C6 Grinding in 3rd

[sambodean]

So the problems right in the title. I have a 1985 f250 with the 6.9 idi and C6. Most of the past trucks Ive owned with C6's have been bullet proof, but this is the first one STARTING to give me grief. I noticed when I was driving home the other day, while in third and final gear, it made a horrible grinding sound for a split second, and then went away. I drove off after inspecting everything and it was fine. Today, it was sporadic. that annoying sound happened 3 more times, before I said screw it, put it in 2, and drove it home on the back roads. It only grinds in 3rd gear, and never stays long. Any advice? I was planning a flush with a filter change. Im assuming some crap is stuck in a gear and causing this. The only problem is, the last time I did a filter change on a tranny, 2 days later the thing was toast. Hopefully the fluid isn't burnt in this one...

 

[FoolhardyIDI]

When ever I hear noise that sounds like its coming from the trans I like to check the u-joint's in the drive shaft. Also the slip yokes can some times have play in them causing a noise. Im sorry I don't know much about the C6 trans.

 

[franklin2]

If you pull the pan, that will tell you a lot. If the oil looks bright red and there is no junk in the pan, then you have a mystery. But if the oil looks brownish and stinks, and there is a lot of junk in the bottom of the pan, then that's not good.

 

[FarmerFrank]

2wd? Not good. 4wd, I'd check the transfer case. Might be a worn gear not holding in place. Not much to grind in a c6 going into third gear other than a clutch pack.

 

[CDX825]

C6s don't have much of a filter. It just a screen to catch big stuff is all.

No point in changing it because if its plugged your in for a full rebuild.

 

[sambodean]

Its 4wd, but that doesn't really make sense to me. if it was the transfer case, wouldn't it only be doing it when in 4wd, and no matter what gear I'm in? Either way, this is sounding like its going blow. Im assuming the first and initial grind is when a piece of something broke loose somewhere, and now, that little piece is stuck in there which occasionally finds its way to something. Ill drop the pan on monday, and change the filter. Hopefully gravity and the flow of the fluid will carry the piece out. Too bad whatever it is that broke, will most likely keep breaking and cause future problems.

 

[Kevin 007]

A T-case could still make noise when it the 2WD position. How does the trans fluid look on the dipstick? Red and sweet smelling? or dark and burnt?

 

[sassyrel]

the direct clutch pack is on, in both 3 rd gear,,and reverse. noise when in reverse???

 

[typ4]

No gears are under power when in 3rd, so likely not a gear train issue. No sense in speculating till you drop the trans pan , also drain the t case to look for pieces.

 

[sambodean]

Dropped the pan today. couldn't really find any shiny particles of metal, but I did find a few pieces of crap that looked like grinded up stone? maybe it was something made out of pot metal? Either way, the oil was still in good shape, so i replaced the screen with a new one, and bolted it up. On my way to draining the torque converter, I ran into an issue. It seems as though its an aftermarket converter? I bumped the engine over at least 6 times and still couldn't find any bolts. Im looking directly on the torque converter itself. The drain is not on the flywheel side, correct? Ive attached a picture that shows a square tab thats welded on the tc... Im assuming thats where the drain used to be. At any rate, can someone tell me which line in the engine bay I need to disconnect to flush this sucker out?

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[sambodean]

Ps, Ill drain the transfer case tomorrow, I just want to finish up the tranny before I move to anything else...

 

[franklin2]

There should be a very large hole in the flexplate, and the drain plug sticks through it. I have drained gas c6's before but never a diesel. I am assuming they have them too but not sure.

 

[sambodean]

There should be a very large hole in the flexplate, and the drain plug sticks through it. I have drained gas c6's before but never a diesel. I am assuming they have them too but not sure.

Theres multiple large holes in the flex plate, but I don't know which one is the drain. I don't want to take off one of the actual bolts that holds the flex plate on. Any way to know which one is the right one? any pictureS?

 

[sambodean]

Update. Got the tc and tranny drained and refilled. Went for a drive and boom, the grinding and the truck slowly came to a stop while it kept grinding. I tried shifting it to park, but the grinding got worse, same with 2nd and first. So I moved the transfer case to neutral and the sound went away, I dropped it to 4l and it started to make the sound again, but I slammed it further back (I had to get home, and I'm not leaving my truck in Richmond) and put it in reverse, no sound, no grinding, and I backed it all the way home lol. Soooo like some of you said, it has something to do with the transfer case. I think it just keeps popping out of gear and the teeth aren't fully meshing, creating the grinding sound. I won't know if anything ruined till tomorrow when I drain the transfer case. Any ideas what's going on?

 

[sambodean]

I worked up the balls to drive it with one foot on the transfer case lever keeping pressure against it in 2h. It came out of gear one time but I just shoved my foot a little harder and it was fine. What causes the transfer case to keep popping out of gear like this? This sound familiar to anyone else? I'm extremely happy is not the tranny giving me issues, but maybe it is? Could it be the splines on the tranny are not joining the transfer case correctly, or is it more likely something in the linkage is coming lose, or some type of worn out bushing that keeps it in gear?