Turbo Diesel Register Frequently Asked Questions Reposted: February 2, 1999

The staff of the TDR receives in excess of 125 inquiries each week.  Most of the questions we receive are about the proper care and maintenance of the Turbo Diesel RAM truck.  Considering that we have a staff of two plus a couple of contractors, it is no wonder that some of these inquiries go unanswered.  To reduce the number of unanswered inquiries, we've compiled the most frequently asked questions and our responses below.  We hope you find this information helpful.
 
Q: What mileage can I expect from my Turbo Diesel RAM truck?

A: You can expect:

16 - 21 mpg - without a load
10 - 15 mpg - with a load

A: Driver variables, truck variables (gearing, 4x4 or 4x2, 2500 or 3500), load variables, seasonable variables (winter mileage is 5% - 10% less).  Each situation is as unique as the individual with the inquiry.
 
Q: I've heard there is a new motor for the 1998 Dodge.  What do you know about it?

A: Everything . . . and nothing.

Everything: We covered the engine in detail in the Fall, 1997 magazine.  Take a look at Issue 18, page 46 - 50.  The reason for the engine?  To meet a new set of diesel exhaust emission laws that go into effect on January 1, 1998.  Hence, the mid-model year introduction of the engine.  The new ratings?

5-speed:

215 hp @ 2600 goes to 235 hp @ 2700
440 lbft @ 1600 goes to 460 lbft @ 1600

180 hp @ 2600 goes to 215 hp @ 2700
420 lbft @ 1600 goes to 420 lbft @ 1600

We're Learning:  As a part of the TDR magazine, we are using the "Question and Answer" column with member comments and factory updates to spotlight the engine.  As an example, the fuel filter has changed, the oil filter did not.  Head bolt specifications have changed; fuel mileage is basically the same.  For details, see Issue 20 and up.
 

Q: So, what's the difference in the engines?

A: To be brief, a new electronic controlled fuel system, a 4 valve/cylinder cylinder head, and an extended power range.  The engine now "revs" from 2800 rpm to 3200 rpm versus a rpm "drop-off" of the old engines that occurred at approximately 2600 rpm.  Remember the equation for horsepower: HP = torque x rpm / 5252 (a mathematical constant).  By virtue of the higher rpm the new engine can "rev" up to, we're able to mathematically "make" horsepower.  See Issue 7 (page 35) and Issue 9 (page 38) for a comprehensive discussion on the horsepower/torque relationships.
 

Q: "I heard there was a new 6-speed manual transmission and an Allison automatic transmission to be introduced.  Is this true?"

A: Advice from `Mr. Someonesaid' is the best reason for subscription to the Turbo Diesel Register.  Our goal is to provide factual information about the Turbo Diesel rather than fuel for an out of control rumor mill . . . . Enough of the soap-box sermon.  The official word from Dodge, "We're not at liberty to discuss future product plans." My crystal ball prediction . . . the 6-speed manual.

. . . perhaps 1999 model year truck.  A different automatic transmission . . . certainly a possibility, but I don't see the financials of another vendor's automatic transmission.  The Chrysler 47RH is already a $1,000 (approximately) option.  Would you pay $3,500+ for another vendor's transmission? Silly, silly rumors . . . .
 

Q: Are thermostat fluctuations normal?

A: Hey, it's normal . . . so says both Dodge and Cummins.  For the gory details, Issues 5, 6, 12, 13 and 16 speak to the subject.  Remember where the temperature sensor is.  It is located at the intake to the block from the radiator.
 

Q: Tell me more about exhaust brakes?

A: As a kid, did you ever stuff a potato up a tailpipe?

The same principle is at work with an exhaust brake.  You close off the exhaust, and you build up back-pressure.  All of the manufacturers' units work with varying degrees of success.  See Issues 9, 10, 11, 13, 14, 15 and 16 for more discussion.  Personally, I would not be without one.
 

Q: 3.54 vs. 4.10 rear gears?

A: It all depends.  You need to answer about a dozen questions to be sure.  But in about 90% of the cases, the 3.54 is the better choice.  Issues 9, 11 and 13 provide more detail on this issue.  If you have a service body loaded with tools and compressors, and you pull a back-hoe for a living, and you live in the Sierra or Rocky Mountains, you probably want the 4.10.  Certainly, the 3.54 is better for fuel mileage as the engine turns less rpm at highway speeds.  Realize if you have a heavy load, the 3.54 may require your patience if and when you tow in the mountainous terrain.  What percentage of the time will you be towing in mountains?
 

Q: Which engine oil do you recommend for my diesel?

A: Many of you inquire about selecting the "best" for your truck.  I hear a lot of questions like, "How about Mobil 1 or the Castrol Syntec synthetic lubricants?"  Good intentions, but these oils are not blended to meet the requirements of a diesel.  The API (American Petroleum Institute) "donut" rating for both oils is CD.  Note the first letter "C" stands for compression engine (a diesel).  The "D" is the specification test the oil was tested at and was able to pass.  The "D" specification was developed in 1952.

The current "C" or diesel specification is CG-4.  Always use diesel engine oil rated API CG-4/SH.  See your owner's manual and TDR issues 2, 3, 10 11, 12, 13 and 15 for more information.

The oil needs to also pass the API S (S stands for a spark/gasoline engine) category and current specification H.  The S classification is needed to address and prevent wear on the sliding camshaft tappets.
 

Q: Is it necessary to warm up my diesel?

A: Extended warm ups are not necessary (check your owner's manual).  Above 50 degrees, drive after oil pressure is up.  Don't ‘stick your foot in it' until the temperature is up.  In cold weather, give it a chance to settle down . . . quit shuttering and shaking.  Driving with moderate throttle will bring up running temperature faster.  Just use common sense.
 

Q: What is causing the chirp I hear?

A: Mice under the hood? No.  Cummins says this noise is normal and is caused by the engine stopping faster than the belt can.  High compression says "whoa" while the fan says "go."  The result is a "chirp" from the pulley.  If the viscous fan clutch is "locked up" at shut down, the "chirp" may be heard in the next county. Belt wear and tensioner condition will also determine the decibel rating of your "chirp."
 

Q: Do you recommend the automatic or the 5-speed?

A: Are you a Democrat or a Republican? My wife says it has to be an automatic . . . so guess which one we have?  Do you do a lot of stop ‘n go driving? Do you like to pretend you are driving a Trans-Am race and enjoy all of those speed shifts?  Do you do a lot of mountain driving? How about trailer pulling?  If you have to back up a vertical driveway with a 20,000 lb. 5^th wheel every night after work, you may want an automatic.  If you are a good driver, you have greater overall flexibility in meeting various road conditions with a 5-speed.  Given identical engines and trucks, you will get better overall mileage with the stick if driven conservatively.  Today's computer controlled automatics are infinitely more efficient than previous units.  The "lock-up" torque converters have put the fuel consumption issue on an equal footing with the 5-speeds at freeway speeds.  Once you look at the pros and the cons, it all boils down to personal preference.
 

Q: What should be done to break-in my engine properly?

A: Floorboard it right out of the showroom!  Not really!!!  Again, check your owner's manual.  Specifically, the manual points out the following: "Your Cummins turbocharged, charge air cooled, diesel engine does not require a break-in period due to its construction.  Normal operation is allowed, provided the following recommendations are followed (if it is practical to do so):

• Warm up the engine before placing it under load.
• Do not operate the engine at idle for prolonged periods.
• Use the appropriate transmission gear to prevent engine lugging.
• Observe vehicle oil pressure and temperature indicators.
• Check the coolant and oil levels frequently."

Other notes on break-in: do not change to a synthetic or partial synthetic oil until after the engine is broken in (give it 10,000 miles).  The Cummins/Fleetguard LF3552 oil filter is the micro-glass version of the stock Dodge filter 4429615 (manufactured by Cummins/Fleetguard, part number LF3349).  By nature of the micro-glass construction (Issue 8, page 72), it can "catch" smaller particles.  I changed the filter at 68 miles.

Today, brakes probably need more of a break-in than do other components in the truck.  Manufacturing tolerances are so much tighter that once everything is warmed up with correct lubricants, you aren't going to do any damage to the vehicle.  Take a look at Issue 17 (page 45) for further discussion.
 

Q: How do I get more POWER (aauurrgghh)?

A: The most important ingredient is more money!!!  Internal combustion engines are nothing but air pumps.  Let them breathe easier.  Add a low restriction air filter and exhaust system.  Bingo!  You have the first element.

Add more fuel, and you have the second.  And you also have a potential warranty invalidation! Your money - your choice.  TDR Issues 3, 8, 10, 11, 12, 14, 15 and 17 all address this most frequently asked question.
 

Q: How does high performance "equate" to engine life?

A: Unfortunately, there is not an equation or formula to compute the effect of additional power and the resulting stress imposed on your engine.  In the simplest of terms: each engine has a finite life.  Assuming proper maintenance, the life is dictated by the amount of fuel that is burned by your engine.  More power equals more fuel.

The conclusion:  If you use the power (fuel), you use up engine life . . . . The Funny-car engine in John Force's 6,000 hp dragster goes how many miles before a rebuild?
 

Q: Do you recommend any particular antifreeze?

A: Both your owner's manual and TDR Issues 1, 9 and 11 speak specifically to this subject.  Very important - use a low silicate product (blended for diesel engines) and good water - preferably distilled or at least de-mineralized.  My well water could cement a radiator shut in 20 minutes!
 

Q: I've heard about a problem with the antifreeze that causes diesel engine cylinder liner pitting.  Sounds serious and costly.  What's the story?

A: It's quite a "story." The technical term is called cavitation erosion and was covered in detail in Issue 8, pages 40 - 46.  The bottom line is that it is not a problem with your Cummins if you adhere to the proper maintenance schedule.
 

Q: Where can I find more information about diesel efficiency?

A: Wow,this could go on for pages.  I strongly recommend you begin by reading the related article in TDR Issue 12 (beginning on page 51).  Then, read it again.  This is heavy duty stuff.  I prefer to think of it as anything that makes that much noise has got to be better.  Issue 12 covers the basics.  But what about volumetric efficiency, brake-specific fuel consumption, torque and horsepower?  TDR Issues 7 and 9 are the key to understanding these technical terms and unlocking the secret to the engine's "sweet spot" for fuel efficiency.  Most currently, we've covered "How to Drive" with a thorough discussion in Issue 20.
 

Q: How can I tell if my truck is performing as it should?

A: Take a look at TDR Issue 17 (page 48).  Warning:  the boost/automatic transmission test portion of the article could be hazardous to your health if you take your foot off the brake at the wrong time!  Then again, you could quickly add that patio sliding door to the house that the wife has been bugging you about.
 

Q: Please explain more about the waste-gate turbo.

A: Take a look at Issue 11 (page 60 - 61) and Issue 17 (page 25).  In a nutshell, the waste-gate design allows a higher boost at low speeds.  At high speeds it by-passes (the waste-gate opens) excess pressure so that the turbo doesn't spin into orbit.
 

Q: What about valve adjustments?

A: There is too much information for me to include in this brief FAQ.  The number of articles published in the TDR - Issues 1, 2, 4, 5, 6, 8, 10, 11, 12 and 16 confirms that, because of the recommended 24,000 mile adjustment interval, this is a much discussed subject.  Remember, a valve adjustment is easy to do.  Isn't it great . . . the new 4-valve Cummins doesn't need one until 100,000 miles!

Q: What causes white smoke?

A: Careful, you can get arrested for that!  Seriously, I had trouble with that one when my `94 was new.  Again, TDR Issue 10 (page 35) has a detailed explanation about white smoke on start up.  The bottom line is that it is unburned fuel and it is a fact of cold-weather diesel operation.  The last paragraph of that article talks about advancing pump timing.  It took that, plus a thermostat change, to stop me from losing sight of those behind me after a down-hill run.
 

Q: Does the TDR have a web page that I can take a look at?

A: Yes, but beware! We're an excellent source for technical information, but we're a bit computer illiterate.  So, don't expect too much glitz.  We're at: http://www.turbodieselregister.com/
 

Q: Do you know of any good sources for filters and accessories for my truck?

A: Geno's Garage is a vendor we can recommend.  To request a catalog, call them at (770) 886-4955.  Or you can request a catalog via the Internet by sending an e-mail to: rpatton@ix.netcom.com.  We will forward it to a member of Geno's staff.  As an example, the following chart includes Geno's prices for replacement Cummins/Fleetguard oil, air and fuel filters:
 

Q: How do I subscribe to the Turbo Diesel Register (TDR)?

A: An annual membership to the TDR runs $35.  You'll be mailed four issues (quarterly) of the TDR over a twelve-month period.  We accept Mastercard/VISA, check/money order and cash.  Include your name, mailing address, and method of payment.  You may subscribe via:

• U. S. Postal Service (our preference)

Turbo Diesel Register
1275 Elk Ridge Cove
Alpharetta, GA 30005
• Internet account: rpatton@ix.netcom.com (works well too); VISA and Mastercard only
• Voice response system (770) 844-1600 (least preferred - no paper trail and the system is usually full by 1:00 p.m. each day); VISA/Mastercard only

A: Absolutely.  Recent copies of back issues are available in original and reprint condition.  The following issues are available as individual publications at a cost of $7.00 each:

• Issue 20 (Spring, 1998) - $7.00
• Issue 19 (Winter, 1998) - $7.00
• Issue 18 (Fall, 1997) - $7.00
• Issue 17 (Summer, 1997) - $7.00
• Issues 13 - 16 are available in reprint form in a single bound volume (Volume IV).  Volume IV is 236 pages and is available for $22.50.
• Issues 9 - 12 are available in reprint form in a single bound volume (Volume III).  Volume III is 198 pages and is available for $20.00.
• Issues 5 - 8 are available in reprint form in a single bound volume (Volume II).  Volume II is 152 pages (advertising pages have been omitted) and is available for $17.50.
• Issues 1 - 4 are available in reprint form in a single bound volume (Volume I).  Volume I is 108 pages (advertising pages have been omitted) and is available for $15.00.

Revised: June 22, 1998