Rear diffuser modification. - Pontiac G8 Forum: G8 Forums -
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post #1 of 5 (permalink) Old 11-14-2017, 10:27 PM Thread Starter
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Rear diffuser modification.

I didn't like the way the rear diffuser looked from the side view, it hangs too low towards the front, IMO. I addded a GXP diffuser hoping it would not only look better, but may not hang down like the original GT diffuser. Well it looked great from the rear, but I felt it still hung down too low in the front. See the before and after image. I'm thrilled with the results! I used some black plastic pieces and machine screws to elevate two outter "veins".
It looks very original. If there is any interest I can share more details on how I did it.
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post #2 of 5 (permalink) Old 11-15-2017, 03:15 AM
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Nicely done and noticed this conundrum when I first brought the vehicle, but never got around to doing anything about it.


"Rather not run the risk of offending anyone, so let me just go ahead and offend someone". -PONY MAN

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post #3 of 5 (permalink) Old 11-15-2017, 07:49 AM
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Please explain. Looks good!
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post #4 of 5 (permalink) Old 11-15-2017, 01:23 PM Thread Starter
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Parts list: 2- ABS black plastic for straps............................................ .......3/4"x 1/4" X 9" *finished size.
2- ABC black plastic for mounting blocks.....................................3/4"x 1/2" x 2" *finished size
2- "L" brackets with 2 holes on ea. side.......................................1 1/2 x 1 1/2
4- #8 pan head machine screws, for mounting block.....................1/2" long
4- #8 pan machine screws, strap to block....................................3/4" long
2- small sheet metal screw, for L bracket to body.........................1/2" - 3/4" long

This was done on a GXP diffuser. Remember: the measurements are based on my particular car. I started with pushing up on the diffuser by hand. Make sure it will move as need without distorting. mine was fine. I measured from the outer bottom edge of the diffuser straight up to a flat surface. it was 11" before modification. The plastic pieces were purchased from Tap Plastic's. I was able to find cut off "scraps" for a couple of bucks. The L bracket was cut at the edge of the two holes, on one end. I used machine screws, and tapped threads in the plastic. You could probably get by with sheet metal screws. I believe the pictures tell a lot. The idea is to strap the front edge of the diffuser to raise it to the desired height. My measurements are based on raising mine by 3/4". It is helpful to use a small jack to prop up the diffuser for measurements and mounting. The materials and method I chose look like... "it belongs there", IMO. Good luck and be patient, it's worth the effort.....
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File Type: jpg getPart_003.jpg (29.4 KB, 91 views)
File Type: jpg getPart_002.jpg (22.7 KB, 87 views)
File Type: jpg getPart_004.jpg (22.1 KB, 89 views)
File Type: jpg getPart_006.jpg (30.6 KB, 83 views)
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post #5 of 5 (permalink) Old 11-15-2017, 09:56 PM
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Nice mod ! I too have always though that both diffuser's look bad from the side,kinda not finished . I have been thinking about getting a gt one and cutting up ,but I think I will try this first , Thanks !
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