NP 231 Transfer Case Upgrades?
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The teralow kit was the only kit ever offered to regear the NP231. It had some serious design flaws and will not be coming back.
That case should have never made it through testing. The low RPM limit is terrible.
I also waited about 6 months for mine. If I had to guess, the wait is even longer now direct from Advanced.
Swap your 44's in and get the lowest gears possible in the meantime, your gears can be had in a week or sooner.
I put the two wheel low kit in my transfer case. Been very happy with it. Comes in handy sometimes.
If you're geared right in the axles, the factory 2.72 low range in the transfer case should be adequate. I've never wished I was lower when in 4WD low range.
Currently running 4.88 gears and 33" tires (2.5 engine/five-speed tranny). Dana 44 rear with 33 spline alloy axles and a Detroit locker in case you're wondering - Dana 30 front with 27 spline alloy axles and an Aussie locker. 2WD low makes it easier to turn sometimes when four wheeling.
If you're geared right in the axles, the factory 2.72 low range in the transfer case should be adequate. I've never wished I was lower when in 4WD low range.
Currently running 4.88 gears and 33" tires (2.5 engine/five-speed tranny). Dana 44 rear with 33 spline alloy axles and a Detroit locker in case you're wondering - Dana 30 front with 27 spline alloy axles and an Aussie locker. 2WD low makes it easier to turn sometimes when four wheeling.
We encounter rocks all the time and having a low ratio with the manual helps. According to GrimJeeper I have 108 C.R. in 1st and 64 in 2nd now.
I re-geared. I still go too fast in low range.
Those who say stock is low enough with a manual have never experienced a lower geared case. I love my doubler. I have stock low range and as low as 7-1. 7-1 is great in the rocks with a manual.
I think maybe there is some confusion between the 2 low kit and the 4:1 kit for the np231 going on here. Maybe I'm reading too much in to it? The 4:1 kit was the thing that supposedly had reliability issues. And I would love to have 4:1. 2 low I have not heard any issues about. Not sure how helpful it is but can't hurt, right?
It would just be stronger, but I haven't heard of a 231 chain failing, even once. I suppose spreading the load out over a wider area would reduce the contact pressure and slow down the rate at which it wears/stretches.
Same with the 6 pin planetary. Haven't heard of a planetary failing on a stock 231 (plenty in the Tera Low 4:1 kit though).
The most common failure mode I see in a 231 is when someone doesn't maintain their front driveshaft and the CV joint seizes, and breaks the case in half.
When I did my SYE I just put a new chain in it, replaced the screen on the oil pump pickup tube and installed new seals.
I seem to remember hearing something along the lines of popping out of gear, like maybe cramming an extra detent in the sector plate didn't leave enough room to make them deep enough to hold. Never had my hands on one but it would be cool to have for sure.
I had both the TeraLow and the Tera 2Lo in the t-case in my TJ before I did the V-8 swap. Yes there were some issues with the TeraLow kit self destructing if you ran @ 3K RPM or higher but I can say I did it to mine more than once and never had any issues. It's still working fine in a friends YJ that I gave it to.
As for the Tera 2Lo kit yes it ads a 5th detent to the shifter. So you shift to 4lo and then it keep on going to 2Lo. You have to cut your stock linkage and lengthen it. And then it's play with it until you get it adjusted to work. I had to file a little off my shifter plate to get it to work.
IMO it'd be like putting a 242 in and trying to use the 231 plate for it.
EDIT: I guess I should add that this was in 2005 and since I had a 4 cyl I needed a 21 spline input instead of the 23 spline that is on the 6 cyl rigs. So I got my TeraLow 4:1 kit for $1K off Ebay.
That added torque was enough for me to blow my first Warn hub. I took out the stock inner shaft also.
It was a FUN snow run BTW...
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When I put the 2WD low kit in my 231 transfer case, I didn't have to adjust linkage or anything. I installed the kit and buttoned it up - done. If you're ever doing a SYE kit in your transfer case, while you've got it apart now is the perfect time to do the 2WD low kit. It just added an extra detent below 4WD low. So I move the shift lever down to 4WD low, and then down one more to 2WD low, and the 4WD light on the dash turns off too.
Here's a link to show you what parts are involved:
https://www.quadratec.com/products/52254_200_07.htm
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When did you get your kit? Mine was a 2005 era kit so it might have changed since then. And I might be wrong about the lengthening it. It might have been that we cut & sleeved it to make it shorter. I just remember we had to cut the linkage. We did the TeraLow & 2Lo kits both at the same time.
I shouldn't really say I did it since I was still on crutches at that time. A buddy who had a shop did most of the work.
I installed it before I ran the TAT last summer (2021). So about a year ago around this time. And I did the actual installation in my shop.
Seems that they have change the design since 2005. I could be mistaken but I don't remember a shift fork in the kit we did. But like I said it was YEARS ago. Let me see if I still have the install directions from it.
I wish. Had one in my childhood '63 GMC. Best transmission in its class ever made. Loved the soundtrack - modern trannys are waaay too quiet! Reverse was located where the Gods intended, left and down. What's up with the right and down crap? Or the occasional left and UP?
the way i think i understand it is, the stock chain can stretch or wear and get sloppy. the larger chain spreads the gear load a bit more, it's mass handles stress a bit better and makes it a bit harder to wear and stretch.
the planetary gear is what the chain cranks, we have 3 small pinions in our housing with X amount of teeth engaged to move the load. torque and horse power are not friendly and 1 could argue for either part that spreading that load might be beneficial in some instances and overkill in others.
plenty of vid's on how to strip junk TC's and snatch the parts to slap a 6 gear together on the bench at home.
the planetary gear is what the chain cranks, we have 3 small pinions in our housing with X amount of teeth engaged to move the load. torque and horse power are not friendly and 1 could argue for either part that spreading that load might be beneficial in some instances and overkill in others.
plenty of vid's on how to strip junk TC's and snatch the parts to slap a 6 gear together on the bench at home.
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