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strange turbo noise?
I have a question for the board.
Over the weekend I was pulling my travel trailer (9-10K pounds) up a 7-8% grade in my 40tow setting. In 4th(direct) gear I was running 20-21 psi boost and just under 1200 EGT(pre-turbo). When I reached near WOT (around 2400rpm) I heard, in addition to or possibly replacing the normal turbo whine a strange, slightly lower pitch sound coming from behind the radio area. I assume that would be noise from the turbo. The best I can describe the noise is a "Eeeet, Eeeet, Eeeet" type sound. If I backed off the throttle even a little the noise would go away. I wondered if it was an RPM or boost issue, so I slowed down and shifted to third and pinned WOT. The boost went back up to 20-21 psi and RPM's up near 3000, but no noise. Later on the trip when on flat interstate I was shifted to OD and went to WOT the look for noise again. It came back, this time at about 17psi and around 2100 rpm. I tried my other chip settings and it will make the noise in any of them.
Unloaded I can run as hard as the truck will go and no noise will show up even up to 24 psi(the max boost I can make) in any chip setting.
Is this surge that everyone talks about? Could it just be my wastegate opening from drive pressure(I have the red line unplugged and capped)? Is my turbo checking out on me? Could it by chance be the serp. belt(it is OEM 80,000 miles on the truck)?
I've never heard this before, but I've also never ran it this hard since last season when I bought the travel trailer I had many issues that put my EGT's way to high to run this hard (leaky up-pipes, boost leaks).
Early '99 7.3L 4x4, supercab, longbed, 6spd, level kit,315/75/16 tires, 6.0 intercooler, Walker BTM, DIY Tymar intake, DP tuner-4 position chip(Stock, 40T, 80T, 80E), firestone airbags, Rancho 9000's, Titan V hitch.