NP218 questions

[GYs_M998]

I am having some issues with my NP218 and am wondering if anyone can lend some experience and point me in the right direction.

Biggest issue is that it will not shift in to 4lo without having to shut off the truck. If I attempt to shift with the truck on (and trans in neutral) it makes a god-awful grinding noise and fights going into 4lo. With the truck off it shifts just fine. I am thinking some sort of synchro? What say ye?

Secondly: when driving, at different speeds a noise comes from the t-case [I believe]. The first speed it happens at is around 30mph or so. And I am not positive, but I think it happens when I ease up on the accelerator. The noise is like a rapid metallic ‘tinging’ on the side of a bell. Is that a stretched chain? I’ve never experienced a stretched chain in a t-case before and I can’t find any audio examples of a stretched chain on the internet. I have tried to capture the noise with my phone, but there is just too much other noise for that to be possible.

any help is appreciated.

 

[Mogman]

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You should start with the -10 Operators manual, you will find information like this, that can save you many dollars and headaches in the future.

• Vehicle must be stopped, engine off, and transmission shift lever
placed in “N” (Neutral), before transfer case can be shifted.
Failure to do this will result in damage to drivetrain.
• Do not place transfer case shift lever in “H/L” (high lock range) or
“L” (low range) on high traction surfaces where little or no wheel
slippage is evident, particularly when encountering sharp,
continuous turns. Failure to operate the vehicle with transfer case
in “H” (high range) on high traction surfaces, particularly when
encountering sharp, continuous turns, can damage drivetrain.

 

[TOBASH]

These are not shift-on-the-fly units.

 

[Mogman]

You may want to carefully inspect the front drive shaft, especially the carrier bearing.
Although possible it is unlikely your truck has enough miles on it to wear out the chain.

 

[Bulldogger]

Don't discount easy fixes like loose brackets or other fasteners. I had a strange noise in my truck and it turned out to be a bracket for some piece of equipment they unbolted from the bed during demil and never bothered to remove the corresponding bracket on the underside, so it fell on top of the transfer case and rattled at certain RPM.
BDGR

 

[Thunderbirds]

I am having some issues with my NP218 and am wondering if anyone can lend some experience and point me in the right direction.

Biggest issue is that it will not shift in to 4lo without having to shut off the truck. If I attempt to shift with the truck on (and trans in neutral) it makes a god-awful grinding noise and fights going into 4lo. With the truck off it shifts just fine. I am thinking some sort of synchro? What say ye?

Secondly: when driving, at different speeds a noise comes from the t-case [I believe]. The first speed it happens at is around 30mph or so. And I am not positive, but I think it happens when I ease up on the accelerator. The noise is like a rapid metallic ‘tinging’ on the side of a bell. Is that a stretched chain? I’ve never experienced a stretched chain in a t-case before and I can’t find any audio examples of a stretched chain on the internet. I have tried to capture the noise with my phone, but there is just too much other noise for that to be possible.

any help is appreciated.

Hey GY,


according to the operators manual, TM 9-2320-280-10, chapter 2-11, page 2-108, that is the correct procedure to shift the transfer case in or out of any place with the transfer case. Keep in mind, transmission shifting and transfer case shifting are not the same and should be done in sequence:

CAUTION
• Vehicle must be stopped, engine off, and transmission shift lever
placed in “N” (Neutral), before transfer case can be shifted.
Failure to do this will result in damage to drivetrain.

 

[GYs_M998]

Thank you all for the inputs.

I will be digging around later today to see if I can’t find anything loose that may be making the noise. I am also going to check the play in the front drive shaft for any indicators that the chain may be stretched.

As for the shifting into 4lo, I read that section of the operators TM and at first my mind rejected the procedure because the trans is in neutral and, therefor, not spinning the output shaft. So in my head it didn’t matter if the truck was on or off. But after thinking about it a little bit, it makes sense to have the truck off because there could still be some spin in the output shaft given that components in the trans could be old and worn. Am I on track, or am I way off base? I can wrench, but transmissions mystify me.

 

[Mogman]

The output shaft will always be trying to spin in neutral and the engine running, there is a mass of components spinning on the input that that are riding on bushings/bearings and clutches that are wet with fluid on the output shaft, simple friction and fluid surface tension dictates the motion will be transferred and has nothing to do with wear.