Exhaust System Clearance
Q: I recently had a 3 inch exhaust system installed on my car and now I do not have much clearance for the driveshaft. What is the smallest diameter driveshaft that I can use that will handle the horsepower and weight of my vehicle?
This is a common and growing problem that we hear about more often than we ever did before. You should always have the driveshaft built before the exhaust system to avoid all of these problems. The high horsepower cars and trucks that need a 3 inch exhaust system also need a strong driveshaft. Unfortunately the tunnel does not always allow for the proper size driveshaft and the 3 inch pipes to all fit into the same space. Some high horsepower cars can use a 3 inch diameter driveshaft with no problems but others may require a 3.5 inch or a 4 inch and now it won't fit with the large diameter pipes. Length is a big factor in the proper selection of driveshaft tube diameter. The long wheelbase cars cannot use a 3 inch driveshaft due to length, rpm and critical speed issues but a short wheelbase car can use a 3 inch or a 3.5 inch if the space allows. Driveshaft critical speed is not a problem with shorter overall lengths. The advice here is to be sure that your exhaust system installer makes room for the 3.5 inch diameter as a minimal choice for a driveshaft tube diameter. Some of you with long wheelbase vehicles may in fact need a 4 inch driveshaft... so be sure to let the installer know what you may need before he begins the work. Better yet...get the new driveshaft first!