D20 W/ Tera Lows Popping Out Of Lo

I have a D20 in my CJ. I was told it was originally a J series/Commando D20. It also has Tera Low gears. The transfer case also uses a JB Fabrication twin stick shifter assembly. The transfer case lever for the rear axle pops out of Lo range when climbing up hills. I should explain to those not knowing that with the twin stick i can control the transfer case outputs individually. It's not like the D18. Left lever is rear output. Right lever is front output.

Descending hills it does not pop out. I also used reverse in Lo range to back down a steep hill without the t/c popping out of Lo range.

Before an off road trip this past weekend, I had the t/c rebuilt. The shop owner commented the detent springs were taller and much stiffer than the old springs.

Unfortunately, the Lo range popping out continued this past weekend. It was bad enough that on a steep road it popped out about every 50 yards or so.
A month ago (before the t/c rebuild) while pre-running the same route, I used a bungee cord tightly wrapped about the shifter handles. Even with high tension, the shifter for the rear axle kept popping out. The only difference between then and this past weekend (without the bungee) was that with the bungee the tension would immediately pull the shifter handle back into Lo.

So I'm looking for two things:

-Is my issue related to having the Tera Low gears in a D20?

-Is there a known issue or solution to this issue.

Please do not respond that I should reinstall the bungee. That's a crutch the the symptom, not a fix.

Thank you for your time.
Joe

 

Looks like the low range gear on the intermediate shaft is warn unevenly.

 

Ues, often times guys will install Heavy Duty shift poppet springs into a D20.
That said, I agree with Joseph.
The low gear of the intermediate is very badly worn looking as if the edge of teeth is worn off.
How old is this TL gear set?

 

1999 or early 2000's according to the previous owner.

Could you guys help me identify which gear you're referring to?
Is it an unobtainium Tera Low gear or a standard D20 gear?

 

The “intermediate gear” is located between the other 2 gears.
It is two gears in one. One gear is helical cut the other low range is “spur or straight cut”.
The spur gear looks to have excess rounding on the edge that engages as if from grinding gears.
It is referred to as an XTL 20 B and can be sourced from Herm.

Upload a clear pic showing the edge of those teeth.

Compare to this new XTL 20 B

 

These are the worn looking teeth they are talking about:

 

Thank you fellas.
I'm showing the pics and discussing with my mechanic.

Beyond the gear looking worn, does anyone have experience with this situation causing my t/c problem?

 

Have the shift rail interlocks been removed? Can the front be shifted into 4 low and the rear into 4 high? The reason I'm asking is, a few years ago I installed a twin stick and removed the interlocks thinking I could use front digs and have the rear in neutral. The first trip in 4 low I about crapped my pants when the rear popped out of low. It sounded like a gun went off. I ran with a 1x4 notched and wedged against the rear shifter and the seat frame. It worked for the season. I pulled the T/C back out and installed the interlocks. The interlocks hold one shift rail locked to the other.
Just my 2 cents.

 

To my above comment, after thinking about it, the shift rail interlocks have to be missing. If these interlocks were in place the front shift lever would have to move first before the rear lever can move. The rear could never pop out. Hope this makes sense.

 

I've heard of the dana 18 popping out when the bore of the intermediate gear gets worn out and the gear tilts on the shaft. In that situation it sounds like a bad pinion bearing being godawful noisy in an unloaded condition.

 

According to JB Fabrication, the J series and Commando cases never had the interlock.

 

I know the Commando used a U shaped shift pattern that could have eliminated the interlock pills. I wish my memory was better when I installed my twin stick. There is information on the internet for the shift rail modifications for a D20 Bronco that also used a U shaped shift pattern. There has to be some kind of safety to prevent the front and rear from being put into high and low range at the same time. I took my interlocks out thinking it would be worth it. I would actually put one in high and one in low range to use as a parking brake. I reinstalled mine because I didn't feel just having front low was worth it. Search for Bronco D20 shift rail modifications for twin stick. I am also assuming that inside the transfer case is installed correctly with all end plays set.

 

I found this on another forum, a discussion on the detents interlocks and jumping out of gear. https://www.jeepforum.com/threads/dana-20-shift-rail-interlocks.4343397/

 

My mechanic rebuilt the D20 for me. Yes, he speaks Jeep. He said the end play was good.
The interlock also prevents 2wd Lo so I was kinda glad it was not present.

 

The corresponding gears to the intermediate also appear to show wear. Somewhat less, probably porportionate to the number of teeth. I too wonder how much use that gear set has seen?
I put tera lows in my Dana 20 a couple decades ago. When I took out the original, 45 year old, gears they looked almost new. I sure hope my tera low gears still look almost new?

 

Yours does not pop out of Lo range?

 

Those gears look shot. I'd be willing to bet that's the primary cause of popping out under load. Doesn't look like a cheap fix, unless you stick with the bunjee option

EDIT: There's an option on OWF. Good luck!

 

No, it does not.

 

I have deal with this problem with my dana 20 case. As other as point out the intermediate gear is worn out causing the gear to slide out of low. It happen when you apply force and will be worse with a teralow kit (way more stress on the internal). I dont think there is a repair possible other than putting new gear.

What happen over time, the trust washer worn out over time causing gear to misaling and will worn out the theets on the intermediate gear. This is the major curse of the dana 20 and every major faillure (t case destroyed) i had, was about this exact issue. Also the conception of the dana 20 has gear moving inside tranfert case to engage low or high and wont help. Dana 300 had upgraded that shiffting issus having a gear sleeve moving over gear, so gear all stay in exact same position all the time.

 

Nice... I've got a NOS D300 awaiting install, thanks for pointing that out.