AKlowriderZ71

iTrader: (22)

I was driving 45 mph up a small hill today, gave a little throttle, boost gauge went to about 4 psi. Heard some screeching over the radio. Coasted and the noise quit. Turned down the radio, tried it again and heard the same thing. Gave it just a little more throttle, the transmission is slipping in 4th, converter locked, screeching when slipping.

This happened last winter when towing snowmachines(~1500 pounds), and the 3-4 clutches(red alto) were smoked. My trans builder went back in with blue alto clutches and a carbonite band. They were all replaced one more time this last summer when I snapped the output shaft and grenaded some other stuff.

So, how do I make this thing stay alive? Should I not lock the converter until later? Should I stay out of 4th gear until a higher speed? I'm looking for good ideas here guys, something besides 4L80E.....

Truck goes to the trans builder tomorrow for teardown. I will report back with what he sees after it's apart.

Thanks,
Roger

FLT

iTrader: (1)

Sounds like you might have a torque converter clutch issue with the noise and all. If you had an issue with the 4th gear band you should also have an issue with 2nd gear. It uses the same part. I guess you will have to see what your trans guy see's and go from there.

AKlowriderZ71

iTrader: (22)

I did hear the same noise when it shifted thru second gear, but I have babied it and kept the trans out of overdrive for now. We will see what it looks like after it's apart.

AKlowriderZ71

iTrader: (22)

I took the truck in yesterday, it made the same noise and slipped in 4th, and made the same noise as the trans downshifted thru 2nd, when coming to stops. Happened every time. So I took Jim for a test drive to experience the problem, and the transmission worked perfectly. It didn't slip or make any noise. He drove it himself a few hours later, and same thing, no troubles. How can that be??

He's gonna pull the pan and take a look for debris, but the fluid (dipstick) looks clean and clear, and doesn't smell burnt. This is a little frustrating for me. Soon I'll be towing snowmachines hours away from home to ride in the mountains, and a breakdown in the middle of nowhere-Alaska would be a huge PITA.

Mangled03gmc

iTrader: (95)

Don't let it shift out of 3rd

Stangbanger

iTrader: (6)

I am kinda of interested in this. My transmission makes a high pitched noise only when the converter is locked in 4th gear. It makes no noise in any other gear and stop if i let off the gas until the converter locks back up. Hopefully its not going up on me.

chevrolet all the way

iTrader: (24)

it sounds like a converter issue if its doing it in lock up. what speed does it lockup and what throttle % does it come out at? also what type of converter.

AKlowriderZ71

iTrader: (22)

I don't have my laptop at work with me to check the settings, but I can tell you that it locks up in 4th between 40-43 mph. The speed limit driving thru Wasilla is 45 mph, and I let it lock up for better mpg. Also not sure what % throttle it unlocks, but I can tip into the throttle a bit, build 4-5 psi boost without it unlocking. Just a little more than that and it will unlock and/or downshift.

The converter is a locally built one, and the builder was given my goals, weight of truck, engine/supercharger/cam specs. It has been in the truck for a year now, and has been working well. It was cut/cleaned both times that I had troubles. It brake stalls to 2500 rpm as I requested, and I would label it as a "tight" converter. Daily driving, it feels stock.

If it is a converter problem, why would it make the same noise as the transmission downshifts from 3rd to 2nd when coming to a stop? I'm just asking because my transmission is really the only part of my truck that I don't completely understand how it works. Besides the fact that they work on black magic & voodoo......

Maybe my trans needs more voodoo and less black magic? lol

chevrolet all the way

iTrader: (24)

well if you are building boost in lockup that is not good for a single disc converter. depending on what the clutch is made out of you probably want it to unlock sooner because that is a lot of stress that is not needed.

transmissions can be crazy and make noises at random times like that. i just replaced my lockup clutch because dyno runs in lockup are not good for it lol. but when it went out there was a noise at the top of 1st and 3rd from the converter. went through the trans nothing replaced that could make a noise but now its gone with a new lockup clutch.

im pretty sure thats gonna be your problem there. but the only way to know for sure is to go through the trans and check it all out

AKlowriderZ71

iTrader: (22)

Gee, thanks!