I'm having some problems on acceleration which I've narrowed down to either a bad pinion angle or poly bushing binding. I replaced my upper and lower control arms as well as the differential bushing, but here's the whole story.
So recently my 2008 GT started having a really bad wheel hop problem. It was bad enough to where the car was effectively undriveable. I am a newbie when it comes to suspension but I first replaced my upper control arm to Whitelines adjustable upper arm (most people would have probably started with the easier to replace lowers) and that solved the problem temporary.
Now, I never noted down the original pinion angle when I had the stock upper control arm on, and I didn't make much effort to adjust the Whiteline upper properly either. Honestly with the crush tube, as some of you may know, there's not too much room for adjustability anyways, plus I figured that the two piece driveshaft would account for any angle difference. Keep in mind I'm also at a stock ride hight here.
Well I was wrong, and I noticed a huge loss of power on acceleration. I also noticed a loud whining sound. I knew the arm was extended fully at the time, and unfortunately Whiteline's arm is only adjustable when it's off the car. So I had to drop the fuel tank and all of that jazz again and this time I put the arm at it's shortest length, which is only at a one inch difference from it's longest length. The car drove better than before with no huge loss of power or whining sound, so that one inch made a whole lot of difference.
Shortly after that, the rubber differential bushing gave out. It was probably the initial cause of my wheel hop problem all along, and the stiffer upper arm probably wore it out faster. I replaced the bushing with Prothanes polyurethane one and it completely solved my wheel hop problem yet again.
Now, just for good measure, and since I knew they would wear out anyway, I ordered some BMR lower control arms with poly bushings to replace the old stock lower control arms. They are must sturdier and lighter than the stock pieces. I greased the external faces of the bushings and used my grease gun to get the internal faces lubed up and torqued everything down pretty good.
When I went for a drive, there was definitely more drivetrain noise as expected, especially since I have my rear seats removed, but there was also something that felt very wrong. The best way I can describe it is that the car feels like it wants to flex it's parts but can't... I think that with all of the poly bushings I have on the car now, it might be binding. There's all sorts of stress noises and things I can tell are not supposed to happen.
BUT, the lower BMR's are a perfect fit and I had success with the upper arm before, so I have a theory that that the lower arm bushings were accounting for my pinion angle being off and now that all of the bushings are poly ones, I'll have to adjust my pinion angle to be absolutely perfect otherwise I'll keep having this problem. I HOPE the pinion angle is the problem. I really don't feel like removing the Whiteline upper arm again to adjust it... I wish I would have gotten an on-car adjustable one. Hell, maybe the Whiteline IS adjustable on-car but it's pretty tight up there and most people say that you can't.
Doe's anyone have any thoughts on this? I've heard of people running all poly bushing on their 05 to 09 cars with no problems, so I'm leaning towards the pinion angle. It will be a pita to measure it and then adjust this arm I'm suspecting though.... but the car is pretty much undriveable right now because of all the binding and noises and I know something is going to break very soon unless I do something.