Finally picked up the G today after all of this work got done. Slightly longer process than expected because the rusted cat bolts broke off when they needed to remove the exhaust for the driveshaft installation and I had to order new cats. Big shout out to Z1 who supplied all of these parts in record time and solid prices and to Trending Motorsports in Frederick, MD who did all of the work!

Total list of items:
1) DSS one piece aluminum driveshaft
2) Whiteline differential busings replaced
3) Rear 370Z axels and hubs
4) Front OEM hubs
5) Kinetix high flow cats, OEM/Z1 gaskets and OEM O2 sensors
6) Brake fluid replaced

So, overall impressions.

1) Thankfully there were no unexpected noises, rattles or lights on the ride home! My biggest worries were rattles coming from the driveshaft, too loud cats and a check engine light - all things that you will find if you scan YouTube for too long. Happy to report that none of these exist - so don't listen too closely to all of the reviews online/YouTube because apparently when you do things correctly, and replace 02 sensors, etc., these things do not take place. Literally there is zero extra NVH compared to previously, with the only exception being that when you get on it and hit about 3K+ rpm you can hear the gasses exiting the cats more pronounced, which is just fine by me. Sounds cool and expected. Other than than, everything is same as before.

2) As you might expect, probably the most pronounced difference is how buttoned down the handling is now. It's like night and day to the point where the weakest part of going into a corner is now the bolstering on my drivers seat that can't keep up with the chassis. Everything is so tight and controlled - you don't realize the gradual decline in handling that takes place over the years until you replace the worn out parts and then the car feels better than new.

As for the driveshaft and cats, I can definitely say that the car is noticeably faster. No question about it. I didn't have too much time to really test out on the way into work today, but the driveshaft makes the car more responsive and everything is just smoother and easier and more direct. I recall that the lightweight flywheel had more of an impact on faster engine revving than the driveshaft, however, that was a long time ago and my memory may be incorrect. Would I say that the driveshaft is the wonder mod that it is claimed to be on YouTube, probably not, but let me get some more seat time before a definitive review.

So, overall, very happy with how this turned out. This was the first time that I worked with Trending Motorsports in Frederick, MD, so although they came recommended, I didn't have a reference for their work quality. Overall the experience there was 100% positive and I would not hesitate to go back to them, which I will likely do next year for a new radiator/fan/hoses/thermostat job to get prepared to drop a new engine in down the road.

Hope this helps any of those looking to go in these similar directions.

 

Great review. Good info. Question: do you have an UpRev tune? If not, that will definitely be worth the investment. With those changes (cats), even if you do have a tune, updating it will make a difference. Check in with Seymore4 for eTune info.

 

I have an older tune from Altered Atmosphere way back in the day, but not an UpRev. I probably won’t do anything additional on the tune until I potentially drop a new engine in the future. Then I can get extra gains at that time from the tune as well

 

I remember when I got my headers put on that there was almost no difference over stock. I’m wondering if that was bc of the stock cats being too restrictive? I’m not sure if it’s the cats or the headers being freed up (or the combo) that is making more power now, but no question the car is much faster, This is kind of what I expected to feel when I got my headers put on initially.

Now that I’ve had more seat time, I can confirm that handling is WAAY better. It feels so firm, almost like a sway bar was added - that big of a difference.

Oh, I almost forgot that I did the Z1 diff brace as well…can’t tell what that adds vs the bushings, but that back end is planted now.

 

One very interesting observation is that my lightweight JWT fly wheel chatter that was very pronounced with the oem driveshaft is all but gone. That was a super pleasant surprise. can the two be related?

Aside from that, I’m having a blast! I used to enjoy driving the car because it was a cool “classic” car to tool around in, but the handling was so sloppy. Now I enjoy driving it because it is a real sports car again!

 

Thanks for posting your results and review! It’s always nice to see and feel the benefit of doing mods.

 

Good review. Did you notice any increase in exhaust noise below 3k RPMs with the HFCs? I've been considering the Kinetix ones as well, mainly to spice up my Borla.

 

Additional noise with my Stillen exhaust and headers is zero. I was worried when I started it up bc I did not want it to add more noise - I can safely say that I can’t tell any difference in noise before and after the cats at idle or normal load. Even when you get on it, it is not really louder, you can just hear the gases moving out faster

 

With exhaust work you sort of need to do the ENTIRE system to really see a benefit, it's all very matched together as an OEM unit, the headers flow as much as the cats, as the exhaust diameter, and as the muffler will all allow in combination.

It really needs to be replaced ENTIRELY to see a big benefit, the stock headers restrict at high rpm, same with the diameter of the tubing, same as the muffler.

Far and away the most restrictive is the factory cats though, next up the muffler, this gets you some mid range gains but the high rpm gains will be SEVERELY restricted by the stock pipe diameter and it's still going to really fall on it's face above 6k with the stock DE headers.

Plus it all needs to be retuned once the system is pieced together or it's still going to perform suboptimally.

There's nothing wrong with piecing it together a little at a time, it's just that you're not going to really feel the gains until all the pieces come together. Especially if you're not getting a retune.

 

I agree with above.

to point out your reduced chatter point with the new driveshaft, I’d say that may just be perception for now. We’ll see. The diff bushing and brace at the same time makes shifts feel way stronger in both auto and manual. A wonderful upgrade for any G this old. Nice treatment your G got.

the stock cats are the biggest restriction. I hope you kept them, those are going for $300+ right now at the scrappers.