Looking for info/experience about building a t-case doubler.
06 LJ with 6spd/231/3.73 on 33s. I’d like to have lower gearing options for better off-road control that won’t effect on-road behavior.
- as far as I know, my NP231 can’t be regeared to 4:1 or anything like that (Teralow 4:1 is no longer a thing, and probably for good reason since they apparently blew up a lot)
- swapping t-cases for a NP241 might be an option, but they’re expen$$ive and it’s not a straight plug in
- regearing the diffs is also expensive and/or time consuming, and I don’t think going to 4.10 would be enough change to justify it, and going to 4.56 would change highway driving (higher RPM)
- Rubicrawlers can only be mated to 42RLEs
So that leaves me with the intriguing option of building a doubler… but also some questions:
- most search results for doublers/crawl boxes/etc are from 10 years ago or so, which seemed like a red flag – is there a catastrophic reason not many people go this route? Or just that most people don’t have the extra wheelbase to extend the drivetrain and/or are satisfied with regearing or other options?
- I’ve found a few options:
- NWF has their BlackBox, which is as complete of a setup as you can buy off the shelf and the most expensive (but still cheaper than buying an Atlas or even most used 241s!) ~$1700
- NWF also has their EcoBox, which is several hundred $ cheaper, you just have to supply all of the guts from a donor 231 and have access to a press to install the ring gear. ~$1000
- Froehlich Suspension makes an adapter plate, which requires cutting up a donor 231 (removing the front driveshaft yoke) and welding the adapter in place of the back half. $475 + donor 231 + probably paying a shop to do the welding
All doubler options would require fabrication of a mount to help support the longer drivetrain, SYE and new driveshafts (longer front, shorter rear), and finagling double t-case shifters. Also, I would upgrade my NP231 with the 6-pinion planetary gear and wider chain.
So… what else can/should I consider? Has anyone built a doubler with an adapter, or know where such a build is documented?