Tech Notes

By Herb Helbig, Chief Engineer—Viper (Retired)

Q: ?I have a 2005 convertible Viper that just turned 19,000 miles. The A/C works great around the city; however, on long drives and high speeds the vehicle gradually loses all blowing capacity coming from the vents (decrease in air velocity). The cab temperature eventually reaches a point were the windows need to be lowered. This occurs typically after about 20 to 30 minutes of driving. I adjust the fan level to max, but I can only feel the coolness at the vent, and I can hear the blower working, but there is no air flow coming from the vents. If I stop the car and let it sit for 15 to 30 minutes, it will work again, but as soon as I get back on the highway, it does it all over again. If the problem is with the vehicle’s vacuum system, how can this be corrected? Or is it something else? I would greatly appreciate your help!

A: This sounds like it might be a problem with the duct work—especially since the A/C works well around town. Look for a restriction when you are experiencing the reduced-flow. Look at the intake area near the base of the windshield near the intake box. Good luck.

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Q: I own a 2008 Viper SRT10® convertible with a set of Eibach springs installed. The vehicle has been lowered 1 inch. Typically, when I release the clutch quickly—at 2 to 3000 rpm rolling in first gear at around 20 mph—the vehicle wheel hops and I feel like I’m destroying the rear suspension. How can I correct this problem? The tire pressure in all four tires is at 30 psi.

A: Assuming nothing else has been changed on the car’s suspension, the hop issue may stem from the change in axle shaft angle because of lowering the car. Make sure that the fasteners are all retorqued properly—especially the shocks and control arms. If the Eibach spring rates are different than the stock springs, that may contribute significantly. Additionally, make sure the shocks are in good shape and show no signs of leakage.

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Q: I’m the new owner of a 2006 Viper SRT10 coupe. The vehicle is black with silver stripe option M91. I need to know the Chrysler touch up paint part number for the M91 silver stripes as my dealer and local body shops are unable to find it. Also, what is the correct oil capacity for the 8.3L engine? My service manual shows 11 quarts; owner’s manual, 10 quarts; and 2006 brochure, 10.4 quarts—all with filter change.

A: The paint you are looking for is VA9. My paint expert suggested that you try to find a Dupont paint. This will give you the best match. The proper oil capacity for your car is 10.5 quarts with a filter change.

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Q: After completing a hard run in my ’97 GTS, I noticed transmission fluid dripping from the transmission. The transmission fluid was changed recently. Is it possible the transmission was overfilled? If so, could this damage the transmission?

A: I’m assuming you had your car on a road course. You didn’t say what area the fluid was leaking from on the transmission. Most likely it’s coming from the vent which is on top of the trans. It’s possible it was overfilled, but it is also possible that the vent was dislodged during reinstallation. You need to take a look and see if the vent is still attached properly. Not easy to do, but you might be able to see it through the shifter opening.

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Q: I have 4,000 miles on my 2009 SRT10. I recently smoked the clutch on a steep incline. During normal driving I still smell a burning odor; however, the vehicle still shifts fine. Do I need a new clutch?

A: Probably not. The dual disc clutch is pretty robust. The smell will probably take a while to dissipate but should eventually go away. As long as the car launches okay and shifts fine, you should be good to go.

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Q: I own a 1996 GTS and I’m considering installing a Mopar® Cat-BackTM exhaust system (P5007274). How much horsepower could the engine gain with this system? Please mention any benefits and drawbacks for this system. Do you recommend any other Mopar parts to increase horsepower?

A: Assuming your car is totally stock, the system should be good for 5 hp at the flywheel. The reason that the number is so small is that the stock system is very low restriction. Benefits will include better sound quality and perhaps reduced sill heat. On the down side, you may experience some exhaust drone on the highway. If it’s bothersome, try shifting up a gear. Some other parts you might consider are rocker arms with a different ratio, camshaft and ported heads. With these changes, the addition of the exhaust system would yield a 25-30 hp increase.