Driveline grind/bucking

[novamodeler3]

An issue with my driveline is leaving me scratching my head, and looking for advice.

Upon rare occasion, while backing down the driveway, I've experienced the tranny to seem like it comes out of gear, followed by a LOUD grinding noise under my feet. Upon a gear change, grinding goes away, and things are fine.

Ive also experienced this issue while at speeds of 65-75 MPH. My remedy was to take it into Neutral, and let the vehicle sit for a minute, select Drive, and no issues.

And the last symptom is a bucking sensation at speeds about 55-65 MPH. Like I'm getting bumped from behind almost. A loud knock or hollow clunk in the left floorboard, around the transmission crossmember.

My ideas: A slipping ring in the transmission. Its a rebuilt factory 4L60E with about 80K mi on the rebuild. (was rebuilt at 150K)

The 4WD is engaging itself without any input from the cab. Could be shorting out and taking it out of gear, and loading up the Xfer case, causing the grinding sound.

Or the front differential is auto engaging and causing the bucking sensation at speed.

I had the wife do a transmission flush, with no remedy. Was curious where to go from here. Pull the 4WD relays and monitor the condition? Remove the electronic actuators for the Xfer case and front diff? My knowledge is limited with the electronic 4WD, and very limited in automatic transmissions.

I need a simple fix for the wife for now, as I'm deployed, and intend to make full repairs when I get home.

Thanks for the help!

-Justin

 

[novamodeler3]

Bump

 

[xanatost]

Sounds like a bad switch. Check a pull-it yard and see if you can find one. If nothing else you will have a spare switch. Mine done that once when I was messing with the button trying to get the lights to come on. If nothing else make sure its in 2 wheel drive and unplug the switch till you can look at it more

 

[novamodeler3]

Sounds like a bad switch. Check a pull-it yard and see if you can find one. If nothing else you will have a spare switch. Mine done that once when I was messing with the button trying to get the lights to come on. If nothing else make sure its in 2 wheel drive and unplug the switch till you can look at it more

Referring to the switch in the cab, correct? I have noticed in the past that sometimes the backlight for the 2HI indication would illuminate intermittently. Usually, a knock to the switch would fix it for a bit. Otherwise, the "AUTO" and 4WD options would shine bright and consistant.

Thanks for the tip!

-Justin

 

[livingez_123]

sound like it might too late for the simple fix. I can imagine the damage done to the trans during all of this.

 

[SunlitComet]

If the grinding occurs and changes with the"tranny" shifting, then it must be torn down for inspection. You might have a bum planetary set.