06 LBZ Slipping Out of Gear

[BearsFan42]

Wanted to see if I'm headed in the right direction.
My son and I were headed out of town, going about 45 in light traffic when the truck popped out of gear. RPM's shot up and so did the speedometer. While trying to get off freeway, it would pop back in gear then back out. No trouble lights on the dash
Got off the freeway shut her down and checked out the truck. I have an Edge tuner installed so I ran the diag and no codes were found.
Finding nothing obvious, fluids all good, no burning smells, etc. fired the truck back up and shifted in and out of gear and it seemed ok. Decided to nurse it back home, and just as I pulled out the gas station, it popped out of gear again. Nursed it all the way home. About every 1.5 miles it popped out of gear and anytime I let off the pedal it popped out of gear, had to basically stop and let it find its way back into gear and get going again. Sometimes it would find its way back into gear at about 15mph and the front right tire would lock up.
Once we got home, threw the truck in 4hi and 4lo to see what would happen as I ran drove up and down the street. Trans shifted all the way up and down without issue in 4hi, never popped out of gear, same in 4lo.
Checked the trans fluid again, full and red no burn smells. Dropped the external filter, and check the magnet for metal, minimal found, similar to what I always find when i change the filter.
Checked the fluid in the transfer case, still full, no burning smell, not much darker then when I put it in last year.
Threw another code reader on the truck to see if the Edge had missed something. Still no codes.
Right now I'm thinking I need to rebuild or get a new transfer case since the trans shifts cleanly all the way up and down when in 4hi or low.
Any advice, thoughts, would be appreciated.

 

[DAVe3283]

Since the speedometer jumped up with RPM, that sure sounds like the transmission and transfer case are working, since the speed sensor is on the transfer case tailshaft.

I'd personally start looking for the problem rearward of that speed sensor. Could be the output shaft splines, driveshaft yolk, u-joints, or rear axle (gears). Pulling the driveshaft is a prerequisite to pulling the transfer case, so it makes sense to look it over first.

The transfer cases are know for an issue called "pump rub", so if you've never done the fix for that, that might be your root problem and the transfer case might be trashed after all.

Let us know what you find!

Sent from my Sony Xperia 1 III using Tapatalk

 

[vern650]

a buddy is currently rebuilding his transfer case in his 04 because it kept popping out of gear. His is a manual tcase, but the internals should all be the same. The shift forks in his case were completely worn out.

 

[dndj]

My son's 05 LLY truck had the same issue. Truck kept going to neutral, then re-engaging. Eventually wouldn't move at all unless he kept his foot on the Tcase shift lever and forced it forward. Tcase shift forks were completely worn out.

 

[BearsFan42]

As an update, went ahead and put in a rebuilt transfer case. Didn't solve the problem.
Thinking it might be the TCM, since the tranny runs fine in 4hi and low. Any thoughts?


A few tips on changing the xfr case. There's a bunch of Youtube videos on how to.
Definitely get the 15mm stubby box end wrench. Makes getting to the top nuts much easier.
A lot of the videos say that you dont need to drop the cross member support at the back of the tranny. They my not need to, but it makes life a lot easier if you do, especially on your back in the driveway, and its not that much work to do. Support the transmission, drop the cross member and the transfer case comes out, and goes in pretty smooth.
When the transfer case is out, and you putting in a new one. Mark the new one with all the locations for the wiring brackets. You can install them once the transfer case is in. That way your not fighting sharp sheet metal while your trying to muscle the case up and in.

 

[JoshH]

Have you pulled the cover off the rear diff to see if there is anything going on inside there that might be causing the problem?

 

[BearsFan42]

Haven't tried that yet. Kinda figured since everything works in 4hi and 4lo, it wouldnt be in the diff, but its worth a look, even for just the fluid change.

When I fired it up after putting in the new Tcase, I did notice a couple new things i had not noticed before, when I fired it up after putting in the new Tcase.
When in 2hi and I put it in reverse or drive, it does not go into gear but the speedometer jumps up to about 5 miles an hour sitting still. When in 4hi or lo, i put in gear and it locks right in and speedometer stays at zero.
When in 2hi and going from R or D back to Park, transmission grinds a bit before going into park. IN 4hi or lo, transmission shifts from P to R to D back to P with out any issues.
.
Another bit of info I forgot to add earlier, when the Tcase was down i check the transmission pin connector (grey cannon plug on passenger side) and found trans fluid in it. Cleaned it all out before re-connecting. Not sure if may that caused a short back at the TCM.

 

[dndj]

Everything you're describing sounds like a Tcase issue since your problem is strictly in 2hi only. The speedo going to 5mph while sitting still means the output shaft of the trans is spinning while stopped, and that would only happen if disconnected from the driveshaft, ie Tcase is not properly in gear (effectively in neutral)

Since you have a new case in there, next is to check the shift linkage adjustment, assuming a manual shift case. Or, the replace the shift motors on the Tcase or possibly the TCCM (transfer case control module - LB7's have them, not sure about LBZ) if it's a pushbutton electronic shift case. It's not going into 2hi.

 

[DAVe3283]

It could also be the output yolk. The problem is definitely behind the transmission.

Sent from my FlashScan V2 using Tapatalk

 

[Mike L.]

Don't assume the new transfer case is good. If trans is grinding while going into park; something in the transfer case is still turning. Hook up a Tech2 and watch what the turbine speed sensor is reading while standing stiil in gear. It better be 0.

 

[kaylabryn]

Have you pulled the cover off the rear diff to see if there is anything going on inside there that might be causing the problem?

This!! Have you put in gear, 2wd and looked underneath and see if the driveline is spinning?? If so, problem is not up front.

 

[BearsFan42]

Between the holidays, rain, and flu running thru the household I finally had a chance to get back under my truck today.
Wanted to thank everyone for the advice. Below is what i found.
Don't have a Tech2 yet.
I did put in reverse in 2hi and the driveshaft spun. Put it in neutral it slowed down, put in in drive and it spun up again. Put in 4hi and everything stopped.
Pulled the diff cover, no broken teeth or parts.. There was built up friction disk material on the drain plug, but not an excessive amount.
Looks like all the parts are intact.
With the tires on the ground, parking brake set, (truck not running), put the truck in neutral and could spin the drive shaft by hand. Had my son spin the drive shaft so i could see all the teeth on the pinion, ring, spider and cam plate Non are chipped or broken.
Assuming i should not be able to spin it by hand under these conditions, thinking worn out friction packs, or possible broken drive shaft ???

 

[dndj]

If what you describe is happening while all 4 wheels are on the ground, sounds like you have a problem in the rear axle somewhere. Broken pinion, stripped splines in the side gears, broken axle, axle outer flange bolts sheared off?

Consider doing your test again, all wheels on the ground in 2HI, trans in neutral. If the ring gear is spinning, it's one of the axle shafts, diff side gears, or something else in the diff. Should be able to see which axle shaft is turning and which isn't if you look closely.

Clutches aren't used for normal drive, so worn out clutches only means the diff doesn't lock up. Would not cause a drive issue.

 

[JoshH]

When your son was spinning the driveshaft by hand and you were inspecting the gears, what was turning? Was the pinion gear turning? Was the ring gear turning? If the ring gear and diff carrier were rotating, were the side gears also spinning with it or were they fixed in place? Were the spider gears spinning? If so, was one of the side gears spinning while the other was stationary? If definitely sounds like it is something in the rear axle that is broken. Could you repeat the test and get a video for us? It shouldn't be very difficult to figure out what is going on if we could see it.

 

[Dallas S]

sounds like a broken axle shaft if everything appears good in the housing...

 

[BearsFan42]

Again thank you for all the advice and suggestions.
I did make a video while testing, but I cant get it to load here.
Pinion, Ring, Carrier, both spiders all spin when turning the drive shaft by hand.
The driver side axel gear spins as well, the passenger side stays stationary.
Thinking this means the driver side is the problem.

 

[DAVe3283]

Yes, something is broken on the driver's side. This is the point I'd personally throw in the towel and have an axle shop deal with it, but if you're ambitious you can pull the driver's side axle shaft out and see what you find. If you do, take photos!

Sent from my FlashScan V2 using Tapatalk

 

[2004LB7]

pull the axle. just a handful of bolts on the axle flange and the axle slides right out. dont even have to take the tire off. obviously if it is broken then the piece inside can be tricky to pull out

 

[JoshH]

Like the other guys said, either the driver's side axle shaft is broken, the bolts holding the flange to the hub are broken or gone, or the splines are stripped on either the axle or the side gear. At this point, it would be pretty easy to pull the center cap off the wheel so you can access the axle flange and inspect a little further to see what you're looking at for the actual problem.

 

[BearsFan42]

Got back at it today, and the driver side axel is broke.
Got so tunnel visioned and set on the transfer case I didn’t pay attention and check everything else. DAVe3283 suggested back at the end of Nov.and I didn’t do it. My fault for being stubborn