Z_WAAAAAZ

It makes sense that the poly mounts are needed, given that the PPF delete brace bushing is so stiff in comparison. I have poly bushings but no reinforced diff arm and managed to crack the arm last weekend while on a canyon run. What they claim makes sense about the subframe mounting point and the brace's stiff bushing transferring more load onto the diff arms.

Rich, my kit did the exact same thing. I ended up dropping a couple washers in between the diff and the little unit that houses the PPF delete brace bushing in order to space it down to line up (and not pull the pinion flange downwards with it).

I've also loosened my diff mounts a couple times to try and move the diff side to side when I was messing with lateral alignment. Go figure, there's basically zero space to maneuver it, hence why I ended up moving the subframes around instead. I'm reasonably sure at this point, though, that there isn't any binding in my upper diff mounts. We'll see when I drop it out of the car this weekend.

The new diff housing I ordered has rubber mounts installed already. The rubber pieces that adhere to my diff mounting plates (lower rubber diff bushings they might be called?) are long gone. I'm gonna have to see if I can make my lower poly bushings work since I'm not gonna be able to get a set of lower rubber ones by Saturday.

richbobby

https://www.good-win-racing.com/Mazd...IaAv7VEALw_wcB

these guys are close to you, yeah?

Kanaan

Its kinda hard to say how bad I certainly still feel something come on and it feels like it got pushed up a few mph to 72-75ish but i wouldn't call it violent, Idk if id want to sit at 75mph for an hour cruising or anything though. I did have the same thing your describing for a while but seems after alot of fine pinon angle adjustments and now this i wouldn't say it feels like its going to self destruct anymore. I suppose i can get a clear bowl of water with a lid and take a video of it might be able to compare that way. Also cruising that fast im turning like 3800-4000rpm (atleast tach indicated) and with the crossmember which i suspect is for sure going to add more NVH, idk if i can quite pinpoint where its coming from. ill need to drive it a bit more to get a better feel for it, started to get rained out and had to stop. Would be nice to find a way to measuring chassis vibrations with an accelerometer or something on a graph to see the frequency's its oscillating at, Tried using an App on my phone but didnt seem to work very good.

We cant forget that all to common NA shimmy that comes on around this speed too ive only experienced that problem once and that was when i took my hardtop off and its been so many years i cant recall exactly what that felt like anymore i think that feels more of a tire imbalance/rumble than the feeling of operating a gas weedeater😆. Briefly thought maybe adding a crossmember that ties the frame rails together straight across maybe induced that na shimmy but i dont see any people with butterfly braces complain of this.. Ill search for my lower diff bushing plate things some more tonight still might swap diff's to test.

sixshooter

iTrader: (12)

No shimmy here. But I have a full cage and V8R's version of the frog arms.

Z_WAAAAAZ

Yeah, 2 day order on most stuff from them to me usually. I need the lower rubber pieces like Kanaan listed above, though. Unless I'm mistaken, I think those mounts still need them.

I'm sure I can find a way to make my lower poly mounts work with the upper rubber bits. I'm going to ditch the PPF delete brace and remount the PPF so I hopefully don't break another diff housing in the meantime. I'm pretty sure I'm just going to plop in a Getrag rear end and don't want to reinforce my housing or buy an FC RX7 one currently.

Now that you mention it, I have a full Motorcraft NVH kit at work that I can bust out. Didn't think I needed to use it because I can already tell my issue is completely localized to the diff. There's a couple units in there, however, that record frequency and severity of oscillations and I might be able to pull some data from those and post it up here to compare to your guys' vibrations. Only issue is that you guys would need similar tools as well. Probably not worth the trouble.

I agree that the crossmember-mounted trans adds more NVH. Mine is more vibrate-y than before but I mostly just feel it in the higher RPM range. It sounds like your vibration may be less violent than mine. I've had the 70mph shimmy before and this is substantially worse. I'm pretty confident something in my driveline would detonate if I ran it like this during a track day.

Kanaan

I just fixed most All of my vibrations I’m pretty sure(more testing to follow), I made that heimjoint ppf delete thing but never ran it much… well I have a full ppf on it now to my crossmember just bolted through the bottom holes and I guess it was bouncing… I drilled a hole in this ppf and threw that heimjoint thing on it bolted it up its solid now it actually makes less noise with the diff being hard mounted to the subframe than it did before… picture this(pic below) but the ppf keeps going and not cut off it shouldn’t matter tho I have personal/safty reasons for leaving it long and bolted to the crossmember. I can confidently say it fixed every vibration I had up to 85ish atleast I had one at 50-62 then the one at 72 that then never stopped I got it up to about 85 or so and started to feel very slight something but at this point that’s probably something else entirely as my tires are pretty roached at this point. I feel a lot better doing it this way as if the heimjoint setup ever fails it hopefully won’t shoot up through my gas tank… hopefully this is maybe some direction to look into for your issues too.

Kanaan

Did the issue change at all once mounting the ppf vs running the delete? wonder if even the stiff bushing still lets it vibrate and bounce a hair? i need to change my diff fluid soon and see if it still dirty's fast.
Edit: i swear i dont always wear a tin foil hat lmao, i just saw when you moved to a ppf it comes on earlier, kinda makes sense its got the same effect since the way I’ve seen the ppf mounted just with the bottom holes is losing out on a lot of rigidity and probably gives more than the bushing, who knows why some people complain about it and some don’t but that’s another rabbit hole for another day idk if I can say it’s driveline angles, mine seem to be dead nuts at the moment.. maybe they do all do it to different degree and rpms and what not..If I get time I’m going to jack it up and run it up without wheels again and see what happens, if it’s gone then I’ll be stumped as to why some would and some wouldn’t unless it’s an axle or something inducing it because my setup was basically the same as turbotims from my swap post.. anyhow my drive wasn't very long and getting late but hopefully ill do a bit more investigating and driving tomorrow but few miles i did do since the solidish mount it was night and day up to the 80's mph

Z_WAAAAAZ

Interesting. Based on this I wonder if both of my diff bracing solutions (KPower PPF delete brace/non-reinforced PPF) have too much flex in them or something then... You've added bracing via the heim joint and Six has added bracing via reinforcing his PPF with a second PPF. Might make sense.

Can you do another test taking the car up to 100+ and let us know if you get any sort of vibration there? Sounds like you have/had a lot of random vibrations at different RPMs/speeds. Mine starts at about 85mph and gets worse from there until the car hits about 135 where it cuts out (verified this with the car in a lift).

After messing with it more, I found my vibration didn't change at all whether the PPF or KPower brace was installed in the car.

Either way, hope your issue is fixed and you can finally enjoy the fruits of your labor with the Tremec!

Z_WAAAAAZ

Quick update: Slight chance have solved my vibration.

I swapped in the new diff housing today. Ran the supplied rubber upper bushings instead of poly, and paired them with my poly lower bushings since I didn’t have rubber lowers. Had to hog out the ID of the poly lowers a bit to fit but they worked.

Took the car up to 4,700rpm in 6th gear (close to the most violent range of my vibration) briefly on the way home and felt almost zero vibration from the rear. More diag needed still, the rubber bushings may just be covering up the vibration. I’m going to try to get the car back in the lift tomorrow and have a buddy drive the car up to 80mph again. Previously, the vibration could be easily felt by hand in the diff. Feeling that will be the real test.

Again, I’m not holding my breath, but the only core difference between my setup and Six’s at this point was the rubber vs poly diff bushings.

richbobby

solid news man!!

Can you elaborate on the bushing setup?

is it a stock style ? The stock rubber stuff is one piece so I’m not really putting together what you are working with.

K power said I should have the alloy shaft early next week. I might order some rubber boys to have on hand, so I can keep moving forward if the alloy shaft doesn’t fix me up

Z_WAAAAAZ

Heck yeah! If nothing else, the vibration is less annoying. I’ll send another update tomorrow night after running the car in the air.

The housing is used, and came with OEM rubber bushings pressed in. I didn’t have the lower rubber bushings that my car came with, though. These guys:



So I used my poly lower bushings on top of the plates instead of the rubber ones pictured above. I’ll take pics tomorrow.

Still hoping that alloy shaft helps as well. The suspense has been building for too long now. Keep us posted!

richbobby

Ah got it.

This is with the k power diff crossmember, too?

Z_WAAAAAZ

I removed the KPower mount and remounted the PPF to my trans crossmember. Didn’t want to break another arm in the meantime, although I know I should reinforce the diff housing regardless.

Z_WAAAAAZ

I jumped the gun on claiming potential victory. The core issue is still present. Diff starts vibrating around 4k in 6th. On the lift it can be felt moderately faintly. On the road, it’s even less apparent. Whatever’s vibrating back there is still vibrating. However, I question if it’s safer to beat on since some of the energy is being diffused by the additional bushing deflection.

Z_WAAAAAZ

Ok, we’re making progress.

Took the car out on the freeway today. Multiple pulls up to 100+ mph (4,700-5k rpm in 6th). Only the slightest abnormal vibration can be perceived as the car reaches 5k rpm/110mph. At 100mph, I wouldn’t notice anything wrong if I weren’t looking for it already. No doubt the root vibration is still present and is just being dampened by the rubber upper bushings. I wonder if Six’s car has always done the same thing but it just can’t be perceived because he’s on full rubber bushings whereas I’m on rubber uppers/poly lowers.

Or there’s still something fundamentally wrong on my car and I’m still at risk of hurting something in the driveline if I track it as is.

sixshooter

iTrader: (12)

Meh. Send it.


Edit: Are your CV axles out of balance?

Z_WAAAAAZ

Yeah, maybe I’m being a bit of a hypochondriac at this point. I’m just scared of having something fail after all these hours I’ve put in to install the swap kit and diagnose this issue.

I’ve ruled out the axles as being a culprit. Ran my new NB axles and the car’s original NA stub axles with no change.