TERA LOW 4:1 CONVERSATION
INSTALLED IN A JEEP NP-231T-CASE
In addition to the other current modifications I am performing on my Jeep, I wanted to add some additional low range gearing. Since I converted my Jeep to an automatic transmission from its original 5-speed setup, the transfer case in an automatic has a longer input shaft than the 5-speed AX-15 models do. I opted to just buy a new factory input shaft; the same one that came in the automatic transmission Jeeps and install it in the transfer case, but I decided on something new.
I thought to myself, well I've had the transfer case out of my Jeep and split open a couple times and figured if I'm going to do this again, I may as well stock the t-case with any future mods I had planned and take advantage of the opportunity while I have the case open. I noticed after looking at other NP-231 4:1 conversions that the Tera Low kit came with a new input shaft. What good news that was for me. I figured I could just buy the 4:1 kit that is designed for an automatic tranny and it will solve both my problems.
For this I called on Tera Flex and spoke with a couple of very helpful and polite employees. They set me up with what I needed and sent one out. Fortunately there isn't as much of a demand for the automatic 4:1 kits as the 5-speed versions so they had one sitting in stock ready to ship out. After getting off the phone, Tera Flex confirmed that the kit would arrive in a week or so. I was excited to start my project and two days later, to my surprise, the UPS guy was sitting there with my kit.
TERA LOW INSTALL STEP 1 (removing the transfer case):
I started by removing the transfer case from the Jeep. This is fairly easy. Simply remove the lower oil drain plug and let all the transfer case fluid poor into a bucket. I then removed both front and rear driveshafts and set them aside for now. The 4x4 linkage and shifter was removed because it's factory mounted to the side of the transmission as well as the t-case. I supported the drivetrain with a jack and jackstands so that I could remove the transfer case skid plate. This will make it easier to drop the transfer case down. I then removed the 6 bolts that bolt the transmission to the transfer case.
These are easy to remove and fortunately are pretty easy to get to with an open end wrench. After removing all mounting hardware it was time to drop the transfer case down using a floor jack and a piece of 1" thick plywood approximately 1 foot square. Be aware that as soon as you remove that transfer case the transmission could leak all its oil out of the output shaft seal area. Keep a bucket handy! Below are some pictures of my stock NP-231 Jeep transfer case laying on the driveway.
(Click on pictures for large view)
TERA LOW INSTALL STEP 2 (swapping the gears & etc.):
It's time to open up the transfer case and spill its guts. The Tera Low kit includes a complete new front half of the transfer case housing which means anything and everything in the old case has to be removed and installed in the new housing.
I started by removing the large retaining nut that holds the front yoke on. This required a nice size breaker bar and some ingenuity. After removing the front output yoke, the case was ready to be opened. I started by removing all the bolts that surround the case clamping the two pieces of the case together. By placing a thin flat-head screwdriver between the two pieces of the cases, I wedged the screwdriver in and slowly opened the case. Below are some pictures of the case just after opening it.
(Click on pictures for large view)