Drivetrain Grinding! Truck Wont Move!

[dyingbreed]

86 k5. 350/th350/np208 with a 10 bolt. So the other day I was driving and out of nowhere my truck stopped pulling and started making this god awful grinding sound. I pulled it over and put it in park where the grinding noise continued. I put it in neutral and dropped into 4lo. The grinding stopped and my truck was pulling again. Then about a half a mile up the road it happened again. This time i could not get it to move at all. 4lo, 2hi, or 4hi. I turned it off and waited about 10 minutes. Turned it back on and dropped into 4lo. It pulled just fine with no grinding. I put it in 2hi and drove all weekend without a problem. Then Sunday night, I broke a ujoint and replaced that on the side of the road. I was so happy because I thought for sure that I had solved the problem. I was pulling into my house when I got a rude awakening that I still had the issue. Truck started grinding, it wouldn't pull. I put it in 4lo and limped into my parking space. Yesterday I got home from work and went to drive it and it would hardly move its own ass. Grinding followed shortly. Then complete drivetrain paralysis. I push it back and there it sits. I think its the tcase. Opinions?

 

[Fordum]

Flexplate, or something in the torque converter or pump.
Unless you have had a total meltdown of the hard parts in the transmission, when you put it in park, nothing in the transfer case would be moving.

Only the front part of the transmission would be moving at that point.

Turning the truck off helping it is a clue too. Nothing else would stop the front end of the tranny from turning.
Check the fluid. Probably gonna find it dark with metal or burnt. Low fluid would cause that, but its unlikely to make that kind of noise.

 

[CherryK5]

Mine was doing that for a while. The pump grenaded.

 

[dyingbreed]

Thanks guys. I've been reading thus forum for almost a year and I've never had to post. Usually I can find a thread where my questions have already been answered but this time I couldn't quite find a thread that fit my symptoms. I'm gonna pony up the membership fee and get into the ck5 thing a little more.

I'm gonna drop my truck off at the 4x4 shop tonight and try to get this thing fixed. It's my dd so I need it and I don't have time to work on it. Any suggestions on what to try to do before I drop cash at the shop? Like any simple repairs to try and fix it?

 

[Fordum]

Check the fluid. Its a 1000 to 1 shot that low fluid would be the cause, but its a free test.
Check the level, and also drop some on a paper towel to watch what happens.
You should just see a red splotch, but you will probably see a ring of debris form.

Transmission repair is one of the most infamous examples of poor work, and outright scams you will find in vehicle repair.

Unless you have had good dealings with this shop before, you might need to get hard quotes and a signed guarantee before they do the work if its the tranny.

Big name chains are not a sure bet either. In fact I suspect that small independents are a better chance than them.

If its the tranny, then probably the pump is coming apart, so there will be metal in the cooler and lines.
It will need to be either flushed well, or replaced.

Your other options for repair of the tranny would be do it yourself, slower, but at least any mistakes will be honest ones, and you will know for sure what was replaced.
Or ordering one from a national store. Unlike the national repair chains, the big name rebuilders are usually a safe bet.

Ask here for recommendations. I'm sure lots of folks have bought rebuilts.

 

[496truck]

It's the t-case.

The fact that you had to mess with the lever to get it into gear is a dead giveaway. I've had this happen to me. Just driving down the street, clunk and griiiiiiinnnnnnd... Messed with the t-case shifter and it went into gear and got me home. Pulled the t-case and brought it to my local trans shop and had it rebuilt. Been working like new ever since. Cost me $600 for a complete rebuild including new shift forks.

What happens is the nylon feet wear on the t-case shifter forks and then they pop out of the groove and can no longer hold the t-case in gear. You can mess with the lever and sometimes get it into a gear and it may or may not stay there very long. The grinding is happening because the t-case is between gears while the trans is turning the input shaft.

 

[dyingbreed]

Ive dealt with the shop before. They are a small 3 shop local chain. I hear nothing but good of them. And my past experiences were good. I'm gonna get the th350 rebuilt because I've done a lot of work on it and its past due for a good rebuild after the abuse I give it. Lol.

 

[Fordum]

I agree it sounded like the transfer case, except for the fact he said it kept grinding after he put it in park.

Of course, if the transfer case was in neutral then the tranny might not have shifted into park.
My truck will not go into park with the transfer case out of gear because the output shaft is freewheeling too fast, so that might be it.

But the noise should have changed when he shifted into park when the parking pawl tried to engage.

 

[diesel4me]

I had one truck with similar problems limp into the junkyard I worked at,and the guy was no mechanic,and wanted us to see if we could tell him what the trouble was,and what parts to buy...one peek under his truck revealed the crossmember had ripped away from the frame ,due to severe rust issues,
and let the tranny & transfer case sag,which in turn caused the lower 2 bolts out of the 4 holding the t-case to the transmission strip out and there was a large gap at the bottom between them,enough to allow the main shaft to hog out the splines in the T-case input shaft!...the slip yoke at the driveshaft was also almost completely puulled apart too...we sold him a transfer case and a used crossmember ,installed it,luckily the tranny shafts splines were not damaged too badly...

I've seen trucks with the rear diff yoke splines strip out too,and make some nasty grinding noises,along with it refusing to move too...

The nylon dewhickey mentioned by 496Truck often craps out just as he stated too,its not an uncommon dilema on the NP208 T-cases...

 

[Blue85]

I agree that the T-case is the #1 suspect. The shift forks can and do wear out making it hard to keep the unit in gear. I had some forks almost completely eaten through and on a hard stop the gears would move forward putting the case in neutral. I even got out to see if the driveshaft had fallen off. Shifting to 4LO and then back to 2HI would get it to move again. The grinding means it is "almost" engaged.

The weird thing about automatic transmissions is that they can move when they are in neutral. It's just the slight drag from the non-engaged clutch plates. It's never enough to move a vehicle, but it can be enough to make the T-case move and get some noise from it (if the T-case is not really in gear). This is why you sometimes hear grinding when the tranny is in N and you shift the T-case. When I had a fragged pump in transmission, it made funny noises whenever the engine was running. I don't think you could have the kind of damage in the tranny to cause this and then get a whole weekend without trouble.

The T-case is relatively cheap and easy to rebuild. You'll have to inspect the gears to see if any real damage has been done. If you're lucky, you just need shift forks and shift pads.