Engine/Transmission (1994 - 1998) Turbo grumblings...

[newtrout]

I'm in love with my new truck! (at least it feels like a new one) Over the past month or two I've added a #8 plate, gauges, BHAF, 15. 5 degree timing, and the full DTT treatment. I had considered upgrading to a new truck with all the good deals out there right now, but for ~$3000 I have a truck that performs better than the 2002 I test drove!



I've got a new noise along with these changes. Twice I've done full throttle runs off the line and when I get off the throttle I get a noise that I heard described earlier as 'playing card in the spokes of your bike multiplied x5'. It sounds like it's coming from air filter/turbo area. I haven't been watching the boost gauge during either occasion. The obvious answer is to ease off the throttle more gently when running max boost, but I'd still like to know what I'm hearing. I heard it one other time when I stayed on the throttle during the big rpm drop from OD to OD lockup. I know that's a no no, but it happens every once in a while... ...



One other question. I've heard about a PCM upgrade that will raise shift points and raise the OD lockup speed. Any suggestions about where to have this done?, prices to expect?, etc?

 

[illflem]

You heard what is called turbo barking. It will happen to anyone who lets up on the throttle fast under higher load/boost. What happens is the turbo suddenly starts turning backwards from 100,000 plus rpm. High pressure built up in the hoses and intercooler has nowhere to go when you let up on the throttle so it flows backwards though the turbo and air cleaner.

It couldn't be good, I try to avoid it by not letting up the throttle all the way at once, rather do it in steps. Disengaging the cruise under load by tapping on the brake is a big culprit, keep your foot on the throttle and let it down slowly. My feeling is it also may cause the the rubber seal on an airbox filter to unseal letting dirt by. It will at least back flush your filter.