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4WD not working properly

Tiny
CARLSP
  • MEMBER
  • 1998 DODGE RAM
  • 5.2L
  • V8
  • 4WD
  • AUTOMATIC
  • 280,000 MILES
I have the truck listed above 1500 with the ND231 transfer case. When I select 4WD High or 4WD Low my front axles lock, the dash light comes on that says 4WD is engaged but I get no power to my front wheels. My vacuum is around 17 inHG. I have replaced the actuator, switch, shift fork and housing that is mounted on the front axles and they will lock up fine, just get no power to the front drive shaft. I have also replaced the linkage. Could it be the vacuum switch on top of the transfer case or low fluid maybe? I am hoping that I do not have to rebuild the transfer case. Any ideas or help would be greatly appreciated. Thank you.
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Thursday, January 13th, 2022 AT 2:44 AM

10 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,133 POSTS
Hi,

The idea that it won't turn the front driveshaft is interesting. Please confirm something for me. Is it the NV (not ND) 231?

Also, this transmission should have a manual-shift transfer case. The 4wd is engaged via the shift lever, shift fork, and the shift lever in the truck. I don't suspect there is internal damage, or you would be hearing noise. Low fluid, although not a good idea, shouldn't cause this.

There is an adjuster on the shift linkage. Are you certain the bolt that sets it after adjustment isn't loose or allowing the linkage not to fully move the shift lever on the transfer case? Have someone shift the transfer case through the different selections while you watch to see if there is an issue with the adjuster. If the bolt is loose, it will allow the shift rod to extend and retract, so it may not fully be going into 4wd. (See pic 1)

Also, the transfer case itself doesn't rely on vacuum.

Let me know what you find.

Joe

See pic below.
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Thursday, January 13th, 2022 AT 7:47 PM
Tiny
CARLSP
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  • 32 POSTS
The tag on the transfer case says ND231 HD. I have checked the linkage and had other people check it as well, the bolt is tight, and it moves the shift lever on the transfer case through its full range of motion. I have even disconnected the linkage and moved the shift lever on the transfer case directly with the same results, no power to the front axles and I confirm there are no noises coming from the transfer case. What if the nylon pads on the shift forks have broken off, could that be a possibility? When I replaced the front axle actuator and linkage it did work fine at first but then just stopped working. I have not been off roading with it just used the 4WD for snowy days here.
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Friday, January 14th, 2022 AT 1:36 AM
Tiny
CARLSP
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  • 32 POSTS
I'm sorry, the tag on the transfer case says NP231HD. Don't know why I kept saying ND, my bad.
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Friday, January 14th, 2022 AT 7:39 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,133 POSTS
Hi,

No problem whatsoever. I had a feeling that is what you meant. The D at the end makes it easy to make a mistake.

Now, a front-axle disconnect system is used to achieve two-wheel-drive mode. The axle disconnect vacuum motor is actuated by a vacuum switch on the transfer case. The switch is operated by the transfer case range rod. Are you certain that it isn't stuck in 2wd at the switch? You indicated the front axle is working properly, correct? See pic 1 below. I realize you have a vacuum, but it should change at the supply hoses at the axle actuator when you go from 2 to 4wd. Is that happening?

Also, which nylon shift forks are you referring to? Do you mean the ones in the transfer case? See pic 1. If that failed, you would feel little or loose restriction when shifting it. I would think that anything mechanical in the transfer case would be making noise in some way.

Let me know.

Joe

See pic below.
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Friday, January 14th, 2022 AT 7:42 PM
Tiny
CARLSP
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  • 32 POSTS
Hi there,

I have not had a chance to check the vacuum lines, it has been too cold to be laying out in the snow. I would assume though that they are working fine seeing as my front axles do lock and the 4WD indicator lamp does light up, which means the actuator is working correctly. The pads I mentioned are the one on the shift forks themselves, made out of nylon/Teflon? Or something like that. The wear pads I believe they are called. If they are worn out or broken could that be a cause? (See pic).
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Thursday, January 20th, 2022 AT 6:28 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,133 POSTS
Hi,

If they are no longer connected to the gear packs, yes that would prevent the engagement. If they are bad, you should see evidence in the fluid when draining it. Have you drained the fluid yet?

Joe
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Thursday, January 20th, 2022 AT 7:32 PM
Tiny
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I will do that as soon as I get some time. I will run a magnet through the fluid to see if there is any kind of metal debris. First though, I got to put a sliding door in, just got a giant hole in the wall and it is cold! Lol. I have bought a seal kit as I am thinking I am going to have to open it up here possibly to figure it out (plus it was on sale for 75% off, lol).
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Friday, January 21st, 2022 AT 4:40 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,133 POSTS
Hi,

Sounds like a good deal. I wish I were there to help. I love doing that kind of work. Regardless, let me know when you get a chance. Pay attention for nylon material. I'm basing that on your original thoughts.

Take care,

Joe
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Friday, January 21st, 2022 AT 5:35 PM
Tiny
CARLSP
  • MEMBER
  • 32 POSTS
Hello again. Well, I finally fixed my 4WD. The issue was the 4WD Vacuum Actuator. The shaft seal of the actuator failed and so the whole actuator filled up with gear oil. The shaft still moved enough to engage the switch to illuminate the dash light but just not far enough to get the collar to lock the axles together. The gear oil prevented it from moving a complete distance. So, the good news is that I do not have to open up the transfer case :) but the actuator was not cheap either. :( Just wanted to let you know and thank you for all your help on this issue. I really appreciate it. Have a great day.
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Tuesday, February 1st, 2022 AT 3:17 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,133 POSTS
Hi,

I'm glad to hear you got it fixed and thank you for the update. Your post will likely help others in the future.

Please feel free to come back anytime in the future if you have questions. You are always welcome here.

Take care.

Joe
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Tuesday, February 1st, 2022 AT 3:22 PM

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