Hi all, I am new here, and I read through the forums, but I did not see this issue any where.

I have a 97 Dodge Ram 4X4. It engages into 4X4 with no problems. The problem is when I switch back into 2H.

1. Driving straight at about 5-10 mph, shift into neutral.
2. Switch back into 2H from 4H.
3. Wait about 2-10 seconds.
4. Hear and feel a loud bang from the front end as it switched back into 2H.

It has been doing this since I bought the truck 4 months ago so I have avoided using wheel drive.

I recently replaced a ball joint, the u-joints on both front axles, had the CAD apart and inspected it. The spline looked fine on the hub, center and outer axle shaft, and it is switching into 4H and 2H just fine (except for the bang).

I am thinking it may be the CAD still because of the delay in the bang after switching back to 2H, but I really don't know if it is that or something the transfer case.

Any suggestions or advice would be appreciated.

Thanks,

 

https://dodgeforum.com/forum/dodge-r...s-section.html

 

Ok. I have a theory about this problem. Please let me know if I am off my rocker. Before this past couple of days I didn't know anything about 4 wheel drive trucks.

Additional Facts:
1. The truck has about 160k miles on it.
2. When in 4 wheel drive, there is a noticible drag on the truck and it slows down much quicker (I don't know if this is normal).

Speculation:
1. Perhaps there is something in the transfer case that is experiencing a lot of friction.
2. Maybe the oil in the case has never been changed or is all gummed up.
3. Maybe there is no oil in the transfer case and all the bearings and chain is severely damaged.

My theory to the bang:

When switching from 4H to 2H, the transfer case is disengaged first, followed shortly after by vacum pressure disengaging the CAD. Because there is a friction induced load in the transfer case, there is a sudden change in speed in the front differential when the CAD disengages, which causes the bang sound and shakes the truck slightly.

Thoughts anyone? I am a newb to 4 wheel drive.

Tomorrow I am going to check the transfer case oil. If it is empty, I will fill it. If it is sludge, maybe fill it with Sea Foam? If it looks good, then onto more research.

Thanks,

 

My Ram is 2wd, but my other truck is 4X4. First thought...NO to Seafoma in xfer case. Check the oil in it, and even change it if you need, but no Seafoam.

Second thought - come to stop before shifting from 4 to 2wd.

And feeling like it has more drag - it does have more drag. You are turning two differentials plus the xfer case. Completely normal.

 

OK, thanks for the information. I also just realized that I left out some importnant information.

When I replaced the u-joints and took apart the CAD, there was very little axle oil in the front axle. I filled it after I was done, but maybe there was already damage done to the front differential, and that is where the extra load is coming from, and that creates the bang when the CAD disengages?

I will try coming to a stop before switching to 2H tomorrow and see how it responds.

Thanks,

 

I think I have read here that the differentials have to have a friction modifier in the gear oil on these trucks. Check some of the other threads on differentials.

Also, if you go to the FAQ/DIY section, you can find the service manual and the parts manual for your truck. Info including the fluids are listed there as well. Handy references to have available.

 

Thanks a million. I really needed a copy of the service and parts manual. This is awesome to just download a copy.

 

Yep. I use it all the time. Confuses the dealer parts guy when I walk in with a printed page with the part number...I just grin and order...

 

our transfer cases are shift on the fly for 2hi-4hi. you need to be in neutral, to shift into 4lo.

that bag is probly the front driveshaft at the ujoint on the axle yoke going bad.....

vacuum lines are probly rotted out, resulting in delayed shifting of the cad unit. replace the lines, and u joint, or bad things will happen, just ask me how i know.

 

Just out of idle curiosity, you aren't using 4x4 on dry pavement are you? That's a good way to break things, and the loud "bang" when disengaging should come as no surprise.

Only need friction modifier in limited slip differentials, which the front is not.