Anybody else experience turbo bark shifting into overdrive? Since I installed my Goerend tranny it usually barks when it shifts into overdrive at least a little, and if I'm really into it, it barks BAD. I'm careful not to let it bark too much by letting off too quickly, but I can't really help this. Sign of turbo wear? Hmmm....

 

With the stock transmission, the loose torque converter didn't let engine RPM drop as much during shifts. With a tight torque converter, the greater engine RPM drop reduces swallowing capacity of the engine. In other words, the turbocharger is suddenly producing more airflow than the engine can accept. The pressurized air in the intake system, since it can't be forced through the engine, flows back through the turbocharger's compressor section.

This flow reversal is technically called centrifugal compressor surge, but has been described on these truck forums as "turbo bark". Surge unloads the compressor impeller and shaft during the flow reversal, then loads them again as the compressor begins to compress air again - this can ultimately lead to cyclic fatigue failure of the impeller or shaft, but the smaller turbochargers used on our trucks can generally tolerate more cycles of surge than large industrial turbochargers before failure.

For those familiar with compressor head/flow maps, head is held constant but flow drops, moving the operating point left to the surge line.

Rusty

 

What turbo are you running, this is very common with large 66 chargers

 

If mine shifts into OD at around 20psi it'll bark the turbo. I usually back off the throttle just a tick when it shifts to make sure it doesn't do it.

 

Just runnin the stocker right now while I save up for a new one.

 

Dang that converter must be pretty tight if your surging a stocker

 

i had a 64/14 from htt that would so bad when towing that i traded it for a 58/14 with the brother in law this thing would bark down to 12 psi pulling the cat didn't sound to good either it would bark 4 to 5 times when going into 4th lockup dave builds them tight

kiley

 

Mine would do it with the stock turbo when I was running a 91 converter. I bought a BD blow of valve because I was told it would help, but it's only designed to open when you lift the throttle, so i just learned to drive around it.

 

Not a sigh of turbo wear!
To prevent barking, be sure you're accelerating when it shifts into OD. THEN back out slowly. Had to do this for two yrs with a KSB-1 and a tight DTT converter. Combine this with locking out OD till over 55 mph and you will never bark again.

Takes a little practice but not that hard, IMO. Just a learned skill and part of driving a bombed automatic.

RJ

 

Yeah my 66 does it alot, but i learned how to drive around it too, i always have to let it hit 4th manually, and im either in the throttle alot or none and it shifts ok

 

Mine does it once in a while to at around half to 3/4 throttle. Full throttle it wont. Just have to learn when your will shift. Then you just let up a bit til it shifts and get back in . Works great like that.

 

Haha...guess I'll play around a little and figure out how to keep it from barking at shift. Sounds like it's not too hard. My converter's a Goerend triple lock w/ the 15 blade stator. Not sure what the 91 or 89 numbers mean.

Dzlfarmboy- what does your truck look like? I pulled at Centerville last weekend and saw you were there, but don't know which truck was yours.

-Josh

 

Black 2001 6" Stack up the middle, pulled in the open class and blew the tires off right off the line and didn't pull nothin. Gonna pull up to the elks lodge in c-town on the 21st with a real sled.

 

Mine barks shifting into O/D too when I'm at 1/2 throttle or so. It really barks if I give it throttle just before it shifts. I think it's worse since I put the 4" pipe on. I keep O/D off until 50mph or so and it's fine.

I've also got a relay wired in that starts the truck with O/d off. I'm really glad I spent the hour it took to install it.

 

Well since my PCM is fried I have to run the lock-up and OD on toggle and I have noticed some pretty serious turbo bark if I shift it too soon. Like others have suggested just lock it out until you are over 55mph and you will be fine.