Torque converter going out?? m1008

[cocco78]

Was reading through a few old threads on torque converters as I think I might have a TC related problem. The trans seems to operate just fine, but there is a terrible "grinding" noise when shifted into R or D, there is no noise in P or N. The noise seems to go away as RPM increases, but at idle or very low throttle the noise is there. I noticed this the other day while in the woods doing some light wheeling, the noise kept getting worse so I headed for pavement and civilization, after a few miles on the road the noise went away but when I started the truck today it was there again. Fluid level is good, not burnt, and trans operates as it should. I haven't had much luck trying to find out what a tc sounds like as its dying, but I would like to catch it before it sends its parts through the rest of the trans!

Any ideas? Any good leads on a quality replacement TC??

 

[Keith_J]

Remove the lower TC cover/access plate and make sure all bolts attaching the flywheel/flex plate to the TC are tight. You have to rotate the engine to get access to all. Use paint pen to mark the ones you have torqued.

TCs expand as pressure builds and torque is multiplied. Loose bolts can scrape. You can also see the rubbing.

 

[Skinny]

You could have a flexplate starting to crack as well. Typically makes noise under heavy loads and then gets worse. Not much going on in a non-lockup TH400 TC. The only thing that could really fail is the stator bearing. It is a one way bearing so it either fails locked up or freewheels in both directions. Symptom of a freewheeling stator is sluggish acceleration. Symptom of a locked up stator is good acceleration but feels sluggish when cruising.

 

[cocco78]

Hmmm, sluggishness might be hard to notice on an 08 with 37s But really I don't think it feels sluggish.

I did read something about the bolts backing out and had planned on checking them. It makes the noise under no load and goes away when throttle is applied, so you only hear it at or close to idle or at speed when you let off the throttle and coast.

 

[Skinny]

Sluggishness with a 6.2opcorn:

Check the bolts. If they are boogered up, just remember that TC bolts are application specific and high grade. Don't replace them with hardware store stuff.

 

[cocco78]

I took off the inspection cover, nothinging out of the ordinary and symtoms still persist. To recap, trans makes grinding noise when put into R or D and goes away as speed or load is increased. No noise in P or N or when going down the road. This seems to point to the TC going out.

Any recomendations on where to purchase a quality replacement? I'd rather not get one at NAPA as I don't want to go through 3 of them before I find one that works.

 

[Barrman]

Check your motor mounts. If the noise only happens when a load is first put on the drive train and then only when the twisting of the drive train switches does the noise happen again? It has me thinking motor mounts, transmission mount, loose cross member, shifting linkage bound up or even the dip stick tube rubbing on the firewall. Is it possible for somebody to shift while you are under the truck? With the wheels chocked and the parking brake on of course.

 

[cocco78]

Noise only happens in 2 situations. 1. after you initially put the truck in gear, with your foot on the brake, it will sit there and grind. When you release the brake and accelerate the grinding will go away and isn't noticable anymore even as the trans is shifting gears. 2. when you are already driving and take your foot off the accelerator as engine rpm drops it will start grinding, like when you coming up to a stop sign, it will continue to grind until you take off again. Or if you shift it to N or P the grinding instantly stops.

This kinda leads me away from the items you suggested, although I have somewhat checked for loose or worn parts as part of my usually maintenance. I have laid under the truck while the wife shifted it in and out of gear and with as noisey as this truck is, it seems the grinding noise is localized to the bellhousing area. I didn't do this with the inspection cover off though, didn't seem like a good idea

I have read that as tolerances change in the TC from wear it can create metal to metal contact that can introduce metal particles into the rest of the trans and eventually kill it. I'm dropping the pan and filter this week to inspect, so busy with work lately its hard to find time for the army truck

 

[Barrman]

Is it brake pedal applied related? The power steering pump supplies the power brakes. There are 3 bolts on the pump mount that will work their way loose into the pulley. They make an awfull racket until you figure out what it is. If you pump bearings are loose, it could just happen when you push hard on the brake pedal.

Try using the parking brake to hold the truck still and then shift gears.

 

[cocco78]

No, it does it without the brakes being applied as well, they have no effect on the noise.

Thanks for all the things to check, now my routine maintenance list is getting bigger!