Click for Coverage
Due to the EU’s Global Data Protection Regulation, our website is currently unavailable to visitors from most European countries. We apologize for this inconvenience and encourage you to visit for the latest on new cars, car reviews and news, concept cars and auto show coverage, awards and much more.MOTORTREND.COM
  • JP Magazine
  • Dirt Sports + Off-Road
  • 4-Wheel & Off-Road
  • Four Wheeler

Nuts & Bolts - May 2014

Posted in How To: Tech Qa on April 3, 2014
Share this

Under Pressure
Q I own an ’08 Chevy 3500HD dualie and recently had the tires replaced with the proper load range tires for the truck, which were a brand recommended by my local tire shop. The other day I took the truck in for an oil change and the technician asked me what pressure I wanted the tires set to. Since I haul a big trailer pretty regularly, I told him to set them to whatever the maximum pressure was on the sidewall of the tire. He came back a few minutes later and said the tire pressure on the sidewall was higher than what was recommended by the sticker on the door, and that if I had him set it to the sidewall pressure, that gas mileage and tire wear would suffer. I told him to go with the sidewall pressure anyway, but that got me to thinking. Should the technician go back to flipping burgers for a living, or am I wrong?
Kyle S.

A While the technician might have been simply following his training, we’d probably tell him not to retire his spatula just yet. Assuming the tires you chose match the recommended load rating for the truck (Load Range E or higher), then we would always default to the pressure that the tire manufacturer states because that recommendation is based on testing with the specific tire at the maximum load that the tire is rated for. The sticker on the door of the truck is representative of the tire load range needed for the truck and the recommended pressure for the OE tires that came on the truck. The OE tires are probably different than what you purchased. We would be suspicious if the pressure on the sidewall was less than what was stated on the door, but not a higher pressure. Going by the pressure on the door with your truck’s new shoes could leave the tires underinflated, which is possibly hazardous at maximum load, not to mention causing irregular tread wear and harming mileage (the exact opposite of what the tech claimed).

We often recommend lowering tire pressure for better traction off the pavement and sometimes on the pavement as well. The on-pavement recommendations are usually the result of putting a heavy-rated tire on a lightweight vehicle, such as a Load Range E tire on a Jeep Wrangler. The stated maximum pressure on the sidewall assumes a maximum load as well, but Load Range E is way more load capacity than a Wrangler can handle. Oversize tires often have beefed up carcasses to deal with the larger sidewall of a bigger tire, but running an E-rated tire at maximum pressure on a Wrangler will do nothing but cause loose fillings. Lowering the on-road pressure to a more reasonable number on a lightweight vehicle actually gives a higher-rated tire a better footprint and a vastly improved ride. But since you’re actually using your truck as it’s intended (hauling heavy loads), we would default to running the maximum stated sidewall pressure.

Synthetic or No?
Q I have an ’80 Chevy K30 with some drivetrain noise. I am going to replace the gear oil with something new. I was wondering if synthetics like Royal Purple would harm the original seals in my manual transmission or transfer case. I have heard (mostly on television) that Royal Purple quiets gear noise and runs cooler. Is this true? If so, should I use the stuff in my old gear boxes?
Matt Todd
Harrodsburg, KY

A Though synthetic lubricants were once a polarizing subject between those who swore by them and those who felt they were a waste of money, these days synthetics are well regarded and have several proven benefits. Plus, several OE manufacturers have started using synthetics right off the assembly line, and this has helped reinforce their value as well as their accessibility to the general public.

Virtually all synthetic manufacturers, including Royal Purple, make several claims about the benefits of synthetic oils, and most of them have independent testing data to back up their claims. I have used a variety of synthetic brands over the years and have had no complaints. In fact, some have been downright impressive. I have a tendency to believe that synthetics do indeed make components run cooler and last longer.

That said, I personally have never had any luck getting a noisy drivetrain component, whether it’s an engine, transmission, transfer case, or rearend, to get quiet simply by switching to a synthetic. Maybe once or twice the noisy part in question has been granted a temporary reprieve, but at least at my house, the noisy part ends up coming out for a rebuild shortly after an attempt to make it quieter with a synthetic or some off-the-shelf miracle additive. This is not the synthetic’s fault, but just a fact of life: Moving parts wear and eventually wear out. While synthetic oils have their place, they’re not really a substitute for rebuilding something if it’s noisy due to excessive wear.

Feeding components a steady diet of quality conventional or synthetic oil and carefully following a maintenance schedule is the best bet for ensuring long drivetrain life. Replacing the gear oil in the tranny and transfer case on your K30 with a good synthetic like Royal Purple certainly won’t do any harm and could actually benefit you by running cooler and introducing less drag. Even so, don’t expect miracles.

As for the seals, synthetics typically have additives that prevent seals from shrinking, so this really shouldn’t be a concern. If you want to play it extra-safe, consider using a good synthetic blend that offers the properties of conventional oil with the benefits of synthetic oil.

Nuts, I’m Confused
Little Diesel
Q I have an ’88 Suzuki Samurai, and I’m thinking of swapping in a small diesel in the future. I’m not sure what diesels are out there that would be small enough for such a swap and was hoping you might have some ideas. I assume it would have to have a different transmission? Any info you guys could provide would be helpful.
Rusty C.

A Diesels are great off-road engines. They make gobs of torque down low, they get great mileage, and they run forever. It’s unfortunate that we here in the states have only just started opening our eyes to the potential of modern compact diesel engines and their advantages; Europeans have enjoyed all sorts of cool diesel engines for many years.

For your application, it would be hard to go wrong with a TDI engine from a Volkswagen. Guys across the pond have been swapping the TDI into all kinds of wacky things for years, and therefore you can find an adapter to mate a TDI to just about any transmission. Fortunately for you, a company called Acme Adapters ( makes everything you need to swap a VW TDI engine into your Samurai, including an adapter for the Sammi’s original tranny, so there is no tranny swap required. Acme’s offerings vary depending on the donor engine you’re using, but the adapters start at $450 and run over $1,000 depending on the options and components you want to use. There’s also a fair amount of knowledge available regarding this swap, including what appear to be detailed blueprints on the Internet to build your own adapter if you have the knowledge and the equipment to do it. The folks at Acme seem to have most of the hurdles figured out, though, so it might be best to go with them unless you just enjoy a challenge.

There are, of course, many other diesel options beyond the VW TDI, but a lot of them were not offered here in the states, which can make sourcing a donor engine (and replacement parts) a challenge. A Cummins 4BT, while another popular compact swap candidate, is a bit much for a Samurai and presents some big packaging challenges under the hood, not to mention a complete drivetrain swap in order to handle all the extra torque.

Submission Information
Confused? Email your questions about trucks, 4x4s, and off-roading tech using “Nuts, I’m confused” as the subject and include a picture (if it’s applicable). Digital photos must measure no less than 1600 x 1200 pixels (or two megapixels) and be saved as a TIFF, an EPS, or a maximum-quality JPEG file. Also, I’ll be checking the forums on our website (, and if I see a question that I think more of you might want to have answered, I’ll print that as well. Otherwise drop it old-school style with the envelope addressed to the address below. Letters published in this magazine reflect the opinions of the writers, and we reserve the right to edit letters for clarity, brevity, or other purposes. Write to: Nuts & Bolts, 4-Wheel & Off-Road, 831 S. Douglas St., El Segundo, CA 90245 fax to: 818.566.8501 Email to:

Connect With Us

Newsletter Sign Up

Subscribe to the Magazine

Browse Articles By Vehicle

See Results