Transfer case pops out of gear

[valveamp]

Hi. I have a Dana 20 T-shift that has been twin sticked. I did some mild off roading today with the case in low range. It popped out several times. What causes this and what can I do about it? I did not do the conversion to twin stick, it was done by a shop. Thanks.

 

[broncojo]

I believe if you read this article it will answer your question, he explains about halfway down about 4low popping out and how to remedy it. You will however have to teardown your case.

http://www.wt4x4.net/tech/twinstick.htm

Here is a pic of mine when I did the fix.

Hope it helps with your problem.

 

[Viperwolf1]

Lots of other causes for it to pop out of gear. Loose output shafts, problems with the spring/ball, worn cluster gear shaft, worn gears, driveshaft out of balance, shifter contacting floor. Is it the front or rear side or both?

 

[phldwsnoc1]

Popping out of gear

There are two, and only two, primary reasons for this.

1. The selected gear is not fully engaged. This can be caused by worn or poorly adjusted linkage, body interference, or internal clearances among other things. If you are sure that you are fully engaging the selected gear, then you have

2. Worn backcut on the speed gear and/or facing hub. These backcuts are engineered into these pieces to prevent this very condition, but if they become worn, usually due to an item in reason #1, the only real option is to replace them and correct the root cause. I will try to find some photos for you. All I can say is once you see it, it makes perfect sense.

I have seen great effort involved in detent balls, springs, rails, and other clever attempts to correct for this, and all of them simply prolong the misery.

Sorry if this is all a bit much. If you are not comfortable with the diagnosis, it's best to find a respectable gearbox tech in your area for help. That can be a problem all in itself...

Good luck!

 

[valveamp]

Thanks for the info. I will see if I can verify the linkage is not causing the problem. I did not install the twin shift, so I can't say for sure if it really is OK. I guess I'll go from there.

 

[valveamp]

Is it the front or rear side or both?

It has been the rear only, cause I have only used that yesterday (rear wheel low). I've only had it in 4WD a couple times and there was no issue. These times were not trail crawling, but snow on a road.

 

[JB Fab]

It has been the rear only, cause I have only used that yesterday (rear wheel low). I've only had it in 4WD a couple times and there was no issue. These times were not trail crawling, but snow on a road.

My guess is that there is a little too much endplay in the rear output. Driveline harmonics from the geometry change of suspension lift or worn out driveline parts can make it worse.
Shifter could be a culprit if they are not shifting all the way into the detent, the edge of the hole is pushing against the shifter handle, or if the boot was installed off center (made worse by a body lift).

I would remove the boot, so you can see the clearances in the hole, and take another ride to see better what is going on ( I have seen loose tranny mounts allow the shifter to bump against the edge of the hole under acceleration/deceleration.

Then again it could be as simple as worn out detent springs.
You could try an adjustable detent kit specifically for the Bronco D20?

http://jb-custom-fabrication.myshopify.com/collections/build-it-yourself-parts/products/adjustable-detent-kit-for-early-bronco-d20

 

[BCH BRCO]

I had a problem with my transfer case slipping out of 2H whenever I drove over a certain undulation on a bridge nearby. I fixed the problem with new springs for the detent balls as shown in JB's post above. Did this fix over 5 years ago and the problem hasn't resurfaced since. A cheap $5 fix!

BCH BRCO

 

[70_Steve]

The information in the article linked to by broncojo is attributed to a CB.com forum user named nobody. In addition to "engineering" that particular way of modifying the shift rails, to twin-stick a t-shift Dana20, he also developed another possible fix for the transfer case popping out of rear low. That fix is to assemble the rear output shaft assembly with a preload on the bearings, instead of an endplay, as specified in the Dana20 Service manual.

The rear sliding gear is what moves when the rear pops out of low range. If you look at the illustrations in the service manual, you can see that the rear sliding gear is outboard (inboard?) of the two tapered roller bearings. So, any side-to-side movement in the output shaft is also transferred to the sliding gear. Putting the bearings under a preload virtually eliminates the side-to-side movement of the output shaft, and of the sliding gear. This will remove one more reason for popping out of rear low.

5-7 in/lbs is considered the best preload to shoot for. Here's links to the Dana20 Service manual and instructions on how to assemble the Extreme Output shaft, which refers to the same rotational torque.
http://www.classicbroncos.com/dana20/dana_20_manual.html
http://cdn.wildhorses4x4.com/downloads/WH/8272 08-08-06.pdf

 

[hyghlndr]

Make sure the handle isn't getting bumped by body flex or trim ring. I was ready to rip one down and noticed the body scratching the shift lever once the boot was removed. A dremel fix and all was good.