Tech Q&A - Diesel World

Diesel Get Up and Go



I own a restored 1992 F-150 4×4, but now I’m finding I don’t have enough get up and go. So I’m looking into converting it to a diesel. I would like to install a 12-valve Cummins in this truck, but I’m having a hard time finding all the information I need. Can you help me out?

Shane Krick

Via Email

The following web sites will help with hardware and tech support. The listed shop below here in Montana will even do it for you, or they’ll certainly help answer any questions you might have about the suitability of the F-150 for a conversion like you’re proposing. The I-6 Cummins is a fairly heavy engine. The half-ton Ford chassis may need a little help to handle the added weight without causing a concern for safety or durability.

Also, be sure to read the following link that describes how to install a Cummins in a somewhat newer F-250 Ford pickup truck. While not an exact match for your situation, there’ll be information that should help answer some of your questions.

Good luck.

ATF Leak

My GM transfer case has a mystery leak. While driving my 2003 Silverado 2500 HD to Charlotte, North Carolina, I noticed a lot of oil on the tailgate and front of the trailer. Knowing I was losing ATF from the transfer case, I kept it topped off until I got back to my home in Beloit.

I changed the output seal, and it still leaked; GM tech thinks the case halve seal is bad. How can that be? After doing a little online research, I found a toothpick-sized hole on the rear case half that indicates the internal pump components had worn through the magnesium case. My question is, do I need to remove the whole transfer case or can this problem be resolved under the truck?

I’m an engine dyno system installer working with Power Test out of Sussex, Wisconsin. I went to Charlotte to install a water-cooling system with a glycol heat exchanger for Carolina Cat.

David Karr

Beloit, Wisconsin

Some New Venture Gear 261 (manual shift) and the NVG-263 (electric servo shift) transfer cases have developed an ATF leak due to the internal fluid pump flange wearing a hole through the rear-case half. If not caught soon enough, the transfer case could suffer complete failure due to a lack of lubrication. GM’s band-aid fix up to this point in time has been to apply a JB Weld epoxy patch over the hole. However, the most reliable solution involves either a new rear-case half or welding the hole(s) closed (magnesium case), and then installing an aftermarket pump wear plate that permanently solves the problem.

You really need to remove the transfer case to do a good job. Gravity will work against you if you attempt to do this from beneath the truck. It is likely possible to split the case halves and complete the repair without removing the transfer case, but it’ll be harder.

There is no gasket used between the two case halves—just silicone sealant. Before re-assembling, clean the case mating surfaces using brake cleaner, and then apply a 5mm bead of RTV gasket compound to the flange on the inboard side of the boltholes. Having the forward half of the transfer case mounted vertically on the bench helps the rear half slide over the various shafts and fittings during reassembly. This allows gravity to work for you, instead of against you.

Removing the transfer case from the truck usually ruins the gasket that seals the transfer case to the transmission adapter.

Bolt Torque Specs:

Crossmember to Frame Bolts: 51 lb-ft

Transfer Case Drain Plug: 15 lb-ft

Transfer Case Fill Plug: 15 lb-ft

Transfer Case Shield Bolts: 15 lb-ft

Transfer Case Speed Sensor: 11 lb-ft

Transfer Case to Transfer Case Adapter Nuts/Studs: 36 lb-ft

Transfer Case Adapter to Transmission Bolts: 36 lb-ft

Transmission Mount to Crossmember Nuts: 29 lb-ft

Transmission Mount to Transfer Case Adapter Bolts: 34 lb-ft

The GM transfer case requires 1.9 quarts of Dextron ATF. I recommend using a quality synthetic because of the somewhat limited amount and because the transfer case can run warmer than the transmission. For a wear plate that will prevent a future problem, visit for their inexpensive “Adapta-Case” wear plate or any related parts.  Let me know if you need any other help.


Howdy Jim,

I have a question about an overheating problem I’ve had with my 2005 Duramax here in Texas. I changed out the thermostats and that helped a little bit, but I’m going to change them again to a set of cooler stats because the engine still runs too warm while towing. I also changed my water pump because it began to leak. I personally suspect that’s due to the engine’s running hot. I’m also planning to install an aftermarket fan-clutch. However, I ran across an article online that’s really interesting and it may be something worth reading: it suggested the turbocharger ducting as being a part of the hot-running problem. Please let me know what you think.

Fred Knopp

Aledo, Texas

Aside from installing the 2006 LBZ cooling system components, there is no other solution that works—at least one that isn’t just a bandage. That said, it’s only a very small percentage of LLY owners who experience overheating. Most owners don’t, and we rarely hear of the earlier 2001-2003 LB7 or the 2006 or newer LBZ/LMM/LML Duramax overheating.

Back in 2006, GM issued a service bulletin (06-06-04-036D) that was designed to address LLY overheating in hot ambient temperatures. The bulletin applied to all 2004 and 2005 LLY Duramax engines. GM’s solution was mostly limited to retrofitting the newer-style LBZ air intake to the LLY engine. This too was a bandage that provided a little help, but ultimately, didn’t solve the problem.

The LLY was a transition engine that saw a number of significant changes, when compared to the outgoing LB7. For example, the EGR cooler was enlarged, which put more heat into the cooling system. Meanwhile, the brand new Garrett VNT (Variable Nozzle Turbine) turbocharger was added, which added restriction to the exhaust system. And lastly, for some reason, the composite 9-blade engine-driven fan was actually reduced in diameter from the 21 inches as used on the LB7 to just 19 inches.

The LLY became the shortest production run of any of the various generations of the Duramax. I suspect the GM engineers discovered what a few owners have, with regard to overheating. Luckily, there’s a fairly easy (though somewhat costly) solution to this heat problem: The February 2009 issue of Diesel World Magazine contains an excellent how-to article showing what’s needed to absolutely solve an LLY overheating problem. You can order this back-issue, and I recommend you do by visiting:

In short, the LLY radiator, fan-shroud, fan, fan-clutch and radiator core support are swapped out for those factory components installed in the 2006-2007 LBZ equipped trucks. The LBZ radiator is approximately inches taller and 7/8 inches thicker, and the fan is 4 inches larger in diameter (23 inches) than those used in the LLY. A few smaller items are necessary to make the full transition to the LBZ spec cooling system, and having the magazine will allow you to do the job correctly. This is the very best solution for solving an LLY overheating problem using genuine GM designed and tested components. Good luck. DW