Introduction

The Dakota/Durango platform, designed and sold by Chrysler from 1997-2004, is the third generation of this mid-sized truck.  Adopting a modern appearance, in stark contrast to the previous box design, this truck is still considered to be attractive.  The chassis, body and interior have shown themselves to be durable, and this truck has a strong following, making it a potential classic as the first trucks will soon reach the 20 year mark.

Despite the availability of the 5.9, 250 hp “Magnum” engine with an updated 46re overdrive transmission from 1998-2003, the truck suffered serious weaknesses in the drivetrain throughout the 7 year run.  The chassis was heavy, tipping the scales at nearly 4,000 lbs, and emissions requirements were tight, requiring a lower compression, hypereutectic pistons to prevent
blow-by.  Cylinder heads in the “Magnum” were also known to crack between the exhaust valves, resulting in un-repairable damage.  In addition, the aftermarket has never embraced the Mopar, leaving sales of performance products at only 3% of total sales.  This meant the options were very limited.

The horsepower motor from the 5.9 Magnum line has been modified many times by enthusiasts. Typically beginning with cold air intake, dual exhaust, SCT tuner, throttle body, and intake.  The cost is in the range of $1200-1500, depending on throttle body choice and exhaust.  This will quickly expose the weakness of the heads, which flow about 210 cfm above .400 lift.  Head swap and roller rockers usually come next, at a cost of $1075 each for updated stock heads (iron) with stainless valves and springs of your choice (not including shipping).  A cam will cost another $200-$300 resulting in about 320 RWHP.  While the stock bottom end can support in excess of 500 hp, getting there will require new pistons or rotating assembly, or forced induction.  But the bottom end will ultimately be consumed by heat.  Prices are exponential with quality, of course. Oh, and don’t forget the weakness of the 46RE transmission.  It won’t be crying tears of joy above 400 hp.

The Problem

After purchasing a 1999 Dakota R/T, 160k miles, to use as a daily driven shop truck, it was quickly determined that the heads were damaged, of course.  After the motor was removed and disassembled, it was determined that a rebuild and new heads would be required.  Choices, stock motor roughly $3000 with new hoses and accessories, or higher performance in the 300 hp range for roughly $5000.  Ouch.

Then we came across an article “World’s easiest 5.3 swap”, on a discussion forum.  Turns out, the LS-style drivetrain shares very similar dimensions to the Magnum drivetrain.

The Goals

1) Insert a modern drivetrain into this soon to be classic truck

2) OEM appearance

3) OEM durability and drivability

4) Minimal modifications

The Solution

A call to Shawn, at RetroLSX resulted in the purchase of an LY6/6L90 combo with pedal, ECU, accessories, harness, and exhaust flanges.  A call to VanPelt Sales resulted in a plastic mock-up long block of the LS1, and a call to Jared at Current Performance resulted in confirmation that integrating the wiring into the Dakota harness was possible.

After a couple of days and a number of adapter plate designs, the LS mock-up sat in the chassis with good drivetrain alignment and no clearance issues.  Another couple of days allowed for the placement of the 6L90 transmission.  Modifications for the drivetrain placement included a 9″ X 3″ cut in the middle crossmember for oil pan clearance, and minor notching of both stock motor perches.  The crossmember modification was reinforced with 2 1/4 inch mild steel tubing welded in.  A spacer was required to place the transmission in the existing crossmember.

Retaining the existing motor perches, as opposed to cutting them flush and welding new mounts, retained the existing triangulation of the front suspension, using the engine block as the compression component during suspension travel.  Stock truck manifolds from the LY6 cleared with mild grinding, and placed the exhaust exit in good position.  Front accessories were retained from the LY6, with the power steering pump attaching to the stock rack and pinion steering assembly.  The air conditioner was relocated using a kit from Current Performance.  An electric fan from a Ford Taurus was attached directly to the stock radiator, and hoses were fabricated from off-the-shelf parts from the local NAPA store.

Dependable Driveshaft provided a 5″ aluminum unit with the correct dimensions, and the truck was moved to Current Performance, where the wiring harness was integrated into the existing distribution block using correctly labeled circuits.

Fuel system was fabricated out of OEM nylon tubing, 3/8 inch, with a Walbro 255 HP pump in the stock tank.  A Corvette filter/regulator was used just forward of the tank on the frame rail, with a 5/16 rubber return line.

A GMC Sierra shifter cable was attached to the column-mounted shifter with minimal modifications, and the drive-by-wire brake pedal was converted to a “franken-pedal”, using half Dodge, half GM structures.

A final weakness was corrected using custom adapter plate and spacers to locate a pair of front rotors to the rear, completing a rear-disc conversion for better stopping power.

The trans tunnel was repaired, and a custom fiberglass console was fashioned to provide for deeper cup holders, an improvement as well.

The Results

With the addition of an Airraid cold air intake, and 2 1/2 inch dynomax dual exhaust, the motor is probably putting out a healthy 370 HP/390 TQ at the flywheel.  Retaining the VVT, at least for now, will hopefully provide more useable torque.  The 6 speed transmission shifts flawlessly, and the drivability is excellent.  The OEM 3.92 gear ratio might be a little aggressive, and fuel mileage may be improved somewhat with a ratio of 3.60-3.70, but initial numbers show a 0-60 time of 5.8 seconds with a fuel mileage of 14 mpg. 10-70 and 30-70 performance is much improved over the lazy magnum feel, and sound levels are comfortable.

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                As we started this project, we intended to replace the stock fuel basket in the 1999 Dakota R/T with a stock LS type unit designed to provide the higher pressure required for LS-style engines. Despite the similarity in products, I couldn’t find a reliable stock replacement that would fit the tank in both diameter and depth. I am sure one exists, and the identification of that part would probably yield a drop in assembly that could be purchased new from Rock Auto or any online vendor for less than $100. It seems that most GM assemblies, however, are smaller in diameter and would require an adapter plate to fit the large hole in the Dakota and Durango fuel tanks.

                After spending time on various websites and forums, it seems the Walbro 255 high pressure pump is probably the solution.   All Gen III Dakotas and Durangos came with a Walbro 190 fuel pump in the basket, and the upgrade to the 255 has been popular among horsepower guys. After removing the original basket and gutting it, a new pump is installed in the stock location with new tubing. The fuel sending unit is retained, and works with the fuel level gauge in the vehicle, and the entire assembly goes back in with a stock appearance.

                With the upgrade in fuel pressure and flow, the stock fuel line on Dakotas and Durangos, which is 5/16 hard line with flexible attachment lines at each end, quickly becomes inadequate. I know that it is common to replace the fuel pump in these trucks with a Walbro 255, but without changing the fuel line, the excess flow just ends up back in the tank through the basket-mounted regulator, and the end result at the engine side of the line is no gain at all.

                We have developed a kit that replaces the pump with new basket parts, and provided 3/8 nylon (OE style) fuel line all the way to the motor. Anybody running a late Gen III or Gen IV LS engine will use a combination fuel filter and regulator with return line that provides adequate flow at 58 psi. For those running Gen III truck motors with the regulator included in the fuel rail, the stock 5/16 hard line will serve as the return line. The stock regulator is replaced with a custom block-off plate and bulkhead fitting to attach to push connectors, and the fuel level assembly is retained.

Check out the video of our fuel system. Remember, even if you don’t replace your engine with an LS engine, this system still provides for much better fuel flow to high horsepower Magnum motors, while providing OEM reliability.

Chrysler Gear Ratios

Posted: August 31, 2012 in Uncategorized
Tags:

1997 – 2006 (ND) – Dakota

Axle

Possible Axle Ratios

C205F

3.21

3.55

3.92

194 FIA (Dana 35)

3.21

3.55

3.92

8.25″

3.21

3.55

3.92

9.25″

3.21

3.55

3.92

1997 – 2006 (HB) – Durango

Axle

Possible Axle Ratios

C205F

3.55

3.92

194 FIA (Dana 35)

3.21

3.55

3.92

8.25″

3.21

3.55

3.92

9.25″

3.21

3.55

3.92

1997 – 2006 (TJ) – Jeep Wrangler

Axle

Possible Axle Ratios

181 FBI (Dana 30)

3.07

3.55

3.73

4.10

4.56

194 RBI (Dana 35)

3.07

3.55

3.73

4.10

4.11

4.56

216 FBI (Dana 44)

4.11

216 RBI (Dana 44)

3.07

3.55

3.73

4.10

4.11

1997 – 2002 (XJ) – Jeep Cherokee

Axle

Possible Axle Ratios

181 FBI (Dana 30)

3.07

3.31

3.54

3.55

3.73

4.10

186 FBI (2000-2002)

3.07

3.55

3.73

4.10

194 RBI (Dana 35)

3.07

3.55

3.73

4.10

8.25″

3.07

3.21

3.55

3.90

4.10


1997 – 2006 (WJ, WK) – Jeep Grand Cherokee

Axle

Possible Axle Ratios

C200FE

3.07

3.55

3.73

C200F

3.07

3.55

3.73

C213R

3.21

3.55

3.73

C213RE

3.07

3.55

3.73

181 FBI (Dana 30)

3.07

3.55

3.73

4.10

186 FBI (1999-2004)

3.07

3.55

3.73

4.10

194 RBI (Dana 35)

3.07

3.55

3.73

4.10

198 RBI (1999-2004)

3.07

3.55

3.73

4.10

216 RBA (Dana 44)

3.55

3.73

226 RBA (1999-2004)

3.55

3.73

226RBI (2006)

3.73

1997 – 2003 Ram Van/Wagon RWD

Axle

Possible Axle Ratios

248 RBI (Dana 60)

3.55

4.10

8.25″

3.21

3.55

3.92

9.25″

3.21

3.55

3.92


1997 – 2006 (D1, DH, DR) – Ram Truck 2WD/4WD

Axle

Possible Axle Ratios

216 FBI (Dana 44)

3.54

3.92

4.09

248 FBI (Dana 60)

3.54

4.10

248 RBI (Dana 60)

3.55

4.10

4.56

267 RBI (Dana 70)

3.54

4.10

286 RBI (Dana 80)

3.54

4.10

C205F

3.55

3.92

C205FD

3.21

3.55

3.92

9.25″ Rear

3.21

3.55

3.92

9.25″ Front AA*

3.73

4.10

4.56

10.5″ AA*

3.73

4.10

4.56

11.5″ AA*

3.73

4.10

The first decision that has to be made is which LS motor to use. They all share a modular platform, but there are differences.

Gen III
When talking about LS motors, we have to talk about the all aluminum engines that replace the LT engines beginning in 1997. Primarily found in Corvettes, Camaros, and Firebirds until 2004, and the GTO in 2004. They were dubbed the LS1, and produced 325-350 hp and 350 lb/ft of tq. Also around 1999-2000 the first Vortec engines began to appear in limited numbers. These were iron block, aluminum head versions of the LS1 intended for truck applicaton. By 2002, Vortec engines were readily available in either 5.3 or 6.0 size, and were produced until 2007.

Gen IV
In 2005, the LS all aluminum engines became the Gen IV. Block changes allowed for higher displacement, if needed, and variable valve timing, displacement on demand, and adoption of newer rectangular intake heads. LS2, LS3, LS7 and LS9 engines have various sizes, and produce a wide range of power depending on the application. The Gen IV Vortec engines followed in 2005, with the same iron block and aluminum head design that worked in the previous generation. There are many variations.

Decision tree

First decision – LS or Vortec. This really comes down to money. The LS is lighter, but LS1 engines make less hp than more modern Vortec engines.

Second decision – Gen III or Gen IV. Once again, money and availability. Gen IV has improvements over  Gen III, with more integrated ECU functions and TCU functions. The availability of VVT is also a nice feature, as any decent wiring shop should be able to retain this, and it does increase low-end  tq in the drivable range.

Third decision – Size. If a Vortec engine is chosen, 5.3 or 6.0 are the sizes. Cost generally dictates.

Fourth decision – Manual or automatic. I am not a transmission expert. There is information all over the internet. If anyone would like to submit a writeup, I would be happy to use it. Here is what I know.

The manual transmission is the Borg-Warner T56. This transmission is used in everything. I will admit, I don’t know much about manual transmissions yet.

Automatic transmissions for these engines come in either 4 speed (4L) or 6 speed (6L). The 4L60E and the 4L80E share a common name, but are very different transmissions. 4L60 transmissions are an updated version of the 700R4. Seems to be regarded as a weaker transmission that the 4L80, but it is lighter and a little smaller.

The 6L80 and 6L90 transmissions are the big kids. They are found in pretty much everything that is high horsepower or heavy after 2006. Six speed with double overdrive (top to gears are under 1:1 ratio), and a clutch to clutch design that allows for push-button or flappy-paddle shifting, snappy gear transition, and durability under load. It also has the TCU built into the transmission, to ease installation and programming.

References:

Wikipedia – GM LS engine, GM Vortec engine, 4L60, 4L80, 6L80

http://www.chevyhiperformance.com/tech/engines_drivetrain/shortblock/0912chp_performance_chevy_ls_engine_comparison/viewall.html.

So moving on to the LS motor. I am not going to spend a lot of time discussing the options for LS motors. I will post a thorough guide to the selection of a motor later in the blog. Websites like LS1tech.com, LS1truck.com and gmhightechperformance.com do a real nice job of that.

According to Richard Holdener of GM High Tech Performance “Even the competition has to agree, the LS family of engines is one hell of a motor.” http://www.gmhightechperformance.com/camaro_now/sucs_1130_ls3_heads_and_cam_test/viewall.html.

This dyno comes from the ls1tech.com forum and was posted in 2009 by member alocker. This represents the rear wheel dyno numbers of a Gen IV LY6 with a cam change. Compare this to the graphs from the previous “performance for the magnum engine” article.   Much more torque and hp across entire range.   But remember, this is a modern engine with huge third party backing, ability to make astronomical power, show improvement in fuel mileage in stock tune, and ongoing support.

And this complete dropout (motor, accessories, ecu, harness) can be purchased for less than a set of heads and intake manifold for the Magnum engine.

http://ls1tech.com/forums/conversions

-hybrids/1111921-72-chevelle-ly6-cam-only-dyno-s.html

A couple of years ago, we began to notice more LS-style motors powering racecars at the drag strip. They were quickly replacing the small block chevy and 5.0 fords. They were replacing the big blocks. Everything seemed to be sporting this new motor.

Then  we saw something that amazed us. A 325 BMW with a parachute. It launched and ran a 8.5 sec quarter mile at 150 or so. Ok, this car was a little massaged, but these motors can power anything.

So why the LS engine. In 1997, the LS1 appeared as a complete redesign of the warmed-over LT line of engines. The generation III engines initially appeared in the corvette, but ultimately appeared in every V8 powered chevy. Production of Generation IV engines began in 2005, which allowed for larger displacement, and advanced electronics such as variable valve timing and displacement on demand. Both Gen III and Gen IV engines were produced in truck models, known as the Vortec. A history of these engines can be found on many websites, but wikipedia “GM LS Engine” http://en.wikipedia.org/wiki/GM_LS_engine and http://en.wikipedia.org/wiki/Vortec.

The 5.2 and 5.9 L Magnum engines in Gen III Dakota and Durango (1997-2004) are based on the original Chrysler small block designed in 1964. The A engine was redesigned as the LA engine in 1971, and included minor changes. That motor was more or less redesigned again in 1992 to solve oil leaking problems, and to add EFI which would be required to help meet modern emissions requirements. The pistons were changed to a hypereutectic design, but the compression was decreased to 9.0 to 1. In 1998, engineers overcame some of the bogginess of these motors by lengthening and tapering the runners of the new “beer barrel” intake, which included an enclosed air gap zone, and by providing a slightly larger cam tuned to the intake. The result was a motor that had very potent low-end torque, but lost hp at higher rpm’s. Relatively low gear ratio’s kept the motor in its range, and made use of the flat and high torque curve. Read more about these motors at http://www.allpar.com/mopar/318.html.

So 250 hp and 350 lb/ft of torque from the Dakota R/T, equipped with the 5.9 Lmotor, 9.25 trac-loc rearend and 3.92 gears seemed impressive. But it was more marketing than engineering, and 12 mpg to push this truck down the road seems excessive by today’s standards.

Discussion of this motor has to include Chrysler’s attempt at the Next Generation Magnum (3.7/4.7) which began to phase out 3.9/5.2 and 5.9 Magnums in 2002. Known as the “PowerTech”, this engine in 4.7 L size provided 265 HP and 335 lb/ft of torque, but never really lived up to its potential.

And finally the Hemi. Introduced in 2003, this is a pretty good engine. It has potent performance, and even more potential. The rumor has been that they will start popping up in salvage yards at a reasonable price, and could be a potential candidate for swap. But they were never designed to fit the Dakota/Durango platform, and just simply don’t fit well. A few attempts have been made to fit the hemi in the dakota, and can be seen on forums, but it seems to be a lot of work for a motor that is not very well supported in aftermarket.

So, after careful consideration, we have decided to swap the LS-style engine into a 1999 Dakota R/T, and provide a kit and separate pieces for other truck owners to do the same.

 

It is hard to make horsepower in the magnum motors. The heads are the limiting factor, as well as the 9 to 1 compression block. They respond well with turbo or supercharger applications, but at a price. The problem is, the limitations in the heads have a near net effect with the application of boost. A supercharger on this truck will see gains of 125 hp with 6 psi, while that same setup on other motors can net 200 hp. Add to the problem the lack of detonation protection, inadequate cooling in the heads, and very little tuning availability, and that $5000 supercharger doesn’t look as good. Advertised claims of 60% rear-wheel horsepower (Procharger 1DB212-SCI) is such a small gain that the company doesn’t even show dyno graphs or provide actual HP numbers http://www.procharger.com/dodge.shtml. Vortech is the only other option, but they stopped making the kit, and results were similar. It doesn’t matter how you provide the pressure, limited flow in the heads correlates to minimal increases in volumetric efficiency.

Here is a sample of a “tuned” truck. The article from delmarvadodge.com “Dodge Magnum Intake Shootout”., describes this truck as “mildly warmed over”.  Here is the actual engine specs.

360 bored .060 over
stock pistons/rods/crank
race balanced
compcam 206/208 .480/.512
iron ram heads 2.02 intake shaved .020
Hughes HD lifters
M1 intake
F&B 50mm TB
Summit truck headers
mini cat
flowmaster, dual outlets, side exhaust
24# ford injectors

An estimated cost of this engine and tuning, and all associated parts is probably $3000, and here is the graph that follows.

delmarvadodge.com “Dodge Magnum Intake Shootout”.

The green line represents the stock “kegger” intake manifold, with the other two being high performance M1 ($300) and Airgap manifolds ($600). The first thing to notice is that even with the highest flow “bang for the buck” iron ram heads, and exhaust, and cam, and injectors (which are way too large for this application), and high flow throttle body, the stock intake was outperforming the other intakes at 50 mph. It didn’t lag far behind throughout the run, relative to cost. The author of the article used a very unusual 50 mph start point, rather than the customary 2000 and up rpm range. It can be assumed that the stock intake was superior earlier in the speed run, knowing the characteristics of the stock intake (flows well in lower rpm range), leading to this unusual presentation. But even the highest peak HP in the study, occurring at 110 mph wheel speed, was nearly matched by the stock intake manifold at 115 mph. But the overall numbers are pathetic for a built V8 engine, barely rising above the stock 200 rwhp (est), that occurs in a much more useful range in the 1999-2004 Dakota RT.

Here is another test of the same 3 available manifolds for this motor, available at hughesengines.com

This test was performed on a totally stock motor with no tuning changes.

And this graph was obtained after changes by an SCT tuner ($400 plus $100 for each additional tune).

Hughesengines.com

The factory manifold had huge torque and superior hp in the driveable range to 4000 rpm of the first graph, and was nearly equal to the maximum “tuned” numbers of the airgap manifold, in this same range. The M1 was far inferior to both. But look at the overall numbers of the stock motor with factory intake and compare it to the $3000 motor in the previous test. We are only given rear wheel speed, but assuming 90 mph represents 3500 rpm, the range of 180-210 rwhp doesn’t give much support to the engine modifications. A gear change on this truck would be in order, but the cost would be $500-700 (why would you do this without replacing all of the bearings), and gas mileage and road noise would be much worse. Who wants to cruise at 2300 rpm?

And finally, here is a graph, again from delmarvadodge.com, showing a 408 Naturally aspirated engine, which would require tuning at the very least. Not much info is given about this motor, but the graph shows decent torque and hp. Once again, this graph begins at 60 mph this time, but give no indication of time to speed or rpm. It is anybody’s guess what performance is like, but 60 mph represents the ability to provide 225-250 hp with 325-350 tq. It is probably the best option of the three, if there is a reason to rebuild a stock engine, but this would represent at least a $4000 engine with entirely new rotating assembly, heads, and all associated hardware.

When accessing the dakotart.com forum, however, you are more likely to find guys saying this (Red comments added):

410, 10.3 comp pistons, P&P Eddies, 254 cam, 30lb injectors, sct tuner, 3800 viper stall, 4:56 yukon gears, hotchkis tvs, m1 4brrl, 58mm f&b tb, 1.7 rr, electric fan, jm longtube headers, B&M hammer shifter, Cope Racing Trans, Viper Brakes, SRT8 Seats, nx wet kit(100 shot) (not street driveable, costly), best time 11.32 @ 118 1.59 60′ on spray. 12.19@109 1.65 60′ n/a

Motor’s shot. R.I.P. 8/17/09. Rebuild in progress! (the problem with pushing these motors).

Forged 408 12.10 @ 111mph on a crappy tune and a stock fuel system except 30lb injectors (408hp and 418rwtq) looking for 430rwhp n/a with the upgraded fuel system and a better tune.) (Money pit).

So when considering a new motor for you dodge dakota or durango for performance, consider the downside of a 50-year-old platform.