VR30 7AT Swap Vibration Issue
 

My fellow 370z enthusiasts, I need your help.

Recently swapped in the VR30 7AT transmission so I could eventually supercharge my Z and not have to worry about the trans as much, but I've run into a problem that my shop and I can't seem to diagnose. As soon as I get up to around 60/65mph my Z starts to vibrate pretty bad. So bad that I can't even really use my rear-view mirror because of it, and it's quite audible. When I did the swap, I bought the aluminum Godzilla Raceworks drive shaft, SOHO transmission mount, and also put in a LOJ flexplate. I had this all done at a reputable shop but it was their first time doing this specific swap.

My instant thought was the driveshaft was un-balanced, as I saw people report the same vibration, and that was the culprit. I had my shop remove the driveshaft and had it sent to get balanced, but according to their testing, it was balanced. They did however say that some of the "tolerances" were maxed out on the driveshaft, but honestly I don't know what that means. At this point I'm still not convinced of the driveshaft's quality, and I'm thinking this may still be the culprit. I talked to someone on reddit who did the same swap in their G37, and he had a similar issue, and was guessing it was either the driveshaft or the mount. SOHO says their mount has polyurethane on it to reduce drive line vibrations, and its made specifically for this swap, so I'm not sure. I had already bought the driveshaft from Godzilla when I saw that SOHO offered one as well with the mount, and at this point I'm almost wondering if I should just bite the bullet and try theirs out to see if it fixes the problem.

Obviously no one wants their Z to vibrate once they get any sort of speed going, so I wanted to see if anyone here had any insight/advice before I do something stupid and spend more money. Any help would be greatly appreciated.

Odd. I have the Fast Intentions flex plate VR30 7AT and Godzilla driveshaft. I’m using a stock type poly trans mount from Z1 with a modified chassis mount. I have no noticeable vibration.
If the driveshaft was balanced properly and you had it checked you could swap another known good driveshaft to see if problem persist.
Or check that trans mount. Maybe some resonance frequency vibrations going on.

My Godzilla shaft was out of balance and once brought back in the vibration went away. It would also happen beginning at 50+ mph like you're experiencing.

Have you tried indexing the driveshaft to each of the 4 available positions on the rear end flange? This is even mentioned in the factory service manual for the OE composite shaft.

I used a poly mount on the OE Z trans and the vibration was insane so i went back to stock. Try modding your OE rubber trans bracket to fit and see if the issue goes away. If it does you can rule out the driveshaft.

If you still have the vibe. the next place to check (unfortunately) is the flex plate. Being I'm not boosting my Z I kept my good condition OE in place during my VR swap.

BTW, don't expect any help from Godzilla with the shaft. They threw every excuse at me regarding the issue being something else, dimensions that never changed like shaft angle (made up with u-joints), distance between trans. and rear end (made up by their own shaft length), rear end angle (didn't budge during trans. swap lol), etc.. When I sent them pictorial proof and receipts proving the shaft was out of balance they completely ghosted. I guess not refunding the $75 i spent on balancing, not including 2 one hour round trips to the driveshaft shop, 2 hours indexing the shaft to the 4 available positions on the rear end flange is more important to them than keeping a customer that will recommend their products.

So I'm starting to notice a trend with you, FrankEtier, and every other post I can find, saying that the Godzilla driveshaft should be fine as long as its balanced, so now I'm leaning more towards my trans mount situation I have. It seems like most people when doing this swap opt for modding the OE mount, I just thought it would be more plug and play for my shop if I provided a whole new mount, so maybe I'll start with that. I really hope it's not the flex plate, as I haven't seen to many people complain about this issue with that, and its expensive lol. I'll get in touch with them after the weekend and see about modding the OE mount to see if that fixes it. Thanks for the insight into your swap, I'm glad you got your vibrations sorted out! It gives me hope!

I'd definitely try this first.

Mine is smooth as glass, maybe better than the Carbon one.

Only been up to 130, but it’s really nice.

Stock VQ37 flexplate
Stock VR30 converter
Stock rear trans mount
Stock rear trans crossmember (modified by me)
Driveshaft specialist of OKC, aluminum driveshaft

Let me know if I can help.

SG

Copy that, I'll add that to the list then, thanks.

Thanks for the list, still leaning towards swapping back in the OE trans mount/crossmember (at least for the start). Tractionless mentioned the flexplate being a potential cause as well, do you happen to think that could be part of it? Either way, I really appreciate it.

If the flexplate and/or converter were out of balance, you could rev the engine in park and definitely feel it.

SG

Need to pull the inspection cover and watch the converter while the car is running. If it is doing the Funky Chicken, someone tightened one bolt all the way down and it caused the converter not be on center.
That happened to my truck when I had the transmission and flex plate upgraded. Loosened them off then snugged them up one at a time before I did the final TQ. That fixed it. Seen it happen when I worked as a tech also.

I agree buying the trans mount is much less hassle than modding the OE but you literally just cut a "window" out of the rear portion of the mount so it can be slid forward and not contact the rubber isolator inside. I did mine with a pneumatic handheld grinder in less than 10 minutes but electric will work as well. If you decide to leave the modded OE mount in place, remember to paint the bare metal you just exposed via sawing. :tiphat:

If you want pictures of how mine looks email me Tractionless@comcast.net as I've seen some that are way over hacked (top rolled portion gone) and look structurally compromised in my uneducated (but plenty of experience) opinion.