Adding A Fourth Gear
The last time we showed you our '97 Wrangler project, it had just received new Dana 44 axles with 4.56 gears from Drivetrain Warehouse. When you consider we're only planning on running 32s under this Jeep, 4.56s seem like a lot of gear. However, we've been planning on ditching the three-speed TF999 transmission in favor of something better since Day 1.
While we're still die-hard manual transmission fans, we do acknowledge the fact that a large number of Jeep owners prefer an automatic. So, without too much joking, it was with a certain obligation to our readers that we ditched our plans of a manual five-speed swap and started figuring the very best way to stick a TH700R4 behind our 4.0LWhile it may seem simple on paper, swapping over to the big Chevy transmission is actually quite an undertaking. We enlisted help from some of the best companies in the industry to make this happen. There are certain considerations to be taken into account, such as crank-sensor relocation, overall driveline length, getting the shifter to work with the factory console, and so on.
For starters, we contacted Advance Adapters and told them what we were up to. You can check out the "Parts, Pieces, and Prices" sidebar on page 69 to find everything the company was able to send us to facilitate the swap. Needless to say, the company's grasp on what it takes to make just about any Jeep swap a reality is mind numbing. Advance Adapters has two TH700R4-to-NP231 adapters that will work. The first is 2.5 inches long and fits the 4WD version of the tranny. It comes with a new 27-spline input gear for the NP231. The second is only 1.50 inches long and works with either the 2WD or 4WD tranny. It includes a new 23- or 21-spline mainshaft that must be installed in the transmission. We followed Advance's recommendations and had the 1.5-inch kit's mainshaft sent off to TCI to be installed in our new transmission.
When considering a company to build our TH700R4, few could match TCI's reputation for quality or flexibility with customer service. TCI routinely custom-builds transmissions, so assembling our Maximiser 4x4 transmission with Advance's mainshaft caused absolutely no drama. TCI's TH700R4 arrived to us fully built with a chrome oil pan, converter, 3 gallons of TCI's Max Shift transmission fluid, TCI's vacuum-operated lockup converter switch installed, and the dyno sheet verifying the transmission had been test run not twice but three times to ensure proper operation before it was shipped out.
Installing a TH700R4 adds a lot of length unless you get creative. Using Advance Adapter's 1.5-inch adapter helped, but we were able to keep our rear driveshaft length within 1 inch of stock by using TeraFlex's Extreme Short Shaft kit (PN 231ESS). Once everything was installed, we called up Tom Wood for a pair of his newly designed, silky smooth 1310 CV driveshafts. The shafts feature Tom's own CVs, not Spicer's. The CVs are forged from steel, not cast iron, and have a modified shape to reduce stress risers and improve grease distribution for longer life and cooler operation.
TAG signed on to be the official shop of our Steal-J buildup, and halfway through the transmission swap, we sort of felt bad for them. We ran into a few glitches and unforeseen problems that would have sent some lesser shops into a tizzy, but the crew at TAG, namely shop foreman Jay Miller, handled every eventuality without throwing one wrench and turned the mess of Jeep parts scattered across the work bay into a reliable runner. Read on for the full skinny on the install.