Vibration after Intrax install

[PCGUY112887]

I just had my Intrax springs put on, along with new KYB struts and HD mounts. I had him cut the bumper so the car doesn't bottom out on it, and everything seems to be great, tight steering and front end it's great. My left side lower ball joint was bad too, so both were replaced.

 

One issue however, now when accelerate from a stop, from around 7-20mph and usually I'm around 2100-2500 RPM's I get a vibration from the front of the car, I feel it through the wheels and the petal and everywhere. I know my alignment is fairly off but I don't see how it could cause a feeling like this.

 

Ideas?

[Cam'ron]

i keep hearing about driveshaft angles on lowered cars, theres shortened dogbones available that are supposed to fix this but i havent actually used them. an alignment is in order as well if you lowered your car

[GutlessSupreme]

A bad alignment could definitely cause that, imho. The driver shafts could be another reason as well.

 

I don't see how shorted dogbones would work? I guess I don't understand.. so they just hold the engine further forward, putting more strain on the lowers, the exhaust and some other things I'm sure...

[Canada]

Is the vibration matched to your vechile speed or to engine rpm?

[PCGUY112887]

Is the vibration matched to your vechile speed or to engine rpm?

 

This I can't decide... I want to say speed since it only happens while accelerating and it doesn't happen over 20mph period regardless of what RPM I am at.

[Canada]

Sounds like you could have something weird going on with your driveline angles. How much did this lower the car?

 

Rules out tire balance and an alingment as they would create issues at higher speeds as well.

[PCGUY112887]

About 1.5-2 inches it went down.

 

I need to test this more, but it seems like the car seems "floaty" and hard to keep in a line at higher speeds, possibly due to alignment.

[GOT2B GM]

Loose CV axle nut?

[PCGUY112887]

BTW

 

[PCGUY112887]

Well I have the alignment now, makes the ride much nicer (I could tell how towed in they were from the way it drove) but it didn't help my vibration.

 

Here is how it goes. If I take off from a stop, around 1800-2300 RPM's accelerating I can feel this vibration in the entire front of the car, through the petal, steering wheel, everything. It's not TOO violent but I can very much feel it. If I am in a turn while accelerating, it doesn't do it, but as soon as my wheels are straight again I can feel it.

 

This doesn't happen past about 20mph, and I never feel vibration at any other time aside from taking off from stoplights and such. If I just accelerate faster to about 2600 RPM's before I hit 20 then I don't really feel it as much either. It's definitely a low acceleration vibration at low speeds.

 

Here is what I have found out so far. Some of the newer GP guys have been putting spacers under their trans/engine mounts to make their axles align, see here.

 

http://www.clubgp.com/newforum/tm.asp?m=3683662&p=&mpage=1&tmode=1&smode=1&key=lowering+vibration&language=single

 

With other w-body cars, there have also been people who have made offset dogbone bushings that are supposed to take care of this vibration.

http://www.zzperformance.com/grand_prix/products1.php?id=130&catid=138

 

However I already have a nice set of poly dogbone mounts from Intense Racing, and I really don't want to try to add spacers to my mounts since 1 of the bolts on my engine mount will probably never work right again if I take it out, it got misthreaded and it's in there good now but if I take it out I would probably have to have those threads in my block repaired to put a bolt back in there.

 

I have seen mentions of shortened dogbone mounts, so I found them here.

 

http://www.wbodystore.com/grandprix/shortened-dogbones-reduces-vibration-on-lowered-cars-p-177.html

 

This is the cheapest option, I am willing to try it but I am afraid they may make my headers hit my firewall, since they would have to pull the engine forward and my engine can't come too much more froward without my headers hitting on the firewall.

[95aquase]

i noticed the shortened dogbone thread last night after i pmed you. so i went out and tried it today. (with ratchet cables)

pulled the motor forward about 1.5in and drove it. the vibration is definatly there. but it is much less noticeable. i think if the vibration is slight enough the dogbones may work.

 

are our mounts the same as newer gps??? if they are i would be tempted to buy the spacer kit

 

 

 

[GutlessSupreme]

Putting shorter dog bones in would probably put a lot of stress on the lower mounts, since they'd always be cranked forward. Although, I can see lower mount spacers putting stress on stuff too (exhaust/etc), but I can't think of how else you could correct the axle geometry.

[PCGUY112887]

I don't know how much shorter the dogbones are now, but they are cheap enough so I just bought them... we will see if I can even install them!

[95aquase]

i am currently ordering the motor and trans spacers and will get them put on soon and keep this thread going for solutions

[PCGUY112887]

Well I got the shortened dogbone mounts, I didn't know how much shorter they were but now that I have them I see that they are far too short for me to be able to install. My headers hit the firewall a bit when I give it gas in reverse anyways, the headers also rub on the fire blanket on the firewall... there is no way I can get enough clearance to install these things, or offset mounts that would torque my engine forward.

 

Any other ideas? I know custom axles was a solution, but where could I get that done? How would I know how the axles would need to be changed?

[95aquase]

i still havnt gotten around to the spacers. which i still want to try out.

[wickedbuick]

It may not be the case, but I had the exact same symptoms from my series one before I swapped. After freaking out for like 3 days , I found that my torque converter to flexplate bolts were loose. You may want to check those with an 18mm wrench through the access hole on the bottom of the engine. You can use a flathead screwdriver or prybar to stick in the flexplate teeth to keep the engine from turning. Probably isn't it, but it's free and quick to check.

[PCGUY112887]

I'm really wondering if it could be my motor mount that is causing it...

 

Reason - Awebb and most other lowered earlier w-body cars never complain about vibration. If it was typical, you would hear a lot more about it, and there would be a "standard fix" already, such as the pogo mod on newer GP's.

 

Mine should be no different, but I noticed how those tranny/motor mount spacers worked, and it got me thinking. My current motor mount is a solid mount sold by NAPA. Apparently this same part # came in 2 versions, 1 a perfectly manufactured version, and the other a "lesser quality" mount that was like 3/4" shorter than what it should have been. I didn't know of this at the time, and just installed the motor mount as usual. It was almost the same height as my blown hydraulic mount that came out, but I didn't think anything of it (not really thinking about the fact that the blown mount was of course going to be shorter).

 

There was a big post on ClubGP somewhere, since they use the same motor mounts and people used solid ones of the same #.

 

So I am really wondering, maybe that extra lowering on the engine was never noticed before, but now it's causing vibrations since I'm lowered.