Vibration/shimmy experiment -- MDX rear subframe brace retrofit

[stiles_s]

This is the first of a few posts I'll make about an experiment I'm doing. My Pilot definitely has a "harmonic" at 70mph that is triggered by the slightest imbalance in rotating mass. I had an old Miata ('90) that had a similar problem, and the aftermarket solved it via a chassis brace (happened to be a rear one).

I got to thinking about this, and got under a friends MDX in hopes that they had some additional bracing. In fact they do. See the photos here:


Pic2:


You're looking up at the rear subframe. Note the brace that is attached to the subframe bolt and runs up to attach to the unibody.

See the Pilot in comparison here w/o the brace:

Note that it even has the threaded hole on the unibody for the brace.

I'm of the firm opinion that a stiffer chassis is "better", and less prone to annoying harmonics.

So, I went down and visited a confused Acura parts counter guy this morning, and ordered the 4 parts I think I'll need to make this work:
- 50360-s3v-000 -- SUB-STAY, RR
- 90168-s3v-000 -- BOLT 14x125
- 50366-s3v-003 -- NUT, FLANGE 12
- 90186-SDA-A00 -- BOLT, FLANGE 1

Circled bits in this really blurry photo:
.

Total of ~$34 for one side. I'll test fit with this one side, and if it fits I'll order the other side to complete the set.

I'll keep folks "posted".

==================================

UPDATED / Directions (YMMV, do this at your own risk, I'm responsible for nothing, etc):

I've verified that the parts fit on my '05 Pilot EX/L, and I'm pleased w/the results (see notes later in the thread). YMMV.

First, check to see if you have the threaded hole in the chassis as reflected in the pics in this thread. if you don't, then you're on your own (see note on Nutserts if you're adventurous).

Here are the parts you need:
Quantity:2 - 50360-s3v-000 -- SUB-STAY, RR
Quantity:2 - 90168-s3v-000 -- BOLT 14x125
Quantity:2 - 50366-s3v-003 -- NUT, FLANGE 12
Quantity:2 - 90186-SDA-A00 -- BOLT, FLANGE 1

1) Either back the Pilot up on ramps or leave it on the ground
2) Do one side at a time -- do not loosen both subframe bolts at once.
3) Remove the subframe bolt you're going to replace w/the new one (17mm socket)
4) Install the new subframe bolt using a 17mm deep-well socket. Torque it to 69 lb-ft
5) Slip the new brace over the post on the subframe bolt, and hand-tighten the nut.
6) Hand-thread the bolt on the other end of the brace into the existing threaded hole in the chassis.
7) torque both the nut and the bolt (17mm socket). According to Tim, torque these to 47 lb-ft.

8) Repeat steps 3-7 for the other side
9) Enjoy

[01MDX]

Excellent post. I have an MDX and now a Pilot. So far I don't think I have the vibration issue but you never know. Interesting that the MDX has it and the Pilot does not - strange.

Let us know if it influences the ride quality at all.

[kuago]

I found this in 2002-2004 MDX, rear cross-beam

25. 50360-S3V-000 SUB-STAY, $15.02 ea.

26. 50366-S3V-003 NUT, FLANGE (12MM) $1.30 ea.

27. 90186-SDA-A00 BOLT, FLANGE (12X33)$.90 ea

28. 90168-S3V-000 BOLT, SPECIAL (14X125)
$ 6.54 ea.

This is the price I got from delray acura in florida!

I hope these will help you and either members, who has problem with the vibration on the rear suspension of their PILOT. I do too have vibration on my 2003 PILOT, EX. at 65 mph.



here a photo of the cross beam of the MDX...

[kuago]

here a photo of a 2003 PILOT

[stiles_s]

Originally posted by kuago
I found this in 2002-2004 MDX, rear cross-beam

25. 50360-S3V-000 SUB-STAY, $15.02 ea.

26. 50366-S3V-003 NUT, FLANGE (12MM) $1.30 ea.

27. 90186-SDA-A00 BOLT, FLANGE (12X33)$.90 ea

28. 90168-S3V-000 BOLT, SPECIAL (14X125)
$ 6.54 ea.

I hope these will helps you and either members, who has problem with the vibration on the rear suspension of their PILOT. I do too have vibration on my 2003 PILOT, EX. at 65 mph.



here a photo of the cross beam of the MDX...

Thanks for posting the factory part diagrams!
Wow, I'm getting robbed, price-wise. Good to know there are other cheaper sources if this turns out to be a useful mod. If not, I'm only out a few bucks

You don't happen to have the part numbers for the Honda diagram, do you? I'm interested in the part number for the bushing (#4) for both the Acura and the Honda. I'm hoping they are the same, but if not that may be yet another interesting path...

[kuago]

50230-S3V-A01 insulator A, Sub-frame mounting (lower).. Check -out hondapartsdeals.com in RI.

this is a part number of acura,MDX. Its is the same number as the PILOT. I just check...


Let me know the install and the outcome of the vibration of your PILOT..

[stiles_s]

Here's a part number comparison of the front and rear subframes. Bolded items are unique/different. Note that the subframes themselves are unique to the MDX which means that my brace might not even bolt up (which is why I only purchased one ).

I'd love to know what the differences are between the MDX and Pilot versions of the front subframe stiffener and dynamic dampers.

[ecsw]

keep us updated!

[Ferdball]

I don't have the pre-drilled holes.

[Ferdball]

Here's a pic of an 03 MDX.

[stiles_s]

Great pics, thanks. Interesting that the 03 doesn't have the pre-threaded holes.
I'll post more info on Wed hopefully, after the parts arrive.

[kuago]

This is not good! I have an 03 PILOT, EX. I just checked it. It doesn't have a predrilled holes with welded nuts in the sub-frame or underbody frame. I cant put that bracing bracket. Damn it! OPSS!

[Ferdball]

Originally posted by kuago
This is not good! I have an 03 PILOT, EX. I just checked it. It doesn't have a predrilled holes with welded nuts in the sub-frame or underbody frame. I cant put that bracing bracket. Damn it! OPSS!

I think its part of the screw. Its called the Early Adopter Screw.

Interesting though, that the 03 didn't have it, but the 04 or 05 has it. It looks like Honda experimented with the idea of the brace on the Pilot, but decided not to put it into production.

Either it didn't work; or it did, and there were political reasons not to implement.

[ctobio]

Well, considering you're paying about $5k less than an MDX, any component that they can save a couple of dollars on and not install means more profit. If the Pilot suffers from a little more body flex than the MDX, so be it. You get what you pay for...

It is very possible that the lower portion of the unibody is the same for the two vehicles. It may save costs on production to simply make all the floorpans the same rather than maintain two different production stages for the floorpan for each model. It's not unusual for a production change to be made like this. On an assembly line, any efficiency that saves time and money (and time = money) will be pursued.

An example I'm familiar with is early VW Bug (and by early, I mean late '60s) Semiautos didn't have the clutch cable tube installed, as a rule, but by the end of the production run, they didn't bother to differentiate the pans and thus the '73s nearly always had a clutch tube welded in place, just like its manual counterpart. It didn't pay to have the production lines make some pans different from others.

[kuago]

Does the 02 MDX have that bracket at all? Coz I got my 03 PILOT on July 2002... Maybe honda engineer is just determining this additional bracket to minimize the vibration issue on the rear cross beam, that was added and put to production for the 04-05 PILOT and 03-04 MDX.. Just a thought!