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2002 Chrysler Sebring Convertible GTC

My car came stock from the factory with a 2.7L Chrysler V-6, mated to the NV T850 5-speed manual transmission. This engine/tranny combo is rated at 200 HP and 190 ft-lbf of torque (to the wheels: 160 HP and 152 ft-lbf torque).

Chrysler 3.5L Engine

I installed a 3.5L Chrysler LH engine from a 2007 Sebring Sedan. At 40641 miles on the clock, the 2.7L engine that was in my car decided to completely get rid of connecting rod #3, and that conrod took out connecting rod #4 in the process. I ended up with a 2.7L V4 engine, which tended to puke oil out of the tailpipe. I strongly believe that conrod #3 failed due to that aluminum flash I found in the engine previously.

Dead 2.7L engine
Dead 2.7L engine

in any case, I had to replace the engine, but did not want to spend $4000 on installing another 2.7L V6 engine that might or might not last 40000 miles. Nor did I want to try to rebuild one from the junkyard, since this engine apparently is infamous around all of the junkyards that deal with Chrysler cars. Therefore, I decided to spend this amount of money in order to see if it was feasable to install a 3.5L engine, instead.

New 3.5L engine
New 3.5L engine

I found the engine at an LKQ junkyard, and it was in a really nice condition. The engine itself looked like a crate engine - it had apparently never been run. Great bargain for $1200, I thought. And so the journey began.

The engine bolted up to the transmission with a little work to the oilpan and engine block. I could purchase an exhaust system from the manifolds to the flexpipe, for a 2007 Sebring sedan, and it also fit. However, the intake manifold would not fit into the engine bay. I would have had to do some major cutting of the bay to make the intake manifold fit. So, I went in search of a manifold that would fit.

3.5L Engine Initial Installation
3.5L Engine Initial Installation

After researching, I discovered that the basic 3.5L engine block is almost completely identical from when the 3.5L engine was first introduced in 1993 to the present day. Obviously, there are differences, but the similarities worked in my favor. For instance, I could try to fit intake manifolds from a 1st generation and 2nd generation Intrepid, and finally decided to go with the intake manifold from a 2004 Chrysler Pacifica. I also tried to use the valve covers off of a 2nd generation Intrepid, but I found this had issues with the PCV valve system sucking in engine oil into the intake manifold.

3.5L Engine with Chrysler Pacifica Intake Manifold
3.5L Engine with Chrysler Pacifica Intake Manifold

I had run into a couple of issues besides this one. First, this new engine was designed to be run by a New Generation Controller computer, not the engine computer in my car. I had to swap out the crankshaft tone wheel and camshaft tone wheel in order to do this. Secondly, and also related to the first issue, was that the idle air control motor on the Pacifica throttle body was also designed to be controlled by the NGC engine computer. I had to have an adapter machined so that the Pacifica throttle body could accept my old engine's idle air motor.

Other issues... I used a throttle cable from a 2.4L 2nd generation Stratus sedan, and the cruise control cable from a Pacifica. I had to order all of the engine accessories separately, since the motor itself was bare of these things. I had to machine off some protuberances from the timing belt cover in order to allow the air conditioning hoses to work. I had to re-work the 2.7L engine wiring harness to make it work with the 3.5L engine. Oh, yeah, and I had to come up with an adapter to let the 3.5L engine mount to the right-hand engine mount in the car.

At this time, the car still needs a hood to be fabricated. I also have to connect up the A/C piping and devise a controller for the compressor, since it is one of those new-fangled clutchless variable displacement compressors.

In any case, my car now runs with a 3.5L engine! And, to use a phrase found elsewhere here, they said it couldn't be done!

Polyurethane Shifter Cable "Booger" Bushings

I replaced the stock shifter cable rubber bushings with these "Booger" bushings from a Dodge SRT-4. They remove a lot of the slop associated with rubber bushings, and make shifting more responsive. I've noticed that it does not take as much effort to shift as it used to do, even considering the change I noted previously when I installed my engine mounts. This is especially true for shifting into 2nd gear. The transmission comes with a dual cone 1/2 synchronizer that enables the transmission to better handle the torque output at 1st and 2nd gear. However, it also makes it harder to shift into those gears. The booger bushings do help in making it easier to shift.

Deyeme Racing Firm Engine Mounts

I replaced the stock rubber front and rear engine mounts with Deyeme Racing firm engine mounts. This was intended to reduce some of the wheel hop I have experienced when starting out from 1st gear.

The normal engine mounts allow some back-and-forth movement of the engine and transmission, so as to reduce noise and vibration that the average Sebring Convertible owner would find unpleasant. However, they also allow the engine and transmission to move about whenever the car is under any decent acceleration. This changes the geometry of the driveaxles, which causes some of the torque transmitted from the transaxle to act against the suspension instead of against the wheels. This causes the suspension to move about, and in so doing will also cause the wheel to move along with the suspension. The wheel will then exert less pressure against the road surface, and will then be more susceptible to wheel hop.

Why is this bad? Well, under normal driving conditions, the driveaxles may be under a little torque stress from when the wheels resist being turned as a result of the car's weight and aerodynamic drag. However, when wheel hop occurs, the driveaxles undergo much greater transient torque stresses. When the wheels actually free-spin due to wheel hop, there's next to no torque stress at all. However, when the wheels regain traction, the driveaxles almost instantaneously undergo a large amount of torque stress due to having to work against a suddenly stopped wheel and having to push the car forward. In 1st gear, due to gear multiplication of the torque from the engine to the driveaxles, the driveaxles themselves could experience momentary torque of up to 2600 ft-lbf due to wheel hop. Under this amount of torque, the driveaxles could very well shear.

Now, the firm engine mounts will cause the engine and transmission to resist moving forward when the car accelerates. The end result is that the driveaxle geometry between the transaxle and the suspension changes less, and allows more torque to be transmitted to the wheels, than to the suspension. This results in less wheel hop, and more torque to the wheels to move the car forward.

A welcome side benefit of these mounts is improved gas mileage. I gained about 2 MPG from these mounts under highway driving, and about 1 MPG during city driving. I reason this is because I improved the torque transfer from the transaxle to the wheels, as discussed above.

Noise and vibration have increased a little, but not much. Under acceleration, it's barely noticeable as a somewhat high-pitched noise from the valvetrain. At idle, engine vibration can be felt. This vibration is more noticeable when the engine is being shut off, as its speed drops to zero RPMs. Other than that, I have not noticed any problem related to noise or vibration. However, another member who also tried firm mounts, reported that he had a lot of undesirable noise. Since he had an automatic transmission, I think his increased noise was due to fluid dynamics that occur inside an automatic transmission. Since I have a manual, I would not see that problem.