Hey all,

So my 04 Z06 is (mostly) all original and I was having what I thought was severe wheel hop. Especially at the dragstrip in 1st and 2nd.

Did some research and found about how the drivetrain judders (shakes) and what the different rear diff and engine mount suppliers offer. They are good looking pieces but I wanted to see what else might be out there so I kept searching. I was able to find a small American business that makes a diff mount for C5’s and C6’s as well other hot rod parts. It’s my understanding it’s a one man show and he does this on a part time basis (besides working a full time job). I was very interested in helping a guy like that!

His web page -> www.farsightindustries.com

I’ve been a product design engineer by trade for closing in on 30yrs and turns out he is a design engineer too! That intrigued me a lot and after speaking to him I was impressed with his thoroughness and decided to give his piece a try.

Disclosure: I’m not being paid for this effort, review, and my vid is not monetized. He did give me a break on part cost in exchange for giving feedback about the install and results. Which I’ve done and I have no ongoing business with farsight. He’s just a small American business doing something fun and when possible I want to help little guys thrive.

I put together a vid showing the results. ->
Feel free to ask any questions…

Regards, Richard

 

If there are any corvette suppliers out there who would like me to install and evaluate a centrifugal style SC... I'd LOVE to have that opportunity.

 

Here is the full "before" video I posted a while back ->

 

Do you have a follow up vid on the response of the aftermarket mount?? Would love to see the comparison.

Thanks

Bill

 

Hi Richard,
So basically far sight industries mount looks like a copy of the Pfadt trans mount? I've heard those type of mounts with just a bushing have a lot of NVH?

Thanks
Christian

 

Hi Bill, the video in the first post shows the results. Towards the end I made before / after comparisons in back to back video clips. The video in the 3rd post is how it was acting when completely stock.

Christian, This farsight mount does several things that peaked my interest.. The brace has a design intent to be extremely ridged and all the compliance is to be taken up by the bushings. Not the brace.
It's shape was designed in 3D modeling software using simulation tools. That's why its shape looks like it does.. LOL.. it's not art, its 100% functional for the intended loading conditions. (this is exactly the kind of thing I do on a daily basis at work)
He took into account not only vertical loading but also fore/aft loading. And he made sure the bushing shapes gave enough compliance so as to avoid vibrations (NVH) coming into the cab. But not enough so as to allow drivetrain judder to start. Time will tell and I'm looking fwd to going to the dragstrip w/a set of sticky tires.

In my Z06 I get zero vibration w/this differential mount.. I actually can't tell its on the car from that perspective. What I do notice is after 20-30 minutes of highway driving, the diff/trans fluid heat up & there is a bit of gear whine that is audible. It's not loud and my wife wouldn't notice. But us car guys would.

 

Little update.. yesterday was 60F and the roads were dry and salt free so I took out it for some aggressive use. TC off and multiple 2500 launches and I had zero tire hop in 1st and 2nd. Laid down three heavy tire spinning 1 and 2nd gear "steer with the rear" type of launches. It was as smooth as I was hoping it would be.
I wonder if the warmer tire and shock temps are making the tire hop go away -vs- doing this at temps in the 30s? Bushings in the farsight mount would be a bit more pliable too.

 

Just my opinion here. That mount looks really nice and may be a nice middle ground between stock type and the race type.
The only reservation I have is the price $$$ $400 is a little steep just for a mount imho.
IF that price comes down by summer when I'm ready to pull my drivetrain apart, I'll strongly consider it.
The saccity mount looks like a decent street mount too and somewhat cheaper, although it is $200 .
I really had hoped to just buy an oem factory gm mount.. I wouldn't trust the anchor/pioneer aftermarket $40 parts store mounts

 

Foggy, my opinion is this. The bar is CNC machined from billet, he uses high quality bits, and its made by a small American business. So yeah $400 is a lot, but all things considered I think its good value.

Quick update: This morning was cold and overcast. (it actually started snowing 20 minutes after I got home) I went on my little route as seen in the vids above. It tire hopped when launching in 1st. So I think the cold temps and combination of tire, PSI, and shock I have are now the root cause. I'm curious how it'll perform on a 80F+ day. I think I'll wait and see before I swap shocks.

So far I've got about 300 miles on this part and other than the obvious drivetrain shake that's been eliminated the next thing I'll mention is that the car seems to be more connected when powering around corners. Throttle inputs just feel more immediate. Which makes sense since the diff/trans only move 10% of what they used to.

Anyway... I like this part and give it a thumbs up

 

In the factory mount video I don't see any drivetrain rocking so I still have to question why the mount needs wings. I never saw the point when Pfadt released theirs. The C5 drivetrain doesn't have any rocking or twisting force so the transmission just needs something to solidly support it.

The Sac City mount really looks really pretty for the price. That style should be all you need.

 

Lionel
I would love to see a comparison video of the OEM mount VS the PFADT Style mount under the same car and same driving conditions. You stated that you didn't see any drivetrain rocking. What you did see is and I believe is the cause of the wheel hop drivetrain shake problem is an oscillation in a circular forward to aft direction when the drivetrain is put under abnormally high torque conditions. Its evident if you look at that video in the 3:18 forward time frame. It not very violent but its enough to upset the cars traction.

In my opinion, wheel hop or as some call it "drivetrain shake" is caused by a combination of C5 drivetrain short falls and or conditions. My 98 MN6 base coupe with the F-45 Shocks was absolutely HORRIBLE for drivetrain shake from day 1 new off the dealer lot. I really never did any modifications or improvements to eliminate or improve it on that car. I just learned the cars laminations and didn't do anything to enter wheel hop situation. The car was always completely Stock.

My 02 ZO6 was a lot more forgiving and I seldom experienced that issue. Even after I highly modified it with more power. I did some improvements to insure against hop.

Here are some of the things that I have used (on several C5) to improve or eliminate the drivetrain hop/shake issue. Better performance shocks, Better engine mounts, Different tires other than the OEM Run Flats.

I have the original PFADT differential mount that I have yet to install. Like I stated previously, my ZO6 is pretty much shake free. I have better tires "Non run flat Toyo Proxis tires" & C6 ZO6 Shocks and that supports 450 RWHP without hop .

Just my 2 cents. Hope this helps someone resolve or improve their wheel hop / drivetrain shake problem.
UP-DATE
wydopnthrtl I don't know how I missed your excellent comparison video between the OEM vs Farsight mount. OUTSTANDING comparison as it shows a significant reduction in that forward to aft circular differential motion. Sorry for any confusion!


Bill

 

I just bought a similar one from a guy in South Carolina who is making them. $275 and looks to be very nicely made. After watching your video I was shocked (but guess I shouldn't be) at the side-to-side movement when cornering. My concern would be that this type of trans mount would take far more cornering load that the rest of the rear suspension is designed for unless the control arm bushings were changed to poly or some other harder material. I already have a set of poly engine mounts that I plan to install at the same time because I don't like the idea of the read diff being mounted "solid" while having softer mounts up front. That twisting force has to go somewhere.

I do really like this trans mount improvement but to me it's part of a complete package. Just on it's own it will help "some" but I don't think it should be a stand alone item.

 

Thanks Bill.

I've got more miles on it now and there are two big things that seem to emerge from adding this part.
#1 I'm far more confident I'm not going to break something when under hard / tire spinning / tire hop conditions. I find that I can launch harder and power shift 2nd.
#2 Powering around corners is noticeably more connected. There is a very direct input / output between throttle and GO. It just seems more responsive when under power. (I wasn't expecting this)

I've yet to try all this on a nice hot summer day. I want to do that before I upgrade the shocks... which I plan to do later this summer.

 

I had the exact same concern before addressing this issue. Here are my thoughts:
- Since vettes are IRS the BIG loading goes directly from the tire to the chassis and NOT through the drivetrain. The drivetrain is free to float and rotate in X,Y,Z. So its only constrained by the three mounts. The major forces on it are mostly due to its own mass vs directional changes in the chassis. (F = m * a)
- I suspect the largest loading on the torque tube is during hard clutch dumps where the front of the trans try's to rotate upward. I think that bending moment far outweighs overall drivetrain loads in XYZ and the small rotational TQ from engine loading.
- This Farsight mount has three bushings. The center bushing is much larger than the outboard pads and takes the brunt of the forces. It has the same foot print as the stock mount too.
- The ouboard pads are free to move in all directions except down. So they don't exactly lock the diff/trans to the crossmember. They only limit rotation and downward forces.

btw.... here is a vid I made from a V8 Z3 I used to own. The diff forces are so high that it rips the mounting cross members spot welds loose from the floor pan. (I added a "T" brace to pinch it all together and hold it firm. But notice how much the diff moved under TQ)

 

Not surprised to see all that diff movement with those giant rubber bushings. I like the way the bushing separates under load - definitely needs a firmer bushing in there.

It was difficult to tell in the video, but it appears that the billet bar part of the mount was either moving or bending under load - not sure which. The version that I bought is straight across the top, like the Pfadt version. It seems like the one you have could flex at the center area due to the greatly reduced mass there, and I would suspect less load bearing capability due to all the missing material the others (like the Pfadt) have. Just me armchair engineering, no real data to back that up of course.

Either way, seeing the diff move side to side under side loading tells me that the a-arm bushing compliance is allowing the axle joints to fully compress and transfer some of that force through the axle to the diff - enough to push it sideways. Poly or firmer bushings would eliminate that I would bet. It may not make a difference immediately, but I think over time it could cause a failure of axle joints depending on how much corning force they're subjected to. For me, I'm going to wait to install mine and do it as part of a complete package now that I've seen just how much movement there is back there.

 

The half-shafts would never fully compress into the differential. If you've ever taken the big nut off the half-shaft and pushed it in fully you'd know the half shaft has way more movement than the suspension bushings could ever compress.

 

OK, then why is the diff moving sideways under corning load? What else would make it do that?

 

What makes sense to me is the engine, bellhousing, torque tube, trans, & diff are all one ridged unit. It will displace as a unit. In the farsight unit the center bushing has compliance. It's not as soft as the stock unit but it has compliance.

btw, there is no way this bar is bending. Its billet and engineered using FEA for the loading conditions. So is the bracket that mounts to the crossmember. Also.. its a wide angle lens camera so we're not seeing a linear image in the video.

 

Centrifugal force. Same reason your butt tries to slide towards the outside of the corner.

The video clearly shows the differential moving to the right when the car turns left. In other words, the differential moves towards the outside of the turn. If your theory was correct then the differential would move left when the car turned left.

 

Sold me...just bought one.