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Discussion Starter · #1 ·
So i finally got the new motor in my 88 w-150 with a np241 and have started driving it. Its winter here in AK so i need the 4 wheel drive to work even just to get up my driveway.

When im moving at any speed even ~5 mph i cant pull the shift lever into 4HI even if i two hand pull as hard as i can. If i completely stop it shifts right in no problem.

Then, if im moving after i stopped and shifted into 4HI i can just let off the throttle and it shifts right into 2Hi with no issues.

I know there is a vacuum connection on the transfer case itself, however, im not sure if that could be connected incorrectly but from the diagram in my FSM it is only to operate the CAD which works fine.

Any help is greatly appreciated.
 

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I can give the way it operates, that may help you come up with an idea.

While moving, when you pull the lever, inside the transfer, the gear gets pushed against the synchronizers, which gets both sides moving at the same speed, so the shift can be completed. After the shift is made, the vacuum switch inside the transfer applies vacuum to the CAD unit. The vacuum causes the collar to lock the two axle shafts together, locking the CAD unit. When that is completed, the switch inside the CAD turns on the 4wd light.



You do not mention clashing sounds, so the syncros are not completely worn out.

You say it shifts fine while stopped, so the linkages are likely ok.

I am assuming that you know the difference, and can feel that the 4wd is working, so that would rule out CAD issues.

I am thinking syncro issues, but that is more a gut feeling, then any experience.

I would check the transfer case fluid level, maybe even change it if it does not look great.

And consider locking the CAD at least for the winter, then next summer you can further check out it operation. It sucks needing 4wd, and not having it because the CAD unit is not shifting, and it seems to act up the most at bad times in the middle of a storm.

Hope something there helps you.
 

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Discussion Starter · #3 ·
I can give the way it operates, that may help you come up with an idea.

While moving, when you pull the lever, inside the transfer, the gear gets pushed against the synchronizers, which gets both sides moving at the same speed, so the shift can be completed. After the shift is made, the vacuum switch inside the transfer applies vacuum to the CAD unit. The vacuum causes the collar to lock the two axle shafts together, locking the CAD unit. When that is completed, the switch inside the CAD turns on the 4wd light.



You do not mention clashing sounds, so the syncros are not completely worn out.

You say it shifts fine while stopped, so the linkages are likely ok.

I am assuming that you know the difference, and can feel that the 4wd is working, so that would rule out CAD issues.

I am thinking syncro issues, but that is more a gut feeling, then any experience.

I would check the transfer case fluid level, maybe even change it if it does not look great.

And consider locking the CAD at least for the winter, then next summer you can further check out it operation. It sucks needing 4wd, and not having it because the CAD unit is not shifting, and it seems to act up the most at bad times in the middle of a storm.

Hope something there helps you.
Thanks for the response. I had the transfer case rebuilt by a local 4WD shop before I did the engine. Think its possible it sat too long and something inside locked up. Ill have to familiarize myself with the internals of the t case.

One other thing to note is i set the linkage as per the FSM. Set shifter in 4 hi and then the lever on the t case to vertical and locked the set screw. Its just strange to me because before the engine rebuild it shifted just fine.

id have to check but I bet it both the t case and engine have less than 500 miles on them.
 

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sounds to me your t-case guy needs a slap , ALL 241 t-cases are shift on the fly up to 35 mph

 
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