roughstock

here's the Story, if I step on the pedal and accelerate, occasionally, my truck will bark the turbo when shifting. I thought this was odd with an auto transmission. Its more likely to do it with a load on it, like driving up a hill. Is this normal? its my first cummins with an auto. not liking it so far.
Any experience or suggestions??
Thanks

BroncoAZ

I've only managed to bark the turbo on mine once, that was when at full boost some dork pulled out in front of me, I went full on the brakes and got the bark noise. I don't think it is normal, but I don't know what would be causing it.

Numidian

My turbo barks if I'm under heavy boost on cruise control and I have to hit the brakes... Otherwise, pressure drops fast enough to not have it happen as I take my foot off the throttle and onto the brake.

roughstock

Mine does it on acceleration, when its shifting up. not when im letting off. Its odd.

JP-4.5

Are you sure it is not a boost leak? Do you have a gauge..

If you are not letting off the throttle I do not think the turbo is barking. Something else is happening,,

gorms

Is the transmission stock or modified? It's not unheard of for a built up trans to "bark" the turbo when the torque coverter locks up. Engine goes from higher rpm/flow unlocked to low rpm/flow locked very quickly and the air the turbo was flowing has nowhere to go.

JP-4.5

I had never heard of turbo barking from shifting? I am curious how the transmission shifting impedes the flow of the exhaust? I understand the rpm dropping but if you were accelerating how would the rpm drop affect the exhaust flow thru turbo?

Always thought you would have to lift throttle to have turbo reverse direction to allow boost to flow backwards.

I have a built trans and have never had the turbo bark upon normal/hard driving when accelerating. I have had the turbo bark when driving hard and let off throttle quickly to correct for rear end getting sideways or tires breaking loose unexpected.

Just curious how barking could happen under normal driving when shifting? Could some other restriction in the exhaust help this to happen? The only restriction in my exhaust are 2 turbos and then 5" pipe.

I was thinking maybe he had a loose clamp and when shifting or locking up the positive boost was leaking out somewhere not reversing flow(bark).

roughstock

JP, I have gauges and smarty Sr, set of #5. I have 4" straight exhaust with large straight thru muffler.
Don't think I have any boost leaks. I can check.
What numbers should I be getting for boost?

Gorms, it is stock. Its a fairly fresh Reman from Chrysler

lane22

under a load 4to lockup my2003 truck will bark the turbo and has had this problem for 227456 miles on truck

StealthDiesel

Turbo barking (if that what the OP has), occurs on the compressor side not the exhaust side of the turbo.

Gorms has it exactly right and turbo barking, especially a larger aftermarket turbo, with an aftermarket auto trans is common.
The guys usually adjust their driving to prevent this as it is not good for the turbo at all.
What they do is lift on the throttle just before the transmission shifts. This reduces boost and prevents barking.

SOhappy

My 2003 did it every time between 3rd and OD when I was being light on the throttle, or towing without the OD locked-out. Don't think it hurts anything.

roughstock

sounds like my condition. Ill try to ease up on throttle going up these hills when It is about to shift. Thanks

Hvytrkmech

Do you have the waste gate turned off through the Smarty?

roughstock

Mines an 2003 model, my truck doesn't have that option.

roughstock

think I may have a boost leak.