Welcome to Top Tech Questions. Oftentimes, readers contact us with questions about articles, or to praise us on what a good job we are doing. But our favorite form of reader communication is tech questions. Our Top Tech section is a place where you ask what’s on your mind, and we answer it. Got a trouble code? Wondering how to get your engine to make more power?
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jason.sands@sorc.com and we’ll do our best to answer it.
Tired Torque Converter
Question: I’ve got a 275,000-mile, ’99 Ford Super Duty with a stock torque converter that has almost completely failed. It shakes the whole truck when it locks up in Third and Fourth, and it will keep shaking until I get the truck up to highway speed. I’m looking for a replacement, and my question is: Due to the bad converter, what’s the risk of the transmission needing some attention? Should I go for a stock converter or a triple-disc unit with a billet-steel cover? What difference would I see between the two?
Garrett Mack
Via email
| For trucks that spend their life towing at stock power levels, a single-disc lockup torque converter is all that’s needed. Save the triple-discs for higher-horsepower performance applications.
Answer: If your transmission isn’t in danger right now, it could be soon. The shuddering means the torque converter clutch is slipping and all that material has to go somewhere. Since transmissions are a closed-loop system, the only place for the lockup clutch material to go is throughout your transmission, cooler, and lines. Chances are, you didn’t fry anything if you haven’t been driving it like this for very long, but we would have a shop at least drop the pan and look. If it still drives OK once the converter is replaced, we’d leave it alone. With your truck’s mileage, there’s a good chance the transmission was rebuilt somewhere along the line anyhow.
Now, a word about torque converter selection: If you plan on keeping a mild chip installed and don’t go nuts with future upgrades, we’d suggest a lower-stall single-disc converter. The lower-stall speed will give your truck added pulling power without the converter being locked, and a good single-disc converter can handle up to 450 hp without much of an issue. If you plan on future engine upgrades, a triple-disc converter might not be a bad idea but its engagement will be a lot harsher than stock.
Overheating LLY
Question: We currently own an ’06 Chevy C4500 Kodiak with the 6.6L Duramax LLY engine. Last summer, during a long, hard tow, it overheated and everything shut down. We were able to pull the truck over, but that was about it. Within a few minutes, it cooled off, started right up, and away we went with no further problems. We have since added dual cooling fans to the front of the radiator but are unsure if this will fix the problem. Is there a permanent solution for this issue?
Les and Debbi Blair
Jackson, Wyoming
| june 2011 Top Tech Questions kodiak Towing
Answer: It turns out that many people who bought the LLY-designated Duramaxes built from ’04 to early ’06 have overheating problems. An EGR cooler for the LLY engines was new, and the cooling system had to deal with the same heat from the engine, plus cooling of the EGR system. It should be noted that this overheating issue usually only happens during full-throttle towing for minutes on end, usually up grades, and while it is very hot out. Towing at a slower speed or custom-tuning via EFILive to reduce engine power are both inexpensive options that can prevent an overheating situation. For those who can’t lift off the throttle, the easiest solution is to install a second radiator inline in the cooling system that is mounted below or behind the front bumper. Since your particular LLY is in a Kodiak, you should have plenty of extra room for another cooler. The supplementary radiator doesn’t need to be all that large (roughly 16 inches x 18 inches) and an electric fan should also be installed on this secondary radiator to promote airflow. Duramax LLY owners who have reported making this type of modification claim their trucks no longer overheat. Even on steep grades during hot weather, about 210 degrees on the coolant temperature gauge is about the highest one would see.
Illegal Tire Pressure?
Question: I just bought an ’11 Ford Super Duty with the 6.7L engine. I replaced my stock tires with new rims and larger-than-stock tires. The stock tires take 80 psi and my new tires max out at 65 psi, so the tire pressure alarm in the dash keeps coming on and telling me my tires are low. My Ford dealer can reset my computer for lower tire pressure, but it won’t because it says it is a liability thing. Any advice?
Piet de Bruyne
Woodland, California
| Not all new trucks come with a tire pressure monitoring system (TPMS). If yours does and you want to change wheels and tires, find a dealer or shop that is willing to work with you and set the low-pressure warning at a more reasonable level. You’ll just have to remember to air back up to max psi when towing. Readers who want to avoid these problems altogether should look for trucks that have a GVW of more than 10,000 pounds—they don’t require a tire pressure monitoring system.
Answer: There’s actually a law that requires manufacturers to put a tire pressure monitoring system on all new vehicles that have a gross vehicle weight rating of less than 10,000 pounds. The air pressure that trips the alarm is based on the maximum loaded capacity of the vehicle. While this works fine for car tires that may vary 5 psi or so from max load to unloaded, diesel truck tires can be run anywhere from 35 to 65 psi unloaded without sacrificing cornering ability or traction. In fact, running tires at or near their maximum loaded rating (80 psi in most cases) in adverse weather conditions can have a detrimental effect on vehicle control. Or, let’s say you’re the kind of person (like Mr. Bruyne) who wants to add larger tires, which require less air pressure for the same weight capacity you’re bound to trip the tire pressure monitoring device.
Unfortunately, there is no provision for this in the law (known as the TREAD act), so diesel owners are stuck with the loaded maximum as their base tire pressure, with warnings going off if they try to air down to run unloaded. We actually spoke with the National Highway Transportation Safety Administration (NHTSA) about this matter and it came back with the law is the law response, so in NHTSA’s mind, it was more unsafe to allow people to drive their vehicles at a lower tire pressure loaded than too high of a pressure unloaded.
So what can be done? Well, if you own a new Dodge, you can press the Light Load button on the dash and air the rear tires down to 45 psi. If you own a Ford or GM, you can find a friendly dealer or shop that has a scan tool, which can reset your tire pressure warnings to a more realistic level, but as you’ve found out, many dealers or shops are reluctant to do so. Another option is to retrain the tire monitoring system to try and alarm at a lower tire pressure level. This is done on 6.7L-powered Fords by airing the tires down to 65 psi (the lowest pressure at which this trick will still work) and then hitting the hazard button three times. A dashboard display will come up indicating the tire pressure sensors are in learning mode (which is actually used to help determine location, not pressure), at which point the driver can jump out of the truck and air down the tires one at a time, until the truck’s horn beeps. Once this is done, air all the tires back up to 65 psi, and you should be able to keep them at that level without any warning lights illuminating.
