally bummed about this one. Intellectually I knew that the engine couldn't be on flexible rubber mounts and the exhaust which is rigidly attached to the engine couldn't be attached rigidly to the frame. But I was hoping for a quick fix!

 

I get a repetitive vibration between 40-60mph in 4th gear when at light throttle .if I take my foot off the pedal it goes away .if I punch it it goes away.only when crusining at the same speed which is unfortunately half of my driving due to traffic and non highway roads ..i am desperate for a fic as it is annoying a d somewhat worrysome .i too have noticed the bar that goes from the exhaust to the transmission and thought about using a high temp gasket permetex tube to possibly put on the end of the rod.let it dry and then reattach in hopes that it might dampen what I'm getting..but not sure if that area is what is causing it ...with the truck started i can most certainly feel alot of vibration in that black bar ..i also get a little bit of vibrarion in the steering wheel but other areas not so much..made me think maybe the power steering was the cause??? I am thinking of trying a differwnt fluid to see if it helps but again not sure if thats the problem ..my main concern is the 40-60mph repetitive vibration/sound .i dunno if its exhaust or transmission or whats going on ...waa thinking of trying a magnaflow overland series with ndt to hopefully take care of it as well but again that might be a 800 dollar throw it at it and hope it fixes it type deal and end up with the same or possibly even worse issue. I know at certain rpms and frequencies sound waves with cause some resonance but I dont understabd it enough to know for sure what to do ...it does feel like its coming from.the drivers side by the brake pedal ..could removing the cat converter and replacing with a high flow one help?? If I kept the same.cat converters and only changed from the y pipe and back would it even help if the issue sounds like its from the cat/manifold area?? My thinking is theres tso areas of restriction.the muffler with all.the baffels and the cats ..i know they say length of the whole system will change the sound waves etc so anyone with more knowledge on exhausts or anyone has any thoughts on all this id appreviate it