Preface: Here in california the end of August means back to school season, Its when our freeways get blasted with additional traffic from soccer moms too busy yelling at the kids to pay attention causing traffic jams from 7am till 6pm. That means that if you have a day job that you will be sitting in that traffic at one point or another.
What does that have to do with a pitch stop mount? you might ask, during very slow traffic with the engine at Low RPM the soft mounts on the differential and engine allow the engine to buck, or rock back and forth. During normal driving you would not feel these effects but in stop and go traffic any time spent at the lower RPM can cause the car to buck and make the already difficult traffic more of a pain to handle
Solution: My soution to the problem is 2 fold, I choose to increase the stiffness of the rear differential mounts as well as replace my stock Pitch stop mount with a much stiffer and thicker model by Perrin. I choose perrin because their mount is in an H configuration rather than and I configuration. By having the most rigidity in the vertical direction it should ( at leas tin theory ) stiffen the engine bucking in the direction where it moves most.
I choose whitelines rear differential bushing filler pads rather than replacing the bushings entirely because they were inexpensive and they do not require a bearing press or a bench press to install. They simply fill the holes that are cut in the factory bushings ( to make them softer ) and in doing so they limit the motion in the rear differential.
Install: Install on the Pitch stop was a 10 minute job. Start by removing the 2 12mm Bolts on the passenger side of the intercooler where it connects to the compressor housing, then the 2 10mm bolts holding the OEM bypass valve to the intercooler and finally the 12mm bolts on the intercooler mounting bracket then remove the intercooler. Always fill the turbo compressor outlet hole with a lint free towel to make sure you dont drop a bolt into the open hole. Use 14mm socket and 14mm wrench to remove the stock pitch stop ( make a note of which bolts go where ). Then grease the new pitch stop and follow the process in reverse. Note - the front and rear bolts on the pitch stop are different torque settings so adjust your torque wrench accordingly.
The install for the rear differential bushings was even easier than the pitch stop. Roll the car backwards onto ramps or jack stands and use a 17MM socket to pull the differential support bolts. The new bushing fillers get greased and slide right into the holes cut in the factory bushings. Top them with the supplied washers and torque them to OE spec. Move forward to the differential support. Use a jack or a trans jack to support the differential as you pull the 17MM bolts from either side, again use the supplied bushings to pack the holes in the factory bushings. Reassemble in reverse and torque to spec.
Results: I feel like I say best install ever after every install I do but this is definitely up there with the master cylinder brace. Driving in traffic this week has been much less of a pain in my left leg and because the car doesn’t buck under low RPM I can let it coast at very low speeds without it being uncomfortable. There is data out there suggesting that these modifications will also improve speeds off the line by reducing the amount of wasted energy absorbed by the bushings but I am not interested in drag racing as a driver so I will likely not see those benefits. As a side note I did feel like the car started faster than normal and the rear end was more planted jumping on the highway this week. It may be related to the reduction in flex of the rear differential or it could just be my butt dyno trying to justify $50 well spent.
NVH: When I began my search for a way to reduce the bucking under slow speeds I found many stories of guys who install pitch stop mounts and trans mounts who were forced to remove those parts because the Noise Vibration and Harshness were more than they could handle. I tend to listen to books on tape while I sit in traffic and I haven't noticed that the noise is any worse than it was previously with my shifter bushings. I dont drive luxury cars and I dont expect a luxury environment. As long as I can listen to my audio books with my volume set to 15 and I don’t feel bad for my passengers who have to deal with too much noise then Im a happy camper.
I would definitely recommend both to any Subaru driver who spends any amount of time in regular traffic.
What does that have to do with a pitch stop mount? you might ask, during very slow traffic with the engine at Low RPM the soft mounts on the differential and engine allow the engine to buck, or rock back and forth. During normal driving you would not feel these effects but in stop and go traffic any time spent at the lower RPM can cause the car to buck and make the already difficult traffic more of a pain to handle
Solution: My soution to the problem is 2 fold, I choose to increase the stiffness of the rear differential mounts as well as replace my stock Pitch stop mount with a much stiffer and thicker model by Perrin. I choose perrin because their mount is in an H configuration rather than and I configuration. By having the most rigidity in the vertical direction it should ( at leas tin theory ) stiffen the engine bucking in the direction where it moves most.
I choose whitelines rear differential bushing filler pads rather than replacing the bushings entirely because they were inexpensive and they do not require a bearing press or a bench press to install. They simply fill the holes that are cut in the factory bushings ( to make them softer ) and in doing so they limit the motion in the rear differential.
Install: Install on the Pitch stop was a 10 minute job. Start by removing the 2 12mm Bolts on the passenger side of the intercooler where it connects to the compressor housing, then the 2 10mm bolts holding the OEM bypass valve to the intercooler and finally the 12mm bolts on the intercooler mounting bracket then remove the intercooler. Always fill the turbo compressor outlet hole with a lint free towel to make sure you dont drop a bolt into the open hole. Use 14mm socket and 14mm wrench to remove the stock pitch stop ( make a note of which bolts go where ). Then grease the new pitch stop and follow the process in reverse. Note - the front and rear bolts on the pitch stop are different torque settings so adjust your torque wrench accordingly.
The install for the rear differential bushings was even easier than the pitch stop. Roll the car backwards onto ramps or jack stands and use a 17MM socket to pull the differential support bolts. The new bushing fillers get greased and slide right into the holes cut in the factory bushings. Top them with the supplied washers and torque them to OE spec. Move forward to the differential support. Use a jack or a trans jack to support the differential as you pull the 17MM bolts from either side, again use the supplied bushings to pack the holes in the factory bushings. Reassemble in reverse and torque to spec.
Results: I feel like I say best install ever after every install I do but this is definitely up there with the master cylinder brace. Driving in traffic this week has been much less of a pain in my left leg and because the car doesn’t buck under low RPM I can let it coast at very low speeds without it being uncomfortable. There is data out there suggesting that these modifications will also improve speeds off the line by reducing the amount of wasted energy absorbed by the bushings but I am not interested in drag racing as a driver so I will likely not see those benefits. As a side note I did feel like the car started faster than normal and the rear end was more planted jumping on the highway this week. It may be related to the reduction in flex of the rear differential or it could just be my butt dyno trying to justify $50 well spent.
NVH: When I began my search for a way to reduce the bucking under slow speeds I found many stories of guys who install pitch stop mounts and trans mounts who were forced to remove those parts because the Noise Vibration and Harshness were more than they could handle. I tend to listen to books on tape while I sit in traffic and I haven't noticed that the noise is any worse than it was previously with my shifter bushings. I dont drive luxury cars and I dont expect a luxury environment. As long as I can listen to my audio books with my volume set to 15 and I don’t feel bad for my passengers who have to deal with too much noise then Im a happy camper.
I would definitely recommend both to any Subaru driver who spends any amount of time in regular traffic.