Noise ID'd. How to fix?

[gymcarm]

In other posts, I have asked about a rumbling noise at idle and a clunk when I shut down. I found the source...The downpipe is HUGE, shiny, and mandrel bent. Not sure who made it, but it sure is a nice upgrade (also noticed the K&N air filter). The downpipe is hitting the frame. Is there an easy fix to gain clearance? Hopefully it is not motor mounts. It may also be something we have to live with.

Any suggestions are welcome. Wonder what else has been done...?

Thanks in advance...Jim

[Billman]

Give it a little clearance with a 'fine' adjustment tool.

Still better than a factory pipe...

[diesel65]

Check your engine mounts, When the engine is sitting on the frame you will get a rumble in the cab and your exhaust pipe will be that much closer to the frame.
Also when your drivers side engine mount goes bad there is a possibility of the oil cooler line rubbing against the bolt on the front differential.
I have replaced many engine mounts in our fleet of vehicles.
For some reason the 1999 Suburban eats them up, we are using GM mounts.

[autocrosser]

I was forced to heat mine with a torch and very slightly give it a little more clearance. I don't think it was settling of the engine mounts. They look good with no squeezing out/excessive compression of the rubber.

It just took a little fine tuning to fix it.

[gymcarm]

Thanks, I will look into the engine mounts first and then adjust the contour of the pipe if necessary.

It was a nice surprise to see these performance mods. It cuts down on the stuff I need to do.

How can I find out if there is a computer mod installed? The truck pulls strong, but with 4.11 gears, it will do that.

[Turbine Doc]

Gym,
If I'm not mistaken a 96 would require a reflash, if that is the case hopefully there is a Z Industries or BD sticker, or any other non GM vendor # on outside of PCM case. If not see if you can find somebody with a tech 2 or Snap On MT2500, go on a test drive with it connected look at fuel rate should be 25-55mm on normal driving, and up to 63mm on hard accel if PCM has a stock program.

It should go to 76mm + if a reflash or GM HD program, other than that probably no other way to know, you might want to give Kennedy a holler to see if he has any ideas. If you have the 76mm program I'd leave it alone as a reflash doesn't offer much more for the $600 asked to reflash for the daily driver.

If one were racing I think it goes to 80mm and has better shift points so I've been told, but IC & gages are required to run this program to be safe. I have read here that GM dealer can reset your PCM to take the HD 76mm program used in 99+ years if you have a good VIN match to your trucks specs.

This is best option IMHO for those without IC and gages as GM safety would be built in, (that said remember in 97 GM also upgraded cooling system to 130gpm pump and dual thermostats).

Heat rejection was/is/can be a big problem of the 6.5, I wouldn't add more fuel until offering some relief here, with down pipe & K/N sounds like a previous owner has addressed it some by removing exhaust and inlet restrictions which keep in more heat.

After trying a reflash PCM and not overwhelmingly impressed for the money, I went to junkyard and got a 99 PCM for mine ($125 vs $600), as a 96 though you might not be able to do this without some trial and error some have encountered problems with the theft deterrent learn which if memory serves correctly is not on the 96. Again check with JK he can maybe set you straight, I think maybe theft deterrent in only 97-99 just not sure of it.

[Bobbie Martin]

I would check the motor mounts first. I had to change ours at around 110,000 miles. They are a PITA, but can be done in one day with not too much trouble. You may be able to loosen the clamp on the turbo and move the downpipe slightly if it still hits. You'll probably have to tweak the exhaust pipe a bit if you move the downpipe.