Jeep Creep: JK Diff Lock Trouble, Engine Swaps and More

Jun. 23, 2015 By Jim Brightly, KF7SCT

In your Jeep Creep questions, please list your first and last names, your hometown, and your state/province/country, so that we can publish that information here. If you donít provide this information, we may not be able to publish your question and answer. Donít forget to be as complete as possible with the description of your Jeep and its problems, too. Send your Jeep questions to [email protected], Attn: Jeep Creep.

Previous Jeep Creep Columns
May 2015

April 2015

March 2015

One Jeep recall from NHTSA this month
Chrysler is recalling certain model year 2006 Dodge Viper and Jeep Wrangler and Liberty vehicles manufactured July 1, 2005, to July 31, 2006. In the affected vehicles, the springs within the clutch pedal position switch that prevents the vehicle from starting unless the clutch pedal is pushed down may break. As a result, the vehicle may not be started when the clutch pedal is pushed down or the engine may crank and start without the clutch pedal being pushed down causing the vehicle to unexpectedly lurch. If the vehicle unexpectedly moves there is an increased risk of a crash. Chrysler will notify owners, and dealers will replace the clutch ignition interlock switch, free of charge. Parts are currently unavailable. Owners will be mailed an interim notification beginning in June 2015, and will receive a second notification when remedy parts are available. Owners may contact Chrysler customer service at 800-853-1403. Chrysler's number for this recall is R13.

Going Commando
My í68 Jeepster is still all stock, but when I pulled out the transmission to replace it, it is a T-86. Some knowledgeable folks Iíve talked with have said that I should replace the T-86 with a T-14. They said the T-14 handles the torque of the 225 V6 better and will last longer than if I replaced it with another T-86. Will the T-14 bolt to the bellhousing in the same bolt setup as the T-86? Or do I need an adapter? What other modifications will be necessary?
Tran Rang
Bisbee, AZ

The 1966-í68 V6 Jeeps used the T-86; the í68 to í71 V6 and 1972-í75 inline six Jeeps used the T-14 (the inline transmissions use a different input shaft). You can bolt a V6 T-14 to your bellhousing without an adapter, but you will need a Spicer 18 10-spline drive gear to replace your T-86ís 6-spline drive gear. You may also require a T-14 transmission mount. And lastly, the T-14 is slightly longer than the T-86, so youíll probably need to the mounting holes in the frame for the cross member. When I last checked, the drive gear and transfer case mount are both available from 4Wheel Parts ( If you canít find a decent T-14 in your areaóand chances are youíll have to rebuild it anyway before you install itóyou can Google it.

More Power?
I have a 2006 Rubicon Unlimited with an automatic transmission and about 85,000 miles on the clock. I would like to add more power. Iíve been towing a camping trailer over to Las Cruces and while the Jeep is great off-road it loses out on the long hills while towing. I like the 4.0L engineóit runs at the same temperature all the time, isnít cranky, and starts every timeóbut I also enjoy using the trailer for camping but not for towing. With a lift and 35-inch tires the six is a little under-powered. Iíve been thinking about a stroker kit or maybe a supercharger, if one is made for this engine. Can you help me?
Stanislaus Ruiz
Carlsbad, NM

I donít think the stroker kit would give you enough additional ponies for towing to warrant the expense. You could drop a V6 or V8 in it but that would bring up a whole different set of problemsónot to mention the expense. I havenít heard about a supercharger for the 4.0-liter, but I have been reading about a turbocharger for the 4.0L straight six (which reminds me an old saying: ďNormally aspirated engines suck!Ē). A turbocharger is basically as close to a free lunch as you can get (after the expense of the installation and the fact that you have to use premium fuel because of the added compression). It uses the engineís own exhaust to boost the engineís power! For 1999-2006 TJs/LJs with 4.0L engines, Gale Banks Engineering ( offers a well-tested, smog-legal in all 50 states, turbocharger that adds 66 horses and 83 lb.-ft. of torque to the Jeep at its rear wheels!

The Banks Sidewinder Turbo for the 2005-06 Jeep Wrangler is specifically designed with a focus on improving low- and mid-range torque, which is ideal for providing the added power needed on the trail. It will also provide all-around improved drivability on the road.

1. Horsepower (peak-to-peakóat the rear wheels): Stock = 138.6 HP, Banks = 201.4 HP, gain = 62.8 HP (45.3%) Note: OEM published horsepower is 190 (measured at the flywheel).

2. Torque (peak-to-peak): Stock = 176.0 lb.-ft., Banks = 249.4 lb.-ft., gain = 73.4 lb.-ft. (41.7%) Note: OEM published torque is 235 lb.-ft. (measured at the flywheel).

3. 0-60 MPH acceleration: Stock = 12.51 sec., Bank s= 9.62 sec., gain = 2.89 sec. (23.1%)

According to Banks, the torque output with the turbo at 1,600 RPM is greater than the peak torque in stock condition. This aggressive torque profile at a relatively low RPM is ideal for rock crawling and trail running. The standard turbo system operates at 6 PSI boost. If you add-on intercooling (for on-road use) and/or water/methanol injection (for off-road use), the boost will be approximately 10 PSI with power increases of 20-30% over the base turbo system.

Again, according to Banks documentation, installation is said to be relatively simple. And all the necessary parts are included in the kit. Iíve been told the entire project can be completed in one day by an experienced and competent mechanic. The system includes a 46 x 58mm oil-cooled plain bearing turbocharger with an integrated recirculating blow-off valve, new Bosch 35 lb/hr fuel injectors, 2-bar MAP sensor and billet throttle body spacer mount with a port provision for the Banks boost gauge, stainless-steel turbine inlet/outlet pipes, and the boost tube includes provisions for water/methanol injection nozzles. The turbocharger has an integrated wastegate/blowoff valve and is completely pre-assembled at the factory. Its Ram-Air intake system is unique to the application and is available with an optional through-the-hood Super Scoop. Both versions of the system are designed with a slightly higher than stock entry point, leaving no compromise for water fording. The Banks Sidewinder Turbo is a simple installation compared to a stroker kit which would require complete engine removal, disassembly and reassembly. A turbo will also deliver altitude compensation by providing boosted air when ambient conditions are diminished (which means it doesnít really care at what altitude it is operating in). The current kit calibration WILL NOT work when used on a non-stock engine.

JK Taillights
I recently began towing a lightweight camping trailer with my Unlimited. Before that I never had any electrical problems with the Jeep but last night my left running lights (side clearance, taillight, and parking light) and the trailerís lights went out. I stopped and turned all the lights out, waited (I was hoping a circuit breaker might kick back in), but nothing changed. I finally tracked down the fuse that blew and replaced it, but as soon as I turned the lights back on it blew again. I disconnected the trailer, changed the fuse again, and it didnít blow. I left the trailer unplugged and drove home with a friend following but still havenít figured out whatís gone wrong with the trailerís lights. And why didnít both taillights and the dash lights go out on the Jeep? Iíve always thought that the taillights and dash lights were on the same circuit so the driver would know if the taillights quit.
Samuel Austin
San Antonio, TX

Thatís always been the case, Samuel, for as long as Iíve been working on cars. Dash lights and taillights have always been in the same circuit, but not on the JK. On the JK, dash lights, left running lights, and right running lights each have its own circuit and protective fuse. The headlights are also on a separate circuit. Since youíve already tracked down the fuse, I donít have to tell you which one it is, but I can tell you what happened. The taillight circuit on the traileróas youíve probably already guessedóhas been compromised. Itís shorting out on the trailerís metal; itís either pinched or worn with bare wire touching the metal. To correct this, either find that spot or route a new wire and replace the circuit. By the way, if it happens again, you can use a jumper wire and connect the right-hand circuit to the left-hand circuit to get you home.

Rubi Lockers
I have a 2007 Rubicon. The front lockers drop in and out. I've found that they lockup when I turn the steering wheel and drop out when I straighten it out.
Pat Maitland
Forest Grove, Oregon

Pat, the electric locker in the front should send a code that a computer module can read when it doesn't work correctly. Also check for drive axle codes, and then follow the diagnostic chart for your model Jeep. You should check also for a loose wire or bare connection under the vehicle to the differential.

Old Iron
Could you give me a recommendation on what to do about rebuilding the engine in my í75 CJ5? Its 304 V8 is getting pretty tired; hard to start, smoking, and loose. I think it needs new rings, bearings, and a valve job. As long as I have it out of the Jeep, I thought Iíd install better intake (maybe even EFI), a mild cam, and maybe some forged pistons.
Brian Westgate
Westminster, CA

I had a í74 Five for many years, during which I installed a 401 V8 in it. Tremendous horsepower and torque increase with virtually no added weight. Or you could also consider a 360 as wellóall three engines use the same block. You might find a 360 or 401 in a Wagoneer, J-truck, or Cherokee Chief thatís hiding out in a back row of a junkyard or pick-your-part (for probably under $200). When you find an engine, make sure it includes the flywheel, or youíll have to have your 304ís flywheel rebalanced to match the more powerful engine.

Continue to drive your Jeep with the tired engine in it while rebuilding the larger displacement engine. The AMC 360 or 401 will bolt directly in place of your current engine. They use all the same electrical components and accessories, could cost less or the same to rebuild, and the 360 would provide you with an additional 75 ponies and 90 lb.-ft. of torque over and above the similarly built 304. The switchover could be done in a few days.

Tranny Info
My í95 YJ is on its second transmission and Iím not sure how long this one is going to last. I think itís the infamous Peugeot five-speed and Iíd like to get rid of it. I think itís the worst idea for a Jeep tranny anyone ever has come up with. What would be a good tranny to install in its place? And what Jeep transmissions can bolt up without having to spend thousands in trannies and adapters?
David Forrester

The cheapest transmission upgrade would be to find a 1989-í99 4.0L Wrangler in a junkyard and pull the AX-15 transmission and transfer case input shaft. The AX-15 has the same 24-inch case length, bellhousing and T-case bolt patterns, and input spline size as the Peugeot transmission.

The Peugeot has a 21-spline output shaft, and the AX-15 has a 23-spline output shaft. You also must remove the input bearing retainer on the NP231 transfer case and replace the input shaft with the later-model 23-spline input shaft. You can usually find the input gear at pick-your-part yards, and itís a pretty much straightforward swap.

The Peugeot also uses an internal hydraulic release bearing to actuate the clutch. The AX-15 uses the same internal hydraulic release bearing. If you use a later-model (í94 and up) AX-15, youíll need to convert to a hydraulic slave cylinder setup, which can also be found in junkyards.

I just discovered that the springs on my í89 YJ Sahara (88,000 miles) are broken. Since I had planned on using them in a spring-over-axle (SOA) conversion, I need to rethink the project. I donít want to spend a bunch of money on new springs from Jeep (if Iím going bigger later), so what springs (if any) can be swapped into a YJ with little or no modifications? Iíve read that Cherokee springs might be used, but are there any other rigs out there that could have springs thatíll work?
Tony Acosta
Julian, CA

If you donít wish to upgrade at this timeóSkyjacker makes a great lift kit for the YJ with a military wrapóperhaps you could do a Google search for stock YJ springs. If you canít find any for a decent price (and donít forget the cost of shipping four heavy leaf springs), you could go ahead and order a new kit, including shock absorbers. A spring-over conversion isnít as easy as just welding new spring perches on top of the axles. Youíll also need a slip-yoke eliminator and a constant-velocity rear driveshaft, longer brake lines, extended Pitman arm, and a full chassis alignment. In my opinion, rather than chasing down a set of used springs, move ahead with a spring-under kit (with all the necessary parts) and do it right the first time.

Longer Wranglers
I really like the longer Jeeps, like the four-door unlimited, but Iím even more interested in the older, longer models. Can you give me some information on them? I mean the CJ6, Scramblers (CJ8?), and TJ Unlimited.
Paul Salmon
Seattle, WN

CJ8 it is, Paul. Scramblers were offered model year 1981 through í86, while CJ6s were manufactured from 1955 through 1976. The LJ models (longer TJs) were available from 2004 through 2006, with Rubicon Unlimiteds available in 2005 and 2006.

I have a request of all the readers out there. Send us your questions. For some reason the questions have fallen off, and I know we havenít answered all your Jeep technical questions. There are no dumb questions; only unasked questions. Send them in and try to stump us.óJim Brightly

As usual, each month, Iím shouting out a huge THANK YOU to Paul Schupp at Rock Lizard 4x4 in Kingman, Arizona, for his invaluable assistance in answering many of the Jeep Creep questions.

Send your Jeep questions to [email protected], Attn: Jeep Creep.

Previous Jeep Creep Columns
May 2015

April 2015

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