Alright so I am trying to go after what I assume to be a trans problem.. I have never had my auto trans slip or act weird so far. Every once in a while though when in 4th gear and I give it a little gas but not enough to downshift it to third (ex going up a slight hill but trying to save gas) around 50mph it makes a bad rattle/ball bearing sound. It does not do this every time so I cant just re create the noise. I dont know enough about the lock up converters and transmissions to diagnose this problem. I am not sure what this could be? I will include that my transfer case is empty ( I dont neglect it, i fill it up quite often but the fluid disappears, no leaks...?) If anyone has any info about this I would appreciate help.

 

Are you saying the rattle sound comes from the drive line region? i.e., under the truck or more likely to me, from the engine bay, like up top?

You fill the TC up often? There is no visual external evidence of leakage path? How about taking some good pictures and posting up?

When was last time trans had any maintenance? Can you track to anything maintenance-wise or other that occurred when the sound occurred?

Yeah, tossing lots of questions to help in diagnosing.

 

Fluid has to go somewhere. No signs of leaking? Strange. Is it leaking into tranny? Check that fluid and see if it is overfull.

 

That's pre-ignition/detonation. Get out of overdrive on hills... remove the spoon from the cup before drinking, take your hands out of your pockets when walking on ice, that kind of thing.

 

Are you saying the rattle sound comes from the drive line region? i.e., under the truck or more likely to me, from the engine bay, like up top?

-yes the rattle is coming from under truck feels like tranny because when the noise happens it sounds like its coming from the middle of the truck maybe toward the back (rear end was just rebuilt so its not gear related)as soon as the noise happens i usually mash down more or turn od off to get it to down shift and the noise goes away.

You fill the TC up often? There is no visual external evidence of leakage path? How about taking some good pictures and posting up?

- I make sure i check or fill the tc up before i know im going somewhere where i may need to use 4x4. Probably once each season, I will see if i can get some pics up tmr the case is fairly clean same with trans, no visable leaks and nothing on the driveway.

When was last time trans had any maintenance? Can you track to anything maintenance-wise or other that occurred when the sound occurred?

-I have put 15k and never done any maintenance on the trans yet 150k on the trans, i dont know its history. I plan on changing filter and fluid when i get a break from rain

I am assuming the tc is leaking into the trans some how.. I havent checked trans fluid levels yet though this was a spur of the moment thought to ask you guys after i came in from sea foaming a few of my cars. Ill check tmr and let you guys know.

 

Can you explain? Im running premium plus octane booster in every fill up, recent plugs, wires, and cap rotor. Doesnt sound like the ignition knock my chevy has if it is..

 

Sounds like spark knock from a blown plenum

 

Why does your engine require so much octane? Let's get that established before going too nuts in the typing department.

Generally, overdrive shouldn't be used except when cruising unladen on flat ground or downhill. Ignoring for now that it's tough on the transmission: When you're in overdrive with engine RPM significantly below the steep slopes of the HP/torque curves and you ask for more power than it can make, the PCM is going to try to oblige by, among other things, skewing the ignition timing just as far as it can. This will lead to dramatically increased combustion chamber temperature, and the risk of detonation increases dramatically right along with it. So push that O/D Off button when you encounter even the slightest hill at relatively low engine RPM -- you'll use less fuel in direct drive with the torque converter locked than you would in overdrive with the engine struggling, anyway.

I'm still a mite concerned that you feel the need to crank the octane so far up. Unless your SCT is tuned crazy hot you shouldn't need it. So... why?

 

That's what it sounds like to me also.

 

^me too.