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Pitch Stop Mount and Rear Diff Bushings

8K views 18 replies 4 participants last post by  RoboTuner 
#1 ·
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.
 
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#4 ·
ive heard nothing but good things about the group N mounts but more so regarding the engine and tranny mounts. i wasn't even aware they made a pitch stop but should have figured. my brother has the perrin, he loves it. ive also heard beatrush makes an incredible forged one for maybe about 30-40 more than the perrin.
 
#5 ·
yea im confusing them with tranny mounts my bad.

i meant kartboy pitch stop. kartboy has a good enough rep on subarus i'll blindly buy anything they manufacture. never been dissapointed.
 
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#6 ·
yea im confusing them with tranny mounts my bad.

i meant kartboy pitch stop
im going to look into it, i feel like group N makes everything haha i wouldnt be surprised if they had a pitch stop too.

I actually am putting in a torque solutions pitch mount simply because my tech swears by them, and it was only $91.00, no way was i going to complain about that... might not be a bad idea to look into that one too, she looks like a chunky one im excited
 
#9 ·
lol yea gotta be honest, was not expecting that close of a similarity, their engine and tranny mounts, which i just purchased, seem to be a much bigger difference than stock, but not enough to make it overly stiff... interesting
 
#10 ·
From my research the group N trans mount and engine mounts use the same linkage materials but has solid bushings, in the case of the trans mount its one very large solid bushing, Which is what the whitelines kit attempts to accomplish by filling the holes cut in the factory bushings. The stock pitch stop on 2012 and newer models is of similar stiffness to the group N mount If Im not mistaken.

Kartboys and beatrush make great products and Im sure you would be happy with any brand over the stock fibre reinforced plastic one. Just keep in mind that the stiffer the bushings the more noise vibration and harshness you will be adding directly to the firewall.
 
#11 ·
agreed, as for NVH i pretty much shot that right out the window haha i purchased the engine and tranny mounts, along with the rear diff bushings and tranny cross member bushings... she'll be solid, but a bit noisy... with everything else i threw in though, thats the least of my worries now!
 
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