RPM vibration in floorboard

[rammertide07]

Today while I was waiting in my truck for my wife...I was playing with the throttle. I was in park, and I noticed at about 1,100-1,200RPM there was a vibration in the floorboard. I tried it all the way through 2,000 rpm and thats the only spot. Any ideas what it could be?

 

[DaveBen]

My guess would be the exhaust system resonating at that frequency. Not uncommon.

Dave

 

[rammertide07]

I guessed it might have been something like that. But I was thinking worst case scenario...maybe something someone else has had experience with. Thanks Dave

 

[JLDickmon]

I'm with Dave

 

[altered]

I like to turn wrenchs for fun and I have messed with a few 7.3's with exhaust and I agree with dave and jldickman, one thing you might want to check if you still have them is the heatshields especially where the downpipe comes down if your using a 4". the clearence there is tight and it's something that could be fine for a while and then start up leaving you to believe something has gone wrong.

 

[BIG JOE]

I like to turn wrenchs for fun and I have messed with a few 7.3's with exhaust and I agree with dave and jldickman, one thing you might want to check if you still have them is the heatshields especially where the downpipe comes down if your using a 4". the clearence there is tight and it's something that could be fine for a while and then start up leaving you to believe something has gone wrong.

Yep, Heat shields.. when the engine torques up.. purdy common.

Slightly loosen the downpipe clamp, at the turbo.. tap a wooden wedge in-between the pipe where it is closest to the heatshield(s).. tighten the downpipe clamp.. Remove the wedge..Done Deal.

 

[rammertide07]

Yep, Heat shields.. when the engine torques up.. purdy common.

Slightly loosen the downpipe clamp, at the turbo.. tap a wooden wedge in-between the pipe where it is closest to the heatshield(s).. tighten the downpipe clamp.. Remove the wedge..Done Deal.

Thanks Joe....but what is the heat shield?

 

[rammertide07]

Speaking of exhaust....has anyone else had problems with birds try to build a nest in them? I've done blasted the birds and nest out once and they keep coming back for more. I'm fixing to put a screen on it the next time they run back up in there and let the truck run.

 

[BIG JOE]

Thanks Joe....but what is the heat shield?

Unless they've been removed.. where the down-pipe curves toward the rear.. there's a sheet metal shield affair (or two) to keep the exhaust pipe heat from heating up the p-side floor area.

When you go from 3.5", to 4+" pipe* set-ups.. the clearance(s) between the new, bigger pipe, and the shields, can be minimal. If you don't allow (Shim) for it, before you tighten all the clamps during the install.. after a new exhaust system "settles-in" (so to speak) ..... When the engine torques over, under loads, or even during a Rev from idle.. The pipe will touch the heat-shield(s)... giving you a PIA, Buzzing, and/or, a Vibration.

There's also a couple places on the mid to lower area of the Firewall that can need attention too.

The Best fix is to loosen ALL the joint clamps.. shoot'm with WD-40 (or the like) then tweak the system side to side**, then block it with shims (I use wood) in a position where it won't/can't touch anything. About 1" + will usually be enough. Bending the heat-shields a tad is good insurance too.

Joe

* Brands/Makers can be a bit different in the QA of the design. IMHO.

** With ALL the clamps loose, including the Turbo clamp [slightly loose], if you [rotate] the down-pipe (pry-bar).. the rest will move side to side. A Helper or two is GOOD.

All the above is for the 99+ 7.3's.. Not sure of the configurations on the rest.

 

[rammertide07]

My only clamp is at the turbo. I had my exhaust welded in. Only other thing I could imagine adjusting are the hangers. I'll check it out as soon as it cools down. I feel like a fish out of water its so humid outside